A tropical savanna is an environment characterized by rolling hills, tall grasslands, and sparse trees. Large parts of Africa and Australia are tropical savannas, as well as Florida. It can be either wet or dry and is in between a desert and tropical rainforest.
Tropical savannas, also sometimes called tropical grasslands, are found in large bands on both sides of the equator. Large tropical savannas are found in South America, Africa, India, and Australia.
Tropical Savanna: Climate and Vegetation
Tropical savannas are typically found in between sections of tropical rainforest and deserts. They occupy a middle ground between tropical rainforests, which require a large amount of rain, and deserts, which need hardly any rain at all. There are effectively two different seasons in tropical savannas, a wet season and a dry season. The dry season is characterized by long periods of dry spells and drought and can be quite prone to fire, while the wet season is characterized by constant humidity.
Tropical savannas have warm temperatures all year round, average monthly temperatures throughout the year stay at 64° F or above. Meanwhile, the average rainfall for tropical savannas stays between 30 to 50 inches. The dry season sees only an average of 4 inches a month. Flooding can occur in savannas, particularly during the transition between the dry season to the wet season. Flash floods can occur during severe thunderstorms, and short-lived floods which last a few days can happen near coastal streams and floodplains.
As far as vegetation, savannas are described with large tracts of enduring grasses, usually between 3 to 6 feet tall. The grasses might also have a canopy consisting of both fire-resistant and drought-resistant trees. There may also be a layer of shrubs.
Distinctions are usually made between shrub savannas, grass savannas, and woodland savannas. Savannas can also be recognized by the types of trees located there, as there can be palm, pine, and acacia savannas.
“If I have ever seen magic, it has been in Africa.” — John Hemingway
Plants found in savannas are specialized to handle long periods of drought. Savanna plants have extra long roots capable of reaching the water table deep beneath the soil. The plants are also covered in thick bark, so they can resist the yearly fires that happen during the dry season. The trunks of the plants can store a large amount of water, and savanna plants drop their leaves during the winter to conserve energy.
Grasses found in savannas also have adaptations that help them survive. Many kinds of grass are bitter tasting for some animals or are sharp which also discourages animals from eating them. Nonetheless, different species have evolved to be able to eat different types of grasses. Many of the grasses in the savanna grow bottom-up, meaning that the tissue responsible for growth doesn’t get eaten by grazing animals. Quite a few savanna plants have organs like corms or bulbs, which similar to cactus arms, store water. This helps the plants survive throughout the dry season.
Soil types in savannas include both edaphic and bedrock types. Soil in savannas is usually formed by laterization (a type of chemical weathering that produces a large variety of soil makeup), and low fertility oxisols (an order of soil) are prominent in the region.
Tropical Savanna: Animals
Tropical savannas are home to a large and diverse population of animals. Tropical savanna animals include the herbivorous animals that feed on the grasses and trees of the region. Africa’s tropical savannas are home to gazelles, buffalo, zebras, rhinos, elephants, warthogs, giraffes, wildebeest, impalas and more. Many herbivorous animals share grazing regions, coexisting together. Grazing animals can divide resources both spatially and temporally. Each animal has its own food preferences and may prefer to eat at a certain area during a certain time of the season. Up to sixteen different species have been known to share one grazing area.
There are also large carnivores that eat the herbivores found in the biomes. Lions, jackals, hyenas, cheetahs, and leopards all live in the savannas of Africa. There are also birds of prey like hawks and eagles that subsist on small animals like rodents.
A majority of animals who live in tropical savanna biomes have wings or long legs, which allow them to migrate during the change of seasons. A large number of animals burrow underground to survive the summer heat, or to rear young. The wide-open plains of the savanna grasslands are excellent habitats for birds of prey. Buzzards, hawks, and eagles are able to fly over the plains and get excellent views of prey, using hot updrafts of air to keep them aloft. There are also occasional trees to build nests in. Most animals do not sweat as a cooling mechanism, so many savanna animals shed body heat through large amounts of exposed skin, like elephants, or through panting like predatory cats and dogs.
The various savannas around the world are home to different types of animals. South American savannas are home to deer, rhea, and capybaras, while Australia’s savannas are home to kangaroos, wallabies, and wombats.
Regional Expressions of Savanna Biomes
Tropical savannas biomes vary depending on their location around the world. The most familiar expression of savannas is the savannas found in East Africa, which are full of Acadia trees. This includes the famous Serengeti Plains found in Tanzania. Africa is home to most of the savanna biome and almost half of the continent is considered savanna.
South America has savannas as well, but these are much less diverse in terms of species than the East Africa savannas. The savannas in South America consist of around 2.5 million square kilometers, running through parts of Colombia, Brazil, and Venezuela. Short twisted trees dot the landscapes of the Brazilian savannas.
Australia is home to savannas in the northern part of the continent. The region is full of eucalyptus trees and kangaroos, as well as saltwater crocodiles, frill-necked-lizards, and venomous snakes.
Preserving Tropical Savannas
Tropical savannas or grasslands are biomes that support a diverse array of animals, and protecting them is important. Savannas can degrade due to overgrazing from livestock, and invasive species brought to savanna biomes by humans can alter the makeup of native animal and grass populations.
Furthermore, large swaths of savannas around the world have been cleared out to make room for the development of agriculture or housing. Savannas and grasslands should be carefully managed and protected so that the biome can continue to support the animals that play a critical part in our planet’s complex ecosystem.