What Are the Earth's 7 Major Biomes?

 by Alice Collins

The Earth is home to an incredible variety of different environments and species, however it is often classified as having 7 major biomes (which are classified by their vegetation, soil, climate and wildlife). These are: Marine, Tropical Rainforest, Grassland, Desert, Temperate deciduous forest, Tundra and Taiga. The largest biome of them all is the ‘Marine biome’ which is estimated to cover over 75% of the earth’s surface. Included in this biome are both saltwater and freshwater environments which are both home to an enormous variety of species,yet an estimated 91% of species are still undiscovered.

Perhaps one of the most well known biomes is the Tropical Rainforest which can be found between the Tropic of Cancer (23.5°N) and the Tropic of Capricorn (23.5°S) in Central and Southern America,Western and Central Africa, Western India, Southeast Asia and parts of Australia. Tropical rainforests have the highest levels of biodiversity of all of the terrestrial biomes, with estimates of between 3-50 million species found living within them.

The grassland biome is characterised by having hot summers and cold winters. Around the world Grasslands can be found in Africa, South America, Eurasia and North America and are home to the ‘big 5’ which include lions, leopards, elephants, rhinos and buffalo, alongside many other animal and plant species.

The Desert biome is characterised by places which receive low and irregular patterns of rainfall (no more than 25cm annually) and therefore are extremely ‘arid’, as well as places which have extreme temperature fluctuations. For instance, in the Sahara desert average day temperatures range between  38-40°C, however at night average temperatures drop to around -3.9 C. However, deserts are not just hot, sandy environments and actually include cold, snowy environments such as the Arctic and Antarctic polar deserts, which despite the visual differences have very similar characteristics. This extreme variation in temperature along with the lack of rainfall makes the Desert biome an extremely harsh environment so the animals which live there are highly adapted.

The temperate deciduous forest biome  differentiates itself from the tropical rainforest by having 4 distinct seasons (summer, autumn, winter and spring) as well as a lower temperature and amount of rainfall. They are found between 40-60° north or south of the equator in a large variety of locations such as Eastern USA, Canada, Europe, Russia, China and Japan and are home to species such as deer, badgers, bears and wolves.

The tundra biome is found  primarily in Alaska, Canada, Russia, Greenland and Iceland and is characterised by having extremely low temperatures, permafrost underlying much of the ground surface and a short growing season. Consequently, tundra biomes are often  and have a simple vegetation structure consisting mainly of shrubs (and a lack of trees) due to the short photoperiod which impedes plant growth.Despite the harsh environment, particular animals thrive in the Tundra biome such as Arctic Hares, Polar bears and Snowy Owls as a result of their specific adaptations.

The final biome is the Taiga Biome which is characterised by having coniferous forest, within subarctic regions, and is often referred to as ‘Boreal Forest’. Subarctic refers to areas in the Northern Hemisphere which lie just outside of the Arctic Circle. Some examples of species which live in the Taiga Biome are Caribou, Great Grey Owls and Beavers.