Kenya is a land rich in biodiversity. Its natural environment is split into many distinct zones, from rainforest, high moorland and wetlands to semidesert, thornbush scrub and grassland savannah. These habitats harbour over 7,000 species of plants and trees, more than 25,000 species of animals and in excess of 1,000 species of birds. This concentration and variety of flora and fauna is greater than that in many other African countries, owing largely to Kenya's two life-giving rainy seasons.
The impact of humans in this region dates back millions of years, and there is archaeological evidence to show the existence of hominids (early man). Over time, they were followed by migrant hunter-gatherer tribes, who roamed across the land in search of resources, and eventually pastoralists, who introduced agriculture. In the late 19th century, agriculture was boosted by the advent of European settlers, who were attracted by Kenya's climate and fertile soil. They laid out plantations and terraced fields in the verdant western hills and valleys. As a result, wildlife was forced into the agriculturally unproductive savannah, where big-game hunters depleted substantial herds of large animals. By the 1940s, the need to establish national wildlife reserves was recognised, not only to protect big game, but also to protect natural habitats and maintain large areas for water catchment.
Wildlife numbers were further decimated during the poaching scourge that plagued East Africa over the 1970-80s. In 1989, President Moi set alight a huge stock of confiscated ivory in a much publicised and successful bid to stamp out poaching; this contributed to a subsequent worldwide ban on ivory trade. Kenya Wildlife Service (KWS) was formed in 1990 to take on the poachers, and it now employs thousands of officers in game management, anti-poaching and conservation activities. Animal numbers have steadily increased in national parks and private conservancies, which have contributed to wildlife protection and increased the mobility of animals on migration routes.