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Unlock This CourseTropical grasslands, also known as savannas, are fascinating ecosystems found between tropical rainforests and deserts. These vast areas of grassland with scattered trees cover about 20% of the Earth's land surface and are home to some of the world's most iconic wildlife. From the African savanna with its migrating wildebeest to the Brazilian cerrado, these ecosystems play a crucial role in global biodiversity and human livelihoods.
Key Definitions:
Tropical grasslands are found in Africa (largest area), South America, Australia and parts of Asia. They typically occur between 5° and 20° north and south of the equator, forming a belt between tropical rainforests and hot deserts.
The climate of tropical grasslands is one of their most defining features. Understanding these patterns helps explain why the ecosystem looks and functions as it does.
Tropical grasslands experience consistently warm temperatures throughout the year, with average temperatures ranging from 20°C to 30°C. Unlike temperate regions, there's little seasonal variation in temperature - the main seasonal difference is rainfall, not temperature.
Temperatures can reach 35°C or higher during the hottest months. This intense heat, combined with low humidity, creates challenging conditions for both plants and animals.
Even during the 'cooler' months, temperatures rarely drop below 18°C. This consistent warmth allows year-round plant growth when water is available.
Daily temperature ranges can be significant, with cool nights providing some relief from the daytime heat. This helps reduce water loss through evaporation.
The most important climate feature of tropical grasslands is the distinct wet and dry seasons. This seasonal rainfall pattern shapes everything from plant growth to animal behaviour.
Annual rainfall typically ranges from 500mm to 1,500mm, with most falling during a 3-6 month wet season. The dry season can last 6-9 months with virtually no rainfall, creating drought-like conditions that test the survival abilities of all living things.
During the wet season, usually coinciding with the summer months, the landscape transforms dramatically. Heavy rainfall, often in the form of intense thunderstorms, provides the water needed for rapid plant growth. Grasses can grow several metres tall and trees produce new leaves. This is when most animals reproduce, taking advantage of abundant food and water.
The dry season presents enormous challenges. With little to no rainfall for months, plants must survive on stored water and nutrients. Many trees become deciduous, dropping their leaves to reduce water loss. Grasses die back to their roots and water sources become scarce, forcing animals to migrate or adapt their behaviour.
The vegetation of tropical grasslands has evolved remarkable adaptations to survive the extreme seasonal variations in water availability.
Grasses dominate these ecosystems, with species like elephant grass growing up to 4 metres tall. They have extensive root systems that can extend deep underground to access water and they can quickly regrow from their base after fires or grazing.
Trees in tropical grasslands are specially adapted to survive both drought and fire. Common species include acacia, baobab and eucalyptus trees. These trees typically have:
These umbrella-shaped trees are iconic of African savannas. Their thorns protect against herbivores and their deep roots can access water 30 metres underground.
Known as the 'tree of life', baobabs can store up to 120,000 litres of water in their massive trunks, helping them survive droughts lasting several years.
Various palm species thrive in tropical grasslands, with their flexible trunks helping them survive strong winds and their deep roots accessing groundwater.
Tropical grasslands support some of the world's most spectacular wildlife, from massive herds of herbivores to apex predators. These animals have developed incredible adaptations to survive the challenging conditions.
The open grasslands provide ideal habitat for large grazing animals. In Africa, this includes zebras, wildebeest, elephants and giraffes. These animals often migrate seasonally, following the rains and fresh grass growth. Their grazing actually helps maintain the grassland ecosystem by preventing trees from taking over.
The abundance of herbivores supports populations of large predators including lions, leopards, cheetahs and hyenas. These predators have adapted to hunt in open terrain, using speed, teamwork, or stealth to catch their prey.
The annual migration of over 2 million wildebeest, zebras and gazelles across the East African savanna is one of nature's greatest spectacles. This 3,000-kilometre journey follows the seasonal rains and grass growth, demonstrating how wildlife has adapted to the seasonal patterns of tropical grasslands.
Tropical grassland soils reflect the climate and vegetation patterns of these ecosystems. Understanding soil properties helps explain agricultural potential and conservation challenges.
The most common soil type in tropical grasslands is laterite or ferrasol. These soils are typically:
The alternating wet and dry seasons create unique soil processes. During the wet season, nutrients are leached downward, while the dry season brings some nutrients back to the surface through capillary action.
Tropical grasslands support millions of people worldwide through various economic activities, though human use often conflicts with conservation needs.
Cattle ranching is the dominant land use in many tropical grasslands. The natural grasslands provide grazing for millions of cattle, supporting beef and dairy industries, particularly in Brazil, Australia and parts of Africa.
While challenging due to seasonal rainfall patterns, some areas of tropical grassland are used for agriculture. Crops grown include:
Many tropical grasslands, particularly in Africa, support significant tourism industries. Safari tourism provides economic benefits while potentially supporting conservation efforts, though it requires careful management to avoid negative impacts on wildlife and ecosystems.
Tropical grasslands face numerous threats from human activities and climate change, making conservation efforts increasingly important.
The primary threats to tropical grassland ecosystems include:
Successful conservation of tropical grasslands requires balancing human needs with ecosystem protection. Strategies include establishing protected areas, promoting sustainable farming practices and supporting local communities in conservation efforts.
The Brazilian Cerrado, the world's most biodiverse savanna, covers 2 million square kilometres but has lost over half its original area to agriculture, particularly soy farming. Conservation efforts now focus on sustainable farming practices and protecting remaining areas through national parks and private reserves.
Tropical grasslands are remarkable ecosystems that demonstrate nature's ability to adapt to challenging environmental conditions. Their unique combination of seasonal rainfall, fire and grazing creates landscapes that support incredible biodiversity while providing important resources for human populations. Understanding these characteristics is essential for developing sustainable management practices that can preserve these vital ecosystems for future generations while meeting human needs for food, livelihood and economic development.