Seventy percent of the world's plants and animals live in forests and are losing their habitats to deforestation (cutting of forest), Loss of habitat can lead to species extinction. The number of wild animals decreases by cutting of forest because If the trees are gone, birds, reptiles, and insects lose their homes and food sources. That will affect the small mammals, which are a food source for mid- and large-sized mammals. It is a cascade effect that leads to species extinction. So, the correct answer is 'Number decreases'.