Biome

A biome, or "major life zone," is a large, geographic region of the earth's surface with distinctive plant and animal communities. There are both terrestrial biomes, such as grasslands and tropical rain forests, and aquatic biomes, such as estuaries.

A biome is also defined as an extensive ecosystem(ecological unit of living organisms and their biotic environment)spread over a wide geographic area, or as a grouping of many ecosystems that share similar environmental features and communities (organisms living together in a certain area). Collectively, biomes comprise the biosphere, which is the thin area of the earth's surface where all organisms live.

Biomes are a dynamic, rather than static entity, and have changed througout geological history. More recently, biomes have been impacted by human activity. Some of these impacts, such as deforestation, have caused significant environmental challenges. It is important that people understand and manage their local, regional, and global impacts, such that future generations can enjoy the wonder of creation that was intended by God. In biblical terms, this is referred to as the "Third Blessing," the role of humans to care for all of creation, both the abiotic and biotic elements.

Biomes represent a superficial and somewhat arbitrary classification of ecosystems. Biologists are not unanimous in their classification of biomes, nor in the number of biomes. Some may classify one region as a particular biome, while others classify the same region as an ecotone (the area where one biome overlaps another) or as part of a different biome. Some biologists recognize particular sub-regions also as biomes, that another scientist may identify only as one biome. In some cases, the word "biome type" is utilized, whereby several biomes are combined into this biome type. For example, the coniferous forest biome type includes the coniferous forest biomes of Europe, Asia and North America.

In general, most biologiest agree on the existence of six major land biomes: tundra, taiga, temperate deciduous forest, grasslands, deserts, and tropical rain forets, and two major water biomes of marine and fresh water. Others add such biomes as temperate rain forests, chaparral, and coniferous forests, among others, and further delineate aquatic biomes into ocean, estuaries, and so forth.

Classification of biomes

It has long been noted that regions of the earth with similar climate tend to have similar plants and animals. For example, regions with long, dry periods with little rainfall (deserts) contain plants and animals adapted to these dry conditions. Such plants may flower and seed during the rare priods of rainfall, and tend to be tough, woody shrubs or succulents.

Biomes are most strongly defined by global distributions of vegetation types, which are influenced by global climate, soils, disturbance, and other physical environment factors. In turn, climate and soil depend partly on latitude, altitude and terrain factors. A biome is composed of the climax vegetation and all associated subclimax, or degraded, vegetation, fauna and soils, but can often be identified by the climax vegetation type.

Biomes represent a useful, albeit crude way of classifying ecolsystems. Classification of biomes vary and no one system dominates biogregraphical studies.

A fundamental classification of biomes is into:

1. Terrestrial (or continental) biomes and
2. Aquatic biomes.

Four specific classification methods are discussed below.

Typical Classification Scheme

The following is a common classification of biomes, that one might find in introductory textbooks on the topic:

Terrestrial Biomes

==== Polar Biomes ==== (Artic and Antartic regions) ==== Tundra ==== (Northern North America, Europe and Asia) ==== Coniferous Forest ==== (Northern hemisphere, south of Tundra)

• Taiga (Northernmost band)
• Coniferous belt ("Spruce-moose" belt)
• Southern pine forests

==== Deciduous forest ==== (Eastern United States, much of Europe, parts of Asia, South America, Africa and Australia) ====Grassland==== (About one-fourth of land surface of the earth) ====Desert==== (Extensive areas found on all continents)

Rain forests

• Tropical rain forest (Found near equator)
• Temperate rain forest (Small relative to tropical rain forest)

Aquatic Biomes

Marine Biome

• Ocean
  • Benthic zone
  • Pelagic zone
    • Neratic Zone
    • Oceanic zone
• Intertidal zone
• Estuaries

Freshwater Biome

• Lakes and Ponds
• Rivers and streams

With the excepton of deserts and the polar biomes, terrestrial biome are generally named for the dominent type of vegetation (climax vegetation), such as deciuous forest and coniferous forests. The subcategories of the Marine Biome (Ocean, Intertidal Zones, and Estuaries) are also considered biomes.

Biomes are often given local names. For example, a Temperate grassland, savanna, and shrubland biome is known commonly as steppe in central Asia, savanna or veld in southern Africa, prairie in North America, pampa in South America and outback in Australia.

Latitude Classification

Latitude is a major climate-influencing factor determining biomes. There is a good correlation between the distribution of climates with latitude, and homogenous vegetation bands. Another major factor is humidity. This can be illustrated by the fact that biodiversity increases away from the poles towards the equator, and increases with humidity.

The most widely used classification of biomes is related to latitude (or temperature zoning) and humidity :

Arctic or Subarctic area

• humid type : Tundra

Subarctic and Boreal area

• humid type: taiga or boreal forest

Temperate cold

• humid type : Temperate broadleaf and mixed forests, Temperate coniferous forests

Temperate warm or sub-tropical

• humid: subtropical moist broadleaf forest
• semi-humid: Subtropical dry broadleaf forests, Subtropical coniferous forests
• semi-arid: Mediterranean forests, woodlands, and shrub, Temperate grasslands, savannas, and shrublands
• Arid: Temperate deserts and xeric shrublands

Tropical

• humid area: tropical moist broadleaf forest (tropical rainforest)
• semi-humid area: tropical dry broadleaf forest, tropical coniferous forest
• Semi-arid area: tropical grasslands, savannas, and shrublands
• Arid area: deserts and xeric shrublands

Aquatic

• continental shelf
• littoral
• riparian
• pond

• coral reef
• kelp forest
• pack ice
• hydrothermal vents
• cold seeps
• benthic zone
• pelagic zone

Altitude and Latitude Classification

Another system of classification takes into account altitude and humidity, ignoring temperature as a factor. This classification is used to define the Global 200 list of ecoregions identified by the World Wildlife Fund (WWF) as priorities for conservation.

This classification gives the following terrestrial biomes :

• Tundra (arctic, humid)
• Boreal forests/taiga (subarctic, humid)
• Temperate coniferous forests (temperate cold, humid to semi-humid)
• Temperate broadleaf and mixed forests (temperate, humid)
• Temperate grasslands, savannas, and shrublands (temperate, semi-arid)
• Mediterranean forests, woodlands, and shrub (temperate warm, semi-humid to semi-arid with winter rainfall)
• Tropical and subtropical coniferous forests (tropical and subtropical, semi-humid)
• Tropical and subtropical moist broadleaf forests (tropical and subtropical, humid)
• Tropical and subtropical dry broadleaf forests (tropical and subtropical, semi-humid)
• Tropical and subtropical grasslands, savannas, and shrublands (tropical and subtropical, semi-arid)
• Deserts and xeric shrublands (temperate to tropical, arid)
• Mangrove (subtropical and tropical, salt and brackish water inundated)
• Flooded grasslands and savannas (temperate to tropical, fresh water inundated)
• Montane grasslands and shrublands (temperate to tropical, high altitude)

Climate Classification

Climate, simply defined, is te long-term weather of an area. World terrestrial biomes are controlled by climate, and in particular by air temperature and precipitation. The Koppen Climate Classification System is the most widely employed system for classifying the world's climates. This system recognizes five major climate types, based on the annual and monthly averages of temperature and precipitation. For example, Moist Tropical Climates are known for their high temperatures year round and for the large amount of rain year round. Further subgroups distinguish specific seasonal characteristics of terperature and precipition. The Koppen symbol is presente by a capital letter and small letter system. Using the Koppen Classification system, terrestrial biomes such as Tropical Rainforest (Af), Tropical Rainforest, evergreen forest (Am), Savannah (Aw), etc.

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