Biosphere: Types of Ecosystems, Global Climatic Change, Working of a Greenhouse

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Types of Ecosystems

On this basis of habitats, ecosystem can broadly be divided as:

Terrestrial Ecosystems

The terrestrial ecosystems cover the entire 29% of the land area found on the earth surface. They are the major source of food and raw material for human beings. Here, the plant and animal communities are more diversified than aquatic ecosystems. Land organisms have a greater range of tolerance than the aquatic ecosystem. As far as productivity is concerned, terrestrial ecosystems are more productive than aquatic ecosystem. There are variations in the terrestrial ecosystems in terms of physical conditions and their response to biotic communities. Therefore, the terrestrial ecosystems are further sub-divided into various sub-types. Major sub-types are upland or mountain ecosystem, low land ecosystem, and desert ecosystem etc.

Aquatic Ecosystem

This ecosystem refers to the 71% of the water present on the earth surface in various forms. Aquatic ecosystem can be further divided into various sub-types. They are fresh water, estuarine, and marine. The variations within the various types of aquatic ecosystem are mainly related to abiotic factors. The limiting factors in aquatic ecosystems are the depth up to which sunlight can penetrate the availability of nutrients and the concentration of dissolved oxygen. It is found that estuarine ecosystems are the most productive of aquatic ecosystems. In marine ecosystems, shallow continental shelves are more productive than open oceans.

Image of Image of types of ecosystems

Image of Image of Types of Ecosystems

Global Climatic Change

The earth has a unique mechanism for stabilizing and controlling the global climate. These mechanisms are as follows:

  • The plants and animals balance carbon dioxide level of the atmosphere which in twin acts as global thermostat. It means these elements control the temperature balance within optimum limits.

  • The water bodies play important role in regulating global climate.

In recent years, the rapid growth of human population, the rate at which we consume the earth’s resources, extravagant lifestyles etc. lead to substantial increase in the carbon level of atmosphere which has accelerated the process of climatic change. Let us discuss some of these processes affecting the climatic change.

Greenhouse Effects and Global Warming

Global warming refers to a gradual rise of atmospheric temperature and consequent changes in the radiation balance mainly due to human action leading to climatic change at different levels – local, regional and global. As per recent estimates, it has been found that the surface air temperature over the past 100 years has increased by about 0.5oC to 0.7oC. This is due to the greenhouse effect.

Working of a Greenhouse

  • In cold countries, a greenhouse is meant for plants, where total heat, especially during winter season, is not sufficient to support plant growth. The transparent walls and roof of the greenhouse are such that these allow the visible sunlight to enter but prevent the long wave radiations to go out. Thus, the sunlight is absorbed by the soil and structure of the greenhouse. It is then re-emitted as heat which cannot pass through the glass. The amount of energy in the greenhouse thus increases until its temperature is high enough for the slight leakage of heat through the glass to take away as much energy as gets in as sunlight. Subsequently walls and roof re-emit absorbed radiation into the house. Thus, during the day time, infra-red radiation passes into the greenhouse and warm the atmosphere and the ground on which the greenhouse stands. Coating of glass with a non-heat radiation film transparent to sunlight further maximizes heating effect of the radiation.

  • Therefore, if our earth has become a greenhouse, then there are certain gases which act like the glass panels of a greenhouse allowing the sun’s rays to pass through but preventing the heat from escaping into the outer space and there by warming the atmosphere. This is happening due to deforestation and industrialization. These gases are carbon dioxide (CO2), methane (CH4) nitrous oxides (NOx) and chlorofluorocarbon (CFC) and hence known as greenhouse gases. Out of these four gases, carbon dioxide contributes about 55%, chlorofluorocarbon contributes about 24%, methane (about 15%) and nitrous oxide (about 6%) towards heating of the atmosphere.

  • Burning of fossil fuels and firewoods, large fleet of automobiles and number of factories emit carbon dioxides. Growing paddies, livestock, waste dumps and coal mining are the major source of methane. The use of aerosols as coolants in refrigerators and air conditioning devices release chlorofluorocarbons into the atmosphere. Nitrous oxide is mainly emitted from chemical industries, and due to deforestation and certain agricultural practices.

  • Construction of greenhouses in temperate region helps the plant protection and ecological balances whereas concentration of greenhouse gases on the earth’s atmosphere upsets the earth’s biological system.

Consequences of Greenhouse Effect

  1. It is estimated that if the present rate of increase in CO2 level continues, it will result in rise of atmospheric temperature by 2oC to 3oC by end of 21st century. This will result in receding many glaciers, melting of icecaps in the Polar Regions, and disappearance of deposits of ice on the other parts of world in large scale. A rise in sea-level of only 50-100 cm caused by global warming would flood low lying areas of the world such as Bangladesh, Maldives as well as densely populated coastal cities from Shanghai to San Francisco.

  2. Because of increased concentration of CO2 and due to much warmer tropical oceans, there may occur more cyclones and hurricanes. Early snow melt in mountains will cause more floods during monsoon. According to United Nations Environment Programme (UNEP), within about three decades, rising levels of seas will be able to and flood coastal cities like Bombay, Boston, Chittagong and Manila.

  3. The biological productivity of the ocean would also decrease due to warming of the surface layer, which in turn reduces the transport of nutrients from deeper layers to the surface by vertical circulation.

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