Abstract ID: 496

Crop vulnerability to drought in southern Brazil: initial insights into the potential impacts of Amazonian deforestation

Amazonia recycles 25 to 50% of rainfall back into the atmosphere by evapotranspiration (1, 2). This is perhaps the most important regional ecosystem service, and could provide moisture to downwind regions in South America. Large-scale conversion of rainforest to pasture or cropland has the potential to change local climate and eventually undermine this service. Transpiration from pasture can be as much as 24% lower than from forest (3) while for soybean crops, which are becoming more important in the region, it is even lower (4). Expansion of pastures is projected to result in warmer, drier conditions in eastern Amazonia (5), while modeling suggests a reduction in the recycling of water from trees back into trade winds, leading to a drier western Amazonia (6). Half of the forest area of Amazonia may be cleared, logged or burned within 20 years (7), while the loss of 30-40% could push it into a drier climatic state (8). Hence, it is crucial to investigate the potential effects of deforestation-induced drought on Amazonia and downwind regions. This study sought to estimate the impacts of drought on the soy and corn harvests in the Southern region of Brazil. Using historical data on precipitation and crop harvests, we estimated the level of crop failure due to severe drought was up to c.68% and c.64% respectively. These results indicate a high vulnerability in the agricultural economy of these regions, which may worsen in future droughts scenarios. Taken together with previous studies (5, 6), they provide a rationale for further research into the links between the hydro-climate functioning of Amazonia and the economic stability of Brazilian agriculture. References: 1. Eltahir and Bras, Advances in Water Resources 17, 101 (1994) 2. Marengo, Revista Brasileira de Meteorologia 21, 1 (2006) 3. Randow, et al., Theoretical and Applied Climatolology 78, 5 (2004) 4. Costa et al., Geophysical Research Letters 34 (Apr, 2007) 5. Sampaio et al., Geophysical Research Letters 34 (2007) 6. Da Silva et al., Journal of Climate 21, 1153 (2008) 7. Nepstad et al., Philosophical Transactions of the Royal Society B-Biological Sciences 363, 1737 (May, 2008) 8. Oyama and Nobre, Geophysical Research Letters 30 (2003)

Session:  Feedbacks to Climate - Effects of deforestation on regional and global climate.

Presentation Type:  Oral