Tropical Savannas and Woodlands

Tropical savannas are grasslands with a scattering of shrubs or trees. Tropical woodlands have a higher density of trees, but they do not form a continuous canopy.

Tropical savanna and woodlands cover about 20% of the earth’s land area, with the largest concentration being found in Africa.

Savanna locations are heavily influenced by the Intertropical Convergence Zone.

Seasonality of rainfall helps control savanna distribution.

Native human populations live largely by pastoralism.

The Serengeti-Mara ecosystem contains the world’s greatest concentration of large mammals.

The Serengeti illustrates many of the relationships that are important in ecosystems.

More than 3 million ungulates of 28 species inhabit the region.

These herbivores consume about 66% of the aboveground net primary production. Probably the largest fraction of any ecosystem. Areas subjected to grazing show primary production about twice that of protected areas. Grazing lawns.

Migrations follow a gradient of forage abundance and nutritional quality. Wildebeest, plains zebras, and Thomson’s gazelles spend the wet part of the year on the southern plains. As forage begins to dry and disappear, they move northwest, then gradually concentrate in the northern area near the Kenyan border. When rains resume, they return south to the plains.

Grazing by the migratory species is complementary. Zebras first, followed by wildebeest, and then Thomson’s gazelles.

Many carnivores feed on the herbivores

Fragmentation of the savanna habitat is a major threat to the wildlife of the region.

Perhaps the largest threat is poaching.

African black rhino African white rhino Indian rhino Javan rhino Sumatran rhino

Distribution of the Javan rhino