A natural community is an interactive assemblage of organisms, their physical environment, and the natural processes that affect them. Environmental factors such as soil type, bedrock type, moisture level, slope, slope aspect, climate, and the natural disturbance regime play a key role in determining a species' ability to survive there. The organisms within a natural community include: plants, animals, fungus, and microorganisms. Natural communities occur in patterns throughout the earth and range in size from thousands of acres, such as a Northern Hardwood Forest, to less than one acre, such as a seep. Natural communities change over geological and evolutionary time, and are not static.
Natural communities classification is used as a management tool. By grouping complex systems into categories, people are able to process information about those systems which may otherwise prove difficult. Ecologists categorize complex natural systems to better understand spatial patterns in nature.