Grasslands cover roughly 23% of Earth’s land surface, making them one of the planet’s largest biomes, yet most of what makes them extraordinary is hidden underground or easy to overlook. Unlike forests, which store their carbon in towering trunks, or deserts defined by scarcity, grasslands are shaped by disturbance. Fire, drought, and grazing don’t destroy them. These forces are the very things that keep grasslands alive.
Grasses Grow From the Bottom Up
The single most distinctive trait of grass plants is where they grow from. Trees and most flowering plants grow from their tips. Grasses grow from the base. Specialized tissue near the bottom of each leaf blade, called an intercalary meristem, keeps producing new cells even after the top of the plant is eaten or burned away. An animal can bite off the upper portion of a grass blade, and the plant simply keeps elongating from below as if nothing happened.
This is why a lawn bounces back after mowing, and it’s why wild grasslands can endure intense grazing by millions of herbivores or recover within weeks of a fire. No other major plant group has this built-in tolerance for destruction on such a scale. It means grasslands aren’t just surviving disturbance. They evolved to depend on it.
Most of the Biomass Lives Underground
A grassland that looks sparse aboveground can be hiding an enormous root system below. In long-term research plots, root mass measured down to 60 centimeters was on average 5.5 times greater than the aboveground plant material. For some warm-season grasses, the ratio was even higher, with roots outweighing shoots by a factor of five in the top 30 centimeters of soil alone.
This underground emphasis has profound consequences. Most of the carbon a grassland captures ends up stored in the soil rather than in woody tissue. The bulk of that root carbon concentrates in the upper 30 centimeters, but a significant share, roughly 16 to 23% more, extends down to 60 centimeters. Across all the world’s grasslands, soil carbon stocks in just the top 30 centimeters are estimated at around 155 billion metric tons. That makes grassland soils one of Earth’s largest terrestrial carbon reserves, and unlike a forest that releases its carbon when it burns, grassland carbon stays locked in the ground even after a fire sweeps through.
They Built the World’s Richest Farmland
Thousands of years of grasses growing, dying, and decomposing created a soil type called Mollisols: deep, dark, and loaded with organic matter. These soils are naturally rich in the nutrients plants need because all that decomposing root material continuously cycles minerals back into the earth. The dark color itself comes from the sheer concentration of organic carbon packed into the topsoil.
Mollisols are now the foundation of the world’s most productive agricultural regions. The American Midwest, the Ukrainian steppe, and the Argentine Pampas all sit on former grassland soils. The fertility that makes these breadbaskets possible wasn’t added by farmers. It accumulated over millennia under grass.
Two Photosynthetic Strategies Split the Biome
Grasslands span climates from cool and wet to hot and dry, and the grasses that dominate in each zone use fundamentally different approaches to photosynthesis. Cool-season grasses (C3 species) thrive in temperate regions with mild summers and reliable rainfall. Warm-season grasses (C4 species) dominate where it’s hotter and drier, because they have an internal mechanism that concentrates carbon dioxide more efficiently, letting them keep photosynthesizing even when water is scarce.
Field experiments show that C4 grasses maintain significantly higher rates of photosynthesis than C3 grasses during drought. In water-limited plots, C4 leaves photosynthesized at rates 2 to 7.4 micromoles per square meter per second higher than C3 leaves, with nearly double the ability to keep their pores open for gas exchange. C3 grasses shut down their photosynthesis earlier as drought sets in, while C4 grasses keep working. The greatest C4 advantage appeared during the hottest, driest stretches of the growing season.
This split explains why the tallgrass prairies of Kansas look so different from the shortgrass steppes of Montana, or why African savannas are dominated by warm-season species. The type of grass that wins depends on the local balance of temperature and rainfall, creating a patchwork of grassland subtypes across every continent except Antarctica.
Animals Engineer the Landscape
Grasslands are shaped as much by their animals as by their plants. Large herbivores like bison, wildebeest, and guanacos keep woody plants from taking over by eating or trampling seedlings. Their grazing and defecation also increases forage quality and keeps vegetation short, maintaining the open structure that defines a grassland. Without them, many grasslands would eventually fill in with shrubs and trees.
Burrowing mammals play an equally important but less visible role. Prairie dogs, vizcachas, wombats, ground squirrels, and pikas collectively reshape the soil itself. Arctic ground squirrels can move as much as 20 metric tons of soil per hectare. Vizcachas build mound complexes spanning 300 to 700 square meters, riddled with up to 100 burrow entrances. This digging mixes nutrients through the soil profile, creates bare patches where new plants can establish, and opens underground channels that help rainwater infiltrate rather than run off.
These burrowing species also clip and prune shrubs, actively preventing woody plants from encroaching. Their foraging favors wildflowers and low-growing, grazing-tolerant plants over tall grasses, which increases plant diversity within their colonies. The tunnels they dig provide shelter for dozens of other species, from snakes and owls to insects and amphibians. Remove these animals and the entire community structure shifts.
Fire Is a Feature, Not a Threat
Most biomes are damaged by fire. Grasslands need it. Because grasses regrow from below ground and store their energy in roots, fire clears away dead thatch and competing woody plants without harming the grass itself. The ash returns nutrients to the soil surface, and the sudden exposure to sunlight triggers a flush of new growth.
Without periodic fire, grasslands accumulate a thick layer of dead material that smothers new growth and shades out sun-loving species. Shrubs and trees gain a foothold. Over decades, an unburned grassland can transition into scrubland or forest. Many grassland management programs now use controlled burns specifically to prevent this, mimicking the natural fire cycles that lightning and Indigenous land management sustained for thousands of years.
The Most Threatened Biome You Rarely Hear About
Despite their ecological importance, grasslands are disappearing faster than forests. Between 2005 and 2020, the conversion rate of natural non-forest ecosystems (primarily grasslands and wetlands) was nearly four times that of forested land. Brazil contributed about 13% of the global total, with Russia, India, China, and the United States each contributing roughly 6%. Both cropland and pasture expansion drove the losses, with a large share linked to international commodity exports for food, animal feed, and bioenergy.
The problem is partly one of perception. Forests have old-growth trees that inspire conservation campaigns. Grasslands look simple, even empty. But their biodiversity is concentrated in root networks, soil organisms, and animal communities that are invisible from the surface. Once grassland soil is plowed, the dense root structure that took centuries to build is destroyed in a single season, and the carbon stored in that soil begins escaping into the atmosphere. Restoring a grassland after conversion takes decades and rarely reaches the complexity of the original ecosystem.
Conservation efforts have historically focused on forests, but the scale of grassland loss is pushing researchers and policymakers to expand protections beyond tree-covered landscapes. The challenge is convincing people to protect something that, at first glance, looks like nothing more than an open field.