Earth Science: Tropical Grassland – Savanna
Savanna grasslands are located between the humid tropical regions and dry deserts. Vast areas of this type of grassland are covered by only the occasional tree, cluster of trees, or scattered small woods.
Savannas are common in Africa, but are also found in India, Australia, and the northern parts of South America, such as the Llanos of Venezuela and Colombia. They are located in the subhumid outer tropical areas with warm air temperatures through out the year, wet summers, and dry winters.
As the distance from the Equator to the tropics grows, the number of dry months increases from less than four to about ten months and the amount of average precipitation decreases three- to sixfold Savanna grasslands have different appearances according to the local climatic conditions.
Savannas may be humid or semihumid, with grasses taller than humans and scattered trees, or dry savannas, with low and mostly drought-resistant grasses. Savanna trees and shrubs show obvious signs of adaptation to the extended drought season. For example, the baobab tree is able to store large amounts of water in its trunk. Riparian forests along rivers are also part of many savannas. The African hippopotamus commonly lives in this habitat.
The African savannas are home to many large terrestrial mammals, including herbivores such as elephants, giraffes, zebras, and antelope. The East African ostrich is a bird of the savanna. The equivalent bird is called the common rhea or nandu in South America and the emu in Australia.
Kangaroos are the largest animals of the Australian plains. Only a small number of the world’s natural grassland areas remain untouched by humans. For thousands of years nomads have taken their herds of cattle, sheep, and goats into the savannas in Asia and Africa to graze and have also hunted there.
Today Africa is at risk from the desertification of major parts of dry savanna grass- lands adjacent to the Sahara, due to over- grazing and severe droughts. Savannas are also threatened by increasing woody plant encroachment due to climate change.
SERENGETI SHALL NOT DIE
The “endless plain” in East Africa is at the core of the African savanna. The ecosystem de- pends on the herds of wildebeest or gnu passing through the grasslands every year during the dry season in search for water. The scientists Bernhard and Michael Grzimek were the first to make an effort in protecting the wild animals of the Serengeti.
Their 1959 documentary Serengeti Shall Not Die {Die Serengeti dart nicht sterben) contributed greatly to increasing global awareness of the Serengeti animal park and its vulnerability to human impact.