A habitat is any natural region where wildlife lives undisturbed e.g. forest, pond, marsh or desert. Most animals and plants which are endangered have become so, not because they have been killed on purpose but because their habitats are being destroyed.
Human activities have changed or destroyed habitats for thousands of years. The natural habitats in almost every country in the world have been affected in some way. Let us take Britain as an example. Nowadays most of the British countryside consists of fields of grass grown specially for cattle and sheep or cereal crops for humans. If you had lived about a thousand years ago, the countryside would have looked very different for most of Britain was covered with forest, made up of broadleaf trees such as oak, ash and beech.
Now there are only relatively small pockets of woodland scattered across the country, one of the largest areas being the New Forest in Hampshire. Throughout the centuries humans have steadily cut down the trees to make room for the human population which has increased enormously particularly during the past 200 years or so. The trees have been replaced by houses, factories, schools, roads, farmland etc. Hedgerows which were planted by humans as boundaries around fields have, to some extent, replaced woodlands, providing homes for many animals and plants. However, even many of these have been destroyed, mostly during the last forty years, and are now regarded as a threatened habitat. Natural heathlands, chalk downlands, marshes, water meadows, hay meadows and ponds are also examples of Britain's disappearing habitats.
As you may imagine, this vast loss of habitats has affected the wildlife that lives in them. Large mammals such as the Brown Bear and the Auroch (wild ox) became extinct in Britain during the 10th Century mainly due to destruction of their forest habitat. Other British species of animals and plants have become extinct during the last few hundred years and many more are endangered today. Although conservation groups are working to protect wildlife, natural habitats are still being destroyed.