The thematic maps of land use and cover, over a 30-year period , were developed in MapInfo Professional 8.5 software. The landscape spatial pattern of the Northern Region of Rio Grande do Sul was configured by four land use classes: Natural, Aquatic, Agricultural Anthropic,and Non-Agricultural Anthropic, and their respective areas, over a30-year period. These classes were later categorized into nine types of land cover: native vegetation, wetlands, water bodies, agriculture, pasture, forestry,bare soil, urbanized area, and road net.The landscape composition was described based on land use and cover changes, expressing the performance of anthropic activities in determining the predominant type of land use, over a 30-year period. The agricultural anthropic land use showed the highest area values, occupying between 85% and 70% of the total study area, over the last 30years . Through time, a sequence of land use dynamics was observed setting an anthropic matrix, nft system predominantly occupied by farming,with agriculture and soil exposed as the most representative land cover types.
The agricultural anthropic land use has been initially substituted by a natura lone; non-agricultural anthropic land use makes up anthropic matrix as a consequence of ongoing urbanization. The Northern Region of Rio Grandedo Sul evidenced an increase of 81,332.85 ha in the native vegetation area, over a 30-year period . This increase became particularly marked in 1990, mainly, in greater slope area to the North and East of the Northern Region of Rio Grande do Sul. The total increase in the native vegetation area resulted in a quantitative remnant, occupying around 25%, of the Northern Region of Rio Grande do Sul total area. This value can be considered below the natural area critical threshold of 30% to ensure the balance between biodiversity conservation and economic development in a biocultural landscape.The intensification of the farming mechanization in the South of Brazil, since1980, with an increase in agricultural productivity per unit area, has been identified as one of the driver of the agricultural reduction area, and the consequent reduction of deforestation and natural vegetation recovery.
The replacement of agricultural anthropic areas with subsequent natural vegetation recovery has been described like a feature of regions where socio-economic factors strongly influence land use changes.The increase of forest areas was also previously reported for regions with lower agricultural potential and marked slope gradient. Similar results and reports for the Northern Region of Rio Grande do Sul were previously related by.The increase in pasture areas of 44,534.71 ha , between 1986 and 2016, may be related to the reduction of agricultural areas, mainly in sloping areas, particularly in municipalities with agricultural technology associated with monoculture .The total area of non-agricultural anthropogenic use for the North Region of Rio Grande do Sul increased by 4039.88 ha, over a30-year period , particularly, as a result of the urbanization expansion,as well as, the exodus of rural population to urban centers. These results are supported by the increase and the reduction of urban and rural populations, hydroponic gutter respectively,of the Northern Region of Rio Grande do Sul municipalities.There was no change in road net value area in the Northern Region of Rio Grande do Sul between 1986 and 2016.
This result is due to the only main roads mapping and rasterization of the study area, due to there solution of the Landsat images be incompatible with the average width of most of the region’s roads. Three naturalness performances of the Northern Region of Rio Grande do Sul,over a 30-year period, were identified: 1) increased naturalness resulting, respectively, from the increase of natural areas with or without minimal anthropic influence, and of natural areas with anthropic influence, equivalent to changes from 0.94% to 2.63%, and from13.33% to 26.29%, of the total study area. Areas of high naturalness are associated with patches of natural vegetation, in the North and East of the Northern Region of Rio Grande do Sul, particularly, through two remnants of natural vegetation, with areas greater than 1000 ha, located in Indigenous Land,respectively, to the northwest and southeast of the Northern Region of Rio Grande do Sul ; 2) reduction of naturalness ,specifically, related to the ongoing urbanization process, equivalent to a change from 0.38% to 0.57% of the total study area; Reduction of the farming matrix, from 85.35% to 70.51% of the total study area, mainly due to the replacement of agricultural with natural vegetation areas.