Biomes Of The World – An Introduction
A biome is a specific geographic region on our planet, which supports similar types of vegetation and wildlife, and has similar climatic conditions. Major ecological community types like tropical rain forests, deserts and grasslands can be called as biomes, and they are occupied by plants and animals specifically suited to their survival in that region. This classification allows us to study and talk about similar geographic zones even when they are geographically spread apart across the globe.
The plants and animals living within a biome are part of a complex and interconnected community. These animals and plants adopt special adaptations to survive in the specific conditions that are native to their biome like the climate, temperature, type of soil, the amount of water and light. Fundamentally all the Earth’s biomes can be classified into terrestrial biomes and aquatic biomes. The terrestrial or land biomes cover about 29% of the Earth’s surface and the rest is comprised of aquatic biomes.
The main terrestrial biomes of the world. [Source: Ville Koistinen]
The biome classifications are made for convenience
The classification of geographical regions into biomes can be done both in a broader or a precise manner, based on the need and convenience of the person who is making the observation. In a broader sense we can classify the earth into forest, grasslands, deserts, tundra, freshwater and marine biomes, but when we observe closely we can see that each of these broader biomes can be further divided into more precise classifications.
For example, the broader biome forest can be sub divided – based on their climatic conditions and the plant life they support - into biomes like tropical forests, temperate forests, boreal forests etc. Scientists use a range of classification schemes like Holdridge Scheme, Whittaker's biome-type classification scheme, The Heinrich Walter classification scheme, The Bailey system etc., to divide earth into different ecological zones.
In many cases it is difficult to define precise geographical boundaries for a biome, as various biomes intervene and overlap with each other to form transition zones or ecotones, where the communities meet and integrate. Marshlands that exist between a lake and the surrounding terrestrial biome can be seen as an example for this transition zone. These overlapping zones are inhabited by species common to both the biomes and entirely different varieties of species specially adapted to the unique living conditions of transition zones.
The difference between a biome and an ecosystem
A biome differs from both ecosystems and habitats. A habitat is the ecological area that is inhabited by a specific organism. It is the place where a particular species of animal, plant or any other organism lives and thrives. An ecosystem is made up of all the living things in an area and their interactions, both between themselves and their surrounding non-living environment. An ecosystem is a complex functional system, whereas a biome is a specific geographical region defined by the species that it populates. A biome can contain multiple types of ecosystems and a variety of habitats.
Terrestrial Biomes or Land Biomes
Some of the major land biomes on our planet are:
Tropical Rain Forest
Tropical rain forests, which are located, near the equator in Central and South America and Africa, have no dry season and they are warm and wet all year around. They receive an average monthly precipitation of at least 60 mm, which is the highest of all biomes. The life in this biome is so abundant that at least half of the world’s plant and animal species make tropical rain forests their home.
The vegetation here mainly consists of tall broadleaf trees, vines and evergreen plants, which create a dense canopy over the forest. The vegetation is so dense that the amount of sunlight that reaches the forest floor is very limited.
Temperate Deciduous Forests
The temperate forests flourish in moderate climates and they have distinct seasons. Located in Eastern United States, East Asia and Europe these forests are populated by deciduous trees like maple, oak and beech, which shed their leaves in autumn.
These forests have four distinct seasons and the plants and animals that live here are adapted to survive the cold winters and warm summers.
Boreal forests are also known as snow forests or Taiga and are located across northern Europe, Siberia, United States and Canada. This biome consists mainly of coniferous trees like pine, spruces and firs, which are capable of enduring long, cold winters and short summers. These conical shaped trees have distinctive needle shaped leaves, which allow the trees to minimize water loss due to transpiration, and have shallow roots that help them in surviving in the thin soil of boreal forests.
The animals in the taiga survive the harsh winters by either migrating to warm locations or by undergoing hibernation.
Temperate grasslands are vast continuous areas of mostly grass covered terrain with cool winters and hot summers and they receive an average yearly rainfall of about 900 mm. The lack of abundance in rain restricts the growth of large trees in this biome. The grasses found in this biome varies in height from 7 feet to 20 -25 cm. Grasslands are found on all continents on our planet, except Antarctica.
The prairies of North America, the steppes of Central Eurasia, the pampas of South America are some of the examples for temperate grasslands. Grasslands support a rich variety of grazing and burrowing animals. The rich soil of the grassland and the availability of grass make this biome an excellent choice for agriculture and cattle raising.
Savannas – also known as tropical grasslands – are vast grasslands, scattered with trees and shrubs, and they remain warm throughout the year. They are found mainly in Africa and they have long dry seasons followed by short rainy periods. They are home to large herds of grazing animals like zebra and giraffe, and for the large predators like lions and hyenas. The trees are specially adapted to prevent water loss, which contributes to their survival in the harsh dry conditions.
These are vast frozen treeless plains that support short grass, lichens and moss like plants. The extreme cold climate combined with the permafrost - a thick layer of frozen soil, rock or sediment that lies just below the surface – that prevents the roots of trees from penetrating the soil, makes the tundra almost devoid of trees. The two types of tundra are Arctic tundra - occurring north of the Arctic Circle and south of the Antarctic Circle - and Alpine tundra - occurring at high altitudes above the tree line on mountains.
Temperatures in this biome can drop as low as -30° F during winter. The Arctic tundra supports a rich variety of plant and animal life. Polar bears, lemmings, caribous are some of the common animals found in this biome and all these animals are specially adapted to survive the harsh coldness of this terrain.
Deserts are barren tracts of lands that receive less than 25 cm of rainfall on an average each year. They are one of the harshest of biomes and have extreme temperature variations during day and night. Deserts are found on all the continents except Europe.
Only a few plants and animals specially adapted to survive the harsh conditions of desert like extreme temperatures and scarcity of water thrive in this biome. Adaptations like long and wide-spreading roots for absorbing moisture from large areas, short and spiny leaves to reduce water loss, leaves and stems with special tissues for storing water can be found on desert plants like cacti.
As water covers almost 71% of our planet, the aquatic biome can be considered as the largest biome on Earth. The aquatic biome can be divided into two regions, marine and freshwater biomes.
The marine biomes consists of the oceans of the world along with coral reefs and estuaries. This biome supports a wide range of life spread across a variety of habitats like beaches to the darkest depths of the oceans and they are all adapted to the high levels of salt found in the waters of the marine biome. Marine biomes play a major influence on the terrestrial climate of Earth and the marine algae found in this biome supplies most of the world’s oxygen.
The ocean is divided into three vertical zones based on the depth and each of these zones have living beings specially adapted to the temperature and availability of light in the zone.
The warm shallow waters of a coral reef is home to a wide variety of life. Coral reefs form at about 45 m deep and they occur in a variety of forms as fringing reefs, barrier reefs and atolls.
The lakes, ponds, rivers, streams and wetlands make up the freshwater biome. The concentration of salt in the waters of this biome is very low. Plants and algae are the main suppliers of oxygen in the freshwater biomes through photosynthesis and they also provide food for animals living in this biome.
Importance of conserving Biomes
In the history of our planet, biomes have undergone changes and movements due to factors like climatic variations. In the recent history, we human beings are significantly causing alterations across almost all the biomes, and it is a cause of concern for the future of our planet. The massive exploitation of natural resources and the grave amount of pollution resulting from human activities are causing terrible changes in many of these ecological communities.
Since our survival – and the survival of all the other life forms on our planet – depends heavily on preserving the healthy balance of Earth’s natural biomes, it is the responsibility of each human being to take part in spreading the message of ecological conservation. Students can play a major role in educating others about the importance of ecological diversity, the consequences caused by human greed on the nature and methods on how we can preserve the biomes and our planet.