By the time Britain became an island, most of the land was blanketed by an extensive forest of broad-leaved trees, mainly oak and elm. The forest canopy was so dense that very few flowering ground plants could survive beneath it.
Through the centuries, the forests have been cut down to make room for human needs. In about 3,500 BC the early farmers found about two-thirds of Britain covered by trees but in 1086 AD the Doomsday Book (compiled for William the Conqueror as the result of a nationwide survey of resources) recorded that only 20 per cent of England was still covered with trees. Nowadays, the only large areas of natural woodland to be seen are the original royal hunting preserves, designated by the Normans as protected forests, such as the New Forest in Hampshire. Otherwise there are only small patches of woodlands which may be remnants of the ancient broadleaved forests.
Today, our countryside is mainly made up of grassland but very little is natural grassland where wild flowers can flourish. Most fields contain special grasses to feed cattle for humans. Almost all countryside habitats have either been created or changed by humans, including hedgerows, heathlands, high moors, marshes, fens, water meadows, ponds, rivers and streams. Over the years, these habitats have been reduced quite drastically to make way for the needs of an ever-expanding human population. As a result the wildlife, which those habitats support, lose their source of food and shelter.
Other human activities have affected the countryside too. During the last part of the Twentieth century vast quantities of poisonous chemicals, such as pesticides (to kill insect pests), herbicides (to kill weeds) and fertilizers (to increase the yield of crops), have been sprayed onto the land. Some of these are washed by the rain into rivers, streams and ponds, polluting the water - thus wildlife on both land and in water is destroyed.