Climate change is driving more intense wildfires, which contribute to air pollution/NPS file

Air pollution and climate-change impacts can have outsized effects on the National Park System, as well as lesser noticed but just as concerning effects. But are those impacts spread across the entire park system, or clustered around a few?

Back in 2019 the National Parks Conservation Association looked at how air pollution and climate change were impacting parks. They have updated that study with a new report, Polluted Parks, How Air Pollution and Climate Change Continue To Harm America's National Parks. Built upon the latest data from the National Park Service, the report paints a concerning current state of affairs across the National Park System.

The new report contains data collected during the height of the Covid pandemic in 2020, data that tracked some decreases in hazy sky and unhealthy air quality categories, said Ulla Reeves, interim director of NPCA's Clean Air Program. However, "I don't know that those drops can be counted on for the future," she told the Traveler during this week's podcast.

"There are many reasons that we are continuously concerned about the impact that air pollution is having on national parks, and one of the biggest outtakes in the report is the 'harm to nature' category," she said. "We don't see any improvement at all. ... What we see is the cumulative consequence of air pollution affecting nature as pollution is deposited into soil and water. So nitrogen deposition, sulfur deposition, and then also the effects of ozone pollution, on vegetation, health, all of those underlying issues in that particular category of 'harm to nature,' we see that there's not an improvement."

While the latest report notes that there have been modest improvements from the 2019 report in both air pollution and climate-change impacts, it still notes that 97 percent of parks have 'significant' or 'unsatisfactory' levels of air pollution. And it adds that the number of parks where significant concern levels in at least one of the air quality conditions analyzed dropped from 96 percent to 70 percent, indicating some improvements in air quality.

Although those numbers can seem contradictory, Reeves explained that they have a lot to do with the 'harm to nature' category in the report.

"What we saw is that there was a drop in the number of parks in the highest concern level in both hazy skies and unhealthy air. Last time we had more parks that were showing significant concern levels for both of those categories. And now we're seeing more of those parks falling into the [lower rated] unsatisfactory category," she said. "And so even though they're not at the top of the charts, they still are not experiencing the clean and clear air that we expect national parks to have for both the enjoyment of visitors but also for the health of people and rangers, and then wildlife and the harm to nature. So when we take all these categories together and look at this as one big air quality category, it is those really high numbers of significant concern in the 'harm to nature' category that ended up pulling numbers back up to that overall 97 percent of our parks are still experiencing high levels of concern whether they are significant or unsatisfactory from any of these air pollution categories."

Whether a park's air quality is deemed "significant" or "unsatisfactory" depends on the degree of impairment. "So when you look out over a scenic view over a landscape, that view is measured in deciviews by how much your view is obscured," explained the NPCA official. "So the significant concern levels means a significant level of visibility impairment, and then unsatisfactory means that you still have hazy skies and you're still losing out on the color and clarity of views, maybe just not as much as the significant concern level. And then, know what we're really trying to get is for our parks to have low concern levels of hazy skies."

Ozone Impacts

Part of the air quality concern lies in ozone levels, which can pose a health issue for humans and have impacts on vegetation and wildlife.

"70 parts per billion is the current ozone standard to protect human health and parks that are exceeding at times the 70 parts per billion are in the 'significant' concern category," said Reeves. "Most of the parks in that category, unfortunately, are in California. California has five total in that category, but also Rocky Mountain, White Sands in New Mexico, Guadalupe Mountains in Texas and Indiana Dunes in Indiana. All are falling into this 'significant' concern level for unhealthy air."

Harm To Nature

In assessing the 'harm to nature' category, NPCA looked at three components: nitrogen deposition, sulfur deposition, and ozone as it affects vegetation health.

"What we see is that the majority of parks are having really severe problems and very high levels of significant concern in the nitrogen deposition category. Two-hundred-and-forty-eight parks have significant concern for nitrogen deposition. That's really concerning," Reeves said. "That's coming from agricultural. That's air pollution that is deposited into soil and water in the form of nitrogen. ... We're just seeing a lot of problems in that pollution that gets deposited into soil and water. We see parks parks just can't escape it. Nature is exposed to pollution 24/7, 365 days a year. They don't get to go indoors when pollution is high."

One thing that really jumps out of the report is that national park visitors are missing out, on average, on 50 miles of scenery because of air pollution and its haze.

"We can't underestimate the importance of being able to see our landscapes and experiencing those long-range views or dark night skies. Pollution that is affecting our views is also affecting our health and having other detrimental consequences," said Reeves. "When we can see the pollution and we are breathing it, we are also missing out on some of the most fundamental experiences of our national parks. We know that many of our national parks have just some of the most stunning landscapes. A really important experience of being human outdoors is to be able to see our own reference point in a landscape and experience the awe of nature when we can have a perspective of our place in relation to the grandeur of nature."

The report found that the primary components that contribute to air pollution and its impacts are fine particulate matter, sulfur dioxide, and nitrogen oxides. Coal-fired power plants are among the greatest contributors to those pollutants, though vehicles also contribute, said Reeves.

"So in a place like California that doesn't have coal-fired power plants, the parks are really getting hammered by air pollution. And a lot of that is from so many vehicles on the road that have uncontrolled tailpipe emissions," she said. "And oil and gas development contributes to this problem, too. So it's a pretty widespread issue. But there are some geographic variations from time to time. And then seasonal cycles can change the way air pollution settles into certain mountainous areas. Salt Lake City is an example that tends to have really high particulate matter, smog problems in the wintertime, because the trapping of the pollution essentially in the the way that air settles in the wintertime."

"...Utah is a great example of where there are coal-fired power plants that have been let off the hook for decades for the pollution that is contributing to haze," said Reeves. "So it's really quite a shame in Utah, the Hunter and Huntington coal plants are contributing to national park air quality problems for a very long time and have honestly been let off the hook."

Humans aren't the only victims of air pollution. High ozone levels can damage tree leaves in a way that interrupts or prevents photosynthesis.

"And not just trees" are impacted by ozone, said Reeves. "There are certain indicator species of plants and trees that are more susceptible. For example, the tulip poplar trees in the Southeast are very susceptible to ozone pollution. Black cherries and other tree species are very sensitive. The other thing with ozone pollution is there are a lot of flowering plants like milkweed that are essential food sources for pollinators. Those plants are very susceptible to ozone pollution."

When it comes to climate change impacts, the NPCA study looked at four "high risk" threats: drought, wildfire, sea level rise, and invasive species. 

"When we take them collectively we find that 14 of our parks have multiple high risk climate threats just of these four that we looked at," said Reeves. "And managing those impacts can be really, really challenging, particularly when we think about budget cuts that the parks may be facing."

Solutions to some of these problems, she said, range from utilizing the Regional Haze Rule, which is designed to deliver and restore natural air quality to national parks, to better policing of polluters.

"We know how to control pollution from industrial facilities, from coal-fired power plants. We need stronger rules on the books to address vehicle air pollution, because that pollution is definitely making its way into national parks as well, not just from the people who are in the parks, but from far away because air pollution travels long distances," said Reeves. "So we know how to do it. But we absolutely do need the political will."

Traveler footnote: You can find the NPCA report here.