Biomes

Biomes are comprised of the major, regionally distinct biotic communities. They are the largest ecosystem units, delineated at a global scale. Biomes are not distinguished by the taxonomic identities of the organisms they contain, but rather on the basis of the life forms of these organisms, their structure, life history, and responses to environmental change. Although specific plant and animal species differ among continents, the same biomes with similar structure, seasonality, productivity, niches and uses by humans exist in different regions. For example, northern conifer forests exist in North America and Asia, and tropical rain forests are found in Africa, Central and South America, and south and southeast Asia. Biomes are usually associated with their climax community vegetation; however, they encompass successional and subclimax community species and animal species, as well as soils. Generally, they are not divided by sharp boundaries; rather, adjacent biomes grade into each other, interact, and function as interdependent parts of the biosphere as a whole.

Classifying the earth into major biome types is a useful approach that allows the development of a common framework and mapping system for these large-scale systems. This facilitates communication among scientists, comparative analyses, and the development of resource and environmental management strategies. However, it is important to note that maps of biomes are human constructions and not usually drawn to reflect a current reality. Rather, they tend to depict an imagined world devoid of human impacts and influence, and one in which processes of succession have reached a climax end-state.

Biomes are delineated by a combination of ecological gradients, including temperature, precipitation, altitude/depth, latitude, longitude, proximity to various features such as oceans and mountains, soil type, salinity, and range of tidal activity. These factors determine the assemblage of animals and plants that live in the biome, and their biological productivity.