Every year, hundreds of millions of visitors flock to the United States’ majestic national parks. However, a shocking new study reveals that air pollution plagues national parks—a lot of them, too. That is, some 96% of national parks reportedly have hazardous air quality. Specifically, 33% are as heavily polluted as 20 of the nation’s most populous cities.

The Shocking NPCA Study

The study, conducted by the National Parks Conservation Association (NPCA) evaluated 417 national parks. It measured signs of degradation based on visibility, health, nature, and climate. A shocking discovery? Some of the nation’s most popular parks, including Joshua Tree and Sequoia, suffered the most from air toxicity. In fact, these parks recorded high-risk ozone levels during the two months when tourism was at its peak.

Perhaps the most salient effect of air pollution is the deterioration of the park’s aestheticism. Polluted air creates hazy skies, thus disallowing visitors from enjoying some of the parks’ beautiful landscape. According to the NPCA, pollution obstructed visitors from roughly 50 miles of scenery. To put this into perspective, that’s close to the length of Rhode Island.

Poor air quality also has negative implications for the health of park rangers and visitors. Particularly, poor air quality impacts children, the elderly, and those with respiratory diseases greatly. Moreover, air pollution impacts wild animals even more seriously, as the study concluded sensitive species were impacted in some 88% of national parks. These disturbances, unsurprisingly, were based on changes in the ecosystems’ water and soil quality.

Additionally, while climate change already presents a risk to all national parks, air pollution only exacerbates its effects. Already, the NPCA recognized 326 parks as significant concerns based on climate change metrics.

Despite growing concerns for the preservation of these parks, DOI Secretary David Bernhardt is yet to propose any ideas. Based on his track record, he’s unlikely to do so.

Trump and The EPA

Although it didn’t pass in Congress, given President Donald Trump’s plan to slash nearly 31% of funding from the Environmental Protection Agency (EPA), many don’t believe the president will push to implement preventive measures during his candidacy. Had House Democrats not rejected this plan, this would be the EPA’s lowest budget in nearly 40 years, despite national parks contributing around $40 billion to the U.S. economy annually.

Bernhardt took office after former DOI Secretary Ryan Zinke, resigned amidst the threat of criminal charges regarding poor ethics. Bernhardt’s confirmation received opposition from Democrats and environmentalists alike, due to mounting concerns he’d continue to follow Zinke’s agenda. As secretary, some of Zinke’s most significant projects include a proposal to open the majority of the U.S. coast to oil and gas drilling and his execution of the single largest rollback of federal land protections. During his tenure, Zinke sought to privatize protected public lands for fossil fuel giants.

Controversy Around Bernhardt

While deputy secretary, Bernhardt contributed to cuts in environmental regulation and helped move forward Zinke and Trump’s push to achieve “energy dominance” in America.

Bernhardt grew to be an even more controversial figure after the New York Times reported he executed an intervention preventing the release of a scientific report on the dangers of pesticides on endangered animals. In the report, the Fish and Wildlife Service found two of the pesticides were so harmful, they “jeopardize the continued existence” of 1,200+ animals and plants.

Previously, Bernhardt was a lobbyist, representing major oil and gas companies including Cobalt International Energy and Statoil Gulf Services. Opponents of Bernhardt say this conflict of interest impedes upon his ability to lead the DOI.

Policies to Protect National Parks

However, there’s still hope for the future of America’s national parks. Under the Clean Air Act, states are obligated to help preserve national parks by introducing new rules and regulations. Additionally, the Regional Haze Rule requires states to develop plans to minimize air pollution in parks by 2021, 2028, and every following decade.

Remaining Optimistic

Stephanie Kodish, the Clean Air program director for the NPCA, told the Guardian remains optimistic about these plans.

“I hope that people think about national parks as bipartisan unifiers. That the connection to our national parks is one that can help us preserve our future […], our culture,” Kodish said. “For the American people, they should serve as a reminder—and a warning cry.”

A warning cry. In a constantly advancing, growing nation, national parks serve as symbols of pure, unfiltered beauty. Many Americans can agree —the disappearance of such natural treasures would be a true shame.