Ecosystem – Geography – UGC NET – Notes

Introduction

• The ecosystem is the structural and functional unit of ecology where the living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a chain of interaction between organisms and their environment. The term “Ecosystem” was first coined by A.G.Tansley, an English botanist, in 1935.
• A unit that includes all the organisms (biological factor) in a given area interacting with the environmental (physical factors) so that a flow of energy leads to a clearly defined trophic (nutrient requiring) structure, biotic diversity, and material cycles (i.e., exchange of materials between living and non-living sectors). Thus ecosystem is a term applied to a particular relationship between living organism and their environment.

Types of Ecosystem

An ecosystem can be as small as an oasis in a desert, or as big as an ocean, spanning thousands of miles. There are two types of ecosystem:

1. Terrestrial Ecosystem
2. Aquatic Ecosystem

Terrestrial Ecosystems

Terrestrial ecosystems are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:

• Forest Ecosystems
• Grassland Ecosystems
• Tundra Ecosystems
• Desert Ecosystem
• Mountain

Forest Ecosystem:

• A forest ecosystem consists of several plants, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests help in maintaining the temperature of the earth and are the major carbon sink.
• The forest ecosystem is most important for humankind. The tropical forests on the earth’s surface comprise a precious ecosystem of varying habitats, species and individual groups of plants interacting with each other. The world has witnessed a major erosion of the forest ecosystem due to deforestation in tropical Asia, Africa and Latin America.
• It is estimated that as many as 25% of the species on the earth in the mid 1980s would disappear by 2025 if the current deforestation rate continues. The forest ecosystem is a source of continued biological productivity and important for climatic stability. More than 500 million people inhabit in these areas.
• The forests contribute to food security, fibre, medicine, and industrial products. But the most important contribution is in the form of genetic diversity. The closed tropical forests all over the world cover only about 7% of the earth’s land surface, but contain at least half and probably up to 90% of the world species.
• We still lack adequate knowledge of this natural wealth. Only about 10% of all the tropical species have been described. The current estimate indicates that half of all the vascular plants and vertebrate species occur in the tropical forests. There is a striking difference between the tropical and the temperate forests in terms of their diversity.
• Miller and Barber have pointed out that species loss through extinction is not a new phenomena in nature. The 10 million species on the earth today are the survivors of the safe population that evolution has produced since life began.
• In the history of the planet, there has been much mass extinction. The last mass extinction was 65 million years ago. Since then, the global bio diversity has reoriented and is almost close to an all time high.

Grassland Ecosystem:

• In a grassland ecosystem, the vegetation is dominated by grasses and herbs. Temperate grasslands, savanna grasslands are some of the examples of grassland ecosystems.
• The grassland ecosystem occupies about 10 percent of the earth’s surface which includes tropical and temperate grassland. The abiotic components and the nutrients present in the soil and aerial environment. The producers are mainly grasses and small trees and shrubs.
• The primary consumers include cows, buffaloes, sheep, goats, deer, rabbits and other animals, while secondary consumers are animals like foxes, jackals, snakes, frogs, lizards and birds etc.

Tundra Ecosystem:

• Tundra ecosystems are devoid of trees and are found in cold climates or where rainfall is scarce. These are covered with snow for most of the year. The ecosystem in the Arctic or mountain tops is tundra type.

Desert Ecosystem:

• Deserts are found throughout the world. These are regions with very little rainfall. The days are hot and the nights are cold.
• The Indian deserts constitute 2% of the total land mass and comprise the sand desert of Western Rajasthan, the salt desert of Kutch in Gujarat and the Alpine cold desert of the Himalayas.
• They are characterised by variations in temperature, low precipitations and high velocity winds and have different types of sand dunes and unique plant and animal species. Sand dune stabilization through biomass is one of the high priority tasks.

Mountains:

• A large part of the forest area of the country and watershed region is included under this category. There are 10 types which represent major formations and biomes. These are the tropical wet evergreen, semi-evergreen, moist, and dry deciduous, subtropical evergreen, temperate, Himalayan and sub-alpine forests.
• It is estimated that these ecosystems harbour 50,000 species of plants and 72,000 animals and also a large number of unknown insects, microbes, etc.