Two hundred years ago, tens of millions of bison roamed North America. There were so many of them that the pounding of their hooves sounded like thunder. These majestic beasts, also called buffalo, were sacred to many Indigenous peoples in the American plains. The people recognized the bison’s contribution to their societies and respected their importance to the ecosystem.

When the Europeans arrived, they viewed the bison as a commodity and a weapon. They killed thousands of buffalo in organized sport hunts, selling their pelts and using their destruction to starve Indigenous tribes and trespass on their lands.

Because of these actions, bison were almost completely extinct by the early 1900s. In the century since then, people have tried to bring the species back. Though bison have never returned in the millions, there are now several hundred thousand buffalo in the United States.

Indigenous groups have been an important part of the repopulation effort. They manage the bison herds and propose laws to protect and expand buffalo territory. They spread the word about how bison can help the ecosystem, an issue that has become even more urgent as climate change accelerates.

One place where the bison are helping is in the southern plains. This area of the country is especially vulnerable to climate change, and extreme drought and floods have been more common in recent years. But the returning bison are making a difference. Grazing buffalo mow down the vegetation, making way for nutritious new plant shoots that replenish the earth and attract other native animals and insects. The bison’s hooves push seeds into the soil to aerate the ground. Birds are attracted to the area because buffalo kick up insects. And the bison’s dung fertilizes the soil as they graze.

Another way the bison help is by creating wallows. These huge ditches are made when the bison roll on the ground to cool off. The wallows turn into microhabitats for other animals that are crucial to the ecosystem. They fill with water after rain and attract insects, frogs, and other amphibians. They also grow bird’s-foot violets, the preferred food of a rare native butterfly.

Troy Heinert, a member of the Sicangu Lakota tribe calls bison “the original climate regulator.” He says, “they did this job for us when we allowed them to be buffalo.” It is time to allow them to be buffalo again.