The natural vegetation of the country has been considerably modified by human occupation. Clearly marked altitudinal variations in vegetation occur around the upland areas and some distinctive mountain flora is found. Tanzania is well known for its game reserves. There are more than 120 ethnic groups in Tanzania of which the largest are the Sukuma and the Nyamwezi. Dar es Salaam is the main port, the dominant industrial centre, and the focus of government and commercial activity, although the administrative function of the capital city are in the process of being transferred to Dodoma.
Forests grow in the highland areas where there is high rainfall and no marked dry season.
The western and southern plateaus are primarily miombo woodland, consisting of an open cover of trees, notably Brachystegia, Isoberlinia, Acacia, and Combretum. In the floodplain areas, wooded grassland with a canopy cover of less than 50 percent has been created by poor drainage and by the practice of burning for agriculture and animal grazing. Similarly, grassland appears where there is a lack of good drainage. For example, the famous Serengeti Plain owes its grasslands to a calcrete, or calcium-rich hardpan, deposited close to the surface by evaporated rainwater. Swamps are found in areas of perennial flooding.