Month: April 2024

The more successful Turén farmers sought to diversify production to cope with price and yield fluctuations and also expanded into new areas to counter the loss of soil fertility the increasing chemical-dependent production system engendered . By 1990, the original colony had expanded from 15,000 to 250,000 hectares and had established a production system of rice, maize, sesame and sorghum, crops favorable to mechanization and that could feed into the agro-industrial system . Agricultural development, and the resultant growth in production of cereals and oilseeds, in Portuguesa between 1949-69 was considered a national agriculture ‘miracle’ as the government invested resources into irrigation projects, roads, windbreaks, housing and a rice processing plant that helped to solidify the new class of farmers in the area . However, while grower strategies of expansion and diversification were important for commercial farmers in Portuguesa, outcomes in the state varied. Successful commercial farmers in the Acarigua-Araure center grouped together in producer associations and used alternative sources of capital investment to expand into more profitable areas of the agroindustrial chain by developing processing plants for oilseed and cotton refining . Unlike the Acarigua- Araure growers, however, Turén producers didn’t have access to alternative financing to enable vertical integration, and although were able to expand and diversify production, became largely subordinated to the more powerful agro-industry sector as they assumed a role as producers of raw materials for processing centers . This dynamic intensified in the late 1970s and early 1980s as Venezuelan agriculture entered a crisis. A confluence of factors including reduced government subsidies and private investment in the sector, stagnant prices,hydroponic dutch buckets and the rapid increase of food imports contributed to a squeeze on the nation’s producers .

By 1983 vegetable production was 15% below 1977 levels, and the area under cultivation had fallen 25% . In the same time period, food imports rose from 35% to 65% of national consumption . Much of the disruption to the agriculture sector was due to OPEC’s—and by extension Venezuela’s—successful efforts to raise oil prices. The resultant influx of petro-dollars to Venezuela’s newly nationalized oil sector drove currency appreciation, which facilitated increased food imports and reduced the competitiveness of domestic producers. The crisis drove further mechanization and intensification in Portuguesa’s agricultural sector, as the state’s commercial elite saw increasing production as the solution to a context of stagnant prices coupled with rapidly rising costs of production . The agrarian malaise reflected the general political and economic crisis of the 1980s as oil prices dropped. The Venezuelan government implemented reforms to boost agricultural production, including deregulating controlled food prices, issuing of low-interest loans, increasing fertilizer subsidies, and mandating that commercial banks lend to a portion of their reserves to farmers . The policy prescriptions fed the so-called Venezuelan ‘agricultural miracle’ of 1983-87 that saw strong sectoral growth and production rises in a number of key crops. Maize, sorghum and cotton production levels doubled over 1983 levels . Continuing macroeconomic woes however pressured subsequent governments to accept orthodox conditionalities of the International Monetary Fund that began to restructure the economy at large and largely dismantled polices aimed at food self sufficiency by reducing agricultural price supports and input subsidies. The implementation of structural adjustment policies, however, resulted in severe social upheaval, including the 1989 Caracazo. The upswell of protest from Venezuela’s citizenry opened political space for the government to reinstate some subsidies to the agricultural sector. In sum, as the 20th century closed Portuguesa had been transformed into dominant agrarian player, with a vertically-integrated commercial agricultural sector.

With Acarigua-Araure serving as the agro-industrial core and as an important regional market for seeds, machinery and agricultural services in the state, Portuguesa functioned practically as an agrarian enclave economy as it became the premier agro-industrial center in the country . The success of the commercial sector was predicated on interventionist state policy that broke up landowner power, provided credit, input subsidies, infrastructure and technical support, and maintained government-protected, domestic markets . The emergent agro-industrial sector had little connection to the earlier agricultural export sector of coffee and cacao, although some traditional latifundio interests did evolve into commercial elite. The agrarian reform sector near agro-industrial commercial development was subordinated to the accumulation needs of the commercial sector. While commercial agriculture established itself in areas with well-developed and largely government-financed infrastructure much of the state remained largely untransformed. Agrarian development established two coexisting production systems: an agro-industrial model centered in the municipalities of Páez, Araure, Esteller, Turén and Ospino; and areas of continued peasant production, especially prevalent in Guanare, Guanarito and Sucre . The peasant sector in the immediate geographical path of commercial agriculture had been displaced and sometimes absorbed into the new industrial sector as labor, or had continued to function largely as before in areas further afield from Portuguesa’s agro-industrial corridors.Portuguesa’s commercial sector is concentrated along the number 5 highway, the major transportation artery in the area that links Portuguesa to the important commercial cities of Barquisiemto, Valencia and Caracas. Agro-industrial crop production is focused near the main transportation corridors while mostly small-scale coffee production is located primarily in the highland areas of Sucre, Ospino and Monseñor José Vicente de Unda municipalities.

Cattle ranching— primarily for milk production—remains in some savanna areas, particularly in low laying lands that seasonally flood and remain relatively far from infrastructure networks in Guanarito and Papelón. In 2001 Portuguesa accounted for 90.5% of domestic sesame production, 51% of rice, 41% of sorghum, 40% of corn and over 30% of sugarcane . In 2013, Portuguesa accounted for over half of all maize production in the country, producing 1,031,765 tons . Portuguesa is not a site of petroleum production or processing. Of theoretical note is that in the oil curse literature, oil development displaces agriculture in terms of share of national GDP, contributes to Dutch disease dynamics that favor imports over national production, and—at a regional level—can displace agriculture at specific sites of production.Yet, Portuguesa demonstrates—in areas with favorable conditions—agriculture can become a regionally dominant sector in particular historical contexts. According to Grinberg and Starosta , capitalist sectors in oil states are limited in their capital accumulation process by the nature of oil rent redistribution. While the capture oil rent allows for their reproduction on a domestic scale they are generally unable to compete in international markets . In Venezuela, a contingent of Portuguesa growers were successful in consolidating a dominant position in supplying domestic markets. Part of this success was also based in expanding vertically in domestic agro-industrial chains, and using smaller producers to help feed the local processing and packaging enterprises they now controlled. The issues of land reform and domestic food production have been prominent controversies within Venezuela in the Chavista period. The intense reaction of commercial grower associations to the 2001 Land Reform Law and its explicit calls for the elimination of Venezuela’s latifundia established an early context of conflict between agriculture elites and the state. The perceived attack on private property rights codified in the Land Reform Law has been cited as one of the primary drivers of sharpening opposition resistance to the Chavista government and of contributing to the 2002 coup de tat that briefly removed Chávez from power . The government’s anti-latifundia rhetoric was portrayed by government critics as generating class conflict, violence and sense of lawlessness in rural areas . Agriculture, food and land reform policies have, thus, served as important points of conflict between the Chavista government and its political opposition and cannot be separated from broader social conflict over the Chavista-era ‘revolutionary’ program. However,bato bucket conceptualizations of dynamics between the state and the commercial agriculture sector as primarily conflictive mask a set of policy relationships that are more ambivalent. A closer examination of policy dynamics reveal that state policies often support sectors of commercial agriculture and reinforce agribusiness socio-economic position in rural areas. Perhaps most salient issue in terms of conflict between commercial agriculture and the state is the threat of confiscation of land via the Land Reform Law. Indeed, the law was one of the most controversial components of the government’s 2001 reform package . Through 2013, 6,897,872 hectares have been recovered, and 11,901,752 hectares have been regularized by the state under the Land Reform Law .

Despite the quantity of land recovered by the state and political controversy and violence connected to the agrarian reform, the process of land expropriation has largely bypassed producers in much of the commercial agriculture sector. The relatively low land seizure pressure on commercial producers in Portuguesa results from government negotiations with estate owners, dynamics between state institutions and producers at the local level, and an increasing policy trend focused on maintaining agricultural production levels rather than on addressing levels of land inequality. It is difficult to ascertain how much land was seized by the government from private interests, especially on the level of individual states. At the time of writing, government data on land recovery and redistribution released by the MPPAT and INTI were national totals and did not break down numbers by individual states or municipalities. There were no available, reliable data on how many private estates in Portuguesa had been subject to recovery by the state or had been occupied by peasant groups. Commercial growers in Portuguesa, however, stated that the threat of expropriation was a central incentive to continue production in the face of low prices and other productive or profitability challenges . In Portuguesa, growers cited the cases of the 2,276 hectare Dos Caminos and the 1,779 hectare Palo Gordo estates recovered in 2012 by INTI as emblematic cases of seizures from landowners in the region. Negotiation with landowners for partial redistribution is often attractive for policymakers as it theoretically speeds up land redistribution and avoids drawn-out legal process and appeals. It also potentially diminishes opposition to reforms as landowners can receive payment for lands lying idle on estates, as under the Land Reform Law estate owners are entitled to compensation for seized lands. Oil revenue theoretically allows the government to pay market rates for seizures, giving it an advantage over more cash-poor countries attempting an agrarian reform that compensates landholders. It is unclear, however, to what degree compensation has been paid in the Venezuela land reform. A high-profile expropriation case involving estates owned by the British Vestey Group was resolved with the government and the company negotiating the transfer of two estates to the government in exchange for the retention of 8 other estates and a payment of £2.4 million . Yet there is no clear data on whether or not payment was delivered to landowners in the majority of cases of land recovery. Some seizures of sugar plantations in the state of Yaracuy, for example, were ultimately implemented under the rationale that private land titles were invalid due to the area being designated as an indigenous reserve before the establishment of the plantations . As the plantations occupied technically state land no indemnity was paid. Regardless, a strategy of negotiation with landowners by the state in policy implementation has implications for the nature of the reform. As in the case of many historical land reforms the division of estates with property owners can often leave the most productive land—with better soils and well-developed infrastructure—in the hands of landowners, which solidifies their relative position in the agriculture system even as it may diminish the size of absolute holdings. Redistribution pressure on private interests in the agrarian sector was also dependent on changing relationships between government institutions and commercial interests. In early periods of the reform government positions at the state or municipal level in some areas were in the hands of politicians that opposed the Land Reform Law. In Yaracuy and Cojedes states early land occupations by peasants were removed violently by state police forces under the control of opposition governors . The subsequent election of Chavista politicians to state-level offices was an important shift in local conditions that allowed peasant groups to re-occupy estates with a greatly reduced—although not entirely eliminated—threat of removal by state security forces . The control of key local offices by Chavista politicians or functionaries, however, did not ensure an even approach to policy implementation. Growers in Portuguesa cited that the changing of directors of MPPAT and INTI at the state level impacted how aggressively redistribution was promoted by the government.

The November 2016 state legalization of recreational cannabis prompted Siskiyou to examine a possible licensure and taxation system for local growers . Amidst sustained, vocal opposition, the proposal stalled for several reasons that further aggravated cultural and racial tensions: A key proponent of licensure was discovered to be running an unauthorized grow, three Hmong Americans died of carbon monoxide poisoning due to heaters in substandard housing, and a cannabis cultivation enterprise run by two Hmong-Americans attempted to bribe the sheriff. These developments were interpreted not as outcomes of restrictive regulations and criminalizing strategies, but as proof that, in the words of one supervisor, regulation was impossible until the county could “get a handle on the illegal side of things.” The sheriff encouraged this interpretation, arguing in an interview that statewide legalization was “just a shield that protects illegal marijuana” and efforts to regulate it would always be subverted by criminals. This anti-regulatory logic prevailed in August 2017 when the county placed a moratorium on cannabis commerce. Still, the sheriff argued for stronger powers, citing an “overwhelming number of cannabis cultivation sites,” which, according to the Sheriff’s Office, continued to “wreak … havoc [with] potentially catastrophic impacts” across the region . Just 1 month later, at the sheriff’s urging, the Siskiyou Board of Supervisors declared a “state of emergency” aimed at garnering new resources and alliances to address the cannabis cultivation problem. Soon, the Sheriff’s Office enlisted the National Guard, Cal Fire and the California Highway Patrol in enforcement efforts, and, by 2018, numerous other agencies joined,planting gutter including the Siskiyou County Animal Control Department, California Department of Toxic Substances Control, State Water Resources Control Board, California Department of Fish and Wildlife and a CDFA inspection station.

These alliances multiplied the civil and criminal charges cultivators might face . Ironically, California’s cannabis legalization has enabled a kind of multi-agency neoprohibitionism at the county level, one that reinforces older criminal responses with new civil-administrative strategies and authorities. The need to “get a handle” might be regarded as a temporary emergency measure, but it may also propagate new criminalizing methods and institutional configurations. The more enforcement occurs, the bigger the problem appears, requiring more resources and leading to a logic of escalation symmetrical to the much-critiqued War on Drugs . And the more cannabis cultivators are viewed as criminal, the less likely they are to be addressed as citizens, residents and farmers.Given concerns about biased county policy and enforcement, the Sheriff’s Office held the first Hmong American and Siskiyou County Leader Town Hall in May 2018 to “foster a closer, collaborative relationship with members of the Hmong-American community,” exchange information about Hmong and Siskiyou culture and educate attendees on county policies . According to public records, racial tensions surfaced at this meeting when some white participants expressed that “our county” had been “invaded” and that Hmong-Americans were not fitting into local cultural norms . Meeting leaders — both government officials and Hmong-Americans — however, identified cultural misunderstanding, rather than criminalization and racialized claims by whites on what constitutes local culture, as the core problem to be addressed. “Misunderstanding” was an inadequate framing, given that Hmong-Americans had attempted to make themselves understood by attending public meetings, forming advocacy groups, signing petitions, demanding interpreters and administrative hearings, and registering to vote since their arrival in Siskiyou. At the 2018 town hall, and numerous prior meetings, they emphasized their status as legitimate community members — veterans, citizens, consumers of county goods, local property owners, “good” growers and medical users — not nuisances, criminals, foreigners or outsiders.

In interviews and public forums many Hmong-American cultivators expressed a desire to comply with the rules. Their efforts, however, they said, were frustrated not only by linguistic and cultural differences, but also understaffed and underfunded permitting, licensing and community services agencies. Hmong-American cultivators routinely told us about their desires to settle down, build homes and plant other crops. “I’m growing watermelons, pumpkins and tomatoes,” one cultivator told us, but he was waiting for a permit to build his house, a process another interviewee reported took 3 years. Though the town hall meeting sought to address cultural misunderstanding, this framing overlooks how misunderstanding — of Hmong-Americans or cannabis producers generally — is produced by criminalizing enforcement practices. Properties given as gifts in the Hmong-American community were seen as evidence of criminal conspiracy, not generous family assistance; land financing networks evidenced drug trafficking organizations, not kin-based support and weak credit access; repetitive farm organization patterns suggested “organized crime” , not ethnic knowledge-sharing circuits. When Hmong-Americans, leery of engagement with government agencies and unfriendly civic venues, self-provisioned services, including firefighting teams, informal food markets and neighborhood watches, these actions were taken to confirm suspicions that they could not assimilate. Now that some Hmong-Americans are considering, or already are, moving away in response to county efforts, the sheriff’s prior description of them as temporary residents seems prophetically manufactured.Anti-cannabis pressure creates a precarious state of impermanence — a season’s crop might be destroyed, infrastructure confiscated and investments of limited resources lost at any moment, disallowing longer-term investments. The impermanence makes noncompliance and deleterious environmental and health effects more likely, thereby perpetuating perceptions of cannabis cultivators as nuisances and dangers.

As enforcement makes private land cultivation more risky, cultivators move “back up the hill,” namely onto ecologically sensitive public lands, thus substantiating characterizations of cannabis growers as criminal polluters. These stigmas even spread to county residents who do not grow cannabis themselves but if perceived to assist cannabis cultivation can face social sanctions. One agriculturalist reported receiving death threats after selling water to cannabis cultivators. Meanwhile, well-resourced cultivators have an advantage over small-scale producers. They can protect their crops from visibility and complaints by concealing them on large plots of land or inside physical infrastructures ; and for white growers there is the anonymity of not being marked as ethnically different and therefore subject to heightened scrutiny. Greater access to capital, land and racial privileges insulates some from visibility and criminalization, resulting in uneven development and disparities in California’s expanding cannabis industry. Additionally, jurisdictions like the Siskiyou municipalities of Mt. Shasta and Weed are welcoming regulated cannabis commerce, thus capitalizing on its expulsion from the rest of Siskiyou and benefiting entrepreneurs with social capital and network access to successfully navigate complex public regulatory systems.After a century of cannabis’s criminal exclusion in California, state voters have elected to integrate cannabis farmers into civil regulation. An important facet of evolving cannabis regulations is local determination. As one interviewee pointed out, a 1-acre farm might be permitted in rural San Joaquin County but would not make sense in downtown San Diego. Yet,gutter berries when cannabis cultivation is disqualified from consideration as agriculture by localities, as it has been in Siskiyou County, it can be substantively recriminalized and placed beyond the regulatory reach of civil institutions. Prohibitionist strategies that blur lines between civil and criminal enforcement lead to penetrating forms of visibility and vulnerability that produce inequity and disparity. The result, as this case illustrates, can be a narrow, exclusive definition of agriculture that affirms dominant notions of land use and community. The definition of cannabis cultivation as agriculture by the CDFA creates an opportunity for service providers and regulators — including agricultural institutions, public health departments and environmental agencies — to craft programs and policies that openly address the negative impacts of production. Owley advises that “if we treat cultivation of marijuana the same as we treat cultivation of other agricultural crops, we gain stricter regulation of the growing process, including limits on pesticide usage, water pollution, wetland conversion, air pollution, and local land-use laws.” Presently, however, many agencies are being enlisted in locally crafted criminalizing efforts, thus limiting their ability to work cooperatively with cultivators and address issues through customary civil abatement processes.

Though unregulated cannabis cultivation can pose threats to public health, safety and welfare, police enforcement is only one of many possible ways to address it. Siskiyou’s cannabis cultivators experience familiar agricultural challenges around access to land, water and credit. These challenges are amplified without technical assistance or institutional support. If recognized statewide as farmers, these cultivators would be better positioned to access agricultural training and support services, thus addressing ecological and social concerns around cannabis production. Additionally, new cannabis cultivators might be considered “beginning” farmers according to the CDFA, and minority farmers, including Hmong-Americans, who experience poverty at twice the national rate , would be considered “socially disadvantaged” under the California Farmer Equity Act of 2017 . Farmers with these designations would, in fact, be prioritized for technical assistance and support from farm service providers — if, that is, they were recognized as farmers. Uniformly treating cannabis cultivation as agriculture would also help enable the collection of accurate and robust data by researchers. This information base is necessary if agricultural institutions are to take an assistive and educational orientation toward cannabis farmers. Continued enforcement tactics that amplify distrust, frustration and confusion will further hinder data collection , leaving little basis to understand basic dynamics of complex, interdisciplinary systems like agriculture . In a criminalized situation, it is inevitable that information is metered and brokered by community leaders in ways that inhibit full understanding of cannabis cultivation. We suggest, for all these reasons, that a decisive break with enforcement-led, prohibitionist trajectories is needed and that agricultural institutions lead civil policy development and support farmers who cultivate cannabis. Agricultural service providers could play a leadership role in addressing the pressing needs of farmers — both those impacted by and engaging in cannabis cultivation. Yet, UC Agriculture and Natural Resources Cooperative Extension advisors, for instance, consistently report that they are currently prohibited from engaging with cannabis issues . Additionally, many county-based agricultural commissions, Siskiyou County’s included, feel that cannabis is not an agricultural enterprise and therefore do not see its cultivators as their clientele. Without leadership from agricultural institutions and agencies, the expanding cannabis cultivation industry is left to develop unevenly across the state — with wealthy private interests capitalizing in some locales while vulnerable and unregulated growers may retreat, to avoid criminalization, into ecologically sensitive areas. UC ANR and CDFA have an opportunity to fulfill their missions and facilitate, for a burgeoning farming population, greater parity in farmer rights, capacities and resource access.Organic strawberry production has become big business in California, generating more than $17 million in sales annually on over 1,200 acres—nearly 5% of California’s total strawberry acreage. But as producers have found, growing this specialty crop without conventional pesticides requires a new toolbox of pest and disease control techniques. For the past five years, researchers from the Center for Agroecology and Sustainable Food Systems have been refining the use of trap crops in organic strawberry systems as a way to limit damage from the western tarnished plant bug and boost populations of the pest’s natural enemies. A serious pest native to California’s central coast, WTPB feeds on developing strawberries, causing gnarled, “cat-faced” berries with enlarged, straw-colored seeds. These damaged fruit can’t be sold on the fresh market. Although some organically acceptable sprays exist to treat WTPB, they’re expensive and relatively ineffective.A broad range of winter weeds in central coastal California, including wild radish, mustards, chickweed, lupine and other legumes, and knotweed, offer a winter food source for WTPB. As the rainy season tapers off in the spring and wild vegetation dries out, the WTPB adults move to flowering crops, including strawberries, and begin feeding. Trap crops planted along the edges of crop fields or within the field have the potential to limit WTPB damage by offering the pests a food source they prefer over the crop itself. “That’s the definition of a trap crop—that it’s a preferred host or food source for the insect you’re targeting when compared with the main crop,” says Sean L. Swezey, the Center’s associate director, and director of the UC Sustainable Agriculture Research and Education Program. Trap crops can also serve as habitat for beneficial insects, which can supplement pest control efforts.Once attracted to the trap crop, pests must be managed so that they don’t eventually disperse into the fields and damage the crop you’re trying to protect.

One can therefore calculate the significance levels for the test of whether the aggregate impact is significantly different from zero. The‐values suggest that the impact becomes significant around 2°C . Using the classification of IPCC, the study found that a negative impact is very likely for the +2°C and +3°C scenarios. As pointed out above, the coefficient on the degree‐days variables are less robust, however, similar results are obtained in a comparable study covering a larger geographical and climatic range gives comparable results. At the same time, the potential decrease in water availability appears to more damaging, especially for junior holders. This analysis studies how climatic variables and the access to subsidized surface water capitalize into farmland values, and how these values would be affected by changes in the climatic variables. Using a micro‐level data set of individual farms in California researchers examined how degree‐days, a non‐linear transformation of temperature variables, and related changes in water availability, capitalize into farmland values. This study found that the standard OLS approach underestimates the true variance‐covariance matrix of the estimator and therefore overestimates the significance of the regression coefficients, including those on the climate variables, because it incorrectly assumes that observations are identically and independently distributed. Nevertheless, the estimates of the impact of a change in water availability remain highly significant, even when allowing for spatial correlation or including random effects, though the significance is of course reduced relative to OLS. Similarly, coefficients on the linear and quadratic degree‐days variables are in line with what one would expect from agronomic studies,dutch buckets system but the estimates seem less robust to the inclusion or exclusion of non‐climatic control variables.

Researchers note also that the limited temperature variation in the study area makes estimation of the effect of temperature or degree‐days on farmland value somewhat problematic. The team has conducted a similar analysis for the eastern United States and found that extending this analysis to a larger area characterized by greater variation in temperature gives highly significant degree‐days coefficients that are comparable in magnitude to the ones presented here. The average magnitude of the impact of a potential decrease in water availability on farmland value appears to be larger than the one caused by an increase in temperature, because a decrease in water availability is harmful for all farms in California—a state that crucially depends on irrigation. On the other hand, the effect of an increase in temperature is mixed, ranging from modest benefits of an increase in temperature to potentially large damages in the Imperial Valley. Several caveats apply to this analysis. Perhaps the most important is that data on water rights is difficult to obtain, and the research team is continuing to develop finer and more accurate measures that might change the coefficient estimates. Moreover, the team’s current measure of water supply uses average annual historical deliveries; in future work, they will include measures of supply reliability that reflect the uncertainty facing water districts each spring, at the time cropping decisions are made. In addition, since the analysis relies on cross‐sectional data it does not pick up any potential changes not reflected in the data, most notably changes in prices, technology, CO2 fertilization, or the potential reduced water‐requirements through CO2 fertilization. “Among the many sessions of the Third World Water Forum, held in Kyoto, Japan in March 2003 , there was one titled Sedimentation Management Challenges for Reservoir Sustainability. Two main messages emerged from that session: Whereas the last century was concerned with reservoir development, the 21 st century will need to focus on sediment management; the objective will be to convert today is inventory of non-sustainable reservoirs into sustainable infrastructures for future generations.

The scientific community at large should work to create solutions for conserving existing water storage facilities in order to enable their functions to be delivered for as long as possible, possibly in perpetuity.” Reservoirs are one of the most common forms of nonrenewable resources, yet their economic studies have been rare. Engineering literatures emphasize that even when reservoirs were structurally sustainable,they could nevertheless become unsustainable due to sedimentation accumulation. The loss of storage due to sediment accumulation is nontrivial and alarming: Mahmood, K. reports that the annual capacity loss of worlds reservoirs due to sediment accumulation is about 1%, though White recently put this agure at 0:5%~1% . A world bank report translated the loss as the need to add some 45 km3 of storage per year worldwide, costing US$13 billion per year exclusive of environmental cost. China, which alone accounted for more dams construction than the rest of the world during 1950 1980,fairs worse, mainly due to the nature of sediment rich Yellow river. Zhou reported that China’s 82; 000 reservoirs are losing their capacity at the average annual rate of 2:3%. Three other frequently cited example of storage capacity loss are Welbedacht dam , Mangaho River project in New Zealand and Tarbela reservoir in Pakistan. If sedimentation issue is not taken care of properly, reservoirs needs to be abandoned after the sedimentation reaches a critical level.But sedimentated sites can’t be easily recycled for reuse. Such recycling efforts could be extremely costly. For example, according to Morris and Fan ,it would cost $83 billion to restore Lake Powell in Colorado river assuming one could and the disposal site to dump 33km3 of sand.Furthermore, there are not many proper sites for constructing reservoirs. Such sites certainly are not growing. Also, since the best sites costs were taken up earliest, alternative sites will be progressively costlier. These facts attest to the reservoir being nonrenewable resource. Ruud et al claim that Green House gases emitted from the reservoirs are positively correlated with the area cooded. In particular, reservoirs which food either upland forest or peat lands in Canada are likely to produce more GHG.

Studies like these further reduce the number of suitable sites for reservoir and provide further evidence of them being nonrenewable resources. There are at least 50000 dams in the world that are more than15m tall, as reported by International Commission On Large Dams . However, the total number of dams in the world is much more. In particular, given that only 7% of dams in the United States are more than 15m tall,using the same proportion, the total number of dams in the world could be more than 1 million.Lots of these dams are reaching their age. Furthermore, public’s perception of large dams as a clean source of energy is also undergoing transformation, and their decomissioning is more frequently discussed topics now than ever. At the same time, one needs a rigorous framework to calculate the economic value of dam at the time it is decomissioned so such decomissioning could be justified by judging it from some economically rational framework. Such value of the reservoir at the time of its decomissioning is the salvage value of the dam. From an operators point of view,the salvage value of dam is stochastic for several reasons: the impact of sedimentation on ecology and human health are not clearly understood.Tolouie reported that desiccated deposits of one sediments could be eroded and transported by wind,dutch buckets causing health hazard to nearby population. Furthermore, Chen et al reported that the presence of sediment against dam could constitute earthquake hazard. The impact of sediment accumulation on ecology alteration and the impact of delta deposition on the probability of flooding are also actively researched field. In legal front, Thimmes et al reviewed recent court decisions on cases against dam operators and found that courts have issued reward against dam operators for the ecological damage caused during the dam operations, and overall conclude that judicial determinations of reasonable reservoir management and reasonable precautionary measures by landowners are generally highly speculative, controversial, and based on limited information. Pansic et al report that currently three major costs associated with dam decomissioning include sediment management , environmental engineering and infrastructure removal . Furthermore, regulatory agencies may continue to impose new conditions on the operators as the new information on the impact of dams arrive, including their impact on Green House Gas stock in the atmosphere.The cost of decomissioning could very well be astronomical if stringent conditions are applied to the operators in the future, and this is consistent with the overall uncertain time dam operators are living in right now. It is clear that the periodical removal of sedimentation is an integral part of the operation of a sustainable dam.There are several techniques to remove sedimentation from reservoirs. We can roughly divide them into four types: erosion prevention, sediment routing, flushing and dredging. Erosion prevention can always be used with the latter. Erosion prevention schemes include watershed management issues such as encouraging people upstream to get involved in the practices that are not going to contribute to soil erosion . The other alternative is trapping sand before it reaches reservoirs; for example, by constructing check dams, though they are not very effective. These methods involve emptying reservoirs periodically or just before the flood. Flushing involves opening a low level outlet to temporarily establish riverine flow through which eroded sediment is flushed. Flushing is distinct from routing as the former deals with settled sediment and involves release of sediment at the season which is different from the season used by sediment routing which releases sediment when they arrive. The timing aspect of sediment release also makes flushing not very popular among environmentalists. Dredging involves mechanically digging up the coarse deposit and removing them from the reservoir.

A detailed description of these methods can be found in Morris and Fan and is also presented in the next chapter.The challenge in finding the optimal sedimentation technology is that any such prescription necessarily relies on the topography of the region and on such minute details as the size of sediment and hence an economic model has to make trade off between the accuracy of representation and simplicity of modelling so that one achieves desired tractability to come up with reasonable insights. Our goal in this paper is to formally represent the reservoir management problem, taking into account the stochastic nature of salvage value of the dam at the time of its decomissioning. The formalization also provides us the following three major insights: ranking of different sedimentation removal techniques from the perspective of their impact on the age of dam is facilitated. optimal sedimentation management is retrieved as a result of a control problem of the operator and the value of the dam at any point. At the end, we are also able to discuss sustainability issue of the reservoir. We contribute to the literature in the following way: this paper is the first one to look at the sedimentation issue in a stochastic framework. We provide detailed study of techniques and discuss qualitative properties of key thresholds that trigger different decision makings . We also provide a new method that slightly modifies Judd’s projection method in solving the nonlinear equations that results from optimizing decision of the operator. We use data from Tarbela dam in Pakistan to calibrate our model. We conclude that for some given cost functions, the dam could be sustainably run. Economic studies of sediment removal techniques so far have been very rare. In 2003, the world bank’s resource economics group developed a policy maker’s manual-type report, called RESCON. Their work provided a brief survey of sedimentation technique and a “look-up table” type Excel based software to facilitate the economic and engineering evaluation of different sedimentation strategies. Another work by Palmieri et al used the RESCON software to show impact of different sediment strategies on sediment removal policy and life of the dam. Huffaker et al provided a detailed economic study of hydrosuction dredging sediment removal system. In particular, Huffaker et al constructed a multi-state model of endogenous reservoir operations and apply singular perturbation solution methods that reduced dimensionality of the optimality system and facilitated the solution of the optimal system. They uncovered a phenomenon called “sediment perching” due to which increased sedimentation in the reservoir makes the sediment control mechanims more effective in the long term. Though they take into account the positive effect of sediment perching on dredging cost, they fail to note that sediment perching alters the natural pattern of sediment flow downstream and may cause undesirable environmental cost and their estimate of the benefit of sediment perching may therefore be upward biased.

The second of these layers includes existing residential neighborhoods, which typically consist of small parcels of land owned by residents who are highly resistant to redevelopment, unless in the context of adding second units to existing houses. Even the process of creating secondary units tends to be slow and to produce relatively few units, despite some municipal programs to encourage it. Commercial and industrial land uses and apartment buildings are likely to be located near major and minor arterials and freeway ramps. Low‐density residential development is more likely to occur at a distance from these roads due to noise and traffic concerns. Mid‐ to high‐density residential development is likely to be attracted to downtown locations, neighborhood centers, and shopping centers; especially in the low‐GHG emissions scenarios in which public policy focuses on redeveloping and building up existing urban centers. Mid‐ to high‐density residential development is also likely to be attracted to railroad stations in these scenarios as new passenger service is added and public policy emphasizes “transit‐oriented development.” Some industrial development is likely to locate near railroad lines in these scenarios, since rail offers more energy‐efficient transportation of many goods. We assumed that locations currently slated for development that are distant from existing cities County, such as the Dunnigan area along Interstate 5 in the north of the county, will serve as urbanization attractors only in the scenario with higher GHG emissions. Census blocks with recent development are distributed fairly evenly between rural and urban areas of the county. We assumed that these blocks with recent growth would attract more urbanization in the future. This is in part because these areas are likely to possess infrastructure such as roads, water lines, sewer mains, and power lines which make development easier and cheaper.

It is also because these areas are likely to contain previously subdivided parcels of land that are not yet built upon,nft hydroponic and land owners that are more interested in subdividing, selling, or building on the land. In scenario with higher GHG emissions, in which planning controls are weaker, census blocks with growth will be a stronger attractor, particularly in exurban locations. In the lower GHG emissions scenarios they will play a weaker role in attracting urbanization, since public policy is more likely to protect non‐urban land, and less left‐over land is likely within urban areas. Previously, our larger research team developed a set of story lines for scenarios reflecting different climate change and urbanization policies for Yolo County in 2050 . These were intended to emulate for the county story lines developed in 2000 by the IPCC , with the addition of a scenario with very low GHG emissions corresponding to an even more stringent policy direction than established by California’s AB 32 legislation. Each scenario corresponds to a broad‐brush story line, which is built upon a set of political, economic, institutional, and demographic assumptions. Each story line is a possible future for urban growth and emissions for the county.As in IPCC scenario A2 , our A2 scenario assumes that population growth would remain high, with an approximate doubling of the current county population to 394,000 . With an increase in population, continued economic growth and technological innovation, the county would see urbanized areas increase by 50 percent. Current preservation and land use policies would remain in place and although new suburban subdivisions would be built, there would be some focus on improving land use through greater land use mix, higher densities, and more infill, and limiting sprawl. Agricultural land would be lost to urbanization while less participation in farmland preservation programs, such as the Williamson Act, would result in less farm acreage and fewer farmers. Even with an increase in population, vehicle miles traveled would remain stable through land use and pricing changes, increased use of alternative modes, and greater fuel efficiencies. Still, the A2 story line would be fossil fuel intensive as a result of more drivers and the dominance of automobiles as the main transportation mode.

In terms of climate, under A2, average temperatures are predicted to increase between 1°C and 3°C for 2050. Changes in cropping systems and technological support for agriculture would continue in about the same way as present, without major societal investment in alternative options to deal with the impacts of global warming. The A2 story line is a near continuation of current demographic, economic, technological, and environmental developments with some improvements and responses to current issues being addressed and implemented. We should emphasize that in terms of suburban sprawl, the A2 story line is by no means a worst‐case scenario. Rather, it should be seen as a continuation of practices in the 1990 to 2010 period. If this story line had been based on prevailing development patterns from 1950 to 1990, suburban densities would be in the range of 4–6 units per acre instead of 8, less development would occur in medium‐ and high‐density forms, and a higher percentage of larger 1–10 acre ranchettes would be created. Suburban sprawl would cover a much larger percentage of the county in that case, taking far more agricultural land out of production. In IPCC scenario B1 , societies become more conscious of environmental problems and climate change, and sustainable development efforts are implemented. Under our Yolo County B1 story line, population would grow slowly, reaching a mid‐range population size of 335,000 by 2050 . Economic development would be moderate, with a shift from the production of goods to a more service‐based economy that is connected to the larger global economy. Technological innovation remains high in the Sacramento region, with an emphasis on small‐scale, green technologies. B1 is a relatively low GHG emissions scenario in which the urban area extends only 20 percent as a result of compact growth through higher densities, increased infill, and a focus on small, locally owned retail stores rather than big box developments that require more driving. As current transportation and emission policies become more stringent and the use of high‐efficiency vehicles and alternative modes increases, vehicle miles traveled would be significantly reduced and transportation emissions with them. 

Agricultural land conversion would be lower in this story line as a result of less urban expansion and the use of farming easements and other incentives to maintain land in farming. Though long‐term temperatures may be lower than in the A2 story line, average temperatures in 2050 do not differ . Consistent with AB 32, voluntary actions in agriculture would place more emphasis on increasing carbon sequestration and decreasing N2O emissions through multiple crops per year, more ecologically intensive practices, reduction of fertilizer use, and efforts to capture methane emissions from livestock. Moreover, there would be greater societal investment in preparing ahead for climate change adaptation options, such as crop breeding, pest management, and resilience to intermittent droughts. Under B1, Yolo County experiences the benefits of slower population growth and improved urban land use practices, resulting in preservation of agricultural land and reduced GHG emissions.To the two IPCC‐based story lines, we add a third scenario with more stringent GHG emissions regulation than AB 32. Under our AB32+ story line, Yolo County experiences slower population growth reaching only 235,000 in 2050, which would have to occur through policies or voluntary actions that affect family planning and migration . In this story line, moderate economic growth focuses on value‐added production economic viability of the local rural sector, and support for ecosystem services generated by closer alignment between the rural and urban sectors . A less resource‐intensive lifestyle would dominate, coupled with an increase in the quality of life through an increase in ecosystem services in both sectors. Priorities would be placed on both regulating services and cultural services . The urban boundary remains at the current extent through strict land use planning policies and development emphasizing efficient use of land, mixed use, intense infill, increased densities,hydroponic gutter and growth in the urban core. More compact development patterns and the promotion of local development and payment for ecosystem services, coupled with many alternative modes of transportation and increased use of zero emission vehicles, would result in a reduction of vehicle miles traveled and GHG emissions from transportation. Although long‐term temperatures may be lowest under this scenario, 2050 temperatures are essentially the same as in the other story lines. In order to both mitigate and adapt to the changing climate, agricultural producers would make major changes in management practices, focusing on ecological intensification rather than on non‐renewable inputs. This would require substantial societal investment in development of new renewable technologies and for diversification of cropping systems to fit site‐specific situations. Practices such as farm scaping and revegetation of riparian buffer zones to mitigate and reduce GHG emissions would also be promoted for their co‐benefits, such as improved water quality .

Markets for products may become more locally based, and efforts would be made to reduce GHG emissions from processing and transport of agricultural products. Overall emissions would be the lowest under AB32+ with a reduction from urban areas due to denser, more balanced land development, less resource‐intensive lifestyles, and improved transportation options. Changes in crop choice and management practices would likewise reduce GHG emissions from agriculture. In addition to modeling these three scenarios using UPlan, we modeled additional versions of A2 and AB32+ in which population was held constant at the B1 level. This step allows us a more analogous comparison of the three story lines.After using UPlan to produce urban growth footprints for the above scenarios, we calculated two main categories of GHG emissions for the new urbanization produced by each. These calculations are very approximate, but help to give a sense of the magnitude of variations that can result from different policy approaches. One category of GHG emissions was from transportation. Household travel surveys done by SACOG show that household vehicle miles travelled vary by a factor of six between households in low‐density per acre and high‐density locations . Some of this difference may be due to household size and composition, but much is likely due to proximity to jobs, shopping, schools, and alternative transportation modes. In addition, many other policy steps in the lower GHG emissions scenarios are likely to reduce driving in the 2050 time frame. These other factors include rising gas or carbon taxes; improved balance of jobs, housing, and shopping within communities; improved bicycle, pedestrian, and public transit options; and other economic incentives such as higher parking charges and tolls. Transportation emissions are also of course dependent on the fuel efficiency of motor vehicles. Average fuel efficiency of American vehicles remained more‐or‐less unchanged from the mid‐ 1980s through 2010, and so for purposes of illustration, this was assumed in the A2 scenario until 2050. In the B1 scenario, we assumed modest efficiency increases of 2 percent a year , and for the AB32+ scenario we assumed improvements of 4 percent a year . Rather than continually improve conventional gasoline engines, these scenarios would most likely see increasing percentages of the motor vehicle fleet converting to hybrid or all‐electric propulsion, with an increasing proportion of the electricity produced by renewable sources.Household energy use was a second category of calculated GHG emissions. In Yolo County domestic energy comes almost entirely from electricity or natural gas, as oil heating is rare in California and use of wood stoves is also low and increasingly discouraged due to local air pollution concerns. Here again we can expect substantial differences in GHG emissions between infill urbanization and new residential development on agricultural land, due to larger unit sizes and a much higher percentage of stand‐alone single family homes in the former case. To calculate household energy use for the three scenarios, we used data from the 2009 California Residential Appliance Saturation Study , a collaboration of the state’s five largest utility companies that surveyed detailed consumption habits of nearly 26,000 households. This study breaks households down by climate zone, and compares energy consumption for single‐family homes, town homes, small multifamily buildings, large multifamily buildings, and mobile homes by California Energy Commission climate zone. Both electricity and gas use for the middle three categories were approximately half that of single family homes, probably in large part because average unit sizes were smaller, and perhaps also because shared‐wall construction tends to be more energy efficient than stand‐alone single‐ family homes.

The Clear Lake release schedule specifies how much water is available annually and monthly to the District during the peak agricultural season from April to September. The decree’s “Quantity” criteria sets allowable seasonal withdrawal limits based on April 1 water levels recorded at Rumsey, known as the Rumsey gauge. If the Rumsey gauge is at or above 7.54 feet, then 150,000 acre feet of water is available for the growing season from April 1 to October 31. Monthly percentages of the ASW are available for release each month. If Rumsey levels are below 3.22 feet, no water can be released that year apart from flood flows. For in‐between levels, ASW are set in the release schedule that increases to a maximum of 150,000 acre feet in what is known as the quantity criteria. As per these stipulations, the District did not make any releases in the severe drought of 1976–1977, as well as in 1990 at the end of several dry years. The Solano Decree also stipulates “Stage criteria” that set limits to draw down, posing an additional constraint to the District’s withdrawal of water in any given month. Clear Lake releases in the winter are also controlled by the 1920 Gopcevic Decree for flood control operation. The highly controlled nature of this lake can be attested by the historical monthly average lake levels which have varied only 5.7 ft on average within a water year, with a maximum range of 10.9 ft and a minimum of only 2.3 ft.The Cache Creek model, run at a monthly time step, uses climate and land cover information to simulate the water balance. It uses the results to simulate the management of Clear Lake and Indian Valley Reservoirs and water supply for irrigation downstream. The model simulates irrigation demand for 20 crop types within Yolo County, grow bags garden which is met through surface and groundwater sources .

The model was calibrated to a historical run from 1971–2000, which formed the baseline scenario. The calibrated model was then run under various combinations of climate and agricultural land use projections as described below. Figure 3.1 shows the study area along with the spatial discretization of the model. The spatial domain of the model covers 5027 square kilometers and includes the Cache Creek watershed up to Capay , and all of Yolo County. The focus of the irrigation water demand and supply analysis is on the District service area , although the model can also simulate irrigation demand for the rest of the county. Table 3.1summarizes each catchment’s characteristics. A water balance simulated for each catchment. Spatial data on elevation, watersheds, and land use were acquired and used to define and characterize each catchment. Elevation data were extracted from the Digital Elevation Model provided by the U.S. Geological Survey. Land cover information was assembled from two sources. For the non‐agricultural landscape, the National Landcover Data Set was used . For the agricultural areas, county reports and DWR Land Use Surveys were used . Upstream catchments were aggregated from the DWR watersheds layer. This aggregation was based on climate considerations, the locations of major infrastructure , in‐stream flow requirements, and flow gauges. Parameters of the rainfall‐runoff module were calibrated against the longest available continuous data from gauges in unimpaired watersheds. These were at Kelsey Creek and Hough Springs on the north fork of Cache Creek , in the headwaters of Clear Lake and Indian Valley, respectively. Goodness of fit metrics were computed for each set of simulated and observed hydrographs. Two groundwater objects were defined and conceptually aligned to the groundwater sub‐ basins delineated by DWR: one below Capay Valley receiving recharge as infiltration from the Capay Valley catchment, the other below the Yolo Valley floor, receiving recharge from the catchments downstream of Capay.

Our model’s treatment of groundwater is similar to the Central Valley application . It is capable of relative comparison among scenarios of groundwater recharge and extraction volumes, but not of simulating absolute groundwater depths. The model simulates the operations of Clear Lake, Indian Valley, and the water delivery through canals. Detailed description of how WEAP simulates reservoir releases through conservation storage and flood rules is available in Yates et al. . Reservoir physical characteristics were obtained from California Department of Water Resouces California Data Exchange Center and the District. Indian Valley operating rules were obtained from the District. Clear Lake operating rules were obtained from the District, and from documentation of the Solano and Gopcevic Decrees described earlier . Details, including the stepwise procedure on implementing the Solano Decree, are available in public documents and through the District. Clear Lake releases during the wet season are controlled by the Gopcevic Decree, for which target storage levels come into play from January to March. These target storages were set as WEAP’s “Top of Conservation” in the model’s Clear Lake reservoir object. The second operating constraint, also from the Solano Decree, is its stage limitation criteria. These criteria were programmed and set as “Top of Buffer” in the reservoir object. The third constraintis the hydraulic capacity of Clear Lake’s outlet channel. Hydraulic capacity varies by the stage; data obtained from the District was used to develop a hydraulic capacity constraint as a function of stage. This expression was set as a hydraulic constraint on the releases from Clear Lake in the model. Outlet flows were then constrained to be a minimum of the hydraulic capacity constraint, and the allowable monthly withdrawal as determined by the Solano decree’s Quantitative criteria—the latter also entirely encoded within WEAP. Clear Lake does not provide carryover storage for irrigation demand. Although Indian Valley does provide carryover storage, typically it is operated with no carryover storage . In general, the District attempts to utilize all its Clear Lake allocation each year. This means that Clear Lake usage is prioritized over Indian Valley as much as possible. In the model’s setting of supply priorities, this translates to a lower filling priority for Clear Lake over Indian Valley. Simulation of reservoir operations was verified by comparing simulated versus observed reservoir levels.

The District’s main conveyance is in the form of 175 miles of mostly unlined canals and arterial ditches that run off the West Adams and Winters Canals from Capay Diversion Dam on Cache Creek. In the model, these conveyances are aggregated into a single transmission link object, with capacity set to the total distribution’s capacity of 750 cubic feet per second , and with an estimated leakage of 40 percent of conveyance flows obtained from calibration attempts and informed by District estimates of mass balances . Seventeen crop categories were modeled for the catchments dominated by agriculture. Table 3.3 lists the different crop categories considered along with county‐wide acreages from four selected years. The crop categories are informed by DWR’s irrigated crop acres and water use portfolio,grow bag for tomato taking into consideration both the crop categories and corresponding acreages available through the county reports as well as estimates of the District scale cropping pattern. An annual time series of total irrigated acreage and irrigated crop areas was assembled at the county level . Individual crop acreages were spatially distributed among the four agricultural catchments using GIS datasets available for 1989 and 1997 through the DWR Land Use Surveys . This allowed a cropping pattern to be represented in the model for the historical period for each agricultural catchment. Each crop’s irrigation water needs were simulated using crop‐specific crop coefficients, irrigation schedules, and irrigation thresholds. Crop‐specific parameters pertaining to irrigation were adapted from the Central Valley application by Joyce et al. , who calibrated the crop and irrigation parameters at the spatial scale of the DWR Planning Area level against four annual estimates of applied water published by DWR for 1998,1999, 2000, and 2001 . In our model, we also used DWR portfolio data available for the same years, but at a finer spatial level—the Detailed Analysis Unit . The irrigation threshold parameter in WEAP was calibrated for each crop to match DWR’s applied water estimates for 1998, 1999, 2000, and 2001 for the DWR’s Lower Cache Creek DAU which closely follows the county boundaries. Figure 3.2 presents the calibrated irrigation schedules and thresholds for each crop. The model’s estimation of water demand represents a departure from the operations of the District. The District solicits water demands from its customers every year in March, and then decides by April how much total quantity will be available. This decision is based on water levels in the two reservoirs and a projection of the season ahead. Since our goal was to look to the future, we used a simulation approach instead of hard‐coding the historical demand based on the District’s historical roster. The latter would not have provided us the means of projecting demand into the future.Yolo County based on the relationship between historical crop acreage, a set of economic variables , and climate variables . To forecast cropping area from the present to 2050, climatic variables were calculated from daily climate projections for the A2 and B1 scenarios generated by the GFDL climate model described above. The second land use projection was based on a hypothetical scenario envisioning an agricultural landscape which adapts to climate change in two ways: by allocating a smaller fraction of land to crops that require large amounts water; and by increasing crop diversity. For example, the acreage of rice, alfalfa, and other water intensive field crops were gradually reduced to the lows observed during a period of severe drought in the mid‐1970s . Likewise, an increase in crop diversity over time was simulated by progressively allocating a larger fraction of land to vineyards, winter grains, almonds, deciduous orchards, subtropical orchards, tomatoes, cucurbits, and truck crops . Since this crop diversification projection is a hypothetical construct, rather than a statistically derived forecast, a future time frame of 2009–2099 was used.

It should also be noted that this approach assumes gradual changes in crop acreage and did not attempt to capture the year to year variability reflected in the historic record. Statewide there has been a notable shift in irrigation methods from surface water applied using flood or furrow irrigation towards low‐volume sprinkler and drip irrigation, particularly for vegetable crops, orchards, and vineyards . These methods can potentially reduce soil evaporation and applied water . Furthermore, a recent survey of grower perspectives on water scarcity and climate change in Yolo County indicates a strong inclination to expand their use of drip and low‐volume irrigation among local farmers . Likewise, incentive programs to promote adoption of improved irrigation technology are seen as a politically feasible water demand management strategy. However, one criticism is that, in some watersheds, such policies have failed to curtail groundwater extraction as some farmers use the “water savings” to expand irrigated acreage or grow more water‐ intensive crops . As such, we included a conceptual scenario which assumes that irrigation technology and efficiency will continue to improve in coming decades but overall irrigated acreage in the district will not. We reflect these trends in the model, by decreasing the irrigation threshold parameter, in a manner similar to the work of Joyce et al. and Purkey et al. . Beginning in 2010, irrigation thresholds for each crop, except for wine grapes, winter grains, and safflower, were assumed to decrease linearly so that by 2099 they reached 70 percent of the historic reference threshold. For the latter crops, no change in water‐saving irrigation technologies was assumed because vineyards are already on drip irrigation, winter grains are mostly supplied by rain and stored soil water, and safflower is already a low water consuming crop.Another measure of water shortage is the frequency of years receiving no water allocation from Clear Lake. For example, if the Rumsey gauge is below 3.22 feet, the initial ASW assessment is for no allocation of water that year. During the historical period the model predicted 6 such years . Model projections for the climate only scenario suggest that the number of years receiving no allocation will increase gradually with time, particularly during the latter half of the century. In the far term under A2, reservoir inflows are very low in some years in response to the warmer and drier conditions.

The sand fraction was separated from the clay and silt fractions by wet sieving through a 0.05 mm sieve. Water retention at various tensions was determined using a pressure plate. Plant-available water holding capacity was estimated as the volume fraction of water retained between 33 and 1500 kPa. A sample of < 2-mm , air-dry soil was placed on a porous ceramic plate and wetted by capillary action; gravimetric water content was measured following attainment of equilibrium at 33 and 1500 kPa. Soil pH was measured 1:2 in H2O and 1.0 M KCl. Phosphate retention was determined using the method of Blakemore et al. and the Bray-1 extraction was used as an estimate of available P . Exchangeable cations were displaced by 1 M NH4OAc at pH 7.0, then the cations were measured in the supernatant using an atomic absorption spectrometer . The cation exchange capacity was determined in 1 M NH4OAc after extraction of NH4 + by 10% NaCl as a measure of CEC. Base saturation was calculated as the sum of base cations by 1 M NH4OAc divided by CEC. Sulfate-sulfur was extracted using monocalcium phosphate as outlined by Schulte and Eik and available micro-nutrients were determined by DTPA extraction . All weight percent data were reported on an oven-dry basis . Non-sequential selective dissolution in Na-pyrophosphate and ammonium-oxalate was used to characterize Fe, Al and Si in various pedogenic pools. Total C and N concentrations were determined on ground samples by dry combustion using a Costech C/N analyzer . Soil microbial biomass C and N were measured using chloroform fumigation and direct extraction with 0.5 M K2SO4 . Briefly, 10 g oven-dry equivalent samples were fumigated for 48 h in the dark,plastic pot and then C and N were extracted with 0.5 M K2SO4. Similar extraction was applied for non-fumigated samples. The non-fumigated control values were subtracted from fumigated values as an estimate of microbial C and N. A Kec/Ken factor of 0.35 was applied for both C and N . Carbon mineralization was measured in the topsoil and subsoil by incubating duplicate soil samples in the dark under laboratory conditions over a 119-day period.

Soil moisture was adjusted to ∼ 80% of field capacity and pre-incubated for one week prior to starting the long-term incubation. Soils were incubated in sealed Mason jars fitted with septa. Carbon dioxide in the headspace of each soil sample and blanks with no soil was measured each week using an Infrared Gas Analyzer. The CO2 emission was normalized to initial total C content of each soil and expressed as CO2-C mg kg−1 soil C. In addition, net N mineralization was measured on these same samples at the end of the 119-day incubation by determining concentrations of mineral N in 1 M KCl extracts at time zero and at 119 days. Quantification of NO3 – used the vanadium chloride method and NH4 + the Berthelot reaction with a salicylate analog of indophenol blue . A correlation analysis was performed to assess soil properties most strongly affected by land-use changes, using IBM SPSS Statistics 22. 2013.All soils were well drained with an A horizon overlying Bw horizons that extended to the depth of investigation . Soil particle-size distribution was similar among the four sites with the majority of the horizons having a loam texture . Some distinct changes in particle-size distribution within various pedons are attributable to more recent tephra deposition that resulted in burial of the former soil profile. Bulk density in subsoil horizons was very low , characteristic of soils formed in volcanic ash . Db was also low in the A horizon of the pine forest , but was higher under agricultural management due to traffic compaction resulting in a reduced pore volume. The agricultural soils displayed a distinct increase in Db and a reduction in total porosity in the topsoil horizons compared to the pine forest soil. Given the low bulk densities, total porosity was correspondingly high, ranging between 60 and 77%, with values decreasing in surface horizons with agricultural management. Plant-available soil water was generally in a narrow range with the exception of the surface horizons of the pine forest soil . The water retention capacity varied from 37 to 53% in topsoil horizons and from 45 to 51% in subsoil horizons with the lowest values in the pine forest.

Soil pH-H2O increased from very strongly acid in the pine forest and tea plantation to moderately acid in the horticultural crops with fallow and intensive cultivation . Regardless of land use, all soils in this study had low CEC characteristic of acidic Andisols dominated by allophanic materials . The lowest values occurred in the pine forest and the highest values in the horticultural soils. The pHKCl-pHH2O values ranging between −0.1 and −0.5 were indicative of a soil colloidal fraction dominated by variable charge materials . Especially notable is the very low base saturation and concentrations of exchangeable Ca and Mg for the PF and TP soils . Exchangeable base cations are a common limiting factor for horticultural production in the studied Andisols since these nutrient cations are extremely low under pine forest. While the horticultural management practice of applying horse manure and lime did not appreciably increase the measured CEC, it was remarkably effective in increasing exchangeable base cations . For example, exchangeable Ca, Mg and K increased from 1.5, 0.3 and 0.2 cmolc kg−1 in the pine forest to 26.3, 3.5 and 1.0 cmolc kg−1 in the intensive horticultural crops, respectively . The high base saturation of over 100% under horticultural land uses compared to < 23% for the pine forest and tea plantation .Organic C concentration in A horizons was highest in PF and 1.0 to 2.0% lower under agricultural management . In contrast, organic C was lower in the PF subsoil while the agricultural sites had elevated organic C concentrations in several subsoil horizons. Organic C stocks in the upper 100 cm of the soil profile were calculated by summing the organic carbon stocks in each individual horizon were present). Organic carbon stocks followed : TP ≈ IH > FH > PF . The agricultural soils contained more organic carbon than the pine forest soil. While horse manure was added to the IH soil for the past 7 years, the TP and FH soils received no organic matter amendments and still had similar pedon organic matter stocks.

As a direct comparison, the IH soil receiving horse manure contained only slightly more organic C than the FH soil located 4 m away that received no horse manure and was fallowed over the past 7 years. Dissolved organic carbon concentrations were appreciably higher in the PF topsoil and throughout subsoil horizons of the TP profile . The horticultural soils tended to have lower overall DOC concentrations than PF and TP land uses. Total N concentrations followed a similar distribution to organic C concentrations among sites with total N stocks in the upper one meter of soil following : IH > FH ≈ TP > PF . The C:N ratio was lowest in the upper 50 cm of the IH and FH soil profiles , while values for PF, TP and lower soil horizons at all sites were generally in the range 16 to 19. The highest concentrations of inorganic N were found in the IH pedon and were dominated by NO3 – . In contrast to the IH soil dominated by NO3 – , inorganic N concentrations were dominated by NH4 + in the TP, FH and PF soils with the highest value in the TP soil and lowest under FH land use. High P fixation , characteristic of Andisols, was exhibited for all land-use types. Under forest vegetation , the soil P retention was consistent at 97% throughout the entire pedon . Change of land use to TP and FH did not appreciably affect P fixation. However,grow bag the IH land use receiving application of horse manure for the past 7 years showed appreciably lower P fixation in the upper 40 cm. Reflecting the high P fixation, available P content was below the detection limit for all horizons of all land-use types, except for the upper horizons of the IH land use .There were several significant correlations among soil properties . Oxalate-extractable Sio showed a positive correlation with the clay fraction, while Feo had a strong negative correlation with pH and exchangeable Ca and Mg. In contrast, Alo showed no significant correlations with other soil properties. For organo-metal complexes , Alp had highly negative and positive correlations with the clay fraction and organic C, respectively. However, Fep showed no significant correlations with other soil properties. Soil pH showed a highly negative correlation with P retention and Feo, along with a positive correlation with exchangeable cations , total N and Db. Soil bulk density showed a positive correlation with exchangeable cations and negative correlation with P retention. P retention had a negative correlation with exchangeable cations .Andisols are characterized by low Db and high porosity due to the abundance of amorphous and poorly crystalline materials and organic matter that contribute to highly stable and very well structured soils under natural conditions. However, the low natural Db may change due to anthropogenic activities.

The evidence was revealed by soil tillage under intensive horticultural crops contributing to increased Db from compaction by potential destruction of soil aggregates due to physical mixing/abrasion by tillage operations. Tillage was reported to destroy macropore pathways of Andisols in Mexico resulting in a lower in- filtration and permeability of topsoil horizons .Chemically, the exchangeable cations have positive significant correlation with Db, indicating the increase in soil exchangeable cations gave rise to the increased soil bulk density . This is probably due to the role of Ca and Mg ions derived from lime and manure in binding soil particles, resulting in the change of soil friable structure under forest to more compact aggregate formation under intensive horticultural cultivation. The water retention capacity varied from 37 to 53% in topsoil horizons and from 45 to 51% in subsoil horizons with the lowest values in the pine forest . These data indicate that the number of soil pores storing plant-available water is lower in the forest Andisols than those converted for agriculture. In other words, the water retention capacity has increased about 50% following conversion from pine forest to agriculture. This implies that the compaction associated with tillage is responsible for increasing the water retention capacity through conversion of macropores to meso/micropores. The water retention capacity in this study was higher than for cultivated Mexican Andisols reported by Prado et al. . The high water retention in Andisols is caused primarily by their large volume of meso/micropores . Formation of these meso/micropores is greatly enhanced by poorly crystalline materials and soil organic matter . Buytaert et al. studied toposequece of Andisols in south Ecuador and reported the large water storage capacity as revealed by water content ranges from 2.64 g g−1 at saturation, down to 1.24 g g−1 at wilting point. The long-term cultivation of agricultural soils in this study has not caused appreciable degradation to the overall Db, porosity or water retention characteristics of these Andisols. While macroporosity was decreased by tillage, the macropore content of topsoil horizons remained > 15% providing adequate infiltration and soil aeration. The loss of macropores is compensated for by the increase in meso/micropores that contribute to increased plant-available water holding capacity. In spite of the increase of bulk density and loss of macropore capacity, field observations confirmed that the agricultural soils in this study retained their high infiltration capacity with no evidence of surface runoff. In Italy, well developed Andisols on flow-like landslides over 70 years experienced low run off and minimal soil erosion owing to a good infiltration in spite of the high slope steepness and the anthropic pressure associated with land management .The pine forest soil was very strongly acidic owing to the strong leaching regime associated with the isothermic/perudic climatic regime. Applications of lime and more recently horse manure to the IH soil were effective in raising the pH of the horticultural soils . In spite of the low soil pH values in the tea plantation, the potential for Al3+ toxicity was not evident as ascribed to the low exchangeable Al3+ concentrations . Threshold values for Al toxicity are generally considered about 2 cmolc kg−1 for common agricultural crops and 1 cmolc kg−1 for Al-sensitive crops .

In order to enhance agricultural advisory service delivery, there is need to harmonize the efforts of extension providers to more effectively address the intensification of maize and adapt to climate change. The Diffusion of Innovations Theory was developed by Everett M. Rogers to analyze the diffusion and adoption of agricultural innovations among farmers. Considered the theoretical basis for agricultural extension, this theory asserts that the adoption of an agricultural technology communicated through specific channels occurs over time among members of a social network . Under this theory, individuals within the network are categorized according to their ability to adopt the technology. This theory follows the top-down “transfer of technology” model where innovations are developed by researchers, disseminated by extension personnel, and then adopted by farmers. In the context of Malawi, agricultural innovations are developed both by researchers within the hierarchical structure of the public extension system and are co-developed at the grassroots level with input and field testing from farmers . Therefore, it is useful to understand the basic elements of the Diffusion of Innovations Theory to evaluate Malawi’s public extension system, but also analyze the extension system as a network of actors that all develop, share, and improve agricultural innovations and information. To effectively analyze Malawi’s complex,cut flower bucket pluralistic extension system it is useful to develop a conceptual framework that draws from the Diffusion of Innovations Theory as well as Social Network Analysis.

Feed the Future’s Developing Local Extension Capacity project led by Digital Green in partnership with Care International, the International Food Policy Research Institute and the Global Forum for Rural Advisory Services developed a “best fit” framework for analyzing Malawi’s extension and advisory services that target key activities for improving the system . This framework outlines extension parameters and characteristics allowing stakeholders to understand the state of Malawi’s extension system and where critical levers for change exist .Within this framework, the frame conditions outside the manageable interests are meant to show factors that influence extension services in Malawi, but are not the focal area for change within the efforts of this study. The critical factors for change within the manageable interests of this study are the characteristics of AIS including 1) the governance structures which I will analyze using Social Network Analysis to understand the development of content, transfer of information, and engagement between stakeholders; 2) the organizational and management capacities which I will analyze as the capacity for organizations to provide EAS and ways in which organizations are structured; 3) the advisory methods used by providers to deliver EAS; 4) the connection to local and international markets; 5) the livelihood strategies integrated into the provision of EAS; 6) the engagement of community members, villages, and farmers in the process of EAS information development and dissemination; and 7) the performance of EAS with respect to climate change adaptation based on the messages communicated to farmers and the effectiveness of information delivery. GoM has developed a pluralistic extension policy that calls for the delivery of specialized services to farmers by governmental institutions, nongovernmental organizations, and private industry. These extension services support farmers to overcome barriers to increasing crop yields and adapting to changing climatic conditions.

Yet, inconsistent recommendations provided by different extension providers regarding best practices to adapt to climate change have remained significant challenges in Malawi. GoM has emphasized the need to improve coordination among extension providers in order to reduce inefficiency, redundancy, and confusion due to conflicting messages to farmers. In fact, few nongovernmental organizations or private companies coordinate their extension activities with DAES under MoAIWD. In order to improve stakeholder engagement amongst extension providers, communicate clear messages to farmers, and improve the adoption climate adaptation practices, there is a critical need to identify what climate change information is currently being communicated to farmers across the extension system.To meet the objectives of the study, I contacted key informants using the snowball sampling method to identify affiliate organizations and individuals who provide extension services to maize farmers in Malawi. The location for this study was chosen based on the projected severity of climate change impacts to Malawi’s maize production across all regions and high concentration of extension providers that operate throughout the country. I developed a professional network in Malawi that connected me to key organizations and individuals who work on extension. This network included staff from IFPRI where I interned, GFRAAS, MaFAAS, USAID, and faculty specializing in extension from LUANAR in Malawi. My researcher team at the University of California, Davis included my advisor and the CoPrincipal Investigator, Dr. Amanda Crump who has worked on agricultural extension issues in Malawi and an experienced thesis committee who provided additional contacts for this research. In total, 130 individuals were contacted through email and phone calls and 19 agreed to participate in virtual interviews through online platforms for this research study. Interviews were conducted in English over the phone from October 1, 2020 to January 1, 2021 with individuals from organizations who provide extension services to farmers. It should be noted that English if the official language of Malawi and is widely spoken among extension providers.

The table below shows how many individuals from each type of organization participated in the research study through in-depth interviews.Through this research, I sought to assess the challenges and successes in communicating climate change adaption information to maize farmers in Malawi in order to improve the development of content and delivery of information by extension providers. Therefore, I focused on understanding the development and dissemination of information throughout the extension system, messaging around climate risk and variability, curriculum and learning tools extension providers use to educate farmers, and engagement with other organizations that support farmers across the extension system in Malawi. I employed qualitative methods to develop a deeper understanding of the participants’ experiences, perspectives, and relationships which are essential to better understand Malawi’s extension system and the stakeholders involved . The research began with a literature review to understand climate change impacts to agriculture in Malawi, climate change adaptation practices for farmers, and the agricultural extension system in Malawi. This was followed by key informant interviews with a sample of identified organizations using an interview questionnaire. A detailed Interview Questionnaire was developed to administer in-depth interviews with all participants. The Interview Questionnaire introduced participants to the intention, goal, and dissemination of the research. This document also informed all participants that their participation was voluntary and asked if they consented to participating in the research. Participants who opted not to participate were thanked and no further communication was made. All participants were asked if they consented to being recorded on the my phone and all who participated consented to being recorded. In addition, a script was developed to introduce participants to questions and a question route was developed to ensure consistency across all interviews. A semi-structured questionnaire was used because I recognized that a detailed explanation of certain topics might be required, and certain responses could not be anticipated prior to the interview. The questions asked during interviews focused on climate smart agricultural practices shared with farmers, extension approaches, and key constraints in delivering effective climate change information to maize farmers. Specifically,flower display buckets the interviews gathered information about the following themes: organizational activities and partnership, information development and dissemination, educational tools, extension methods, climate smart agricultural practices, and communication successes and challenges . In order to evaluate the validity of the content obtained during interviews, I tested the instruments developed for this study prior to use with several members of my research team at UC Davis and at MaFAAS by phone. This allowed me to understand if the questions were clear and could be answered in the time allotted for the interview. After testing, I made several format and phrasing changes to the Interview Questionnaire to improve the quality of the guide and ensure that participants could understand the questions being asked.

Each interview lasted between 60-90 minutes depending on the participant’s responses and elaborations. In preparation for this study, I sought approval from the Institutional Review Board and Committee on the Use of Human Research Subjects at UC Davis and the Malawi Government through the National Commission for Science and Technology’s Framework for Guidelines for Research in the Social Sciences and Humanities. This process required the submission of a research proposal to be reviewed and approved by the National Commission for Science and Technology in Malawi. In order to comply with Malawi’s requirements, this research was first affiliated with a local research institution; LUANAR. This affiliation was initiated with an extension faculty member of LUANAR, Mr. Paul Fatch, on July 28, 2020. All appropriate forms and documents were provided to UC Davis and the Malawi Government. The UC Davis IRB deemed this study to meet the criteria of exemption on August 24, 2020. I obtained a permit from the Malawi Government on September 29th, 2020 was approved to proceed with all interviews.Qualitative data analysis used for these interviews involved analyzing the relationships between themes in my data in order to understand the phenomena and derive a theory about information generated during the interviews. The data for this research were collected through in-depth interviews with 19 participants who provide extension services to farmers in Malawi. All phone interviews were recorded using my mobile device or computer and were transcribed using Word. After all interviews had been transcribed, each interview was coded to identify common patterns and themes using NVivo. NVivo is a Qualitative Data Analysis computer software package that helps a researcher analyze qualitative data produced during interviews. Using NVivo significantly improves the quality of qualitative research analysis by reducing the number of manual tasks and allowing the researchers to easily discover themes in the data . The data analysis process began by developing a project database in NVivo. The unit of analysis for the study was the “organization.” Therefore, I analyzed patterns, themes, and relationships between organizations instead of the individuals representing those groups. A unique “case” was created for each organization to ensure that the organization’s associated information such as type of organization was linked to them and stored in the NVivo Classification Sheet in order to compare information between organizations. After building the NVivo project structure, coding took place in order to sort the data into meaningful segments. I used both inductive and deductive methods to develop theme codes that were generated both from the theoretical framework used and those that reflected emerging themes present in the data. The words and phrases directly mentioned by the participants were then combined to formulate a connection and relationship between related words or phrases in order to develop broader themes. The model explorer tool in NVivo was then used to visually map the ways in which different themes related to one another in order to derive greater meaning from the data. This analysis was then connected to existing concepts and the theoretical framework used and existing concepts discovered through the literature review. In addition to theme codes, relationship codes were also developed to record the relationships between stakeholders and the transfer of information between organizations. Relationship coding occurred any time an interview participant mentioned information sharing or a partnership between two organizations. Organizational relationships were categorized in three district ways. First, if an interview participant mentioned one organization receiving information from another the relationship was coded as “Organization X receives information from Organization Y.” Second, if an interview participant mentioned information sharing between two organizations, but did not specify which organization developed the information, the relationship was coded as “Organization X shares information with Organization Y.” Finally, if one organization was associated with another, such as the Department of Agricultural Extension Services is part of the Ministry of Agriculture, the relationship was coded as “Organization X is associated with Organization Y.” Relationship coding allowed me to visualize the stakeholder network and the dissemination of information through a Network Sociogram that was exported from NVivo into a data visualization software, Gephi. The Network Sociogram produced through Gephi allowed for the visualization of the complex network of relationships and organizations that are central to information sharing within Malawi’s extension network, and organizations that are not as closely connected to others.Social network analysis was used as the analytical method for understanding and evaluating Malawi’s extension network.

As most of the continental United States got settled toward the end of the 1800s, and land became more scarce and costly, yield-increasing innovations and practices became the major source of increased agricultural output. Cochrane suggests that the quest for higher yields led to the research and extension activities that resulted in the introduction and adoption of chemical fertilizers, pesticides, and improved varieties during the 20th century. The relative scarcity of labor has led to . the development of capital-intensive equipment and practices for the application of new inputs and the continuolls introduction of laborsaving tillage and harvesting technologies in the United States . . Technological change has been largely responsible for the continuous increase in agricultural supply, the increased capital intensity of agriculture, and the growing dependency on chemical inputs. As we approach the end of the 20th century, it seems that agricultural resources and environmental quality are getting more scarce. The increase in the value of these inputs suggests the development and adoption of innovations that will conserve water and reduce soil erosion and pesticide use. Scientific breakthroughs in genetics and biochemistry and a substantial reduction in the computing costs over the last 15 years suggest that many of the developments of the future will rely heavily on the use of biotechnology and computers. The direction of technological change in agriculture should also be affected by changes in macroeconomic conditions and tax laws. The increase in real interest in recent years and the tax reforms of the 1980s, in particular the move away from cash accounting and the treatment of capital gains as ordinary income, are likely to lead to the deemphasis of the development of capital-intensive technologies in agriculture. Nevertheless,cut flower transport bucket it seems likely that technological changes will continue to improve productivity and increase agricultural supply over time.

Agricultural products are basic commodities-essential products which command very high prices when scarce but very low prices as they become abundant. Table 1 presents farm-level demand and income elasticities for major food groups in the United States. It shows that the demand elasticities for major agricultural commodities are less than unitary and, in some cases , very close to zero. The cross-price elasticities of food items are positive, indicating that these commodities are substitutes. Income elasticities of nonmeat items are close to zero and may be even negative . The demand for meats is quite responsive to income, and the income elasticities of chicken and beef are slightly less than one. Wohlgenant’s estimates of income elasticities of the demand for beef and chicken seem to be higher than in other studies. The results of Haidacher et al. suggest that income elasticities of these products are closer to zero than one . Haidacher et al. also find that demand and income elasticity for food quality are quite high, and consumers are ready to pay substantially more for higher quality food. While overall demand elasticities for vegetables are quite low, these demand elastici ties vary throughout the year. Demand and income elasticities for fruits and vegetables are low during their season and become quite high during their off-season . Demand functions for agricultural products in many other developed nations have features similar to those in the United States . It seems that the growth potential of the markets for standard agricultural commodities in developed nations is quite limited, but product quality improvements may increase farmers’ revenues substantially. Mellor argues that developing countries have the potential to provide faster growing markets for agricultural commodities, since demands for these commodities grow in those nations faster than supplies. The rapidly growing nations of Asia provide especially good markets for feed grains and meat products because the food consumption patterns of these countries have not yet stabilized and the income elasticities of their meat demands are quite high. Agricultural systems are subject to much randomness and uncenainty. Much of the randomness results from natural phenomena.

The production of crops depends heavily on weather conditions, and yields vary as rainfall and climatic conditions change from year to year. Pest and disease problems are other contributors to the randomness in agricultural production_ Economic conditions are also contributors to the randomness faced by agriculture through their impacts on inputs’ prices, credit terms, and demand conditions. Prices of agricultural commodities are varying quite substantially over time in response to changes in demand and supply conditions around the globe. There has been much variability in real prices of agricultural inputs over the last 20 years. The prices of many agricultural inputs depend heavily on the price of oil, and the random variations in oil prices destabilized the prices of these inputs. Some inputs are imported, and their prices vary as exchange rates fluctuate. The real prices of credit for short- and long-term agricultural activities have varied in response to economic conditions and government policies. Actually. government activities have been major resources of randomness and uncertainty for the farm sector. Some of the government activities, besides monetary policy, which are likely contributors to randomness and uncertainty facing farmers include the agricultural commodity programs and marketing orders which terms have been varying frequently and sometimes drastically; immigration laws, the minimum wage, and workers’ health and safety regulations; pesticides and environmental quality regulations; and tax policies on both state and national levels. There is a growing body of evidence that farmers are risk averse and are ready to give up some of their average income in return for less variability of the economic conditions they face . The evidence suggests that smaller farmers are more likely to be more adverse to risk 1 than larger ones. Moreover, farmers are especially susceptible to downside risk, and their aim is to reduce it . Many agricultural inputs and activities and institutional regulations and activities aim at reducing randomness and u ncertai nty faced by farmers. Some government policy interventions are also designed to reduce randomness and instability facing producers and consumers. Redesign of such policies should recognize the impacts of public stabilization activities on private storage activities and provide coordination mechanisms for the control of different stocks .

Glenn Johnson coined the term “asset fixity,” and its interpretation has been the subject of much controversy. According to Tweeten , it was originally used to denote situations when gaps between purchase and resale prices of agricultural assets result in fixed asset-use levels under a wide range of prices and in inelastic supply responses. It was also used to denote what Williamson defined as asset specificity, namely, the tendency of many agricultural assets and forms of capital to be specialized and not easily convertible to uses outside the agricultural sector. This rigidity is not restricted to physical assets such as the tomato harvesters or milking barns, etc.; it also applies to different forms of human. capital. Hence, the transition of workers and assets in and out of the agricultural sector is not smooth. Changes in economic conditions-in particular, periods of down scaling and reduction of demand for agriculturally related skills-are likely to result in severe human adjustment problems. The specificity of many agricultural assets and skills cause their value to vary substantially with prices and conditions of agricultural commodities. In spite of the dramatic changes in technology and substantial increases in the sizes of farm operation, the agricultural sector has, on the whole, a competitive structure . Family farms are still probably the dominant form of operation, even though many of them have become businesses grossing several million dollars annually. Structure and behavior seem to be competitive in the production of major field crops, livestock, and dairy products. There is much vertical integration and centralization in the production of poultry and eggs, and there is a substantial amount of venical interaction in the production of some fruits and vegetables. In spite of these cases,procona flower transport containers the competitive model is very useful as a basis for analysis in the farm sector. Competitive behavior has been assllmed in empirical analyses of price determination along the food marketing chain . Rausser, Perloff, and Zusman question this assumption and suggest that contract theory and models of noncompetitive behavior are more appropriate for modeling the input markets to the assembly, processing, and distribution components of the food marketing chain. The nature of the products and the prevalence of long-term contracts in these markets led to rather fixed prices for processing and handling components of food items. This rigidity of response to change in economic conditions is in contrast to the flexibility of farm products which are produced by competitive markets. Agriculture, like many other sectors of the economy, frequently faces imperfect credit markets. In particular, bankers use other signals besides interest rates to allocate credit, so that not all the demand for funds at a given interest rate is met, and some of the better investment projects may not be financed. It has been argued that credit market imperfections are the results of lack of perfect information on behalf of the lenders. Banks may not flawlessly discriminate between loan requests, and they have developed several mechanisms to assist them in screening applications and insuring repayments although these devices have their faults.

Collateral financing has been used in many agricultural investments that might have caused discrimination against individuals with small landholdings with worthwhile worthy projects. Moreover, instability of prices and income has affected the ability of farmers to borrow and invest. Credit is likely to be more easily available in periods of agricultural prosperity than agricultural recession, thereby hampering the ability of the farm sector to withstand hostile environments. The growing reliance on debt-service financing in the agricultural sector in the middle 1980s may reduce some of the inequities and inefficiencies that are associated with collateral inactivity. But even with debt-service financing, credit markets are far from perfect. Credit availability constraints are likely to limit farmers’ ability to adapt to and survive stricter policy regulations. Agricultural production is the outcome of an interaction between human activities and natural resources and the physical environment. Such activities involve the deployment of resources that are exhaustible or have a slow renewal rate. Topsoil, groundwater, and water quality are obvious examples of such agricultural resources. Hueth and Regev argue that pest vulnerability to pesticides is / another exhaustible resource that has to be preserved. The argumentation as to the ,likelihood of the greenhouse effect suggests that some view even temperate weather as an exhaustible resource. In any case, heavy dependence on the use of chemical inputs, groundwater, and soil-eroding practices is causing depletion of exhaustible agricultural resources and is likely to reduce the productive capacity of the agricultural sector in the long run . Agricultural activities are also the causes of environmental externality problems. Agricultural runoff and seepage of agricultural chemicals contaminate bodies of water, reducing their value as sources of drinking water as well as fishing and recreation sites. Straw burning and intensive tillage practices pollute air resources and reduce air quality. These externality problems must be taken into account in the designing of policies that affect the agricultural sector. The externalities, and particularly the resource exhaustibility problems associated with agricultural production systems, are becoming increasingly severe over time. For example, the intensive use of center-pivot irrigation of the last 20 years has led to substantial depletion of the OjalIala aquifer, leading to curtailment of irrigation activities in some parts of Texas, the High Plains, and Oklahoma . In the literature on exhaustible resources , it is argued that, unless rates of technological change are extremely high, the efficiency prices of exhaustible resources tend to increase over time. Moreover, free market prices of exhaustible resources may diverge substantially from their efficiency prices, and government intervention may be needed to assure efficient utilization of these resources. Social management of natural systems involving exhaustible and slow-to-renew resources such as forests and fish populations requires resource dynamic considerations to be incorporated explicitly into policy making frameworks. It seems that such considerations will call increasing weight in the management of agriculture in the future. There are many differences in environmental conditions, economic situations, and productivities between regions in the United States. The qualities of natural resources such as water and soil are the subject of much heterogeneity. human capital, wealth, and preference vary substantially among farmers.

We additionally profiled the root transcriptomes of 1-month-old tomato plants under well-watered, waterlogged and water-deficit conditions. We hypothesized that genes directly involved in the biosynthesis and deposition of suberin will be highly correlated in both water-deficit and the introgression line population. By combining both introgression lines, waterlogging and water-deficit datasets in a weighted gene correlation network analysis3, we identified modules of co-expressed genes . A module containing 180 genes was significantly enriched in suberin-related genes . This was confirmed by intersection with a public dataset profiling gene expression in tomato DCRi lines . DCRi lines activate suberin-associated genes in the epidermal cells of fruit, which leads to suberization of the fruit surface. The ‘royalblue’ module contains several orthologues of well-known suberin biosynthetic gene families such as glycerol-3-phosphate acyltransferases , 3-ketoacyl-CoA synthases and feruloyl transferases . In addition, putative tomato orthologues of known transcriptional regulators of suberin biosynthesis: AtMYB41, AtMYB63 and AtMYB92 , among others, were found in this module.Although translatome profiles exist for the exodermis, these data do not provide resolution of the developmental gradient along which suberin is deposited. To refine the candidate suberin-associated gene set, we conducted single-cell transcriptome profiling of the tomato root. We used the 10X Genomics scRNA-seq platform to profile over 20,000 root cells. We collected tissue from 7-day-old primary roots of tomato seedlings up to 3 cm from the tip to include the region where suberin deposition is initially observed. Gene expression matrices were generated using cellranger and analysed in Seurat. Once the data were pre-processed and filtered for low-quality droplets,25 liter pot plastic the remaining high-quality transcriptomes of 22,207 cells were analysed.

After normalization, we used unsupervised clustering to identify distinct cell populations . These cell clusters were then assigned a cell type identity using the following approaches: We first quantified the overlap with existing cell type-enriched transcript sets from the tomato root and marker genes extracted from each of the clusters. An individual cluster was annotated as a specific cell type given the greatest overlap between the two sets and a significant adjusted P value . Then, to map gene expression dynamics across maturation, we examined cell-state progression by calculating pseudotime trajectories using a minimal spanning tree algorithm. The tree was rooted in the root meristematic zone , and clusters were grouped into 10 cell types to reflect existing biological knowledge on differentiation of the tomato root . Lastly, genes with previously validated expression patterns in tomato, transcriptional reporters and predicted cell type markers given their function in Arabidopsis, were overlaid on the clusters to refine annotation . Given the successful annotation of these cell types, we focused on the mapped developmental trajectories deriving from a presumedcortex–endodermal–exodermal initial population . Given the suggested link between suberin and drought tolerance, as well as the decreased suberin levels in both control and ABA conditions in our tomato mutants, we hypothesized that the slmyb92 and slasft lines would be more sensitive to water limitation compared with wild-type plants. We subjected 4-week-old well-watered plants to 10 days of water-deficit conditions . Suberin deposition and monomer levels were studied in the root system of slmyb92-1, slasft-1 and wild-type plants in both the water-sufficient and water-limited conditions. Under water-sufficient conditions, suberin deposition was only faintly observed in wild type, and exclusively in the exodermis, while being completely absent in both mutant lines . Consistent with this observation, very low levels of suberin monomers were detected, with no significant differences observed in the very long chain fatty acids, primary alcohols, ω-hydroxyacids, α-ω-dicarboxylic acids and aromatic components of suberin .

Under water limitation, however, deposition of exodermal suberin was increased, with both mutant lines having lower levels than wild type . The transcriptional regulator mutant slmyb92-1 showed a general reduction of most monomer groups compared with wild type. The slasft-1 mutant, in comparison, was primarily depleted in ferulic acid and its esterification substrates, as well as in individual primary alcohols and ω-hydroxyacids . Furthermore, stem water potential, stomatal conductance and transpiration rate were significantly decreased in response to water-limited conditions in both slmyb92-1 and slasft-1 relative to wild type, and leaf relative water content was also decreased in slmyb92-1 . When considering all physiological traits collectively using principal component analysis, slasft-1 showed a milder water-deficit response compared with wild-type plants, while slmyb92-1 was more extreme . These data demonstrate that decreased suberin levels in the tomato root exodermis directly perturb whole-plant performance under water-limited, but not under water-sufficient conditions. Furthermore, changes in specific suberin monomers and the lamellar structure that were observed between the two mutants in response to water-limited conditions may differently influence the extent of the physiological response.In the well-characterized Arabidopsis root endodermis, suberin is deposited as a hydrophobic layer between the plasma membrane and the primary cell wall5 . Developmentally, suberin biosynthesis and deposition occurs as a second step of endodermal differentiation, the first being the synthesis and deposition of the lignified Casparian strip. Suberin serves as an apoplastic barrier and a transcellular barrier, thus contributing to the regulation of the movement of water and solutes to the vascular cylinder.

Our collective observations demonstrate that, relative to Arabidopsis, the components of the pathway are conserved; their spatial localization is distinct; ASFT and MYB92 are critical regulators of suberin biosynthesis given their phenotypes as single loss-of-function mutant alleles, as opposed to their redundancy in Arabidopsis and exodermal suberin has equivalent function to endodermal suberin and can function in its absence . Spatially, in the tomato root exodermis, suberin lamellae are deposited between the exodermal primary cell wall and the plasma membrane all around the cell, similar to the Arabidopsis root endodermis and other suberized apoplastic barriers such as the potato periderm . In a temporally similar fashion to the Arabidopsis endodermis, there is a non-suberized zone at the root tip, a patchy suberized zone in the middle of the root and a continuous suberized zone nearer to the root– hypocotyl junction . We obtained clues to the underlying genes controlling exodermal suberin biosynthesis over developmental time by co-expression, single-cell transcriptome and genetic analyses. Conservation of the genes within the suberin biosynthetic pathway between Arabidopsis and tomato was evident from the functional genetic analysis of SlCYP86B, SlGPAT, SlLACS and SlASFT mutants. Despite the same genes controlling suberin biosynthesis, novelty in tomato is observed with respect to their tomato spatial expression and the critical contribution of SlASFT in primary cell wall attachment and inter-lamella adhesion of the suberin barrier. This phenotype has never been observed in Arabidopsis or potato asft mutant roots. In addition, members of the GPAT4 subclade have been regarded as exclusively involved in cutin biosynthesis, and here, SlGPAT4 was shown to participate in the formation of exodermal suberin . We focused on SlMYB92 as a candidate due to its expression at the end of the exodermal trajectory. Although the precise timing of these trajectories is largely predictive in nature,25 litre plant pot we note that the expression of the biosynthetic enzymes does not completely overlap that of SlMYB92 and suggests that SlMYB92 is not the sole transcriptional regulator of suberin gene expression. Our ability to obtain increasingly differentiated exodermal cells is probably limited by our ability to completely protoplast cells with secondary cell wall deposition. Therefore, the lack of SlMYB41/53/93 expression in the exodermal trajectory does not mean that these genes are not expressed in the exodermis. In Arabidopsis, single loss-of-function mutants of MYB41, MYB53 and MYB93 show no changes in suberin levels, while that of MYB92 shows a delay in suberization. By contrast, this extreme phenotype and compositional profiling in hairy roots and stable lines was observed in tomato when only MYB92 was mutated. The residual suberin levels found in the slmyb92 mutants could be regulated by other MYB transcription factors. Indeed, mutants in tomato orthologues of Arabidopsis MYB41 and MYB63 showed exodermal suberin phenotypes , suggesting that these genes may be expressed in later exodermal developmental stages. ABA-mediated regulation of tomato exodermal suberization is morphologically consistent with what is observed in the Arabidopsis root endodermis, with an increase in both the magnitude of suberin deposition and the proportion of the completely suberized zone, despite the distinct spatial localization.

At least in the case of the slmyb92 and slasft mutant alleles and the ABA assays, this transcription factor and biosynthetic enzyme influence both developmental and ABA-mediated suberin deposition patterns . Further analyses of mutant alleles of the tomato SlMYB41 and SlMYB62 transcription factors will determine whether a coordinated developmental and stress-inducible regulation of suberin biosynthesis is the norm for exodermal suberin. The degree to which this regulation is dependent on ABA signalling, as it is in Arabidopsis , also remains to be investigated. What remains to be identified, however, are the factors or regulatory elements that determine exodermal-specific regulation of these enzymes and transcriptional regulators, as well as how they are activated by ABA and why their activity is ABA-independent in S. pennellii. External application of ABA can be considered a proxy for both drought and salt-stress response. We tested the necessity of suberized exodermis for whole-plant performance under water-limited conditions in mature tomato plants . The strongly reduced response of slmyb92 and slasft plants to ABA was similarly observed upon drought stress. In both experiments, slmyb92-1 and slasft-1 failed to reach fluorol yellow signals and suberin levels equal to those of the control. Under control conditions , we detected overall low suberin levels, which were near the detection limit of 0.003 µg mg−1 and reduced our ability to identify significant differences between the lines. This was consistent with the lack of distinct fluorol yellow signal in mature root sections under water-sufficient conditions . The effect observed in chemical suberin quantification may have also been attenuated by the sample comprising whole root systems with highly branched lateral roots and including root areas with immature suberin. AtMYB92 is also known to regulate lateral root development in Arabidopsis together with its close orthologue AtMYB93, and differences in suberin within different root types are a possibility. Regardless, suberin monomeric levels were clearly decreased in the slmyb92-1 and slasft-1 mutants in a distinct and overlapping fashion in response to water-limited conditions. Consistent with its function, slasft-1 was primarily defective in accumulation of ferulate, primary alcohols and ω-hydroxyacids , while slmyb92-1 had defects in fatty acids and the predominant unsaturated C18:1 ω-hydroxyacids and dicarboxylic acids . The more extreme perturbation of physiological responses in response to water limitation in slmyb92-1 suggests that suberin composed of these fatty acid derivatives plays a role in controlling transcellular-mediated uptake of water . How the transcellular pathway operates in a root system where this apoplastic barrier is located four cell layers from the vascular cylinder remains an important and open question. The role of exodermal suberin as an apoplastic barrier to water flow has been studied in maize and rice, where it was determined as a barrier to water flow, although maize and rice also present a suberized endodermis. Thus, the role of exodermal suberin alone has never been studied with respect to its influence on plant responses to water limitation. The precise role of endodermal suberin, independent of the Casparian strip, has been studied in Arabidopsis, which lacks an exodermis. In 21-day-old, hydroponically grown Arabidopsis plants, the horst-1, horst-2, horst-1 ralph-1 and pCASP1:CDEF1 mutants with a functional Casparian strip but with reduced suberin were monitoredfor the importance of suberin in water relations. These mutants, except for horst-2, have higher Lpr and root aquaporin activity relative to wild type. One can extrapolate that the decreases in stem water potential, transpiration and stomatal conductance relative to wild type in water-limited conditions are a consequence of decreased suberin or perturbations in suberin composition . Assuming that our suberin-defective mutants have higher root hydraulic conductivity, our hypothesis to reconcile our observations with the higher Lpr would be that our mutants have compromised water-use efficiency under water limitation. This could lead to a delayed onset of the drought response such that the water loss is too great to recover by the time stomata are closed. The mechanisms by which this occurs need to be determined and could benefit from further exploration. The levels of lignin in the exodermis and endodermis were not altered in the mutants of the identified transcriptional regulators , and perturbations in endodermal lignin alone have no influence on root hydraulic conductivity in Arabidopsis, thus, lignin plays no role in our observations.

To evaluate whether the availability of land use types influenced bee abundance and diversity, we ran Pearson’s chi-square tests of independence. We tested whether the frequency of occurrence of each land use type across study sites was associated with the number of 1) captured bees, 2) abundance of the three most common bee tribes, 3) bee genera, and 4) bee tribes. All analyses were conducted in R. We present evidence for the effects of different local and landscape factors on bee abundance and diversity in the Colombian Andes, a region for which this type of studies are scarce. Bee abundance and diversity were influenced by several habitat factors including flower availability, elevation, and unshaded crop cover within 1 km. Contrary to our hypotheses, bee abundance decreased, although diversity increased in farms with higher habitat complexity, and both local and landscape factors greatly influenced bee community composition. Our first research question examined which local and landscape factors influenced bee abundance and diversity. In general, bee abundance was predicted by flower abundance and elevation. Our results coincide with other studies documenting a positive response of bee density to floral resources , and the unresponsiveness of some groups such as Meliponini to flower availability . We found overall bee abundance was greatly influenced by the abundance of Apis and Trigona bees in areas with high flower abundance. Other studies have documented the positive responses of Apis to the spatial aggregation of floral resources and mass-flowering crops , and have suggested Apis can exclude other bees from accessing flowers through interference or exploitative competition . Like Apis, Meliponini are social and generalist bees. While there is niche overlap among Meliponini species,grow raspberries in a pot and between Meliponini and Apis bees, there is resource partitioning among Meliponini but not between Meliponini and Apis . Thus, a possible explanation for the differential influence of flower abundance on different bee groups may be mediated by their competitive interactions with Apis.

Other factors influencing bee abundance may be related to traits specific to bee groups. For example, Augochlorini abundance decreased with pasture cover within 1 km and increased with % vegetation between 1-3 m. In our study, percent of vegetation cover between 1-3 m was negatively correlated with the percent of vegetation between 0-1 m, which is the strata at which we found more flowering herbs in unshaded land uses. Further, pasture cover within 1 km was negatively correlated with forest or agroforest cover within 1 km. In general, Augochlorini are associated to forest areas , are soil or wood nesters, and use more flowering herbs and vines as feeding resources in comparison with eusocial bees . Thus, use of nesting and food resources by this tribe may explain their abundance patterns. Elevation had a strong influence on the abundance of Apis and Trigona bees. Elevation may act as a filter structuring biological communities because of its inverse relationship to temperature, which may influence species distributions based on their tolerance to cold environments and to climatic fluctuations, among other biophysical variables . Apis and native Trigona cf. amalthea and T. cf. fulviventris have broad altitudinal and geographic ranges as well as high reproductive capacities with colonies of ~10000 and >2500 individuals respectively . The combination of these two factors may explain the high abundance of these genera in our study region, yet it still does not totally explain their positive response to high elevations. It is interesting to consider that, when we excluded these hyperabundant genera, bee abundance was not responsive to elevation. This suggests other mechanisms that favor some groups and undermine others may be at play in the highlands of this region. Bee richness and evenness were also predicted by elevation. We found a strong gradient of bee richness within a relatively narrow altitudinal range , which is considered a hump in general altitudinal-diversity gradients . Potts et al. found richness of bee taxa decreased with elevation in the Alps due to thermal tolerance of bees found along the elevation gradient.

This is consistent with the richness gradient we found, which may also be influenced by the response of different groups to other conditions changing with elevation such as agricultural disturbance. In our study region elevation was positively correlated with the percent of eroded soils at the landscape scale , and the number of land use units on pasture and conventionally managed crops increased with elevation. This suggests rates of disturbance increase with elevation, possibly acting as a strong environmental filter excluding species associated with forests and complex habitats and favoring species with high tolerance to disturbance. This may explain the reduction of rare species and the high presence of Apis and Trigona bees in high elevations, which is reflected in an inverse relationship between evenness and elevation. Bee richness and evenness decreased and dominance increased with unshaded crop cover at the landscape scale. Thus, our results suggest that changes in dominance within communities are associated with the availability of complex habitat at the landscape scale, also found in other studies . Changes in dominance may be associated with the negative responses of rare solitary species to landscape simplification , and with the ability of some groups to equally use complex or simplified habitats. Apis and T. spinipes, closely related to T. cf. amalthea, have been considered hyper-generalist species that do not show negative responses to environmental disturbance and occupy simplified lands , thereby increasing their abundance within the community in areas unfavorable for other bees . Thus, although we cannot differentiate effects of elevation, agricultural disturbance and landscape simplification, these factors and their interaction may sort bee groups in and out of local bee assemblages in this region.

Vertical structure of the vegetation and flower abundance influenced bee richness as well. The stratum at which we found bees was 0-3 m, thus bees at higher strata were not sampled and these results may reflect our sampling bias. However, a study conducted along an ecological succession gradient using different sampling methods reported bee richness and abundance increased in low vegetational strata, and decreased in areas with dense canopy cover . In general, dense canopy reduces sunlight reaching the understory, which in turn influences flowering of herbs . Bee activity may follow the distribution of flowers in the vertical strata , which may explain our results. Our second research question addressed changes in bee community composition. Changes in the composition of bee communities were influenced by elevation and flower abundance. This is consistent with the elevation-richness gradient we found, and may be explained by the degree of specialization and distribution of different bees in our study region. Specialization of plant-pollinator interactions declines with increasing elevation , and biological groups in mountainous regions have narrower ecological niches and altitudinal distributions as elevation decreases . The degree of specialization along elevation gradients may also interact with negative effects of disturbance, thus the changes in community composition in our results may indicate either genera turnover or differential loss of species along the altitudinal range. This has additional implications in light of climate change. Studies have shown increasing temperatures and their influence on thermal tolerance have driven range shifts of different organisms towards higher latitudes and elevation . However, shifts do not only depend on physiological responses but are conditioned on species interactions such as competition and mutualism, and on variation in dispersal abilities . Further studies could target range shifts of bee communities in Anolaima, where environmental change and dominance of highly competitive species are concentrated in areas with higher elevation, possibly influencing range shifts. Our third research question evaluated whether the availability of different land uses was associated with differences in the diversity and abundance of bee genera and tribes. The influence of local and landscape habitat factors on bee abundance and diversity can be linked to current land uses in the region. In general,best grow pots abundance and richness was higher in low-impact land uses, and in areas associated with human constructions. Unshaded traditional crops and fallow lands can have high floral abundance and diversity . Thus, plant richness may beget bee richness in these land uses. Also, we found nests of different groups in human constructions, and foraging on flower and medicinal gardens and on forbs surrounding houses.

Constructions offer areas with favorable features for nest thermoregulation and unmanaged flowering plants may represent continuous floral resources. Thus, human resources may have inadvertent yet important positive impacts on bee populations. We did not find high bee abundance or richness in habitats with high structural complexity i.e. forest or agroforests. Most areas in this land use correspond to shaded coffee crops. In this region, farmers manually exclude forbs that grow despite the low incidence of light into the understory, and rain-fed coffee shrubs typically bloom synchronously only during two or three days a year. This means the understory of this land use does not offer a continuous availability of floral resources for bees. When flowering, trees may offer feeding resources at the canopy level. Tree availability positively influences bee diversity and the long-term availability of flowering trees positively influences abundance of solitary bees in shaded coffee agroforests in Mexico . Some solitary bees are associated with high forest strata, even at the end of the flowering season, perhaps due to supplemental floral resources provided by honeydew and sap from the canopy . Besides food sources, trees also offer nesting resources. Nates et al. found living trees were the most frequent nesting substrate for stingless bees in eastern Colombia. We frequently found Meliponini nests in Inga trees or in abandoned bird nests in citrus trees found in shaded coffee areas. Other studies have found Augochlorini nest in wood and even in bromeliads growing on trees . Therefore, despite the under story of agroforests is not greatly used by bees, the canopy may offer important resources for bees in Anolaima. However, a dense canopy or the presence of high flowering resources distributed across the landscape may influence negatively the local provision of pollination services to coffee shrubs . We also found evidence for the negative effect of conventional crops for bee richness, despite their smaller scales when compared to other agricultural landscapes. Conventional crops in this region are both monocrops and polycrops managed with high agrochemical use . For example, chlorpyrifos and neonicotinoids are systematically used twice a week on tomato for protection from white flies. In extreme cases, application mixtures also include antibiotics to treat cattle from Dermatobia flies. Apis and Trigona were using floral resources in these crops. This suggests bees have different degrees of tolerance to chemical disturbance. For example, while Apis bees and the stingless bee Partamona helleri have different resistance to certain pesticides, both are negatively impacted by mixes of biocides . Thus, species less sensitive to pesticides can thrive in areas with high-impact management, subsidizing the pollination of plants where other bees cannot tolerate agrochemical disturbance. However, areas with high agrochemical disturbance represent a sink for rare bee species yet also a potential threat for bees with relative high resistance to agrochemicals in Anolaima. Different local and landscape factors influence bee abundance and diversity in Anolaima. Some factors were associated with the increase in abundance of two hypergeneralist groups, Apis and Trigona, and with reductions in the representation of rare species, reflected in changes in evenness and dominance within local bee assemblages. This suggests a process of biotic homogenization with the loss of some species and the spread of others, especially in high-elevation areas. In addition, we found that factors that may directly affect bee physiology, such as elevation, interact with resource availability and space to influence the composition of bee communities. We found that land use types such as unshaded conventional crops have negative impacts on bee abundance and diversity, despite the high heterogeneity of agroecosystems in the study region, and that other land uses such as pastures may not benefit some bee groups but are not adverse for others. This suggests bee communities are highly responsive to agricultural management in small-scale farming systems. Our study calls for attention to assess the effect of environmental change on bee communities in mountainous regions where climate change may influence elevational range shifts, such as in the Colombian Andes.