Ecological restoration is an attempt to reset the ecological clock and return a damaged ecosystem to its predisturbance state—to turn a disused farm into a prairie or to convert a parcel of low-lying acreage into a vigorous wetland. Precise replication of the predisturbance condition is unlikely to occur because each ecosystem is the result of a sequence of climatic and biological events unrepeatable in precisely the same order and intensity as the original sequence. However, close approximations of the predisturbance condition are often possible, with differences from the original apparent only to professionals.

Within this limitation, restorationists strive to re-build ecosystems that, if not exactly like their original predecessors, possess the qualities of a healthy ecosystem. These properties include:

• dominance of indigenous (native) species
• sustainability or the ability to perpetuate
• resistance to invasion by non-native or pest species
• the presence of healthy functions such as...