Grassland habitats are places that receive more rain than deserts but less precipitation than forests. Most of the plants here are grasses, which don’t need as much water as forest vegetation. Grasslands are usually found in the dry interior of continents, between the mountains and deserts. One-fourth of the planet is covered by grasslands.
Between the Forest and the Desert, these regions host a mosaic of grasses, shrubs, and scattered trees. A savanna or savannah is a mixed woodland-grassland biome characterized by trees being sufficiently widely spaced so that the canopy does not close, maintaining an open canopy despite a high tree density. Savannas are often believed to feature widely spaced, scattered trees and are marked by seasonal water availability, with most rainfall confined to a single season. The term entered English via historical forms such as zavana, savannah, and related spellings, evolving through explorers’ writings over centuries.
Geographical Extent and Nomenclature
Grasslands occur on every continent except Antarctica, each with distinct local names: savannas and veldts in Africa; pampas in South America; steppes in Europe and Asia; prairies or grasslands in North America; and rangelands in Australia. The Serengeti in northern Tanzania and southwestern Kenya is one of the world’s most famous grassland regions, hosting zebras, gazelles, wildebeests, cheetahs, lions, and leopards. The Eurasian Steppe is among the largest grasslands, stretching from Hungary to China. Kangaroos and flightless birds like emu and ostriches inhabit Australia’s rangelands, while North American grasslands are home to deer, antelope, rabbits, and prairie dogs.
Biophysical Structure and Fire as a Regulator
Wildfires can be bad business, but sometimes they help the habitat stay healthy. Nutrients are released into the soil by microbes that become more active when the soil temperature rises. Because the stems and buds of grasses grow underground, they aren’t damaged by fire and therefore grow back quickly. Grasslands are maintained by a combination of low rainfall, regular fires, and grazing by animals, which together keep woody plants in check and allow grasses to dominate the ecosystem.
Plant Diversity and Dominant Grasses
Grass isn’t just … grass. Many different kinds of grasses grow in the habitat, including wild oats, foxtail, buffalo grass, and sunflowers, among others. The flora varies by region, with tropical savannas hosting acacias and baobabs in East Africa, while temperate savannas feature different species adapted to their climates. In some grasslands, herbaceous grasses dominate, while trees may be present but are comparatively sparse.
Animals of the Grasslands
Grasslands support a wide array of wildlife. In Africa, giraffes, elephants, buffaloes, zebras, gnus, and antelopes rely on grasses and tree foliage to survive. Predators such as lions and cheetahs stalk herbivores across the open plains. In North American prairies, species like deer and pronghorns roam the grasslands, along with smaller mammals such as prairie dogs. Australia’s rangelands host a variety of herbivores and birds adapted to open habitats, while Eurasian steppes contain saiga antelope and vultures among other wildlife.
Savannas, Fire, and Human Influence
Savannas are subject to regular wildfires, and the ecosystem appears to be the result of human use of fire. Intentional controlled burns typically create fires confined to the herbaceous layer that do little long-term damage to mature trees, helping prevent more catastrophic wildfires. However, these fires can kill or suppress tree seedlings, thereby maintaining an open grass-dominated landscape. Prior to European settlement, Aboriginal land-use practices, including fire, influenced vegetation and may have maintained and modified savanna flora. Grazing by large herbivores reduces competition between grasses and woody plants, potentially boosting tree growth, while also reducing fuel loads and fire intensity.
Human Impacts and Land Management
In many savanna regions, including parts of Australia and South America, large areas have been cleared of trees to improve pasture and forage for livestock. Techniques such as felling, girdling, and mechanical clearing with chains and heavy machinery have reshaped savannas, sometimes leaving many trees as seedlings or resprouting plants. Introduction of exotic plant species and changes in grazing pressure can alter soil structure, nutrient dynamics, and woody plant establishment. Climate change may further influence savanna dynamics by increasing woody encroachment or altering fire regimes, which in turn affects biodiversity and ecosystem services.
Types of Grasslands: Savannas vs. Temperate Grasslands
The two distinct types of grasslands are savannas and temperate grasslands. Savannas are typically warm with a pronounced rainy season and a long dry season; most precipitation falls during a few months, and trees are present but not dense enough to close the canopy. Temperate grasslands are found in mid-latitudes and are characterized by richer soils and sparser trees. Elephants are predominantly in African savannas, while temperate grasslands host burrowing animals such as prairie dogs and have different plant communities and fire regimes. Human conversion of temperate grasslands to agricultural land has led to declines in specialist species, including pollinators reliant on native grasses and wildflowers.
Table: Key Features of Grassland Biomes
| Feature | Savanna | Temperate Grassland |
|---|---|---|
| Location | Africa, parts of South America, Australia, Asia | North America, parts of Europe and Asia, Australia |
| Climate | Warm, distinct wet and dry seasons | |
| Vegetation | Grasses with scattered trees | Mostly grasses, few or no trees |
| Wildlife | Giraffe, elephant, zebra, antelope, lions, cheetahs | Prairie dogs, deer, grazing mammals |
| Fire role | Important for maintaining openness | Fire less frequent, soil-rich |
In the Americas, savannas can be confused with other grassland types, but their open canopies and seasonal rainfall patterns distinguish them from closed-canopy forests and more densely wooded landscapes. In Africa, the Serengeti’s vast open plains are iconic for wildlife migrations and predator-prey interactions that unfold across the open grasslandscape. The Savanna’s structure-open, with widely spaced trees-allows sunlight to reach the grasses and supports a high diversity of herbivores and predators, creating a dynamic and interconnected ecosystem.
