Why Drought Might Not Wreck the Amazon

As our climate continues to change, the fate of the Amazon rainforest remains uncertain. Some studies have shown that droughts could turn the Amazon into savannah, while others have predicted that the trees will remain, despite there being more pronounced dry seasons than there are today.

Climate change's effect on the rainforest is, of course, normally presented as a separate issue from the threat of deforestation, which increased by nearly a third last year in Brazil after a decade of deforestation slowing down.

New research published in the Journal of Climate brings the two together, showing that the trees of the Amazon may be able to withstand droughts better than we thought, but that areas of forests that have been cut down will fare worse than undisturbed regions.

The research, done by scientists from the University of Exeter and Colorado State University, suggests that many climate models overestimate the effects of drought on the Amazon rainforest because they don’t take into account how well the trees themselves can recycle water during dry periods. When this is taken into account, the stress the forest is placed under is reduced, producing a more realistic scenario for what the Amazon will be facing in the coming decades as the planet warms and precipitation patterns change, the researchers say.

Key to this is the process of moisture recycling. According to the researchers, up to one-third of all rainfall in the Amazon can be traced back to moisture being absorbed by trees from the soil, moving through plants’ roots and to their leaves. During droughts moisture recycling can actually increase, raising atmospheric moisture as trees pull more water from the ground.

Distrubed areas of forest, which include areas of otherwise intact forest bordering pastures, will fare worse than undisturbed areas because they don’t maintain the ability to recycle moisture as well, the researchers found.

Report co-author Dr. Anna Harper noted that moisture recycling doesn’t make the rainforest immune to droughts, but it can reduce the severity of them, which is yet another reason to protect intact forest systems.

The characteristics of the changes coming to the forests of Amazonia have potentially far-reaching implications, influencing the weather well-beyond South America. Other recent research shows that under extreme deforestation scenarios, potential changes in precipitation patterns and atmospheric moisture could bring drought and reduced spring snowmelt to places as far away as the Sierra Nevada in California, as well as the Pacific Northwest.