Succession
Ecosystems are "dynamic." This means that ecosystems change over time.
During the ice ages, glaciers once covered areas that are tropical rainforests today. Both natural forces and human action cause ecosystems to change.
If there is a big ecosystem change caused by natural forces or human actions, the plants and animals that live there may be destroyed. Or they may be forced to leave.
Over time, a new community will develop, and then that community may be replaced by another.
Succession
Primary succession is the type of ecological succession that happens on new lands - lands where life has not yet existed. Primary successions can take place after lava flow cools and hardens into new land, or a glacier recedes exposing new land.
Secondary succession is the type of succession that happens after something destroys the habitat, such as a flood or natural disaster. Abandoning a field that was once used for agriculture can also lead to secondary succession.
