Climatic gradient across the Amazon basin. The hydrologic Amazon basin is demarcated by a thick blue line; the mean daily precipitation during the three driest months of the year are overlain onto four land-cover classes. The arrow emphasizes the trend from continuously wet conditions in the northwest to long and pronounced dry seasons in the southeast, which includes Cerrado (savannah/woodland) vegetation. Image courtesy of NATURE and caption text excerpted and modified from Davidson at al. (2011)
The combination of deforestation, forest degradation, and the effects of climate change are weakening the resilience of the Amazon rainforest ecosystem, potentially leading to loss of carbon storage and changes in rainfall patterns and river discharge, finds a comprehensive review published in the journal Nature.
An international team of researchers examined 100 studies looking at the effects of disturbance and climate change on the functioning of the Amazon Basin. The found that while the Amazon may be resilient to individual disturbances, multiple interacting disturbances — including fire, logging, deforestation, fragmentation, and global and regional climate change — undermines its resilience.
The researchers warn that events like the droughts that affected vast areas of Amazon rainforest in 2005 and 2010 could worsen if deforestation, forest degradation, and climate change worsen. Both deforestation and forest degradation from fire and logging reduce forest transpiration, which accounts for roughly a third of the moisture that forms precipitation over the Amazon basin. Meanwhile warmer temperatures in the Atlantic reduce the amount of moisture that reaches the basin. Drought exacerbates the risk of fire, which further degrades the forest and releases smoke which disrupts rainfall.
The authors note that current development plans will greatly increase the risk of deforestation and fragmentation across much of the Amazon. Meanwhile a spate of dams could affect the discharge of rivers already impacted by drought.
The Amazon basin today and future fire risks. Image courtesy of NATURE and caption text excerpted and modified from Davidson at al. (2011)
The researchers conclude will a call for further study to better understand "the trade-offs between land cover, carbon stocks, water resources, habitat conservation, human health and economic development in future scenarios of climate and land-use change."
"Brazil is poised to become one of the few countries to achieve the transition to a major economic power without destroying most of its forests," they write. "However, continued improvements in scientific and technological capacity and human resources will be required in the Amazon region to guide and manage both biophysical and socioeconomic transitions."