Swidden agriculture—often called "slash-and-burn"—has been practiced on every inhabited continent throughout human history, and for decades it has been blamed for the destruction of the world's rainforests. However, a new study of more than 18,000 forest patches around the world found that the environmental impact of swidden is more nuanced and less destructive than the term "slash-and-burn" suggests—and that unwritten social rules in small societies, not government oversight, often regulate land use closely enough to support both harvests and forest regeneration sustainably over time.