A pioneer organism, also known as a disaster taxon, is an organism that moves into an area that was empty before, or one that helps restore life in places where most living things were destroyed by a natural disaster, mass extinction, or another major event that killed most of the life in the area. A group of these organisms that can reproduce together and continue to grow in number are called a pioneer species.

Natural disaster

After a natural disaster, pioneer organisms often include lichens and algae. Mosses usually grow after lichens but are not considered pioneer organisms. These pioneer organisms may prefer certain temperature conditions. Lichens tend to live in areas with more rain, while algae and mosses prefer areas with more moisture.

Pioneer organisms change their environment to create conditions that support other living things. In some cases, other organisms can also act as pioneer organisms. Birds are often the first to live on newly formed islands, and seeds, such as those from coconuts, may be the first to grow on empty soil.

Extinction event

Because the fossil record is not very detailed, scientists often identify pioneer organisms as those that lived close in time to an extinction event, such as hundreds, thousands, or even a million years before or after it. For example, after the Permian–Triassic extinction event 252 million years ago, Lystrosaurus, an animal with tusks related to mammals, was considered a disaster taxon.