Grasslands cover roughly a quarter of the Earth's land surface. These ecosystems support large herds of grazing animals, from bison to wildebeest. Periodic wildfires help maintain grasslands by preventing trees from taking over. Agricultural expansion has converted much of the world's native grassland into farmland. Conservationists are working to protect remaining grassland habitats from further loss. According to the passage, what role do wildfires play in grassland ecosystems?
