The endangering of species
1. Why do species of animals and plants die out?
2. Do you know any examples of extinct or endangered species?
3. How does human activity affect ecosystems?
The planet Earth is always changing with habitats undergoing continual alterations and modifications. Natural changes come about gradually usually causing only a slight impact on species. However, when changes occur at an abnormally fast pace, species are not given sufficient time to adjust to new circumstances. The fast pace of environmental changes can create disastrous results like the loss of natural habitats that is the primary cause of species endangerment. The most influential forces in the process of habitat loss are human beings. Almost every region of the planet has been affected by human activity. Global changes in climate due to the release of greenhouse gases, the extinction of species in devastated and polluted habitats, degradation of coral reefs and depleting forests of the Amazon jungle are all the results of human activity. Charles Darwin wrote that the extinction of species makes up a part of the evolutionary process. A steady rate of extinction is a normal phenomenon in the course of evolution. Different species have always evolved and died out as a result of climatic changes and their inability to adapt to survive in their highly competitive environment. Yet, in the aftermath of human social and technological advance that was initiated in the 17th century, the rate of extinction rapidly accelerated because of the enormous population growth and increased resource consumption. At present, most of the world's habitats are changing much faster than most species can evolve or adapt to the transformations. The current global extinction rate is estimated at about 20,000 species per year, which translates into a loss of one species every 20 minutes. Researchers and biologists claim that we are in the middle of the greatest mass extinction episode since the disappearance of the dinosaurs 65 million years ago.
According to estimates, the Earth has already been home to 0.5 billion species during its evolutionary history. Of all the species that have ever evolved the ones that exist today constitute only 2% of the total number. The remaining 98% have either died out or evolved into new species. Scientists have classified about 2 million different species of animals, plants, insects, algae, fungi and micro-organisms that live today. It is believed that the actual number may well be over 10 million species. But the numbers are falling at alarming rates. At least 50% of all currently existing species will be either extinct or endangered by 2050 if the present trends continue. More pessimistic observers predict that perhaps as much as one-fifth of all the species that live today will have disappeared by the end of the century. Already, about 20,000 plant species and 5000 animal species around the world are defined as endangered while thousands more become extinct each year before biologists even manage to identify them. A critical situation has emerged in the Earth's largest sanctuary of species - tropical forests. They serve as home to more than 50% of all world's species and are presently under severe threat of irreversible devastation. Although tropical forests may look as though they are lush, they are in fact highly susceptible to destruction. This is because the forests are being excessively cleared and the soils in which they grow lack basic nutrients. If the current rate of loss of tropical forests does not slow down, huge quantities of plant and animal life will disappear.
The extinction and endangerment of species are a direct result of the destruction of natural habitats by human activity. As different species evolve, they usually adapt to the specific habitat or environment that best meets their survival needs. If the needs cannot be satisfied, species may face extinction, Such human activities as cutting and clearing forests, commercial exploitation - hunting, plant collecting or trade in animal parts - pollution, drainage of wetlands, urbanisation, road and dam constructions, the conversion of shrub lands into grazing fields have destroyed or severely damaged many natural habitats. Habitat fragmentation is yet another cause of species becoming endangered. The isolation and division of habitats into smaller areas reduces genetic diversity and makes species less adaptable to environmental changes. Fragmented habitats may become too small to sustain a population of species.
Overexploitation of species constitutes another significant contributor to species extinction and endangerment. The high rate at which certain species are being used puts them under a serious risk of becoming extinct. Unrestricted whaling for oil and meat at the beginning of the 20th century is an explicit example of human greed. Excessive hunting has brought many species of whales to extremely low population sizes. The same relates to fish populations. Because the fishing industry has expanded, larger, faster and better equipped ships can locate large shoals of fish and catch them faster and in larger quantities. The massive increase in fish consumption has brought many fish species to the brink of extinction. In addition, the rarer a species becomes, the higher its price and so the greater the incentive for fishermen to catch it. This commercial pursuit leads to an even more critical situation and makes it harder for the endangered fish species to survive. Marine life suffers greatly not only due to mass hunting but also due to general environmental decay. It is subject to heavy water pollution that destroys their habitats, the coral reefs being an outstanding example.
Commercial exploitation in the form of hunting has always endangered the survival of species. Ever since Homo sapiens appeared, a great many species have died out because of excessive exploitation. Scientists believe that the early humans initiated the process of species extinction. They are likely to have contributed to the extinction of the giant flightless bird or the dwarf hippopotamus thousands of years ago. A more current and popular example is the Dodo bird of Mauritius that died out a few hundred years ago due to excessive hunting and habitat destruction. The history of the American Bison is particularly dramatic. Before the 1800s, huge herds of the species
covered the American plains. When people recognised their commercial value, bison were hunted to extinction.
Animal species have always provided humans with food and other goods that have turned into expensive luxuries as species have declined. Animal furs have been highly valued goods for centuries. They have been used for clothing, rugs and tents. Thus, the population of the Koala bear dropped rapidly when Europeans arrived in Australia and began mass hunting of the bear for its valuable skin. Many predators have faced similar extermination because of their marvellous furs. The snow leopard, the Caspian tiger, the Siberian tiger and the cheetah are all victims of excessive hunting and poaching. Many animal species continue to suffer for other products they provide. Crocodile and snake skins are desired by the leather industry. Wonderful and rare butterflies are hunted for decoration. Elephant ivory tusks are luxury products all over the world, which has put the species population in considerable danger. Each year up to 150,000 elephants are killed just for their tusks. Similarly, the rhinoceros is hunted for its horn which is believed to be a medicine and an aphrodisiac in Asian countries. Consequently, rhinos top the list of endangered species. Millions of other animals die each year to gratify human's sophisticated whims.
Unstoppable human development and the swift pace of urbanisation are equally relevant contributors to animal endangerment. The devastation of entire ecosystems tends to occur in areas that are rich in biological diversity. Many plant and animal species are typically attracted to well-watered areas in a moderate climate. People display the same tendency and the clash is usually to their sole benefit. It is estimated that by 2025, Latin America will be 85% urbanised, Asia 65% and Africa 55%. This rapid suburban growth will pose a grave danger to the existence of a variety of species that will disappear under slabs of concrete unless the right measures are adopted to save their lives.
Developing and spreading agriculture creates equally serious threats to natural habitats. Entire ecosystems are transformed into pastures and grazing fields that sustain only few plant species for animal consumption. The original diversity is thus devastated. Each year billions of plant populations are eaten by domesticated herbivores or are ploughed under by farmers. Because of the specialised feeding habits of many herbivores, most plant species are considered useless and consequently wiped out from the fields. Excessive grazing is known to destroy the soil capacity to grow more plants. This, in turn, leads to the desertification of land. Because population growth is about 4% per year, there is an increasing pressure to bring more and more land under cultivation and cattle grazing. There is additional pressure to produce more and more food to maintain the required level of income. That is why most commercial farmers use chemical substances like pesticides and herbicides to ensure better crops. The chemicals are toxic and remain in the soil for years threatening many organisms.
An important cause of species endangerment is the pollution of natural environment. Millions of tonnes of toxic substances are released into the air, soil, rivers, lakes and oceans. They have a devastating impact on ecosystems. Sulphur dioxide and other greenhouse gases cause degenerative diseases of vast plant populations. Acid rains damage greenery and soil. Industrial waste containing heavy metals, detergents or fertilisers is released into fresh water reservoirs. Contaminated water cannot sustain the life of fish and other water organisms. Oil spills lead to ecological disasters destroying coastal ecosystems and wildlife.
These are all effects of human activity. We keep destroying natural habitats although, ironically, we depend on animal and plant species more than they depend on us. People need animals, so saving species is of key importance. Plants and animals have medicinal, commercial, agricultural, ecological and recreational value for humans. About 40% of all medications are based on animal and plant products. Species that provide them save our lives and enhance progress in pharmaceutical industry. There are thousand of species that have not been screened for medicinal values yet. It is worth keeping them alive in case they become a source of medicine for incurable diseases. Moreover, people depend on animals and plants as sources of food. Cereals provide more than 80% of the world's foods and help create new crops that grow in poor soils or drought-stricken regions.
Plants and animals are the foundation of healthy ecosystems. When species become endangered, it serves as an indicator that the health of the whole ecosystem is in peril. Losing just one plant species can trigger the loss of up to 30 other insects, plants and other higher animal species. The survival of rich ecosystems such as rain forests or coral reefs depends on their natural biodiversity and complex interactions between different forms of life.
Mankind has a lot to gain from the preservation of species and a lot to lose if species keep dying out. It is important to understand now that endangerment means there is still time to react whereas extinction is forever. The natural environment does not follow geographic, national, economic or political divisions. What happens on Earth, actually affects Europeans, Asians, Americans, Africans or Australians in the same way. It is our mutual responsibility to start healing our planet before it turns into an empty desert.
Speak your mind.
1. What forms of human activity do you consider to be the most devastating to natural habitats? How can their effects be reduced?
2. What should people do to prevent endangered species from becoming extinct?
3. Do new forms of life have a chance of evolving in the future?
4. Are humans an endangered species?
5. Would you be ready to join or start an animal welfare organisation? What projects would like to put into practice then?
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