Our national parks provide a haven for some of our nation’s most cherished, iconic and native wildlife species, such as the brown bears of Katmai National Park. ©Brad Josephs

Our national parks protect some of our nation’s most cherished, iconic and native wildlife species, such as the brown bears of Katmai National Park and the bison—America’s national mammal—of Yellowstone National Park. But, according to some, there’s a dark side to that safety. They would argue that conservation success inside some parks comes at the expense of neighboring, unprotected habitats; that parks displace extractive impacts, such as fishing, hunting and logging, to other, nearby areas.

Fresh research, however, is turning that contention around. A new study shows that while national parks enhance bird diversity inside their borders, large parks also support higher diversity of both birds and mammals in nearby unprotected areas.

And here’s a fun fact: while today Denali National Park and Preserve is known for its abundant and diverse wildlife, what was there 70 million years ago was “huge.”


The bison of Yellowstone National Park are exceptional. They comprise the nation’s largest American bison population on public land. Unlike most other herds, this group has thousands of individuals that are allowed to roam relatively freely over the park’s expansive landscape.

Wildlife outside national parks

We know that national parks help conserve wildlife and protect biodiversity within their borders. Some feel, however, that such ecological success inside some parks makes nearby areas even less safe for animals and plants since they must absorb not only the negative impacts that would normally occur on the land, but also the ones that would have taken place on the highly safeguarded habitats within the parks.

When we move from the land to the water, however, it’s a different story. Marine parks often report biodiversity “spillover,” meaning that species protected within marine park boundaries produce an abundance of eggs, larvae and adults that then disperse and increase the biodiversity in surrounding habitats.

So, to answer the question of whether terrestrial parks displace biodiversity losses or provide biodiversity spillover, researchers from the University of Montana and NASA-affiliated scientists recruited other scientists from 10 countries to conduct a comprehensive analysis of bird and mammal diversity inside and outside of parks across Southeast Asia, one of the most biodiverse regions on Earth.


Marine parks, such as Ang Thong National Marine Park in Thailand, often have a “spillover” effect. That means that species protected within the marine park’s boundaries produce an abundance of individuals that then disperse into surrounding habitats, increasing biodiversity there, too.

To conduct their assessment, the researchers called on NASA’s Global Ecosystem Dynamics Investigation (GEDI), which operates a near-infrared laser instrument on the International Space Station that provides vertical information on forest structure. The unique data provided by GEDI allowed the scientists to control for 3D forest structure in a way that simply wasn’t possible a few years ago with only satellite monitoring. The GEDI allowed them to go beyond forest cover and get at the structural diversity and habitat heterogeneity of forests, which is important for biodiversity. This means that the study’s results will hold across different forest types.

After compiling a massive database of bird and mammal observations across the region, the researchers found that national parks do, indeed, enhance bird diversity inside their borders. But mammal diversity was higher outside large parks.

Those results, published in the science journal Nature in August 2023, were surprising. Hunting is a key concern for Southeast Asian wildlife conservationists and a prime suspect for why diversity has often been assumed to decline outside of parks. It was thought that hunting bans within park boundaries only displaced these activities to nearby, unprotected areas and undermine their net benefit.

The United Nations is aiming for significant expansions of global protected areas. The strategy, often called the 30 x 30 Movement, is to conserve 30% of Earth’s lands and waters by 2030. ©Bob Wick, BLM, flickr

Their work, say the researchers, provides clear justification to designate protected areas that are as large as possible, as larger parks had significantly stronger influence on mammal diversity in the surrounding landscape. Recent work in the region suggests that some wildlife species are persisting in small parks, but this apparently doesn’t scale up to such areas having landscape-wide spillover effects.

While massive expansions to global protected area coverage will be difficult and expensive, it will be worth it. And we should do it now, as it will only get more difficult in the future with exasperating socio-political setbacks.

The findings are especially timely for the United Nations, which recently announced ambitious biodiversity conservation targets that include significant expansions of global protected areas. The UN strategy is to conserve 30% of Earth’s lands and waters by 2030, known as the 30 x 30 Movement.

Alaska’s Denali National Park and Preserve is unique: it’s 6 million acres of wild land, bisected by one ribbon of road. It’s also a world-class area for dinosaur tracks. ©jose maria vazquez, flickr

Dinosaurs inside Denali

Every year, thousands of people visit Denali National Park and Preserve to experience its stunning natural landscape and glimpse its large mammals, such as black bears, caribou, grizzly bears, moose and wolves. But around 70 million years ago, Denali was equally impressive for its big fauna.

In a paper published in the journal Historical Biology in July 2023, University of Alaska Fairbanks scientists revealed that they had documented the largest known dinosaur-track site in Alaska. The site, located in Denali National Park, has been dubbed “The Coliseum.”

The Coliseum is the size of one-and-a-half football fields and contains layer upon layer of prints preserved in rock; a mix of hardened impressions in the ancient mud and casts of tracks created when sediment filled the tracks and then hardened. Unlike some other places that contain dinosaur tracks, this one isn’t just one layer of rock with tracks on it. It is a sequence through time: a record of multiple species of dinosaurs over many generations that thrived in what is now Interior Alaska nearly 70 million years ago.

For a dinosaur track to form and be preserved, conditions must be just right. The consistency of the ground influences the depth, shape and size of a track. If the ground is too hard, the resulting print will be very shallow and not show much detail. If the ground is too soft, the track could collapse in on itself. In some places, fossilized tracks make it look as though dinosaurs were walking up impossibly steep inclines. But this is where the geology of the ground has changed dramatically over millions of years; the dinosaurs would have been roaming over much flatter ground. ©Mia & Steve Mestdagh, flickr

The scientists report that when they first visited the site (after a seven-hour hike to get there), it seemed unremarkable in the context of the park’s vast landscape: just a rocky outcrop rising about 20 stories from its base. On a closer examination, however, they discovered a dinosaur trackway at the foot of a cliff. Then dusk approached, and what they saw when the sun angled itself perfectly on the rock beds left them flabbergasted.

In the Late Cretaceous Period, the cliffs that make up The Coliseum today were sediment on flat ground near what was likely a watering hole on a large floodplain. As Earth’s tectonic plates collided and buckled to form the Alaska Range, the formerly flat ground folded and tilted vertically, exposing the cliffs covered with tracks. In addition, the research team found fossilized plants, pollen grains, and evidence of freshwater shellfish and invertebrates—little clues that added together show what the environment looked like as a whole.

The area was part of a large river system, with neighboring lakes and ponds. Its climate was warmer than it is today; more like that in the Pacific Northwest. There were coniferous and deciduous trees, and an understory of ferns and horsetails.


In the Late Cretaceous Epoch (100.5 million years ago to 66 million years ago), the climate in what is now Denali National Park was warmer than it is today; more like that in the Pacific Northwest. There would have been coniferous and deciduous trees, and an understory of ferns.

Based on the tracks, a variety of juvenile and adult dinosaurs frequented the area over thousands of years. Most common were large, plant-eating, duck-billed and horned dinosaurs. The scientific team also documented rarer carnivores, including raptors and tyrannosaurs—many times the size of Denali’s biggest brown bear there today—as well as small, wading birds.

From all signs, it was an amazing ecosystem, then as now.

Preservation within the nation

It’s clear that the beneficial effects of national parks go far beyond their official borders. They preserve biodiversity—one of our best insurances against harms to our health—wherever they are designated and in their greater regions.


The time to move forward with the expansion of protected areas is now, say scientists.

Another important facet of the National Park Service’s mission is to safeguard fossil sites, such as The Coliseum. And while such world-class spots must be protected from disturbance and theft, the National Park Service encourages visitors to explore for fossils in their geologic context to better grasp the evolution of ecosystems and landscapes through time. But do leave such fossils undisturbed for others to appreciate.

If we could muster the courage and enthusiasm to make 30 x 30 a reality by creating more large, national parks, who knows what other megatreasures we’ll uncover.

Here’s to finding your true places and natural habitats,