Africa's rainforests are rich in fauna; six kilometers (four miles) of land may be home to as many as 400 species of birds, 150 species of butterflies and 60 species of amphibians. Important mammals include the African forest elephant (Loxodonta cyclotis), the gorilla (Gorilla spp.), the black colobus monkey (Colobus satanas), and the okapi (Okapi johnstoni), a donkey-like relative of the giraffe. The canopy and scrubland of the Central African rainforest is home to some of the most endangered and best-known rainforest animals, such as forest elephants, pythons, antelope and gorillas. Gorillas, a critically endangered primate, are essential for seed dispersal. Gorillas are herbivores that roam the dark, dense rainforests as well as the sun-drenched swamps and jungles. Their droppings spread the seeds in sunny areas where new trees and shrubs can take root. As such, gorillas are keystone species in many African rainforest ecosystems The form of vegetation affects the "surface albedo," or reflectivity of a surface, by absorbing more heat than bare ground. In turn, this heat carries moisture from forest trees into the atmosphere, where it condenses as rain. In other words, tropical forests cool the local climate and contribute to precipitation. Conversely, a reduction in vegetative forest cover means a reduction in heat absorption, which leads to a reduction in water uptake into the atmosphere. Tropical rainforests play a key role in the functioning of Earth's natural systems. For example, 50-80% of precipitation in the Amazon rainforest alone comes from transpiration. Changing the albedo of the Earth's surface affects global weather by altering winds and ocean currents patterns and changes in the distribution of precipitation. Global weather patterns could emerge if deforestation continues.