Dam removal is a relatively new area of science. It wasn’t until the mid-1990s that tearing down a dam to restore a river became a regular occurrence across the United States. Most dam removals have been studied and monitored closely to ensure that results meet expectations and to avoid harmful consequences. But there haven’t been many comprehensive reviews of the field of dam removal to answer broader questions, such as: How many dam removals actually helped fish recolonize rivers? How long did that take? What were the effects of releasing sediment stored behind dams?