Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. This series of largely predictable changes that occur in a community over time is called ecological succession. Ecological succession is slow and gradual and can take many years.
As ecological succession occurs, types of species (both plants and animals) present in a community change in response to the new environmental conditions. Examples of such environmental conditions include fires, climate change, and human activities, such as clearing forests in order to plant farm fields.