The Great Plains are defined by grass, but a slow-moving invasion of trees is reshaping the landscape. Known as woody encroachment, or the "green glacier," the spread of species like eastern red cedar is visible from the air in places such as the Nebraska Sandhills, where ranchers see orderly windbreaks giving way to scattered cedars across open range. The change threatens the prairie's biodiversity and its resilience, according to ranchers and ecologists quoted by Grist.
The economic stakes are clear. Texas A&M AgriLife Extension estimates that woody encroachment across the 10 Great Plains states represents $4 billion in lost range production, as trees crowd out the grass cattle need. Ecologists also warn of losses among insects, birds, and small mammals, and the thirsty trees could put additional pressure on water supplies in an already arid region.
The encroachment is tied to a breakdown of the prairie's natural cycles. Fire, grazing, and drought historically kept woody plants in check, but fire suppression and overgrazing have let trees take root and spread. Prescribed burns are a proven tool, particularly in the Flint Hills of Kansas and the Osage Hills of Oklahoma, where a long culture of burning has preserved tallgrass prairie. In other areas, however, getting landowners comfortable with fire remains a slow process.