Abstract
ABSTRACT This study evaluated historic land use and land cover changes in the Arroio Marrecas watershed (Caxias do Sul, Rio Grande do Sul state of Brazil) and simulated future land use scenarios until 2034. Spatial and temporal simulations were conducted with the Conversion of Land Use and its Effects - Small Regional Extent (CLUE-S) model. Three land use scenarios were developed to include public policies and agricultural trends in the study region for 20 years (2015-2034). Geospatial analysis of different land uses showed that areas that were originally covered grasslands and forests decreased, which can be attributed to the expansion of intensive agricultural uses, such as fruit farming/forestry and urbanization. The reallocation dynamics of land use with CLUE-S was primarily driven by the soil class (especially Typic and Humic Dystrudepts and Lithic Undorthents), with limited effects of altitude and slope. Analysis of the land use maps of the Arroio Marrecas watershed until 2015 identified major human-induced changes that were driven by expanding agricultural production and urbanization. The allocation of land use derived from the proposed future scenarios with CLUE-S showed that in this regional context, Humic Dystrudepts and Rhodic Kanhapludults were the key drivers of the allocation of agricultural expansion. Conversely, natural resource conservation was indicated to most likely occur in Typic Dystrudepts. The main limitation of this approach is the recognition of driving factors that have a high correlation with each land use as effective predictor variables.
Highlights
The Arroio Marrecas watershed is primarily dominated by agricultural land uses and includes drinking water sources that are crucial for the growing population of the municipality of Caxias do Sul, Rio Grande do Sul State.It has been widely recognized that agricultural expansion has had environmental impacts, such as ecosystem fragmentation, loss of biodiversity and soil, water pollution and disruption of biogeochemical cycles across the world (Rockström et al, 2009) and in Brazil (Dias et al, 2016)
This study evaluated historic land use and land cover changes in the Arroio Marrecas watershed (Caxias do Sul, Rio Grande do Sul state of Brazil) and simulated future land use scenarios until 2034
Analysis of the LULC spatiotemporal dynamics of the LULC in the Arroio Marrecas watershed revealed an increase in anthropic activities, especially the more intensive activities, such as annual crops, fruit growing and forestry, based on agro-industrial inputs (Table 3)
Summary
The Arroio Marrecas watershed is primarily dominated by agricultural land uses and includes drinking water sources that are crucial for the growing population of the municipality of Caxias do Sul, Rio Grande do Sul State (which had more than 500,000 inhabitants in 2017).It has been widely recognized that agricultural expansion has had environmental impacts, such as ecosystem fragmentation, loss of biodiversity and soil, water pollution and disruption of biogeochemical cycles across the world (Rockström et al, 2009) and in Brazil (Dias et al, 2016). Land use and land cover (LULC) assessments usually include spatial and temporal dimensions that allow comparisons of different sites and times to be made in spatial modeling applications (Galharte et al, 2014). These spatial assessments can be enhanced by the inclusion of future LULC scenarios (Shearer, 2005). The CLUE-S (Conversion of Land Use and Its Effects - Small Regional Extent) model was developed at the University of Wageningen (Netherlands) to perform spatially explicit simulations of LULC changes from empirical analyses of the suitability and allocation trends of LULC identified in areas of interest.
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