Table of Contents

What Is Grassland Ecology?

Grassland ecology is the scientific study of ecosystems where grasses and other herbaceous plants—rather than trees or shrubs—are the dominant vegetation. Grasslands cover approximately 40% of Earth’s land surface (excluding Antarctica and Greenland), making them one of the most widespread biomes on the planet. This field examines the species, processes, and interactions that sustain these open landscapes, from the soil microbes beneath the surface to the herds of grazers that roam above it.

The Grasslands of the World

Grasslands exist on every continent except Antarctica. They go by different names depending on where you are:

Prairies in North America
Pampas in South America
Steppes in Central Asia and Eastern Europe
Savannas in Africa, South America, and Australia
Veld in South Africa
Downs in Australia

These aren’t just the same thing with different labels. Each type has distinct climate conditions, species compositions, and ecological dynamics. But they share a fundamental characteristic: grasses run the show.

Temperate Grasslands

Temperate grasslands occur in the interiors of continents, roughly between 30 and 60 degrees latitude. They experience hot summers, cold winters, and moderate rainfall (250-900 mm per year)—too little to support dense forest, too much for desert.

The North American prairie was once the largest temperate grassland on Earth, stretching from Manitoba to Texas, from the Rocky Mountains to Indiana. It supported 30-60 million bison, enormous populations of elk and pronghorn, and an astonishing diversity of grasses and wildflowers—tallgrass prairies in the east could have over 300 plant species per hectare.

Today, less than 4% of the original tallgrass prairie remains. Most was converted to corn and soybean fields, making it one of the most altered ecosystems in human history. The deep, fertile soils that made prairies ecologically productive also made them irresistible to farmers.

Tropical Savannas

Tropical savannas combine grasses with scattered trees. The African savanna—home to the Serengeti’s famous wildlife migrations—is the most iconic example. South America’s Cerrado, Australia’s tropical savannas, and India’s dry deciduous forests are other major examples.

Savannas are defined by a strong wet-dry seasonal cycle. During the wet season, grasses grow rapidly. During the dry season, they go dormant, and fire often sweeps through. This cycle of growth, dormancy, and fire maintains the grassland character—without fire and drought, many savannas would gradually convert to closed forest.

The African savanna supports the greatest concentration of large mammals on Earth. The annual wildebeest migration in the Serengeti-Mara ecosystem—roughly 1.5 million wildebeest, plus hundreds of thousands of zebras and gazelles—is the largest mass movement of terrestrial animals anywhere on the planet.

Montane Grasslands

High-altitude grasslands—alpine meadows, paramos (tropical high-altitude grasslands in the Andes), and montane grasslands in East Africa—exist above the treeline or in areas where cold temperatures and wind prevent tree growth. These ecosystems support unique species adapted to harsh conditions: low-growing cushion plants, specialized pollinators, and animals with adaptations to thin air and extreme cold.

Why Grasses Dominate

Here’s the key question: why grasses? What gives grasses their competitive edge over trees in these environments?

The Secret Is Underground

The single most important thing to understand about grasslands is that most of the biomass is underground. While a forest stores most of its carbon in tree trunks and leaves visible above ground, a grassland stores 60-80% of its biomass in roots.

Grass roots can extend 2-3 meters deep in tallgrass prairies. These root networks access deep soil moisture during droughts, store energy reserves for rapid regrowth after disturbance, and create a dense mat that resists invasion by competing plants.

When fire burns through a grassland, it destroys the above-ground vegetation—but the growing points of grasses (called meristems) are at or below ground level, protected from fire. Trees, with their growing points at their branch tips, are far more vulnerable. A fire that barely inconveniences established grasses can kill young trees outright.

This is why fire and grasses have a symbiotic relationship. Grasses fuel fires (dry grass burns readily), and fires favor grasses over their competitors. It’s an ecological feedback loop that has maintained grasslands for millions of years.

Grazing and Grasses

Grasses evolved alongside grazing animals. Unlike most plants, grasses grow from their base rather than their tips. When a bison bites off the top of a grass blade, the plant continues growing from below. A tree that loses its growing tip is damaged or killed; a grass barely notices.

This adaptation explains the coevolution of grasslands and large herbivores. Grasses are, in a very real sense, designed to be eaten. Grazing actually stimulates many grass species to grow more vigorously—a phenomenon called compensatory growth. Moderate grazing can increase grassland productivity compared to no grazing at all.

The Ecology of Fire

Fire is not a disaster in grasslands. It’s a necessity.

Natural grassland fires—ignited by lightning or, for millennia, by indigenous peoples—serve several ecological functions:

Removing dead material: Old, dead grass (thatch) accumulates and shades out new growth. Fire clears it, letting sunlight reach the soil surface and stimulating new growth.

Recycling nutrients: Fire rapidly converts dead vegetation into ash, releasing minerals like potassium and phosphorus back into the soil where plants can immediately use them.

Controlling woody plants: Fire kills tree seedlings and shrubs that would otherwise invade grasslands. Without periodic fire, many grasslands convert to scrubland or forest within decades. This process—called woody encroachment—is one of the biggest threats to grasslands worldwide.

Maintaining diversity: Different plant species respond differently to fire. Frequent fire favors fire-adapted grasses and forbs (wildflowers). Infrequent fire allows woody plants to establish. Managing fire frequency is a tool for maintaining specific community compositions.

Grassland fire ecology has direct implications for conservation management. Restoring fire to landscapes where it’s been suppressed—often for a century or more—is one of the most effective conservation strategies for grassland ecosystems. But prescribed burning near urban areas is politically and practically difficult, creating a persistent management challenge.

Soil: The Hidden Half

Grassland soils are among the most fertile on Earth. The combination of deep roots, high below-ground productivity, and slow decomposition (in temperate climates with seasonal freezing) produces thick, carbon-rich topsoil.

Prairie soils—technically classified as Mollisols—have dark, organic-rich A horizons that can be over a meter deep. They contain more carbon per hectare than most forest soils. The world’s most productive agricultural regions—the American Midwest, Ukraine’s black earth (chernozem), Argentina’s Pampas—are almost all on former grassland soils.

Carbon Storage

Grasslands are seriously underappreciated as carbon sinks. While forests store carbon in wood above ground, grasslands store it underground in roots and soil organic matter. This carbon is more stable—it’s protected from fire and decomposition by being locked in soil.

Globally, grassland soils store approximately 34% of the terrestrial carbon pool. That’s more than forests in many estimates. And unlike forest carbon (which is released when trees burn or decompose), soil carbon can persist for centuries to millennia.

This has important implications for climate change policy. Current climate strategies heavily emphasize tree planting, but converting grasslands to forest can actually release more carbon than it sequesters—breaking up grassland soil releases stored carbon, and young trees take decades to compensate. Protecting existing grasslands may be more effective for climate mitigation than planting new forests in many contexts.

Soil Biology

A single teaspoon of healthy grassland soil can contain a billion bacteria, several meters of fungal hyphae, thousands of protozoa, and hundreds of nematodes. This microbial community drives nutrient cycling, decomposition, and soil structure formation.

Mycorrhizal fungi—which form symbiotic associations with plant roots—are particularly important in grasslands. These fungi extend the effective root network of grasses by orders of magnitude, helping plants access water and nutrients (especially phosphorus) from soil volumes far larger than their roots alone could reach. In return, plants provide the fungi with sugars from photosynthesis.

The below-ground food web in grasslands is extraordinarily complex. Bacteria and fungi decompose dead plant material. Protozoa and nematodes graze on bacteria. Larger soil organisms—earthworms, beetles, ants—physically mix the soil and create channels for water and air. Remove any part of this web and soil health degrades rapidly.

Grassland Biodiversity

Grasslands are far more biodiverse than they might appear to someone driving past at 60 miles per hour.

Plant Diversity

A healthy tallgrass prairie can support 200-300 plant species per hectare. Most of this diversity comes not from grasses but from forbs—wildflowers and other non-grass herbaceous plants. Forbs provide essential habitat for pollinators, fix nitrogen (legumes), and contribute to the complex root architecture that makes grassland soils so fertile.

The timing of flowering in prairie plants is staggered across the growing season—different species bloom in spring, early summer, midsummer, and fall. This provides continuous food resources for pollinators and creates the characteristic shifting color display of a healthy prairie through the year.

Animal Communities

Grasslands support some of Earth’s most spectacular animal communities:

Large grazers: Bison in North America, wildebeest and zebra in Africa, guanacos in South America, kangaroos in Australia. These animals shape grassland structure through selective grazing—creating mosaics of short-grazed and tall-ungrazed patches that increase habitat diversity.

Burrowing mammals: Prairie dogs, ground squirrels, viscachas, wombats. Prairie dog towns can cover thousands of hectares and support entire communities of associated species—burrowing owls, black-footed ferrets, rattlesnakes—that depend on the burrows for shelter.

Birds: Grasslands support specialized bird communities, many of which are now endangered. North American grassland birds—meadowlarks, bobolinks, grasshopper sparrows, greater prairie-chickens—have declined more than any other bird group on the continent, primarily due to habitat loss.

Insects: Grassland insect communities are enormous and ecologically critical. Pollinators (native bees, butterflies, flies) service grassland wildflowers. Decomposers (dung beetles, fly larvae) recycle nutrients from grazer dung. Herbivorous insects consume more grassland biomass than all the large mammalian grazers combined.

Threats to Grasslands

Grasslands are in trouble. Big trouble.

Agricultural Conversion

The biggest threat by far. Grasslands grow on excellent soil, receive adequate rainfall, and occupy relatively flat terrain—exactly the characteristics that make good cropland. Approximately 50% of the world’s temperate grasslands have been converted to agriculture. In North America, less than 4% of tallgrass prairie and less than 30% of mixed-grass prairie survive.

Conversion continues. Between 2016 and 2021, approximately 1.6 million acres of grassland were plowed in the Great Plains states of the US. The Cerrado in Brazil—a tropical savanna with extraordinary biodiversity—is being rapidly converted to soybean and cattle production.

Woody Encroachment

When fire is suppressed, trees and shrubs invade grasslands. This is happening on every continent. In the American West, juniper and cedar have expanded into sagebrush steppe and grasslands. In African savannas, bush encroachment reduces grazing capacity and displaces grassland species. In Australian savannas, woody thickening changes fire behavior and reduces grass productivity.

The irony is that fire suppression—often motivated by a desire to “protect” nature—actually destroys grassland ecosystems. Grasslands need fire like forests need rain.

Overgrazing

While moderate grazing benefits grasslands, excessive grazing degrades them. Overgrazing removes too much above-ground biomass, weakens root systems, exposes soil to erosion, and shifts plant communities toward weedy, disturbance-tolerant species.

Overgrazing has degraded vast areas of grassland worldwide—particularly in arid and semi-arid regions where vegetation recovers slowly. In Central Asia, parts of Africa, and the American Southwest, overgrazing has contributed to desertification—the conversion of productive land to desert.

Fragmentation

Even where grasslands haven’t been plowed, they’ve often been fragmented into small, isolated patches. Small grassland patches can’t support wide-ranging species, can’t sustain natural fire regimes, and lose species over time through stochastic local extinction. Many grassland-dependent species need large, connected landscapes—the kind that barely exist anymore in most of the temperate world.

Climate Change

Rising temperatures, changing precipitation patterns, and increasing atmospheric CO2 all affect grasslands. Higher CO2 levels tend to favor woody plants over grasses (because trees and shrubs benefit more from CO2 fertilization), potentially accelerating woody encroachment. Changing rainfall patterns alter which grass species can survive where.

On the other hand, grasslands are more resilient to climate variability than many ecosystems. Their deep root systems tolerate drought better than shallow-rooted vegetation. Their below-ground carbon storage is less vulnerable to fire than above-ground forest carbon. Some researchers argue that grasslands will be more stable than forests under future climate scenarios.

Conservation and Restoration

Protecting remaining grasslands and restoring degraded ones are among the most important—and most underfunded—conservation priorities.

Protected Areas

Less than 5% of the world’s temperate grasslands are in protected areas, compared to about 12-15% for forests. This disparity reflects a persistent bias in conservation toward forested landscapes. Grasslands lack the charismatic appeal of old-growth forests, and their biodiversity—much of it underground or in inconspicuous wildflowers and insects—is easy to overlook.

Organizations like the IUCN have increasingly recognized this gap and are pushing for expanded grassland protection. The challenge is that most remaining grasslands are privately owned (in North America, over 85% of remaining prairie is on private land), requiring conservation approaches that work with landowners rather than around them.

Restoration

Restoring grasslands from cropland is possible but difficult. It requires:

Seed sourcing: Collecting seeds from local native plant populations, not generic commercial varieties
Soil preparation: Breaking compaction layers, sometimes inoculating with mycorrhizal fungi
Disturbance management: Establishing prescribed fire and/or managed grazing regimes
Patience: Prairie restoration typically takes 10-20 years to develop a diverse plant community and decades longer to rebuild soil organic matter to pre-agricultural levels

The science of grassland restoration has improved dramatically in recent decades. Large-scale restorations—like the 11,000-acre Neal Smith National Wildlife Refuge in Iowa—demonstrate that diverse prairie communities can be rebuilt, though they remain ecologically different from remnant prairies that were never plowed.

Working Lands Conservation

Because most grasslands are privately owned and used for livestock grazing, conservation increasingly focuses on maintaining grasslands as working landscapes. Managed grazing—using livestock to mimic the historical grazing patterns of wild herbivores—can maintain grassland biodiversity while providing economic returns to landowners.

Programs like the USDA’s Conservation Reserve Program (CRP) pay farmers to take cropland out of production and plant it to native grass. Since its creation in 1985, CRP has enrolled over 20 million acres—but recent policy changes and rising grain prices have reduced enrollment, and some conservationists worry about the program’s long-term future.

Why Grasslands Matter

Grasslands provide ecosystem services worth hundreds of billions of dollars annually:

Carbon storage in soils
Water filtration through deep root systems
Erosion prevention on vulnerable slopes
Pollinator habitat for species that also service crops
Livestock forage supporting rural economies worldwide
Biodiversity conservation for thousands of species found nowhere else

They also have cultural significance. Indigenous peoples worldwide have deep connections to grassland landscapes—the Plains peoples of North America, the Maasai of East Africa, the gauchos of South America. These cultural relationships often incorporate traditional ecological knowledge about fire, grazing, and plant management that modern ecology is only beginning to appreciate.

Key Takeaways

Grassland ecology studies the most widespread yet most endangered terrestrial biome—ecosystems covering 40% of Earth’s land surface where grasses dominate over trees. These ecosystems are maintained by fire, grazing, and drought, which together prevent woody plant invasion.

Grasslands store enormous amounts of carbon underground, support spectacular biodiversity (much of it below the soil surface), and provide ecosystem services that humanity depends on—from food production to water filtration to climate regulation.

Despite their importance, grasslands have lost more area to conversion than any other biome and receive less conservation attention than forests. Protecting remaining grasslands and restoring degraded ones is among the most urgent and underappreciated priorities in conservation. These are not empty, featureless landscapes waiting to be plowed. They are ancient, complex, and irreplaceable ecosystems—and we’re running out of time to save what’s left.

Frequently Asked Questions

What is the difference between a prairie, a steppe, and a savanna?

All are grasslands, but they differ in climate and vegetation. Prairies (North America) receive moderate rainfall and support tall grasses. Steppes (Central Asia, parts of North America) are drier with shorter grasses. Savannas (Africa, South America, Australia) are tropical or subtropical grasslands with scattered trees. The distinctions are primarily about rainfall, temperature, and tree density.

Why don't trees grow in grasslands?

Trees can grow in grasslands—they're kept out by fire, drought, grazing, and soil conditions. Fire kills tree seedlings while grass roots survive underground. Periodic drought stresses trees more than grasses. Grazing animals preferentially browse young trees. Remove these pressures, and many grasslands would convert to forest within decades.

Are grasslands endangered?

Yes, grasslands are among the most endangered ecosystems on Earth. Approximately 50% of the world's temperate grasslands have been converted to cropland. North America's tallgrass prairie has lost over 95% of its original extent. Grasslands receive far less conservation attention than forests despite being equally biodiverse and ecologically important.

What animals live in grasslands?

Grasslands support large grazing mammals (bison, wildebeest, kangaroos), predators (wolves, lions, cheetahs), burrowing animals (prairie dogs, ground squirrels, wombats), birds (meadowlarks, ostriches, secretary birds), and enormous communities of insects and soil organisms. Below ground, grassland soils contain some of the highest densities of invertebrate life on Earth.