Figure 18.16 Ecosystem engineers. While beavers are not very abundant, the dams they build, like this one in Grand Teton National Park, Wyoming, have a major effect on community structure. Beaver dams flood terrestrial communities, which kills most terrestrial plants. In addition, the aquatic community changes from species that live in flowing streams to those that live in nonflowing ponds.

Photos by (left) Tom & Pat Leeson; (right) Malcolm Schuyl/FLPA Image Broker/Newscom.