concept

Ecosystem engineer

An organism that changes its habitat physically, not only by eating and being eaten. Jones, Lawton and Shachak introduced the idea in 1994 and split it in two: allogenic engineers modify material outside themselves — a beaver damming a stream, an earthworm rebuilding soil — while autogenic engineers *are* the modification, their own bodies being the structural change. Corals, kelp, trees. It is the concept that explains why a large tree does not build a habitat so much as constitute one.