Alpine lakes in the Wind River Range, like this one in the Dinwoody drainage, hold pure, clear water. But their chemistry is being changed by air pollution. A variety of sources, from vehicle exhaust to industrial sites to agriculture and natural activity, contributes to a buildup of nitrogen and other chemicals. The accumulations have caused changes in the population of small organisms and is predicted to affect plants, fish and ultimately trees. (Angus M. Thuermer Jr./WyoFile)

Thirty years of research in the Wind River Range shows that air pollution is killing microorganisms in lakes and changing the alpine ecology despite federal rules that mandate pure air in the wilderness there.

Scientists have detected up to seven times the natural background level of nitrogen in the Winds and across the Greater Yellowstone ecosystem, a federal air-quality specialist says. Those chemical changes killed some forms of diatoms – microscopic phytoplankton — and spurred the growth of algae.

Data from water samples and lake-bottom core evidence in the Teton and Beartooth mountains reveal the changes. Workers with the Bridger-Teton National Forest and others ventured to remote sites in the Bridger Wilderness to collect samples at alpine lakes starting in 1984.

Using that data, sensors measuring air pollution and weather stations, they documented chemical changes, the death and upheaval in populations of small, living organisms, and species of lichen dying.

Data from 30 years of water samples taken from the Bridger Wilderness in the Wind River Range show changes in the chemistry of alpine lakes. Researchers documented the loss of some microscopic aquatic species and types of lichen. This aerial view of the Cirque of the Towers shows the mountain snowpack, where many airborne pollutants end up, and the abudant granite that is a poor buffer around alpine lakes. (Angus M. Thuermer Jr./WyoFile)

“When you start seeing the biological response — losing these species of lichen, (the appearance of) more algae — those are the things we’re more concerned with,” said Ted Porwoll, an air-quality specialist with the Bridger-Teton National Forest who outlined the worries in a PowerPoint slide show to audiences this fall. He’s also the co-author of a 2010 report that outlines some findings and research needs.

The pollution has implications for land managers and beyond. Wilderness areas are supposed to be “untrammeled by man” and are protected as Class I airsheds, the cleanest standard in the nation. National parks are to be kept “unimpaired for the enjoyment of future generations.” The Clean Air Act of 1963 launched modern federal standards.

Nitrogen deposition

National park and forest managers in the 20-million acre Yellowstone ecosystem can’t control what blows into or rains and snows on their reserves. The pollution comes from a variety of sources including auto exhaust, forest fires, industrial plants, big agriculture, oil and gas fields and nature itself.

“There’s no regulation on those things,” Porwoll said of the airborne pollutants. “All we can do is sit at the table and say we are concerned. We are not regulators.”

The pollution is killing species, nevertheless. Ironically, loss of some species is revealed by the proliferation of another — alpine lakes that were once crystal clear have become home to algae. In these cases one type of diatom is replaced or overwhelmed by another.

“Our biggest concern is nitrogen,” Porwoll said. High lakes are clear because “they’re considered very sterile. They’re limited to how productive they can be — how much biomass they can produce.”

Pollution with nitrogen upsets that balance in a process that’s called eutrophication.

“They’re basically being fertilized,” he said of the lakes. “We’ve changed the actual lake chemistry. We can see it in the water.”

Natural deposition for nitrogen is about 2 ¾ pounds per acre per year, more commonly stated as 0.5 kilograms per hectare per year. It might be explained by this example; Natural deposition would be like spreading most of a 3-pound bag of lawn fertilizer across an acre in the wilderness every year, according to calculations made by WyoFile.

Water and snow surveys, however, find nitrogen at 2.5 to 3.5 kg/ha/year in high elevation areas in the ecosystem. That’s up to seven times the normal level.

Using the lawn fertilizer analogy, that would amount to spreading a 20-pound bag of lawn fertilizer across the same acre. All of this takes place in thin, rocky soil or even on sheets of granite itself.

In the Wind River mountains, an angler casts in crystal clear water. Changes to the chemistry of high mountain lakes caused by pollution is affecting the mix of microorganisms. At some places in the greater Yellowstone ecosystem, excess amounts of nitrogen it is altering the mix of aquatic bugs. (Angus M. Thuermer Jr./WyoFile)

“More than likely, it’s coming from the sky,” Porwoll said. The precursor carried in the atmosphere is NOx, or nitrous oxide, which comes from combustion and auto exhaust, among other things.

The critical load of nitrogen for diatom health is 1.5 kg/ha/yr. Organisms like lichen become stressed at 3 kg/ha/yr. Plants reach the critical load level and start changing at 4 kg/ha/yr.

Organisms under stress

Toxic stew:
Here’s a look at how some of the chemicals that are killing some diatoms and lichen in alpine areas of the greater Yellowstone ecosystem are transported and formed. Coal-fired power plants, cars, trucks and high-temperature combustion from other sources produces nitrogen oxide which deposits in the rain and snow as nitrates — basically fertilizer. Sulfur and volatile organic compounds carried in the atmosphere end up as nitric acid in rain and the snowpack. Big agriculture, industrial plants, traffic, forest fires and other sources contribute. Air toxics like mercury and BTEX emissions (benzene, toluene, ethylbenzene and xylenes) come from natural and various man-made sources. Those include snowmobiles, vehicles, natural gas processing, condensate tanks, pipelines and fracking. Ammonia from livestock and crop production is deposited as ammonium.

To determine whether there have been changes in diatom health, researchers retrieved lake-bottom sediment core samples from the Teton and Beartooth mountains. The type of dead diatom cells found in different eras reveals the shifts.

“You can still identify them hundreds of years later,” Porwoll said of the shells of the microscopic life.

“Hundreds of times in lakes around the world things were pretty much the same for thousands of years,” he said. “In the last 100 years, since kind of the industrial age began, you see a shift in species.

“It’s kind of known which species are tolerant of nitrogen and which don’t compete well with more nitrogen in the water,” he said.

In the Greater Yellowstone area, “you see a pretty big shift in species,” he said. “Nitrogen-tolerant species (are) on the increase.”

A seemingly innocuous land organism also is affected by nitrogen. Lichens are a combination of algae (and/or cyanobacteria) and fungus, and some types can’t stand the changes.

“There’s places we can see an effect on lichens,” Porwoll said. “All the high-elevation areas are at or above the critical load for lichens. You see certain species dying out,” but the implications for other life is not yet understood.

Increased nitrogen also has reduced the diversity of larger organisms — macroinvertebrates — in some places in the ecosystem. Aross the entire 20 million acres “aquatic bugs are next,” he said.

Alpine flowers are on the cusp of being replaced by grasses as levels of nitrogen increase. Effects to them begin at 4 kg/ha/yr. In places where whitebark pine has been killed by insects or diseases, the understory of grouseberry also has disappeared, due in part to increased nitrogen.

“Whortleberry is gone under whitebark,” Porwoll said. “Now it’s waist-deep grass.”

Ammonia, a key ingredient in fertilizers, is another worry, deposited in the mountains as ammonium. Scientists detect hot spots from Jackson Hole north to the east side of Yellowstone Park, which Porwoll and others believe comes from big agriculture in the Snake River plain to the west.

Cornices and mountain snowpacks hold the vast amount of precipitation that falls in the alpine zone and they contain many of the pollutants that go on to affect lakes and aquatic species. Jackson, near where this photograph was taken in the southern Teton Range, sees about 17 inches of precipitation annually, much of it coming in the form of snow in the winter. (Angus M. Thuermer Jr./WyoFile)

“This is a big menace that is showing itself,” he said. “The more and more fertilizer that gets used, (the more) gets up in the air.”

Monitoring reveals high levels of sulfates, nitrates and ammonium in the snowpack and water samples from around West Yellowstone, in the southern Wind River Range and around Steamboat Springs, Colorado. Steamboat is downwind from a coal-fired power plant.

If the trend continues, scientists predict fish will die next, then trees.

Researchers look at multiple pollutants

Nitric acid is among the contributors to these environmental changes. It is formed from a combination of airborne sulfur monoxide and volatile organic compounds (VOCs). VOCs are chemicals that vaporize at room temperature, like paint thinner. BTEX is shorthand for a group of them, standing for benzene, toluene, ethylbenzene and xylenes. They come from petroleum derivatives, and many affect the central nervous system.

Thin alpine soils and an abundance of granite provide little buffering against the effects of such chemicals.

While fish die-offs due to chemicals — first called episodic, and then chronic acidification — haven’t yet been seen in the ecosystem, they’ve happened elsewhere where the same pollutants accumulate.

“There’s been fish die-outs,” in Norway and Quebec, Porwoll said, places downwind from industrial sites.

Pollution also cuts visibility. In the pristine Winds, on some high-pollution days it is been reduced from the normal 180 miles to fewer than 70 miles, a reduction of 62 percent.

“One of the things Clean Air Act says is that in Class I areas, you will protect visibility,” Porwoll said. “We’re not supposed to allow the air quality to degrade. Visibility is a measurement of air quality.”

Researchers use a transmissometer to calculate how murky the air is. It measures how much of a light beam is lost along a 5-kilometer path. One of only two in the country is located near the White Pine Ski Area above Pinedale, Porwoll said.

Another nearby device collects particles in the air to determine what’s causing the pollution. “It’s basically sucking crud out of the air, captured on one of four different filters,” he said.

Ozone is not in the mix in Porwoll’s ecosystem assessment. It’s plagued the upper Green River valley, believed to be caused in winter by emissions from vehicles and oil and gas fields, compounded by high-pressure inversions, sunlight and snow cover. Ozone has been detected in the rural valley at levels higher than pollution in Los Angeles.

“We haven’t seen any effect up high yet on the vegetation that we can connect to ozone,” Porwoll said. Some of the reasons may be that the ozone is believed trapped in the valley and reaches high levels when most vegetation is dormant.

What’s being done?

Views in wilderness areas of the Wind River Range and in national parks are supposed to remain pristine. Air pollution has changed that and at times reduced visibility from the normal 180 miles to as few as 70. Here a climber looks out at Gannett Peak, Wyoming’s highest, and other mountains from 11,722-foot-high Scenic Pass in the Fitzpatrick Wilderness. (Angus M. Thuermer Jr./WyoFile)
Views in wilderness areas of the Wind River Range and in national parks are supposed to remain pristine. Air pollution has changed that and at times reduced visibility from the normal 180 miles to as few as 70. Here a climber looks out at Gannett Peak, Wyoming’s highest, and other mountains from 11,722-foot-high Scenic Pass in the Fitzpatrick Wilderness. (Angus M. Thuermer Jr./WyoFile)

Scientists use a variety of devices, monitors and surveys to track pollution across the ecosystem. Among those are CASTNet, a clean air status and trend network, passive ammonia collectors, and bulk sampling from snow surveys and containers at fixed stations. Sensors that are part of the National Atmospheric Deposition Program and the IMPROVE network (Interagency Monitoring of Protected Visual Environments) are part of the ecosystem-wide surveys. Ion exchange resin tubes, which collect depositions of nitrogen, help track that chemical.

Scientists establish “critical load” measurements they use to warn of expected or observed changes. Federal land managers, states or other stakeholders then establish “target loads” that “designate how much or how fast we want ecosystem recovery to occur,” Porwoll’s PowerPoint presentation says.

“Another thing we don’t have is a list of good indicator species,” he said. When developed, that list will show researchers where to concentrate their observations in the hopes of detecting changes as soon as they occur.

When teams first struck out for the wilderness in 1984, they were seeking to establish baseline measurements in anticipation of acid rain affecting the high-altitude lakes in the Wind River Range. They would arrive at a site with a horespacker’s load of gear, including rafts, dry suits and various devices to collect water samples from different depths in a lake.

In some instances, a helicopter was used to transport duplicate samples to ensure that what was toted out by horse didn’t degrade.

“We started out looking for acid rain,” Porwoll said. “Turns out we should be looking for nitrogen.”

The data dating back to 1984 remains critical, however. Researchers collected it before profound changes took place around the ecosystem.

“If they hadn’t started in ‘84 it would take us a lot longer to identify a trend,” Porwoll said.

Angus M. Thuermer Jr.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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  1. Excellent article, Angus. Having worked on the Bridger-Teton acid deposition program the during its first seven years, 1985-92, I was upset that the Forest Service didn’t certify wilderness impairment based on the first five years of data we collected and analyzed.

    Instead, the USFS rolled over and let the BLM issue fistfuls of drilling permits, which led to the present heavily-industrialized state of the upper Green River Basin. That the air and water quality in the Class I wilderness downwind would deteriorate was predictable years ago. That the responsible federal and state agencies let it happen is a disgrace.

    (C. L. Rawlins wrote Sky’s Witness: A Year in the Wind River Range, which describes the wilderness monitoring work and natural history of the area. It’s available on iBooks, from Henry Holt & Co.)
    Chip Rawlins
    Jelm, WY