JOAN CARTAN-HANSEN, HOST: In the early 1800s, John Colter explored the region we now know as Yellowstone National Park.

When he got back East, he described boiling mud, shooting water and steam coming from the ground.

And people didn't believe him!

Today, Yellowstone is among the most visited places in the world.

In our other Yellowstone video, we describe the area's geological features.

In this video, we learn another reason why Yellowstone National Park is unlike anywhere else on the planet.

[MUSIC] STUDENT ONE: Wow, Yellowstone is really cool.

STUDENT TWO: Yes, but I still don't know what to do for my biology report.

Joan?

CARTAN-HANSEN: How about Yellowstone National Park?

The Greater Yellowstone Ecosystem is the last intact temperate zone ecosystems on the planet.

STUDENT TWO: What do you mean?

CARTAN-HANSEN: Well, let's ask a biologist and a conservationist.

BROOKE SHIFRIN: A temperate zone ecosystem means an environment that has four distinct seasons, along with a variety of kinds of habitats.

CARTAN-HANSEN: Yellowstone National Park was created in 1872.

It is the heart of the Greater Yellowstone Ecosystem, an area of over 28,000 square miles.

The park itself is almost 3,500 square miles.

That's bigger than the states of Delaware and Rhode Island combined.

Most of the park is forested.

The grasslands have mostly blue bunch wheatgrass,and then there's desert shrub lands.

SHIFRIN: Well, Yellowstone is incredibly unique because we have all of our native wildlife species here, which is not the case in a lot of places, especially in the lower 48 states.

We have iconic animals like grizzly bears, wolves, elk, bison.

STUDENT TWO: Grizzly bears?

CARTAN-HANSEN: Yellowstone is home to two types of bears: grizzly bears and black bears.

Grizzly bears are larger and they have an obvious shoulder hump.

Black bears are smaller, have no hump and their fur comes in a number of different colors.

SHRIFIN: Grizzly bears are incredibly intelligent.

They're very complex.

They are what is called an umbrella species, which means that if you are protecting the type of habitat that grizzly bears need, you're probably also seeing some sort of benefit for a number of other kinds of animals as well.

STUDENT ONE: What other types of animals?

CARTAN-HANSEN: How about elk?

[ELK BUGELING] Yellowstone has big herds of elk, mule deer and pronghorn antelope.

SHRIFIN: These are called ungulates, and these big herds of ungulates that migrate across the landscape, their movement is sort of like the beating heart of this region.

CARTAN-HANSEN: While these ungulates are important to the ecosystem, if there are too many of them, they can be destructive.

The natural predator for these prey animals is the wolf.

But wolves were essentially eliminated from the lower 48 by the 1970s.

SHRIFIN: When you are missing a link in that food chain, you risk having one of those animals be too abundant.

And so, what we saw was once wolves were reintroduced to Yellowstone, that it balanced things out in terms of how many elk there are, how many bison there are.

And therefore, we saw a really positive impact on the ability of willows around creeks to return, grass to return in a more healthy way.

This is a great example of how wolves play a really important ecological role in our environment.

CARTAN-HANSEN: Wolves were re-introduced to the park in January of 1995.

Today, scientists estimate there are now about 90 to 110 wolves in the park and about 500 in the Greater Yellowstone area.

Not only did wolves prove to be good for the ecosystem, but they also draw a large number of tourists.

Yellowstone National Park is the now the best place in the world to view and study wolves.

STUDENT TWO: Wow, I didn't know that.

What about buffalo?

STUDENT ONE: Uh, they're called bison.

STUDENT TWO: No, buffalo.

Aren't they?

SHIFRIN: There's actually no difference between a bison and a buffalo in the context of here in the lower 48.

And so American bison, by many indigenous peoples, are referred to as buffalo.

CARTAN-HANSEN: But, in scientific lingo, they're called bison.

The American bison is the largest land-dwelling mammal on our continent.

A male can weigh as much as two thousand pounds.

Their fur is perfectly designed for extremely cold temperatures.

Scientists think they don't feel the cold until the temperature hits about 40 below zero.which it can do in Yellowstone.

SHIFRIN: If you're a bison and Yellowstone National Park it's a really smart idea to hang out around geysers or other thermal features because those features mean that there's less snow, they provide so much heat and so it's a lot easier to find grass as a bison in those places.

CARTAN-HANSEN: Yellowstone is the only place bison have lived since prehistoric times.

But by the late 1800s, so many bison had been killed that the animals neared extinction.

The remaining ones in Yellowstone made up the last free-range herd in America.

And those were used to rebuild today's bison populations.

They may look harmless but bison are quick, agile, can run up to 35 miles per hour, and they can be grumpy.

SHIFRIN: Bison and elk and grizzly bears and wolves are all so exciting to see in a place like Yellowstone National Park and it's really important if you see them to give them a lot of space and a lot of distance.

That is critical to keep yourself safe and to protect those animals as well.

CARTAN-HANSEN: There's more to Yellowstone than mammals.

The park has over a thousand plant species, 300 types of birds, 16 species of fish, five types of amphibians, six types of reptiles and scientists don't even know how many microscopic bacterial and archaea species thrive in the geothermal features.

Sadly, Yellowstone itself is endangered.

Climate change takes its toll and one other big factor threatens the park.

SHIFRIN: Yellowstone does get a lot of people.

I think increasingly our concern is that we are potentially loving these places to death.

CARTAN-HANSEN: And that's why biologists like Shrifin study in Yellowstone.

They want to save it.

SHIFRIN: I would say if you are interested and curious about your environment and animals and what makes nature work the way it does, there is so much opportunity to pursue a job in wildlife biology.

It is fun.

You get to spend time outside.

You get to learn a lot about things that people around the world find fascinating and you get to become an expert on those things.

And so I would absolutely recommend becoming a biologist!

CARTAN-HANSEN: So, do you think Yellowstone would be a good topic for your biology report?

STUDENT TWO: Yes, but where can I learn more?

CARTAN-HANSEN: I'm glad you asked.

If you want to learn more about Yellowstone, check out the Science Trek website.

You'll find it at ScienceTrek.org.

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