Agricultural Land Clearing in Brazil's Heartland Degrades Weather and Decreases Maize Yields

Abstract:

To date, over 50% of the Brazilian Cerrado has been cleared predominantly for agropastoral purposes. Here, we use NCAR's Weather Research and Forecasting model to run 15-year climate simulations across Brazil with six land-cover scenarios: 1) before extensive land clearing; 2) land-cover observed in 2016; 3) Cerrado replaced with single-cropped (soy) agriculture; 4) Cerrado replaced with double-cropped (soy-maize) agriculture; 5) eastern Amazon replaced with single-cropped agriculture; and 6) eastern Amazon replaced with double-cropped agriculture. All land-clearing scenarios (2-6) contain significantly more growing season days with temperatures that exceed critical temperature thresholds for maize. Evaporative fraction significantly decreases across all land-clearing scenarios. Only our Tocantins sub-region experiences significant decreases in precipitation as a result of both eastern Amazon land-clearing scenarios. Altered weather reduces maize yields between 6–8%, when compared to the before extensive land clearing scenario; however, soy yields are not significantly affected. Our findings provide evidence that land clearing has degraded weather in the Brazilian Cerrado, undermining one of the main reasons for land clearing: rainfed crop production.