Land use and climate change impacts on runoff and soil erosion at the hillslope scale in the Brazilian Cerrad

Authors: ANACHE, JAMIL - Universidade De Sao Paulo; Flanagan, Dennis; SRIVASTAVA, ANURAG - Purdue University; WENDLAND, EDSON - Purdue University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/22/2017
Publication Date: 12/13/2017
Citation: Anache, J., Flanagan, D.C., Srivastava, A., Wendland, E.C. 2017. Land use and climate change impacts on runoff and soil erosion at the hillslope scale in the Brazilian Cerrad. Science of the Total Environment. 622-623:140-151. doi.org/10.1016/j.scitotenv.2017.11.257.

Interpretive Summary: Land use in Brazil is changing drastically, with hundreds of acres of native forest land being converted into cropland (largely for sugarcane production) every year. The impacts of these changes on soil erosion and soil resources are not clear, either in the current day or potentially into the future with climate changes. An efficient and effective way to determine the effects of land use, soil, slope, and climate on runoff and soil loss is through the application of computer simulation models. Of most interest in this study were 4 treatments: undisturbed forest land, continuously-tilled land with no vegetation, continuous pasture land, and land under conventional sugarcane production. Here we used 5 years of measured experimental data from field plots in Brazil to adjust input parameters to the WEPP (Water Erosion Prediction Project) model, so that it could do as good a job as possible in predicting runoff and erosion from measured storm events. Then we used those adjusted values for soil infiltration, susceptibility to soil detachment, and crop growth in additional model applications with long-term (100-year) inputs of generated current and projected future climates. We found that the WEPP model did a good job at matching with the observed runoff and soil loss, and that the land management had a large effect on the results. Greatest measured and simulated soil loss was from the continuously-tilled land with no vegetation, followed by the sugarcane cropland. Erosion from the native forest land and the continuous pasture was about the same, and much lower than the other 2 treatments, and this result was the same under the current and all projected future climate scenarios. These findings impact land managers, farmers, extension agents, soil conservation agency personnel and others involved in land management in Brazil and elsewhere, in efforts to create sustainable systems and minimize soil erosion. Sustainable soil loss rates equivalent to natural forested lands may be obtainable through use of conservation systems that maintain live vegetative cover on the soil surface during most of the year.

Technical Abstract: Changes in land use and climate can influence runoff and soil erosion, threatening soil and water conservation in the Cerrado biome in Brazil. The adoption of a process-based model was necessary due to the lack of long-term observed data. Our goals were to calibrate the WEPP (Water Erosion Prediction Project) model for different land uses under subtropical conditions in the Cerrado biome; predict runoff and soil erosion for these different land uses; and simulate runoff and soil erosion considering climate change. We performed the model calibration using a 5-year dataset (2012-2016) of observed runoff and soil loss in four different land uses (wooded Cerrado, tilled fallow without plant cover, pasture, and sugarcane) in experimental plots. Selected soil and management parameters were optimized for each land use during the WEPP model calibration with the existing field data. The simulations were conducted using the calibrated WEPP model components with a 100-year climate dataset created with CLIGEN (weather generator) based on regional climate statistics. We obtained downscaled General Circulation Model (GCM) projections, and runoff and soil loss were predicted with WEPP using future climate scenarios for 2030, 2060, and 2090 considering different Representative Concentration Pathways (RCPs). The WEPP model had an acceptable performance for the subtropical conditions. Land use can influence runoff and soil loss rates in a significant way. Potential climate changes, which indicate the increase of rainfall intensities and depths, may increase the variability and rates of runoff and soil erosion. However, projected climate changes did not significantly affect the runoff and soil erosion for the four analyzed land uses at our location. Finally, the runoff behavior was distinct for each land use, but for soil loss we found similarities between pasture and wooded Cerrado, suggesting that the soil may attain a sustainable level when the land management follows conservation principles.