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Chapter: 11th 12th std standard Geography earth space Higher secondary school College Notes

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Ecosystem management and conservation : Current Extinction Rates

From the most arid desert to the dripping rain forest, from the highest mountain peak to the deepest ocean trench, life occurs. Scientists estimate that between 3 and 30 million different species inhabit Earth. They vary in sizes, colors, shapes, life cycles, and inter � relationships. Even obscure organisms contribute to essential ecological processes of the biosphere.

Ecosystem management and conservation

 

From the most arid desert to the dripping rain forest, from the highest mountain peak to the deepest ocean trench, life occurs. Scientists estimate that between 3 and 30 million different species inhabit Earth. They vary in sizes, colors, shapes, life cycles, and inter - relationships. Even obscure organisms contribute to essential ecological processes of the biosphere. Think, for a moment, how remarkable, varied, abundant, and important the other living creatures are with whom we share Earth.

 

In recent times, humans have become a serious threat to all other life-forms. Rapidly expanding human population and activities, amplified by the power of technology, threaten to eliminate much of the diversity of the biosphere. Humans have become a natural force, levelling mountains, diverting rivers into new channels, and causing soil erosion on the order of 25 billion metric tons worldwide per year. Humans destroy wildlife directly by over harvesting animals and plants for food and commerce. These impacts initiate species extinction and unique and complex characteristics of the biosphere may be permanently lost. Let us learn in this lesson, about extinction in general, how to manage and preserve the biosphere.

 

Extinction: Extinction is neither a new phenomenon nor a process caused only by humans. Studies of the fossil record suggest that more than 99 percent of all species that ever existed on the Earth are now extinct. Most of those species disappeared long before humans came on the scene. The geological record shows that a number of widespread biological catastrophes have caused mass extinctions from the Earth. The best known of these occurred 65 million years ago when dinosaurs disappeared, along with at least 50 percent of existing genera and 15 percent of marine animal families. An even greater disaster occurred at about 250 million years ago when two-thirds of all marine species and nearly half of all plant and animal families died out over a period of about 10,000 years.


Current Extinction Rates

 

The rate at which species have been lost appears to have in-creased dramatically over the last one hundred years. Before humans became a major factor, extinction rates from natural causes appear to have been one species lost every five to ten years. Between 1600 and 1900 A.D., human activities seem to have been responsible for the extermination of about one species per year. During this century, especially since World War II, the rate of extinction appears to have accelerated to dozens or even hundreds of species per year. We cannot be absolutely sure of these rates because many parts of the world haven't been thoroughly explored and many species may have disappeared before they were studied and classified by biologists.

 

The main reason for the current increase in extinctions is habitat loss. Destruction of tropical forests; coral reefs, estuaries, marshes, and other biologically rich ecosystems threaten to eliminate millions of species in a human-caused mass extinction that could rival those of geologic history. By destroying habitat, humans eliminate not only prominent species, but also many not even be aware. It has been suggested that millions of species could be lost in the next few years if this destruction continues.

 

Let us now discuss, about how the growth of population and technological progress were responsible for the destruction of biological resources and extinction of very many species from the Earth.

 

As shown in the figure no. 8.1. the first population increase was about a million years ago, and the discovery of fire and the invention of tools that enabled our ancestors to be a more effective society. The second population increase corresponds to the domestication of plants and animals about ten thousand years ago. The third expansion of growth, of which we are a part, was stimulated by the scientific and industrial revolution. If the present trend continues, the world in 2100 will be more crowded, more polluted, less stable ecologically and more vulnerable to disruption. So the choices we make now determine what our lives and those of our children will be like in future.

There are three points worth making about the capacity which is fundamental to our understanding of current dilemmas in managing the Earth system.

 

1.                 We are animals, with the same basic biological limitations of birth, growth, reproduction and death of other animals, and with the same basic competitive drives towards the acquisition of material resources. In the natural animal world, co-operative behaviour occurs and is generally interpreted as behaviour most appropriate for individual survival.

 

2.                 In the human world, the competitive instinct, both at the individual level and at community and national levels, emphasizes short ' term gain, threatening long ' term survival. The consequences of over sue and abuse may be overcome through technological development and better management and levels of co ' operative behaviour in relation to the use of natural resources.

 

3.                 Human consciousness and achievements, apparently freeing us from the controls that the environment exerts over wild animals, seem to have endowed us with the idea that we are free to exploit the environment. The consequences of overuse and abuse may be over come through technological development and better management.

 

Recognizing these three points and raising awareness of the implications for each of us and our children's children are essential prerequisites for enabling us to initiate the necessary action that will generate sustainable development. Unlimited growth of population in an environment of finite resources is impossible because growth will eventually deplete the available resources and the population will collapse. To save the Earth from such an event, one should understand the relationships of our Earth system and its components. One way to help you to understand the relationships of our Earth system and its components, is to use concept maps.


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