For a national park going on 140 years old, the fact that Yellowstone National Park has a wildlife assemblage about as diverse as that which existed 200 years ago is a testament to the park's wildlife managers.

Wolves have regained a foothold of sorts after having been extirpated a half-century ago, grizzly bear numbers have grown since the mid-1980s, and some progress is being made on efforts to see bison regain some of their wintering grounds outside the park.

But as a draft report to the World Heritage Committee on various aspects of Yellowstone's ecosystem makes clear, ever more human pressures, largely in the form of hunting, development, and ranching, are forcing park managers to be more hands-on in their approach to wildlife in the world's oldest national park.

According to the report, which is open for public comment at this page through January 20:

* Human relocation into the park of a grizzly or two from other bear populations could be necessary by 2022 to avoid genetic inbreeding in Yellowstone's grizzly population;

* While hundreds of thousands of non-native lake trout are being netted in Yellowstone Lake every year, more aggressive netting operations are needed to prevent the big fish from totally overwhelming the native cutthroat trout;

* Without access to lands in Montana beyond Yellowstone's borders, the park's bison could not only "exceed the capacity of the environment to support them," but also "die in large numbers from starvation during drought conditions or a winter with deep snowpack that limited available forage."

This shouldn't come as a surprise in light of the development that has occurred outside, and to a much lesser extent inside, Yellowstone's borders. Roads, towns and cities, and ranches all fray corridors necessary to prevent the park from becoming a genetic island for species such as bears and wolves. Hunting can take a toll on wolves that roam outside the park.

Add to these issues climate-change impacts, and preserving the park's natural resources for the enjoyment of future generations becomes even more challenging.

Still, David Hallac, chief of the Yellowstone Center for Resources, says park managers are making progress in these and other areas. But he does acknowledge that some of the progress might be slower than some observers might like. Referring to the park's bison herds and gaining permission for the animals to range north into Montana and onto their traditional wintering grounds, Mr. Hallac says "there’s no question that progress has been slow and it’s been incremental."

"But I do think things do take time," he quickly adds. Back in the mid-19th Century "there were millions of free-ranging bison in the West and the Midwest. That has swung dramatically in terms of free-ranging bison."

Part of the problem with gaining permission for Yellowstone to be fully free roaming, offers Mr. Hallac, is that society has not accepted bison as wildlife “outside of protected areas."

‘We’re in the process of working with the public to get them to learn that bison are wildlife and we want them to be managed as wildlife,” he says.

At the Greater Yellowstone Coalition, Mark Pearson also sees the park making progress in some of the wildlife areas of concern.

“The overarching thing is that they are making some significant progress on a number of fronts. That’s encouraging. Like bison and lake trout in particular," Mr. Pearson, GYC's national parks program manager, says. "In the past year I think, certainly since the last iteration of this (report to UNESCO), but just over the past year you’ve seen some big changes in bison management, with hopefully the adaptive management change on the northern side” of the park.

What Mr. Pearson was referring to was a move in 2008 by the state of Montana to sign an agreement with the Church Universal and Triumphant to allow some bison access to the Royal Teton Ranch just north of Yellowstone. Under the agreement, state and federal agencies worked to push the northern migratory range for bison 7 miles north of the park. A year ago more than 300 bison migrated out of the park and onto habitat in the Gardiner Basin.

However, the park's report to UNESCO did not mention that nearly 700 bison that wanted to move north of the park were rounded up and spent much of the winter corraled at the park's Stephens Creek Bison Capture Facility. That, says Mr. Hallac, was simply because the report was more of an overview, not a detailed analysis of all the park's issues.

While an agreement was reached last spring to provide bison access to 75,000 acres further north in Montana to Yankee Jim Canyon, park officials say hearings in Montana courts later this winter "are expected to include testimony from Park County, Montana, and the Park County Stockgrowers Association, two groups seeking to limit bison travel north of the park boundary due to concerns about public safety and property damage."

As for the future of lake trout in Yellowstone Lake, that currently seems to hinge on efforts to raise $1 million privately to help pay for more intensive netting. While park officials say they need $2 million per year through Fiscal Year 2017 to afford the necessary netting operations, so far they've only been able to budget about $1 million per year.

"The Yellowstone Park Foundation, YNP's primary fundraising partner, has agreed to take this on as a project and is optimistic about raising the funds required," the draft UNESCO document notes.

Mr. Hallac, who came to Yellowstone last year from Everglades National Park, is confident fisheries experts will be able to stifle the threat posed by lake trout for a variety of reasons.

“From a geographic standpoint, the problem is not likely to get worse. The fish are not likely to crawl across the land and infest another lake," he says. “We can capture the fish. Not only can we capture the target fish, but we can avoid the non-target fish, which are the cutthroat trout, which we’re trying to restore.”

Crews are employing radio telemetry to hone-in on where the lake trout spawn and when, says Mr. Hallac, and that will help perfect efforts to eradicate the fish.

While the UNESCO document notes that the genetic fate of Yellowstone's grizzly bears is tied to the arrival of just two bears to the greater Yellowstone ecosystem per generation that survive and breed, the closest population of grizzlies is in the Northern Continental Divide Ecosystem that includes Glacier National Park.

"...natural gene flow by bears moving across the landscape between the GYE and the NCDE may be several years away," park officials note in the document. "The average dispersal distance for subadult male grizzly bears in the GYE is 70 km. The distance between the two occupied ranges of the GYE and NCDE populations is currently 165 km, more than two times the average dispersal distance..."

"If natural gene flow does not occur within 2-3 decades, it may become necessary to implement plans for translocation," the report adds.

Yellowstone's current wolf population numbers around 100 individuals, according to park officials, and an agreement the park reached with Montana officials has reduced the quota of wolves that might be hunting in districts along the park's northern border. That agreement, park officials note, should reduce "the potential for signficiant mortality of wolves living in YNP."

Traveler footnote: You can read the draft UNESCO report and comment on it until January 20 at this NPS website.