Deforestation is when people cut down lots of trees in a forest. People do this to make room for roads, cities, farms, and other things people use. It is sometimes done to get wood to burn or to make paper. When people cut down the trees, the animals that live in the forest don't have anywhere to live anymore, so they have to move away. Deforestation also causes climate change because it takes away trees that help our air stay clean and healthy.