The sky is broad, the land is rugged and the air fills your lungs with joy. But for many adventurers, the true appeal of a trek through a national park is the fine detail: the living flora and fauna, often rare and unusual, that quietly populate the landscape.

U.S. national parks are each home to an average of 415 species of wildlife — often hundreds more — and over a thousand different plants. Yet there’s not really such a thing as the “average national park.” Each has its unique characters, families, sights and sounds. From tiny but tough pikas to trumpeter swans and Dutchman’s breeches, these wild expanses are full of surprises.

So where are most of those surprises found? Casago analyzed National Park Service data to find out which parks have the most wildlife and plants per 100 km² and which have the greatest biodiversity overall.

What We Did

Casago sourced the number of species of amphibians, birds, fishes, mammals and reptiles in each national park from the National Park Service’s Integrated Resource Management Applications (IRMA) portal. We combined the figures to give the total number of animals overall and per 100 km² in each park and calculated additional figures just including birds. And then, we did the same for plant species.

Key Findings

  • Congaree in South Carolina has the greatest density of wildlife species, with 362 per 100 km².
  • However, Biscayne in Florida has more overall: a total of 1,002.
  • Carlsbad Caverns in New Mexico boasts 194 bird species per 100 km², the highest density.
  • Cuyahoga Valley in Ohio has the densest plant biodiversity of all, at 935 species per 100 km².
  • The Great Smoky Mountains in North Carolina and Tennessee have the highest number of plant species overall: 2,278

Biscayne Boasts Over 1,000 Species of Wildlife

A recent study suggests that boosting the paths and links between America’s national parks would lead to a boost in the diversity and survival outlook. The authors propose the rather cute idea of building “ecological bridges” over and under highways to reverse the effects of habitat fragmentation. For now, however, our first map shows how many different animal species (amphibians, birds, fishes, mammals and reptiles) are found per 100 km² in the 20 separate parks with the densest variety of wildlife.

Infographic showing all American National Parks Ranked by Plant Biodiversity

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Congaree in South Carolina is one of America’s smaller national parks, but with 362 wildlife species and 804 plant species per 100 km², it packs a mighty punch and makes for a good choice for wildlife spotters on the east coast.

The park’s success story can be attributed to its unique landscape, with floodwaters from the Congaree and Wateree Rivers regularly depositing nutrient-rich soil on the landscape. Plus, its huge hardwood and pine trees create towering canopies that shelter some 385 different creatures in total. You might spot bobcats, wild pigs, opossums and river otters as you walk or kayak around.

Infographic showing all American National Parks Ranked by Animal Biodiversity

Click here to see the full-size image

In terms of sheer diversity, however, Biscayne in Florida takes the crown with 1,002 different wildlife species. Some 698 of these are fish species, making Biscayne — with its “aquamarine waters, emerald islands, and fish-bejeweled coral reefs” — a particularly fine destination for those who fancy underwater life.

A special mention goes to Redwood in California for sheltering more mammals than any other national park. These include the dusky-footed woodrat, mink, skunk, Botta’s pocket gopher (🎥) and the California vole. Some 115 of Redwood’s 706 wildlife species are mammals, although some (such as bats and bears) come and go with the seasons (or with their moods).

Carlsbad Cavern Has Birds. And Bats. Lots of Bats.

For some wildlife lovers, it don’t mean a thing if it ain’t got wings. The British call them twitchers: “someone whose hobby is studying wild birds in their natural environment.”

In Carlsbad Caverns, New Mexico, you’ll find around 367 of the things, or 194 per 100 km² — the densest variety of birdlife in an American national park. The Cave Swallow is a local specialty you won’t see in too many other places. They build mud cup nests in the caves and return to them each year. (Here’s a handy guide to which birds you might see at Carlsbad around the year). Watch out, though — those caves are also home to 400,000 Mexican free-tailed bats, which flock out at night (🎥) in a spectacle of terror or wonder, depending on how you feel about bats.

Infographic showing top 10 American National Parks for bird watching

Click here to see the full-size image

A special mention here to the Grand Canyon National Park, which boasts an astonishing 456 bird species (the most of any U.S. national park) but doesn’t make the chart because they’re spread out over such a massive expanse. If you’re very lucky, you might spot a Californian condor — one of just 400 in the world.

Great Smoky Mountains Has the Greatest Diversity of Plant Life

“Towering or tiny, massive or delicate, living or fossilized, trees are found in almost every national park,” says the National Park Service. But while trees are the humbling big hitters of America’s national parks, nature’s ground-level players — from orchids to cacti, moss to herbs — will delight and fascinate anyone who takes the time to stop awhile. Here are the ten parks with the densest variety of plant life per 100 km².

Infographic showing top 10 American National Parks for plant lovers

Click here to see the full-size image

Skunk cabbage, bloodroot, squirrel corn and Dutchman’s breeches: plant life at Cuyahoga Valley in Ohio is a universe of its own. You’ll find some 935 plant species per 100 km² at Cuyahoga (and 1,232 altogether). Thankfully, there are trails to help you navigate this astonishing landscape, such as the Brandywine Gorge Loop, featuring those Dutchman’s breeches, three-petalled trilliums and Mayapples.

Infographic showing top 20 American National Parks for wildlife spotting

Click here to view full-size image

Great Smoky Mountains, spanning across North Carolina and Tennessee, is 16 times the size of Cuyahoga Valley, but if you can navigate without relying on GPS, you may spot up to 1,000 more plant species. With a total of 2,278 plant species and 620 animals, Great Smoky is America’s most biodiverse park. The Smokies also score high for mammals (107 species) and reptiles (56), and experts reckon the park could hide up to 100,000 unrecorded species.

The shelter from the mountains, wet weather and humid climate makes the Smokies a lovely spot for a plant to set up home. One species that finds it just right is the rock gnome lichen, which grows in colonies of narrow, blue-gray, strap-like lobes called squamules, of which only 35 one-meter patches are known to exist. This lichen loves the foggy mountains but is vulnerable to pests and hiking boots.

Take Only Memories

A wildlife trip to a national park makes for a welcome alternative to urban life and the computer screen. But to stand your best chance of spotting some gems and avoiding harm to the park’s natural life, experts suggest the following:

  • People only, no pets.
  • Keep quiet and stay still where possible.
  • Dress in natural tones and don’t wear scent.
  • Keep your distance and never feed wildlife.
  • Take only memories (and pictures); leave only footprints.

And don’t forget to look at the clouds. There are some really good ones out there!


We sourced all the national parks in America with their coordinates from Wikipedia. For each park, we then downloaded detailed records of all species present from and park area sizes from Parks Expert.

For each park, we extracted the number of amphibians, birds, fish, mammals, reptiles and vascular plants by counting records of approved species that fell under any of the six categories. The numbers of amphibians, birds, fishes, mammals and reptiles were combined to get the total number of animals and vascular plants to get the total number of plant species.

To get the density of species, we calculated wildlife species (all five categories of animal species), bird species and vascular plant species per 100 km² for each park. Parks with less than 100 km² area were excluded from further analysis.

Our data was collected in February 2023.


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