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The earth is home to millions of different species of animals and plants - many of whom humans have never seen!
However, due to human activity, some species of animals and plants are in danger of becoming extinct - killed off and to never, ever return...
There are a few different ways in which humans can cause various species of animals and plants to become endangered:
Humans have relied on eating animals and fish for food since the beginning of evolution, however, over-hunting certain types of animals and overfishing has caused the population of these animal groups to drop to worryingly low levels.
Humans have also been responsible for destroying many natural habitats (homes) for many different types of animals and plants. For example, the construction of enormous cities has seen many forests, swamps, plains and rivers built over - removing the natural homes of many different types of animals.
Also, humans have destroyed the natural habitats of many different animals and plants by polluting the area. Acid rain, caused by air pollution, has killed many different types of plants and trees. Water pollution has lead to different types of fish, marine life and birds dying as the water they live in becomes poisonous. Even the seas have become filled with rubbish - especially plastic (which does not rot very quickly) - which has killed many different types of animals.
The destruction of habitats can have terrible effects for many years - for example, the population of bees has dropped worryingly due to the lack of places for them to collect nectar from flowers and create their beehives - and because there are fewer bees, it is having an effect on the number of plants and flowers reproducing. Bees carry pollen on their backs when they visit flowers, and in doing so, help plants reproduce with one another, grow seeds and increase their population.
Climate change is also responsible for destroying many habitats. The rise in global temperatures has caused:
Certain species of animals and plants have become extinct or endangered due to rival animals and plants moving into their area. This has often been caused by humans. For example, grey squirrels were introduced into the British Isles in the 1800s but become rivals to the native red squirrels. Grey squirrels are bigger, stronger and more robust than red squirrels and drove the population of red squirrels to becoming endangered.
It is illegal to hunt or kill endangered animals, and many efforts are being made to protect them from further harm.
We have to:
Other factors which affect animals...
Over the course of history many species have become extinct. This is part of the natural process. Species may become extinct because of changes in climate (i.e. the ice age), competition with other species, a reduced food supply, or combinations of all of these. Most natural extinctions are isolated events that happen over a fairly long period of time. Some, however, are major events that can cause mass extinctions and happen quickly. Perhaps the most famous of these was the extinction of the dinosaurs, which may have been due to a large meteorite striking the earth.
Today many conservationists are concerned with human interaction causing species to become extinct. This is because human interaction has increased the rate of extinctions beyond what normally should occur in nature. More extinctions reduces the planet's biodiversity and can have adverse affects for all life on Earth.
Many species have been hunted to extinction or to the point where they are critically endangered. One example of this is the American Bison. There were millions of bison in the Great Plains of North America until the arrival of the Europeans. Hunting was so intense that only a few hundred were left by the time the animals became protected. Fortunately, they have survived on farms and ranches and are no longer endangered.
Species that live only on islands can also be easily hunted to extinction. Even the arrival of a small tribe can quickly eliminate an island species.
Beside food, animals are often hunted for specific body parts like their fur, feathers, or horns. Sometimes these animals are the top predators and, therefore, do not have a large population to begin with. These species can be quickly hunted to extinction.
In Africa, the elephant was heavily hunted for its prized ivory horns. The population went from many millions to a few hundred thousand. Today the elephant is protected, but the population continues to drop in some areas due to poachers.
Another example is the tiger in China. The tiger was nearly hunted to extinction for both its valuable fur as well as its bones, which were traditionally used for medicine. Today it remains classified as endangered species.
One of the main threats to animals today is loss of habitat. This comes from the expansion of humans, especially from agriculture. As vast areas of land are cultivated to grow food, natural habitats are destroyed. This can destroy many of the cycles of life necessary for organisms to survive and for biomes to thrive.
Pollution from humans can kill off a species as well. This is especially true is fresh water biomes such as rivers and lakes. Sewage and run-off from industrial plants can poison the water. When one species is affected, other species can die off as well causing a chain reaction as the balance of the ecosystem is destroyed.