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.

Since then, the popularity of off-road sports has exploded, and the vehicles are far more powerful than they once were, which advocates say makes the restrictions even more necessary today.

Donald Trump rescinded the Nixon-Carter executive orders and directed agency leaders to draft new rules to open lands to off-road vehicles.

Opponents warn that desert tortoises, western snowy plovers, lynxes, grizzly bears and sage-grouse are especially at risk from increased off-road vehicle activity. Trump’s move is “reckless and nonsensical”, said Vera Smith, director of national forests and public lands for Defenders of Wildlife.

“This rescission is yet another loss for wildlife and natural places,” Smith added.

The move is part of a broader Trump effort to open public lands to industry and other uses that threaten endangered wildlife and sensitive ecosystems. The administration has attempted to gut the Endangered Species Act, opened public lands to grazing, expanded logging access on public lands, opened protected waters to fishing, boosted oil exploration in protected waters and attacked other rules that limit the exploitation of natural resources.

“What’s so frustrating here is that the Trump administration is taking a very systematic approach to dismantling protections for public lands,” said Randi Spivak, director of public lands for the Center for Biological Diversity. “Public lands are already so stilted to extraction that we need more protections.”

In a fact sheet posted with the orders, Trump labeled the off-road vehicle limits “outdated and burdensome”.

“President Trump believes the American people should be able to access and enjoy their public lands without being burdened by unnecessary and outdated regulations,” the fact sheet states.

The Nixon-Carter executive orders required off-road vehicles to use roads or trails that the federal agencies established to minimize ecological harm. The Bureau of Land Management and National Park Service already have more than 500,000 miles (800,000km) of roads available for use between public lands and parks. The National Park Service also allows limited snowmobile use in Yellowstone national park.

However, the Nixon-Carter restrictions prevented the vehicles from going everywhere in a park, which they will now be able to do.

That is a problem because the vehicles’ routes carve up wildlife habitat, fragmenting it into smaller and less functional tracts that are not suitable for many animals. The damage further stresses species that are already endangered or threatened, and the habitat loss can lead to species loss.

The roads and snowmobiles also present a problem for grizzly bears and other predators. Research shows bears begin to leave habitat regions when there is at least one mile of road per square mile. The new rules will force them into closer contact with humans. State and federal agents kill hundreds of thousands of predators annually because they come into contact with humans, a practice that some advocates have previously characterized as a “bloodbath”.

“This will end badly for the bears,” Spivak said.

Aquatic life also does not do well near off-road vehicle tracks because vehicles damage the plant life around streams’ edges that keep the water cool and habitable, or send sediment into the streams.

“Even when the first executive orders were put in place, the science was clear that there needed to be regulations, and there were way fewer … and they were smaller,” Spivak said. “They’re needed even more today.”

Spivak said environmental groups cannot sue over the rescission of the executive orders, but they will watch the new rule-making process closely and take action if needed.

Already, the US Forest Service is preparing to open 5m acres (2m hectares) of parkland to vehicles, mostly in Idaho and Montana, according to the New York Times.

“As the United States marks 250 years of independence in 2026, we must shine a light on our nation’s greatest natural treasures and ensure every American can recreate on these majestic lands,” a Forest service spokesperson said in a memo announcing the opening.