What are tropical savannas?

Tropical savannas are landscapes of grass and scattered trees that occur throughout the world’s tropics. Tropical savannas can be almost treeless grasslands or denser woodlands—as long as the canopy cover of the trees is not so dense that it shades out the grass.

Note that some people use a narrower definition of tropical savannas, restricted to landscapes that are largely grassland with scattered trees or scrub. Landscapes with a continuous grass layer below and regular tree cover above, as seen in much of far northern Australia, would be called tropical woodland rather than savanna under this defintion.

We use the broader definition of tropical savanna that includes both woodlands and grasslands because the ecosystem processes and management issues are similar across both landscapes in north Australia.

Where do you find them?

Tropical savannas are found in Africa, Australia, South America, India and South-East Asia – (see map). They cover a little less than a third of the world's land surface. In Australia, tropical savannas encompass around one quarter of Australia, stretching from the Indian Ocean in the west to the Pacific in the east. They border desert country to the south, rainforest on the east coast and are fringed by floodplains and peppered with monsoon forest patches in the north.

In Africa, tropical savannas form a broad semi-circle from the western Ivory Coast across to a southern border with northern Namibia. Approximately 45% of South America is savanna and exists as two large patches north and south of the equator. Approximately 10% of India and South-east Asia is considered savanna.

How do Australian savannas differ from African ones?

Australia, unlike Africa, does not have large animals such as giraffe, zebra, wildebeest, lions and leopards. In Australia, much of the plant material is eaten and re-cycled by insects such as termites! More than 40 thousand years ago, however, there were large grazing animals in Australian tropical savannas, such as giant wombats and kangaroos. Debate continues as to why these animals became extinct. Some argue that it was mainly because of climate change, others say that the ancestors of Australian Aborigines who arrived on the continent at least 40 thousand years ago, could have hunted them into extinction, and many say it was a combination of climate change and human action that removed many of the large animals from the Australian savannas.

Why are the tropical savannas important?

People consider tropical savannas to be important for a number of reasons. We list two of the most prominent reasons below, taking Australia’s tropical savannas as an example.

High in Biodiversity Tropical savannas are a major reservoir of biodiversity – some areas of tropical savanna may have a similar biodiversity level to tropical rainforest. They are home to hundreds of species of native plants, mammals, birds, reptiles and amphibians and tens of thousands of different species of invertebrates. Many species in all these groups are found nowhere else in the world.

There are a few reasons for this. The tropics are generally found to have a higher biodiversity for any given area than regions in higher latitudes. This may relate to several factors, such as: (i) less frost; (ii) higher energy levels from the more intense sunshine reaching tropical ecosystems; (iii) the large areas of rainforest that are found in the tropics; (iv) tropical temperatures and humidity don't vary as much over time as they do in higher latitudes. Additionally, the tropics tend to be less intensively developed than the temperate areas of the world. This is particularly the case in Australia, and much of the natural habitat in northern Australia is relatively intact compared to that in southern Australia.

Rich in Culture The tropical savannas are also important in cultural terms. The Australian tropical savannas for example, are home to a diverse and distinctive Aboriginal culture. Aboriginal communities manages a large fraction of the land area of the region. The didgeridu and the band Yothu Yindi come from the tropical savannas.

There is also a long history of pastoralism in northern Australia which has some of the largest cattle stations in the world.

Tourists and locals also value the tropical savannas for their wild and spectacular natural features. This part of Australia has world heritage areas like Kakadu National Park, Purnululu National Park.