Since 1980, the rainy season in Brazil's Cerrado region has dragged on for 36 days, with rainfall falling by almost 37 percent and average temperatures rising by 1.5 °C, jeopardizing sustainable soybean and maize crops. The scientists linked this to the destruction of natural vegetation - the first time they have been able to separate the contribution of deforestation from the effects of global climate change. The work is published in the journal Nature Sustainability.

The Cerrado is a tropical savannah that occupies one-fifth of Brazil's land area and has record biodiversity. Half of its natural vegetation has already been destroyed for agriculture: The region produces 12 percent of the world's soybean crop (the main livestock feed), as well as corn, rice and coffee. Associated with the agricultural boom are changes in the regional climate, which is becoming hotter and drier due to decreased evapotranspiration, which is beginning to threaten crop losses. Separating the effects of global and regional climate change from technological advances in agriculture can be difficult.

Researchers led by Argemiro Teixeira Leite Filho of the Federal University of Minas Gerais assessed the impact of deforestation on soybean and corn production in the Cerrado. The researchers used data on daily changes in meteorological indices from the BR-DWGD database and land use and land cover data from the MapBiomas project from 1999 to 2019. Using machine learning, removal of trends from the data series, and modeling, the authors were able to separate climate signals associated with local vegetation loss from the effects of global climate change.

It turned out that compared to 1980, the rainy season, which is important for agriculture, came 36 days later on average. Total rainfall decreased by 36.7 percent and temperatures increased by 1.5 degrees Celsius. Ninety-nine percent of the crop area was affected. In areas with extensive loss of natural vegetation (more than 80 percent), climate change was even more pronounced. Temperatures rose by one degree every five to six years, the rainy season was delayed by two years, and rainfall decreased by 200 millimeters every five years. Reduced rainfall means that 65 percent of soybean acreage is moisture deficient and 20 percent of maize acreage could be left without a crop.

The logical step to mitigate climate change in the region caused by deforestation is to plant new forests. However, scientists have recently discovered that this will not have a similar cooling effect: After deforestation, the temperature on the ground rises by an average of 0.5 degrees Celsius, while after planting green areas it drops by only 0.1 degrees Celsius. This is due to the slow recovery of parameters such as leaf area index, vegetation index, evapotranspiration and albedo.