The Trump administration is executing a controversial plan to allow dirt bikes, ATVs, trucks, snowmobiles and other off-road vehicles to drive through tens of millions of acres of public lands and national parks, which environmental groups warn threatens endangered species and the environment.

The plan’s opponents say the impacts will be wide-ranging and that the vehicles will likely destroy sensitive habitats, harm waterways, drive large predators like grizzly bears into contact with humans, and otherwise damage pristine public lands and parks.

The Nixon administration more than 50 years ago issued an executive order that limited off-road vehicles’ access with the aim of protecting wildlife and preventing disputes on federal land. The Carter administration issued a second order providing similar environmental protections.