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Yellowstone is facing ‘unprecedented’ changes to climate and habitat

The park’s stewardship of wolves, bison and grizzly bears continues, but many amphibians are in decline, as are trumpeter swans, Arctic grayling and cutthroat trout.

Yellowstone’s successful stewardship of such marquee species as wolves, bison and grizzly bears continues, but the park “is now faced with an unprecedented rate of change in climate and habitat conditions.”

A fascinating look at one of America’s premier natural places — and the management changes of keeping it that way — popped up Wednesday in a fresh assessment of “vital signs” at Yellowstone National Park.

America’s first place set aside as a national park “is now faced with an unprecedented rate of change in climate and habitat conditions,” says the report from the park’s Yellowstone Center for Resources. A few of these might be generally accepted as positive, but a far greater number are plainly negative.

The park’s successful stewardship of such marquee species as wolves, bison and grizzly bears continues; elk numbers are dropping in some areas but have shown signs of stabilizing at new, lower levels.

Bighorn sheep appear to be recovering from a pinkeye epidemic in 1982, and an especially harsh winter in 1996-1997, that sharply reduced their numbers.

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But many amphibians are in decline, as are trumpeter swans, Arctic grayling and two types of cutthroat trout.

The park’s native trout are stressed by aquatic invaders, including lake trout introduced illegally some time ago, presumably by anglers or “bucket biologists” who thought adding some 30-pound lunkers to Yellowstone’s waters would be a nice improvement.

And as in so many parts of the West, the constant influx of invasive plant materials in tire treads or boot soles continues; there are now three dozen particularly noxious species among the 200-plus non-native plants that have taken root in Yellowstone.

Since the park’s creation, Yellowstone’s management goals have included preservation of natural resources through restraint on direct human interference with its ecological practices.

Now, in a move that brings to mind the current debate over what to do about the wolves of Isle Royale, park managers have begun “evaluating the feasibility of establishing management targets” for species abundance, habitat acreage and other resources.

That’s been challenging; it’s not easy to determine the target population of trumpeter swans or the percent of suitable wetland habitat occupied by boreal toads, especially in an ecosystem that is expected to be dynamic and is now faced with an unprecedented rate of change in climate and habitat conditions. 

Some would even say that it is not appropriate in a national park, where our goals are largely to put the pieces of the ecosystem into place and then allow natural processes to prevail.

To a degree Yellowstone can be considered, like Isle Royale National Park, in the framework of “island biogeography” —  an ecosystem isolated by altitude, instead of water, from its surroundings in Wyoming, Montana and Idaho. But such isolation carries no protection from global warming and the climate changes it is driving.


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  • Average annual temperatures have risen dramatically since 1989 — up 4.6°F for the average low, and 3.5°F for the average high.
  • Average peak snowpack in the park has declined by 22 percent since 1975, from 14.5 inches of “snow water equivalent” to 11.3, and the average length of the winter season has decreased from 208 days to 185 since 1980.
  • Total precipitation in the park since 1976 has generally been below historical averages.
National Park Service

As has happened across much of the mountain West, these changes have placed the park in a situation of continuing and worsening drought, with a rising risk of wildland fire.

You might think that water quality in a place as vast and remote as Yellowstone might be immune to development activities beyond its borders. Not so much:

The state of Montana has found that a portion of Reese Creek on the park’s northern boundary only partially supports cold water aquatic life. The suspected cause of the impairment to the Creek, where Yellowstone cutthroat trout are present, is periodic dewatering associated with irrigation activities outside the park. …

As a result of mining activity 8 km from the park, tailings remain in the Soda Butte Creek floodplain, impairing the segment that extends downstream to the park boundary. Because of its impaired status, park staff periodically measure the total and dissolved arsenic, copper, iron, and selenium in the water. Iron concentrations at the park boundary exceeded the Montana standard for aquatic life. …

A major bright spot in the report concerns improvements in winter air quality as a result of snowmobile regulations that took effect in 2002, limiting snowmobile access to the park, requiring a shift to cleaner, four-stroke engines and shifting some of the snow season’s tourism from individual sleds to snow coaches.

Carbon monoxide (CO) and particulate matter (PM) are monitored at West Yellowstone and Old Faithful, where oversnow vehicles (OSVs) are most concentrated. These pollutants have declined since 2002 as a result of fewer snowmobiles in the park and the “Best Available Technology” (BAT) requirement. …

The new rules on snowmobiles have also brought improvement in the park’s “winter soundscape,” the report says, meaning things are quieter for longer periods than they used to be. However:

Nitrogen deposition is emerging as an issue because although the BAT-required 4-stroke engines emit less CO than 2-stroke snowmobiles, they emit about 15 times more nitrogen dioxide.

Speaking of noxious interlopers, the park’s native trout are under pressure from aquatic nuisance species. In addition to the lake trout, which were deliberately introduced, the threats include some particularly troublesome snails:

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First detected in the park in 1994, New Zealand mud snails are now in all of the major watersheds, where they form dense colonies and compete with native species. Confirmed in the park in 1998, the parasite that causes whirling disease in cutthroat trout and other species has been found in the Firehole River and the Yellowstone Lake watershed.

Another nonnative species, the red-rimmed melania, a small trumpet snail imported by the aquarium trade, was discovered in the warm swimming area at the confluence of the Boiling River with the Gardner River in 2009. … The species has a narrow temperature tolerance (18–32°C)  and is unlikely to survive  downstream of the Boiling River during the winter, but it could  appear in other thermal waters in the park.

The National Park Service has been fighting the lake trout since the middle 1990s and last year hired commercial fisherman to remove more than 300,000 of them from Yellowstone Lake. It hopes to keep reducing the population by 25 percent each year until it “collapses to an insignificant level.”

But the battle of the weeds may just be getting started:

During each of the last three summers, dozens of park staff and volunteers participated in surveys of more than 20,000 acres (about 1% of the park), mostly along roads where invasive plants are more likely to become established. They found that more than a quarter of this area was infested with weeds. Based on program priorities, 112 acres were selected for treatment in 2012. Plants were physically pulled on 41 acres; the rest were treated using herbicides. …

Some infestations can be eradicated if the species is treated  when the outbreak is still small; other species, such as spotted  knapweed, are so common that stopping them from spreading is the primary goal. This strategy has helped prevent high-priority  invasive species from moving into backcountry areas where control is more difficult. Most of the approximately 37 species targeted  for treatment are listed by the states of Idaho, Montana, or Wyoming as “noxious weeds,” which means that they are considered  detrimental to agriculture, aquatic navigation, fish and wildlife,  and/or public health.

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A summary and link to the full report, as well as links to recent reports on Yellowstone’s wolf and bird populations, are here.