US: Recent research surrounding the impact of drought in the Amazon has provided contradictory findings as to how tropical forests react to a drier and warmer climate, according to a new study published in the August 2 Early Edition of the Proceedings of the National Academy of Sciences (PNAS). The study examines the response of Amazon forests to variations in climate conditions, specifically considering how those changes may influence forest productivity. These findings provide possible context for why previous studies have offered varying conclusions. Scientists from the Instituto de Pesquisa Ambiental da Amazônia, the University of Florida-Gainesville, and the Woods Hole Research Center co-authored the paper.
The study used a combination of remote sensing and field-based studies, including MODIS Enhanced Vegetation Index (EVI) data from the 2000-2008 dry seasons in the Amazon Basin. This was integrated with climate data from 1996-2005 recorded at 280 meteorological stations. Statistical relationships between EVI and several variables were also analyzed for both the entire Amazon Basin and for an intensively studied site (Tapajos).
Paulo Brando, the paper’s lead author, said, “Our study builds on field studies and remote sensing studies to demonstrate that relatively undisturbed Amazon forests are quite tolerant of seasonal drought, unlike other types of vegetation and severely disturbed forests. Our study also points to several potential mechanisms controlling seasonal and inter-annual oscillations in vegetation productivity across the Amazon Basin. To date, discussions of these mechanisms have been largely lacking in the scientific debate about how Amazon forests may respond to climate change.”
Scott Goetz, a co-author, explains, “This analysis captures, in great detail, how forest productivity varies with meteorological measurements, particularly during drought years. Our findings build upon earlier work but take those several steps further by actually making the link with climate, and examining how forests respond by flushing new leaves.”