Human-caused fires have the potential to hugely alter tropical forests—and the world at large. In this episode, we talk to Dr. Jennifer Balch, of the University of Colorado–Boulder. She discusses a long-term experiment in which she and her team deliberately lit fires in the Brazilian Amazon, with the aim of simulating the fires that are often released when people use burning to clear land. The forests were resilient to initial burning, but when a major drought hit in 2007, things changed quickly. The combined effects of drought and fire have huge implications, from grassland incursion and climate change to rainforest loss at previously unmeasured levels. The article is part of a BioScience Special Section on Tropical Forest Responses to Large-Scale Experiments.