A camera trap image of a black bear near Grand Teton National Park.
A camera trap image of a black bear near Grand Teton National Park. (Photo: © Charlie Hamilton James/National Geographic)

The National Park Service has frequently been touted as "America's best idea," and as the groundbreaking agency celebrates its 100th birthday, it's easy to understand why.

Ever since it was established on Aug. 25, 1916, the National Park Service has been charged with preserving the ecological and historical integrity of hundreds of nationally protected places, all of which are classified under an array of designations — from parks and monuments to preserves and memorials.

To honor the legacy of what is arguably one of the country's most important ecological achievements, National Geographic magazine is devoting its May issue to the 34,375-acre Greater Yellowstone Ecosystem and the associated national park.

According to the National Park Service, this region "is one of the largest nearly intact temperate-zone ecosystems on Earth, [and its] diversity and natural wealth includes hydrothermal features, wildlife, vegetation, lakes, and geologic wonders like the Grand Canyon of the Yellowstone River."

One of the most intriguing stories in the issue is Todd Wilkinson's "Threatened Species Are Thriving in Yellowstone. Now What?" which features gorgeous camera trap images by photographers Charlie Hamilton James, Michael Nichols, Drew Rush and others.

A cougar is captured on the prowl by a camera trap.
A cougar is captured on the prowl by a camera trap. (Photo: © Drew Rush/National Geographic)

The image above, photographed by Drew Rush, shows a cougar "caught on the prowl by a camera trap set behind an elk rack on a cliff. [...] Notoriously elusive, cougars vary their range in response to their prey, mostly elk and deer. In winter, they favor the shallow snow in the northern reaches of Yellowstone."

The outstanding photography is paired with Wilkinson's examination of the effects Yellowstone's preservation has had on wildlife conservation.

"Greater Yellowstone exists as a flagship for 'rewilding.' It not only hosted the reintroduction of wolves — a lost species — but also served as a critical reservoir in the recovery of grizzly bears, bison, elk, Rocky Mountain bighorn sheep, sandhill cranes, and trumpeter swans. The area is the only essentially intact bioregion in the country — and one of the few in the world that still are home to all of their original mammals and birds."
A camera trap image of a mule deer near Grand Teton National Park
A camera trap image of a mule deer near Grand Teton National Park. (Photo: © Charlie Hamilton James/National Geographic)

To make sense of Yellowstone's encouraging conservation gains, Wilkinson talks with Susan G. Clark, a Yale professor and the founder of the Northern Rockies Conservation Cooperative in Jackson, Wyoming.

Clark explains that there are currently about 5,000 wild American bison within Yellowstone — an impressive number when you consider the species was nearly hunted to extinction by the late 19th century. However, that stronghold pales in comparison to the 35 million bison that historically roamed the West.

The same applies to grizzlies, which have all but disappeared from 95 percent of their historical range in the lower 48 states. Currently, there are about 800 grizzlies in Yellowstone and a few hundred more spread throughout the contiguous United States, but that represents just a tiny fraction of the estimated 50,000 that once lived in these parts.

Two grizzlies fight over a bison carcass in Yellowstone National Park.
At Firehole River in Yellowstone National Park, two grizzlies fight over a bison carcass killed by the Canyon Pack wolves. (Photo: © Michael Nichols/National Geographic)

So the question is, what does it really mean to "thrive" when you're working with the bare minimum? And where do we go from here to ensure sufficient habitats for species that are recovering?

"What’s important is not just having a checklist of species and calling it good," Clark says, "but preserving these animals’ natural histories, protecting migration patterns, and turning grass into meat — which is then recycled across the landscape in the food chain."

A cougar, photographed by a camera trap along a busy game trail above the Buffalo Fork River near Grand Teton National Park
A cougar, photographed by a camera trap along a busy game trail above the Buffalo Fork River near Grand Teton National Park (Photo: © Charlie Hamilton James/National Geographic)

Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.