Global Grasslands: The Undervalued Biome That Feeds the World

Grasslands — terrestrial ecosystems dominated by grasses, maintained by climate, fire, and grazing — cover approximately 40% of Earth's non-frozen land surface, making them the most extensive biome after desert. They range from Arctic tundra grasslands to tropical savannas, from the Tibetan Plateau to North American prairies. Despite their ecological importance — as carbon stores, biodiversity habitats, and the ancestral home of the grasses and ruminants underpinning human agriculture — grasslands receive far less conservation attention than forests, and have been more extensively converted to human use than any other biome. Over 70% of North American tallgrass prairie has been lost; the pampas of South America are similarly transformed; and Eurasian steppes continue to be degraded by overgrazing and cultivation.

Grassland Soils — Hidden Carbon Stores

Grassland soils store approximately 350 billion tonnes of carbon — accumulated from the extraordinary root systems of grasses that extend metres deep, creating organic-rich soils over centuries. Unlike forest carbon stored primarily in above-ground biomass, grassland carbon is sequestered deep in soil where it is protected from rapid decomposition. The conversion of grassland to cropland releases a significant fraction of this stored carbon — and cultivation-induced soil carbon loss from global grassland conversion represents a major component of land-use emissions. The deep, dark soils of the American prairies and the Ukrainian steppe — some of the most productive agricultural soils on Earth — are the product of thousands of years of grassland carbon accumulation that agriculture is steadily depleting.

The Prairie Dog — Grassland Keystone

The black-tailed prairie dog of North American grasslands is one of ecology's most studied keystone species — an animal whose presence or absence determines the biological character of hundreds of square kilometres of prairie. Prairie dog colonies create a heterogeneous landscape of different vegetation heights and structures that supports over 200 associated species — including the black-footed ferret (which depends entirely on prairie dogs for food and burrows), burrowing owls, swift foxes, mountain plovers, and dozens of grassland bird and reptile species. The near-elimination of prairie dogs — through poisoning campaigns, plague epidemics, and habitat loss — triggered cascades of decline across the prairie ecosystem that ecologists are only now beginning to fully document.

Grassland Restoration — Rewilding at Scale

The ecological restoration of degraded grasslands has emerged as both a conservation and climate priority, given the extraordinary carbon, biodiversity, and ecosystem service values of native grasslands compared to the degraded agricultural systems that have replaced them across most of the world. Active restoration approaches range from simple fencing and cessation of overgrazing (allowing natural regeneration of native grass communities), through reseeding with native grass species and forbs, to the reintroduction of native large herbivores that maintain open grassland structure. The American Prairie Reserve project in Montana — assembling a contiguous protected area on the shortgrass prairie of the Northern Great Plains through land purchase — has successfully reintroduced bison as a keystone grazer across growing areas, with bison grazing, wallowing, and dung deposition rapidly recovering the soil structure, plant diversity, and invertebrate communities of native prairie far more effectively than passive restoration or management by domestic cattle.

Grassland Restoration — Prairie Reconstruction and Rewilding

The restoration of native grassland on former cropland and degraded pasture is among the most ecologically and climatically beneficial land use changes available — yet it has been implemented at a tiny fraction of the scale needed to meaningfully address grassland biodiversity loss or soil carbon depletion. Native prairie reconstruction — seeding decommissioned cropland with diverse mixtures of native grasses and forbs — has been shown to restore significant biodiversity within 5-10 years and soil carbon stocks over decades to centuries. The USDA's Conservation Reserve Program, which pays farmers to take cropland out of production and establish permanent vegetation cover, has enrolled approximately 10 million hectares at various times since 1985 — providing measurable biodiversity and water quality benefits but typically using non-native grass monocultures rather than native prairie reconstructions that would maximise ecological value.

The Great Plains — Ecology of the American Prairie

The tallgrass and mixed-grass prairies of North America's Great Plains are among the most biologically productive and most thoroughly transformed ecosystems on Earth. Before European settlement, approximately 900 million acres of prairie covered the interior of the continent, supporting an estimated 30-60 million bison — the largest aggregation of large mammals in the historical record — alongside elk, pronghorn, wolves, grizzly bears, prairie dogs, and thousands of invertebrate species. Today, less than 5% of tallgrass prairie and less than 20% of mixed-grass prairie remain in anything approaching natural condition, with the rest converted to cropland, planted pasture, or urban development. The speed and thoroughness of this conversion — largely accomplished within a single human lifetime following the extirpation of bison and wolves in the 1870s-1880s — makes it one of the most ecologically catastrophic land transformations in recorded history.

The ecological importance of bison to prairie function is increasingly understood through research in remaining prairie preserves and through bison reintroduction experiments. Bison graze more selectively than cattle — seeking out the most nutritious grass patches and creating grazing lawns of highly palatable short-grass surrounded by taller, less heavily grazed grass — producing a heterogeneous mosaic of vegetation structure that supports dramatically higher plant and invertebrate diversity than uniform cattle grazing. Bison wallowing — rolling in dust depressions that create bare, disturbed soil patches — creates essential habitat for specialist ground-nesting birds and invertebrates that require bare soil. Bison dung supports specialist dung beetles that are absent from cattle-grazed prairie. These ecosystem engineering functions are absent from modern cattle-dominated grasslands, contributing to the biodiversity deficit of converted prairie even in areas where grass cover has been maintained.