But this patch of degraded forest, about the size of a soccer field, is a scientific experiment. Launched in 2000 by Brazilian and British scientists, Esecaflor—short for "Forest Drought Study Project" in Portuguese— set out to simulate a future in which the changing climate could deplete the Amazon of rainfall. It is the longest-running project of its kind in the world, and has become a source for dozens of academic articles in fields ranging from meteorology to ecology and physiology.

Understanding how drought can affect the Amazon, an area twice the size of India that crosses into several South American nations, has implications far beyond the region. The rainforest stores a massive amount of carbon dioxide, a greenhouse gas that is the main driver of climate change. According to one study, the Amazon stores the equivalent of two years of global carbon emissions, which mainly come from the burning of coal, oil and gasoline. When trees are cut, or wither and die from drought, they release into the atmosphere the carbon they were storing, which accelerates global warming.