Biomes are major communities of living things, and they are classified according to the type of vegetation, and adaptations animals and plants have made to their environments.
There are many types of biomes, but they occur in seven basic groupings:
There are two major groupings of biomes in water:
The seventh major grouping of biomes is human cities and towns, since humans are part of nature too. The animals and plants that have survived replacement of the original habitats with human constructions have often adapted very well to their new environment.
Forest biomes include tropical and temperate forests, coniferous, deciduous or evergreen forests, and various types of woodlands. Grasslands include savannas, prairies, steppes and meadows. Deserts are always dry, but may be hot or cold.
Freshwater biomes include lakes, ponds, rivers, streams, marshes and wetlands, while marine biomes include temperate and tropical seas and oceans, tidal shorelines and coral reefs. Different biotic communities are found at different depths of the sea and include the euphotic (sunlit), disphotic (dimly lit) and aphotic (dark) zones.
The land and aquatic biomes have all been affected to some degree by human activities and overpopulation, and some have been devastated or destroyed altogether. To limit further damage, it is important to consider an entire biome when thinking about conservation, rather than trying to conserve a single species, since everything is interconnected, and each biome is a repository for the earth's biodiversity.
Forests, for example, contain millions of species in a diverse range of biotic communities. They are particularly important because they act as a buffer to climate changes, and because they produce oxygen through photosynthesis. The massive amount of logging and forest depletion over the last few decades has reduced the forest cover of the planet; in the case of tropical forests by over fifty percent.
Aquatic biomes are equally, if not even more important, since water is the basis of all life, and like forests the seas and fresh water masses contain countless species and biotic communities. The oceans particularly also have a great effect on the climate because they act as heat sinks, and because they contain plankton which carry out most of the photosynthesis on Earth, and thus supplying most of our oxygen. Almost all fresh and salt water masses have suffered from pollution, especially from agricultural run-offs and industrial dumping of chemicals into them.
Human habitation biomes include cities, towns and villages, and have replaced many habitats, and displaced or destroyed many communities. Many animals and plants stay or move into the cities when their habitats are destroyed, a process called synanthropization. Members of the city biome include mice, sparrows, starlings, spiders, cockroaches, dogs, cats, and of course, people.
The only biomes currently not in danger of being damaged, polluted, or depleted are the biomes of human habitations.