BRAZIL — Fallen logs are rotting, the trees grow sparser and the temperature rises in places sunlight hits the ground. This is what 24 years of severe drought looks like in the world’s largest rainforest. 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. …This resulted in the loss of approximately 40% of the total weight of the vegetation and the carbon stored within it from the plot. The main findings were detailed in a study published in May in the journal Nature Ecology & Evolution.