In the summer there is lots of rain. In Africa the monsoon rains
begin in May. An average of 15 to 25 inches of rain falls during this
time. It gets hot and very humid during the rainy season. Every day
the hot, humid air rises off the ground and collides with cooler air
above and turns into rain. In the afternoons on the summer savanna
the rains pour down for hours.
There are several different types of savannas around the world. The savannas we are most familiar with are the East African savannas covered with acacia trees. The Serengeti Plains of Tanzania are some of the most well known. Here animals like lions, zebras, elephants, and giraffes and many types of ungulates(animals with hooves) graze and hunt. Many large grass-eating mammals (herbivores) can survive here because they can move around and eat the plentiful grasses. There are also lots of carnivores (meat eaters) who eat them in turn.
South America also has savannas, but there are very few species that exist only on this savanna. In Brazil, Colombia, and Venezuela, savannas occupy some 2.5 million square kilometers, an area about one-quarter the size of Canada. Animals from the neighboring biomes kind of spill into this savanna. The Llanos of the Orinoco basin of Venezuela and Columbia is flooded annually by the Orinoco River. Plants have adapted to growing for long periods in standing water. The capybara and marsh deer have adapted themselves to a semi-aquatic life.
Brazil's cerrado is an open woodland of short twisted trees. The diversity of animals is very great here, with several plants and animals that don't exist anywhere else on earth.
There is also a savanna in northern Australia. Eucalyptus trees take the place of acacias in the Australian savanna. There are many species of kangaroos in this savanna but not too much diversity of different animals
Plants of the savannas are highly specialized to grow in this environment of long periods of drought. They have long tap roots that can reach the deep water table, thick bark to resist annual fires, trunks that can store water, and leaves that drop of during the winter to conserve water. The grasses have adaptations that discourage animals from grazing on them; some grasses are too sharp or bitter tasting for some animals, but not others, to eat. The side benefit of this is that every species of animal has something to eat. Different species will also eat different parts of the grass. Many grasses grow from the bottom up, so that the growth tissue doesn't get damaged by grazers. Many plants of the savanna also have storage organs like bulbs and corms for making it though the dry season.
Most of the animals on the savanna have long legs or wings to be able to go on long migrations. Many burrow under ground to avoid the heat or raise their young. The savanna is a perfect place for birds of prey like hawks and buzzards. The wide, open plain provides them with a clear view of their prey, hot air updrafts keep them soaring, and there is the occasional tree to rest on or nest in. Animals don't sweat to lose body heat, so they lose it through panting or through large areas of exposed skin, or ears, like those of the elephant.
The savanna has a large range of highly specialized plants and animals. They all depend on the each other to keep the environment in balance. There are over 40 different species of hoofed mammals that live on the savannas of Africa. Up to 16 different species of browsers (those who eat leaves of trees) and grazers can coexist in one area. They do this by having their own food preferences, browsing/grazing at different heights, time of day or year to use a given area, and different places to go during the dry season.
These different herbivores provide a wide range of food for carnivores, like lions, leopards, cheetahs, jackals and hyenas. Each species has its own preference, making it possible to live side by side and not be in competition for food.
In many parts of the savannas of Africa people have started using it to graze their cattle and goats. They don't move around and soon the grasses are completely eaten up. With no vegetation, the savanna turns into a desert. Huge areas of savanna are lost to the Sahara desert every year because of overgrazing and farming.
A home to many animals, the Australian tropical savanna is one of the world's largest tropical savannas. The world's other savannas cover two fifths of Africa and large amounts of India and South America. The Australian tropical savanna is an area of dense grass and scattered trees that stretches across northern Australia from Broome to Townsville.
A savanna is usually very flat and with few trees and shrubs, this is because the fires destroy most of the trees and shrubs which usually aren't fire resistant. This happens frequently during the summer. This is also because savannas across the world have a limited water supply and bigger vegetation such as trees are the first to die out. Most savannas are near the equator, but the Australian savanna is south of the equator, which causes this region to have summer while we are having fall. Savannas usually occur only in a climate that has both a rainy and dry season. Each of these different seasons is very extreme.
The dry seasons, or "the dry", of the Australian savanna can last up to five months, from May to October. With each dry season come forest fires. These forest fires occur often, and geographers believe that fire keeps the savanna healthy. The tropical rain forest trees, that would have otherwise grown in that climate, don't grow because they are destroyed by the fires. Though the fires don't destroy all of the underground grasses, the fires limit the growth of any vegetation that isn't fire resistant. Usually the temperatures are cooler, with clear skies and low humidity.
During this time, water is key. The rainy season, or "the wet", can be pretty bad too. Some savannas around the world get ten inches of rain, and some ten full feet. Some pools, ponds, lakes, rivers, and streams flood. Much of the Australian savanna rain falls in heavy bursts of thunderstorms and monsoons. During the wet, which lasts from December to March, it is hot and humid. Temperatures can get as high as 50°C but usually stays around 30s (°C).
Marsupials dominate among the animals in this area of Australia. Marsupial's are mammals whose young are born undeveloped. The premature marsupial baby spends most of its growing up attached to the mother's nipple in a pouch. Marsupials are different from other mammals because they give birth to such undeveloped offspring while other mammal's young are much more mature. The animals include the Echidna, Eastern Gray Kangaroo, the Koala Agile and Whiptale Wallabies, Walaroos, Possums, Gliders, the Northern Qoull, and the Golden Bandicoot. These animals live in or near the few trees in this area for shade, food, and water. In the other parts of the tropical savanna, the reptiles dominate. The saltwater Crocodile, which is found here, is the world's largest reptile. It can grow to be from 7 to 8 meters long.
The vegetation in Australia differs from that of other Savannas. The acacia, part of the 1,200 members of the pea family, is the most common tree in other savannas. The acacia tree does grow in Australia but only in tropical and subtropical areas so, it's not the most common. Acacia's produce a gum called gum arabic, this is used in drugs, foods and others. The acacia's flowers are yellow or white and they grow in bundles.
The most common tree in Australia is the eucalyptus. They are famous for their oil, gum, and timber. The eucalyptus grows in warm climates and they are the most important tree for timber in Australia. The bark of some of these trees furnishes tannin, which is used in medicine.
There are many threats to this biome. The foreign pests and weeds that have been brought to this biome, such as the wetland weed Mimosa, threaten the survival of the region's ecosystems and native species. The Australian government has sponsored programs to clear away brush for agricultural reasons. When some of the farmers took over land, they brought with them new systems that caused some species to become endangered. The Aboriginal people have been stripped of their homes so that the government can make more room for agriculture. The World Wildlife Fund (WWF) in Australia is reacting to this destruction by working with the communities to stop the clearing programs.
This savanna is unique in many ways, including its climate, its animals, its vegetation, and its beauty. It's not quite like the other savannas of the world. It provides a home for the animals we don't have anywhere else in the world. Its vegetation is unique too. The area of the world it is in makes its climate extremely different from the others around the world. The entire planet would suffer greatly if we destroyed this biome.
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