A research report, A Recent Systemic Increase in Vapor Pressure Deficit (VPD) over Tropical South America, by HAS Associate Professor Ali Behrangi and collaborators was recently published in the October issue of Nature, scientific reports.
Behrangi and colleagues analyzed decades of ground and satellite data and compared the trend to data from models estimating climate variability over thousands of years. The team used data from NASA's Atmospheric Infrared Sounder (AIRS) instrument aboard the Terra satellite.
The research shows that the atmosphere above the Amazon rainforest has been drying out, increasing the forest's demand for water and leaving ecosystems vulnerable to fires and drought. Analysis shows that about half of the changes have resulted from elevated greenhouse gas levels and the remainder from human activity, primarily the burning of forests to clear land for agriculture and grazing. Recent mega droughts in the Amazon (2005, 2010, and 2015) have intensified the forest's atmospheric aridity and the slow recovery of the region's hydrological system. If this drying trend continues over the long term and disrupts the ecosystem's ability to function normally, many of the trees and species that live there may not be able to survive. The research findings demonstrate that the change is well beyond what would be expected from natural climate variability.