In biology, the variety of plants, animals and fungi that first colonize a barren habitat is known as a pioneer community. These organisms are the first in the order of biological succession for that habitat and are followed first by seral communities and then by climax communities. Generally, some drastic change to the habitat occurs, destroying the previous biological community, before the pioneer community organisms enter.
On a large scale, pioneer communities arise after natural disasters, such as wildfires, major flooding or volcanoes, wipe out the previous community. However, there are small-scale examples as well. For instance, when a boulder becomes dislodged from a hillside, it may present a formerly buried surface to its environment. Any lichens or moss, as well as the animals that interact with them, constitute a pioneer community of that boulder.
The organisms in pioneer communities are specialized to take advantage of the newly open environment, They tend to include such organisms as grasses, which have greater access to sunlight after trees have been removed through fire or other events. They tend to grow and reproduce quickly. Barring another disaster, they are eventually overtaken by seral community organisms that grow more slowly but out-compete the pioneer organisms over time.