The vegetation of the river Gambia and its creeks provides a favourable habitat for animals, and birds. The river abounds in fish and river creatures, including the hippopotamus and the crocodile. Among the 500 bird species that have been recorded are the kingfisher, the cuckoo, the swallow, the heron, the sunbird, the hawk, and the grass warbler.
The swampy region closest to the river, with its dense masses of mangrove trees often growing more than 100 feet (30 m) high, abounds in wildlife but has been of little use for either agriculture or human settlement. The grass-covered river flats of the lower river are rendered useless for cultivation due to the salt water that periodically inundates them, and settlements on them are few.
The flats of the middle and upper river are of some agricultural value, however. Much of the grassland is regularly cleared, and the light soils are easily cultivable. The annual flooding of the fertile alluvial loams of the middle flats makes them especially suitable for intensive rice cultivation. On the light sandy and well-drained soils of the higher slopes, peanuts (groundnuts) grow particularly well. Cultivation and settlement have therefore taken place in the middle flats and on the higher slopes, with many villages being located on the borderline between the flats and the plateau, thus avoiding both the flooding of the lower slopes and the increasing aridity of the higher terrain. The river Gambia originated from the FUTA djallon high land in Guinea Conakry through Senegal.