Over the 6 years of study, except perhaps for 2013 when we focused on other study priorities, we never experienced ideal conditions to adequately test the flood extension concept. We were either in a severe drought, during which the Yolo Bypass did not flood from the river, or we experienced severe and sustained flooding, which made it impossible to contain flood waters within study fields. Based on these experiences, studying the concept of flood extension appears to depend on the occurrence of moderate flood events at the right time of year , provided fields are appropriately designed to hold water and allow efficient immigration and emigration of potentially large numbers of juvenile salmon. However, significant outreach and communication is necessary with landowners to maintain floodwaters on their fields during the natural drainage period. Because these events cannot be predicted well ahead of time, these communications—and availability of robust infrastructure—need to be constantly maintained even outside the flood extension period. As suggested in the previous section, such potential actions would need to be taken in a way that maintains hydrologic connectivity and salmon access, so that salmon can successfully locate potential managed habitats, use them for rearing, and then successfully emigrate from them at the appropriate time. Timing of such potential manipulations is critical because previous sampling has shown that salmon quickly emigrate from the floodplain during large scale drainage events , leaving relatively low densities of salmon in remaining ponded areas to potentially benefit from flood extension. Although our use of hatchery salmon gave us more experimental options during drought conditions, the use of these fish resulted in additional challenges. Our approach relied on a non-traditional use of hatchery salmon, which required a suite of permits and approvals to execute the project. As noted above, the project coincided with a major drought, so access to hatchery salmon was limited as a result of low salmon population levels. In addition, use of hatchery salmon affected the time-period when we could conduct experimental work. We were unable to test salmon response to early season flooding ,ebb and flow tray because the hatchery salmon were too small to receive coded-wire tags as required under our permit conditions.
Similarly, the timing of our work was affected by the availability of holding tanks at our partner hatchery , and by the availability of transport staff and vehicles to move salmon to our study site. While we were able to assess many important biological metrics in our study, direct measurement of the population-level effect of floodplain rearing on agricultural habitats proved elusive. A traditional approach to addressing this question involves inserting CWTs into very large numbers of experimental salmon and estimating the population response from expanded CWT recaptures in the ocean fisheries. Recoveries of CWTs in adult salmon from experimental releases made in the Yolo Bypass have generally been very low , making it difficult to get a high level of resolution with which to reliably compare survival rates, including with values in the literature. Although CWT recoveries could potentially be improved by increasing the number of tagged salmon, the effort required even to collect a single data point would be substantial and is limited by the availability of surplus hatchery salmon. A related issue is that it is difficult to design a survival experiment that provides a useful comparison to other management strategies or migration corridors. For example, it is challenging to assess the incremental survival value of flooded agricultural habitat versus adjacent perennial channels . Telemetry can partially address this issue, but current acoustic tagging technology does not allow estimates of survival once smolts emigrate from the estuary, and is also limited in the size of salmon that can be tagged. Ultimately, addressing the question of population-level effects will likely depend on a combination of measured field data, incorporating new methodologies for assessing survival to adulthood , and fish population models.Our observations must be considered within the constraints of the infrastructure in the Yolo Bypass during the time of our field work. In the intervening years since our field studies, there has been a substantial amount of progress in improving Yolo Bypass infrastructure to support native fishes. During 2017-2018, an inflatable dam fish barrier and collection facility was constructed at Wallace Weir at Knights Landing Ridge Cut . This facility can enhance potential water distribution options for managed flooding studies under relatively low flow conditions when only Yolo Bypass tributary flows are available, including sources from Colusa Basin, which may not always have suitable water quality for juvenile salmonids.
It is important to note, however, that these local water sources are not useful unless there is improved connectivity with the Sacramento River, allowing wild juvenile salmon to access seasonal habitat throughout the Yolo Bypass. To that end, the joint Environmental Impact Statement/Report was finalized in 2019 for a project that will improve connectivity between the Sacramento River and Yolo Bypass with a proposed notch in Fremont Weir . This proposed facility would allow managed flows at lower Sacramento River stages than the current weir structure, thereby increasing the frequency and duration of seasonal inundation, and providing improved access to the floodplain from the Sacramento River fish migration corridor. This upgrade is required as a condition of the 2009 Biological Opinion for Salmonids for long term operation of the federal and state water projects . Our study did not specifically address these new facilities or their operations, and how the concept of managed agricultural floodplain habitat can be integrated into the primary purposes of these improvements. Hence, potential use of flooded agricultural fields as juvenile salmon rearing habitat should be evaluated in light of both a modified hydrology and local land use and infrastructure changes. Additional research is needed to address the efficacy and suitability of different potential water sources, hydrology timing, connectivity with the Sacramento River, and related issues, such as the effects of operations on land use and other species or life stages .Using conservation easements to protect farmland from urbanization is a relatively new application of a technique that has been used in land preservation programs in the United States for about a century. Landowners who voluntarily sell easements or donate them for tax benefits, in effect give up development rights on their land in perpetuity while still retaining basic ownership . Only in the past 20 years in California, and slightly longer in several other states, have state and local programs employed easements for the express purpose of keeping farmland in production. The more traditional uses have been for preserving land with natural resource or recreational values, such as riparian areas, wetlands, habitat and trails. Thousands of agricultural acres — primarily grazing land — have been covered by environmentally oriented easements over the years. In part this is because farmland is a form of open space, a passive environmental amenity. But protecting agricultural production with easements intended to protect more specific natural resources, such as habitat and riparian areas, is more difficult for much of California’s farmland, because orchards, vineyards, vegetable cultivation and other intensive crop production constitute a “working” rather than “natural” landscape. While sustainable agriculture offers considerable promise for minimizing the impacts of farming on natural resources, intensive crop production still generally involves chemical applications, the use of heavy machinery and other industrial like activities.
We address it only in the context of conservation easements, by examining the agendas of local organizations with land conservation objectives. We identify 34 California organizations that emphasize farmland protection to varying degrees, and examine the mix of agricultural and other conservation purposes in their missions, drawing primarily from open-ended phone and personal interviews with program managers and from mission statements.The 34 California programs that fit our standards for having an interest in farmland protection include 30 nonprofit land trusts and four open space districts. Land trusts are nonprofit, community organizations founded and run by volunteers and small staffs, while open space districts are local government entities governed by publicly elected boards . All four of the state’s open space districts are included on this list. But the 30 land trusts are only a small portion of the more than 130 land trusts that operate throughout California, according to the 1998 directory of the national Land Trust Alliance . Among 20 different types of resource conservation purposes noted in the directory for individual California trusts , farmland/ranches ranked eighth in the frequency of mention. The top mentions were watersheds/water quality, rare species habitat, scenic views, wetlands, river corridors, trails and forests/timberlands. To select 30 farmland-oriented land trusts, we first identified 37 organizations that cited a farmland or ranch purpose in the LTA directory. Next, we added about 10 other trusts identified as having an agricultural orientation by other sources such as state and foundation programs, the American Farmland Trust and our own files. Finally, after speaking with program managers and reviewing mission statements, we narrowed the list down to 30 trusts. The final list does not include land trusts that acquired easements on grazing acres or other farmland primarily for environmental,4×8 flood tray rather than agricultural purposes. The two essential selection criteria were an expressed interest in the preservation of farmland as an agricultural resource and the intention to use conservation easements. For our purposes the farmland criterion encompasses both cropland and rangeland. The few California trusts that have forestry or growing of trees as their only “agricultural” activity were not included. Otherwise, we defined “farmland” and “agriculture” broadly. For example, one manager for a coastal land trust described the scope of his agricultural program as including, “all agricultural uses in accordance with sound and generally accepted agricultural management practices, such as breeding, raising, pasturing and grazing of livestock; production of food and fiber; breeding, raising and boarding horses, bees, poultry and other fowl; and planting, raising, harvesting other agricultural, horticultural and forestry crops.” In applying the second selection standard, use of easements, we emphasized intention rather than accomplishment. It was not necessary for an organization to have actually acquired specific easements. Rather, we deemed it sufficient to express an intention to acquire easements for farmland protection in the future. One justification for this liberal approach was recognition of how difficult it is for a new land trust to complete its first easement transaction, primarily due to funding limitations and landowner resistance . The trusts we identified are located in 29 of California’s 58 counties .
A few operate in more than one county, and the California Rangeland Trust has a statewide orientation with an emphasis on the Sierra foothills and Central Coast hillsides. Twenty-one of the 34 programs are concentrated in coastal areas, with 14 in the Bay Area alone . The Central Valley has nine and Sierra foothill counties have two. Least represented in relation to area and population, Southern California has only two organizations on our list, in Ventura and San Bernardino counties. No such programs are located in the major counties of Los Angeles, Orange, Riverside and San Diego.Both nonprofit organizations and public agencies are legally able to acquire and hold conservation easements on private properties that restrict their future use. The key is their noncommercial and public interest character, which under federal law allows them to accept contributions of money or land interests as tax deductions. Nonprofit land trusts specifically qualify under section 501 of the Internal Revenue Code. But the California land trusts and public agencies have distinctly different forms and operational procedures. Land trusts are independent, nongovernmental entities with no formal accountability to the community or its political bodies. Volunteer boards of directors, who fill their own vacancies, govern them and a number have small staffs and membership or donor rolls. Because of their grassroots origins, flexibility, citizen participation and conservation credentials, land trusts are an attractive alternative to local government as the major mechanism for acquiring and holding easements . No California county and city governments directly operate agricultural easement programs, although they frequently require the donation of easements as mitigation for approving development projects. The open space districts and several regional conservancies organized by state government are the only public agencies in California with active easement programs. Unlike the nonprofits, the districts are accountable to their communities via separately elected governing boards or are extensions of county government and the elected board of supervisors.