Bachelor of Biology
A biome is a region of the world with a unique set of plants and animals that have adapted to that region’s climate and other environmental factors.
The climate, especially the temperature and the amount of annual precipitation (rain or snow) are decisive, especially for plant life; and it is the plants that give the characteristic physiognomy of the different biomes. In this way, a forest, a jungle or a meadow are almost completely defined by the plant community. However, only plants do not make a biome, there will be a multitude of animals and other organisms adapted to living in a forest, in a jungle or in a prairie. All this local biota makes up the biome, but plants give it its characteristic shape.
From this definition it is clear that biomes are closely related to climatic zones, and their limits often coincide with the limits of these areas. Like all natural limits, the border between two biomes is not a defined line, but the typical plant formations of the two biomes are intermingled on the sides of the limit, and thus we have a more or less extensive transition zone between two biomes that is called ecotone.
Biomes sometimes occupy large geographic areas that have similar climatic and ecological characteristics, but are not completely homogeneous, and different ecosystems often appear within them. The diversity of the world’s biomes is one of the reasons why the biodiversity of our planet is so great.
What are the types of biomes that exist?
There are many different types of biomes in the world, and the number and names can vary according to the classification system used. However, we have seen that the “identity” of the biomes, the most identifying features of each one, are given by the type of vegetation that grows in the region. In this way, some of the most common biomes include:
forests: Forests are regions covered mainly by trees or shrubs. Sometimes there are one or two dominant tree species, and forests made up of tree species can be recognized (such as the beech forests of Europe, the pine forests of North America, or the beech forests of southern of South America) or, there may be mixed forests, with various species. The distinctive feature of a forest is that it is an environment clearly dominated by woody species (trees or shrubs). Forests can grow in temperate or warm regions, and depending on the amount of rainfall, they are differentiated into dry and humid forests. The more precipitation there is, the growth of the vegetation becomes more and more exuberant, for this reason, the most humid areas of the planet are dominated by extensive forests, where the vegetation is so dense that it is difficult to traverse through it. These forests are known as jungles. The boundary between a forest and a jungle is very diffuse, and to avoid confusion they are sometimes called rainy forests. On the contrary, as rainfall decreases, the forest loses its exuberance, and is frequently dominated by thorny shrubs; These are the dry forests. It usually happens in these dry forests that one season of the year is quite rainy, so we speak of a dry forest with a wet season.
In summary, forests are a set of biomes that have in common that they are dominated by trees, and sometimes cover extensive regions. They develop in temperate and warm climates where there is an average annual precipitation (amount of rain that falls in a year) of around 1000 mm. In temperate or warm zones with rainfall greater than 2000mm, rain forests or jungles develop, while dry forests grow below 1000mm.
When rainfall is insufficient to allow the growth of forests (still dry) some environments dominated by grasses, with few trees. These biomes are called bed sheets, if they occur in a warm climate (such as the great African savannah, in central Africa, the Venezuelan plains, the Brazilian cerrado, or the north of the Chaco ecoregion, in Argentina and Paraguay). It is common for savannahs to border jungle areas and desert or semi-desert areas.
If these grassland environments develop in temperate climates, a biome known as grassland or prairie, such as the great plains of North America, the pampas in South America. Finally, in cold climates, these grasslands are dominated by hard grasses and are called steppes, like the Patagonian steppe in South America.
Below 500mm of rain per year, this amount of water is too little to allow the development of vegetation, and in these arid regions, the deserts. Deserts are regions with little rainfall and a large amount of sand or rock. Deserts can be hot or cold, such as the Atacama desert in South America, the deserts of northern Mexico, or the Sahara desert in Africa. A desert is not an uninhabited region: the image of deserts as immense regions of sand and oases is a characteristic of the deserts of Africa and Asia, which, moreover, are hyper-arid (that is, it rains practically nothing, and they can spend years or decades without rain). Most deserts in the Americas are not of this type, and are characterized by some form of plant life, often low shrubs, cacti, and some dry-adapted grasses. Again, the boundary between a desert and a savannah, a dry forest or a steppe is very diffuse and difficult to determine, and extensive areas of ecotone may exist.
In the polar regions a biome known as tundra, in which there are no trees and the ground is covered with small plants and other organisms such as lichens, adapted to extreme cold. The tundra floor is covered with snow for many months of the year, and it is also common for the ground to freeze, and blocks of ice form underground. This frozen ground is called permafrost. Tundra is most common in the polar regions of the Northern Hemisphere; while in the southern hemisphere it is found in some regions of Antarctica and the extreme south of Argentina and Chile.