Biomes are large areas of the Earth with similar abiotic (climatic and geographic) and biotic (living) factors.

Think of biomes as very large ecosystems. There are some disagreements within the scientific world as to how the world is divided into biomes. On a macro level, there are generally divisions into five or six major biomes. On a micro level, some scientists have developed systems which divide the earth into hundreds of biomes. For our purposes, a five-part division is utilized, as follows:

AQUATIC BIOME
Broken down into two basic regions, freshwater and marine.

-Freshwater - Salt concentration is usually less than 1%. The different types of freshwater regions are:

--Ponds and Lakes - Generally isolated bodies of still water.

--Streams and Rivers - Bodies of flowing water which moving in one direction.

--Wetlands - Marshes, swamps, and bogs


-Marine
Covers about 75% of the Earth’s surface. The different types of marine regions are:

--Oceans - The largest of all the ecosystems. Separated into zones based upon depth as follows (from shallowest to deepest): intertidal, pelagic, abyssal, and benthic.

--Coral Reefs - Found in warm, shallow waters, they act as barriers along the shores of continents, islands and atolls.

--Estuaries - Formed in areas where freshwater meets salt water. The resultant intermediate salt concentrations in estuaries are what make them a unique ecosystem.


DESERT BIOME
Defined by precipitation levels, with rainfall less than 50 cm/ year. The different types of desert are:

-Hot and Dry - Examples are the Chihuahuan, Sonoran, Mojave and Great Basin in North America, the Southern Asian realm, Neotropical (South and Central America), Ethiopian (Africa) and Australian.

-Semiarid - Examples are the sagebrush deserts of Utah, Montana and Great Basin, and the Nearctic realm of North America, Newfoundland, Greenland, Russia, Europe and northern Asia.

-Coastal - Occur in moderately cooler areas with more seasonal rainfall than other deserts. An example is the Atacama Desert in Chile.

-Cold - Experience very cold winters with high overall rain and snowfall. Winters are much longer than the relatively short, moderately warm summers. Cold deserts are found in the Antarctic and Greenland.


FOREST BIOME
Dominated by trees and other woody vegetation. The different types of forest regions are:

-Tropical - Occur in the equatorial regions of the planet. They have very distinct seasons - rainy and dry, with no winter at all. Days and nights are 12 hours in length.

-Temperate - Found in eastern North America, northeastern Asia, and western and central Europe. Seasons are well-defined and there is a distinct winter period. The climate is considered moderate, with four to six frost free months and a growing season of 140-200 days.

-Boreal (taiga) - The largest of the terrestrial biomes, taiga can be found in Eurasia and North America. Two-thirds of boreal forests are found in Siberia, with the other third spread throughout Scandinavia, Alaska and Canada. Summers are short and moist, and winters are long, cold and dry. Growing seasons are generally no more than 130 days.


GRASSLAND BIOME
Dominated by grasses. Different types of grasslands include:

-Tropical (savannas) - Cover large areas of South America, Australia, India, and almost half of Africa. Warm or hot climate areas with rainfall ranging from 20-50 inches per year. Tropical grasslands are dependent, interestingly enough, on long periods of drought followed by thunderstorms resulting in a series of fires which keep the grasslands from converting to tropical forests.

-Temperate - Experience less rainfall than tropical grasslands, and temperatures vary more from summer to winter. Examples of temperate grasslands are the veldts of South Africa, the puszta of Hungary, the pampas of Argentina and Uruguay, the steppes of the former USSR, and the plains and prairies of central North America.


TUNDRA BIOME
Noted for its extremely cold climate, lack of precipitation, poor soil nutrients, and short growing/reproductive seasons. The different types of tundra regions are:

-Arctic- Located in the northern hemisphere, arctic tundra has cold, desert-like conditions most of the year, with temperatures ranging from -30F to 54F. The growing season is no more than 60 days per year.

-Alpine - Found throughout the world at mountainous altitudes. Temperatures usually drop below freezing at night. The growing season is about 180 days.


Why Are Biomes Important?
Conservation of biomes should be a matter of utmost importance for all citizens of the planet. For example, water is the basis of all life, making preservation of the aquatic biome a priority. Water is needed for drinking, crop irrigation, maintaining a constant atmospheric temperature, providing living and breeding environments for countless species, and supplying, through the photosynthetic processes of plankton, most of the oxygen needed to support animal life on the planet.

As noted previously, many scientists disagree on how to divide the earth into biomes. They agree, however, on the necessity of preserving all biomes. Each ecosystem is unique in and of itself and each serves as an important habitat for different lifeforms. And, as in all life, each part is tied to every other part. Destroy one, and the rest are sure to follow.