Extinction is Forever!
To become extinct is to be gone forever. Even before the arrival of humans on Earth, species became extinct quite naturally. Natural extinction happens when a species declines in numbers gradually but steadily at the end of its evolutionary period on Earth. The length of this period depends on how well a species can adapt to changes in climate and changes in other animals and plants around it. This process of extinction can take a very long time - sometimes several million years - and the extinction of one species is immediately followed by the appearance of another in a continuous cycle.
The case of the dinosaurs is the most well-known example of natural extinction. These reptiles appeared on Earth about 200 million years ago and dominated both land and sea for almost 100 million years. It is not certain why the dinosaurs became extinct, but their disappearance was a natural one and new species of animals evolved to replace them.
The rate of extinction has speeded up unnaturally over the last 400 years, rising sharply since 1900. This increase in the rate of extinction is directly related to the increase in the human population over the same period of time. Humans have caused great damage to the planet, as wild habitats have been taken over, forcing animals and plants into smaller and smaller areas, until some of them have become extinct. We have also polluted some habitats with chemicals and refuse, making them unfit for wildlife. These causes of extinction are known as indirect destruction.
Animals may also become extinct through direct destruction. This includes the hunting and capturing of animals. Humans have always hunted and killed wildlife but early humans lived more in harmony with nature, they killed animals for essentials like food and clothing. When guns were invented mass destruction of species was possible. Animals have been, and still are, killed for meat, clothing,medicines, feathers, eggs, trophies, tourist souvenirs - and sometimes just for amusement. Some species are still captured in the wild for the live pet trade, even though their numbers are dwindling.
The extinction of at least 500 species of animals has been caused by humans, most of them in the 20th century. Today there are about 5,000 endangered animals and at least one species dies out every year. There are probably many more which become extinct without anyone knowing.
The main threats to species then can be cited as poaching, habitat loss and climate change. The International Union for Conservation of Nature has its own "Red List" of endangered species ranging from "least concern" through to "critically endangered". It is their assessment which we'll refer to here.
"Dead as a dodo"
The dodo has become a symbol of extinction. It was a turkey-sized flightless pigeon which lived on the island of Mauritius. When sailors landed on the island for the first time in the sixteenth century, they killed the helpless bird for food. The dodo's eggs and young were eaten by dogs, cats, pigs, rats and monkeys which man had introduced to the island. The dodo, unused to predators, very quickly declined in numbers - and it was extinct by 1681.Read More: Habitat destruction