This is a rush transcript from "On the Record," July 27, 2009. This copy may not be in its final form and may be updated.

GRETA VAN SUSTEREN, FOX NEWS HOST: In 2009 it's trendy to be an environmentalist, but President Theodore Roosevelt started that trend more than 100 years ago.

Joining us live is Douglas Brinkley, author of a brand new book "The Wilderness Warrior, Theodore Roosevelt and the Crusade for America."

And here is the big news -- this sure-to-be bestseller hits the shelves in just hours, right Doug?

DOUGLAS BRINKLEY, PRESIDENTIAL HISTORIAN: You got it, thank you.

VAN SUSTEREN: You know, Dough, first of all, I thought your last book on Katrina was big and took a lot of research. I think this one might be a little thicker. Tell me about Theodore Roosevelt. Why did you write this one?

BRINKLEY: I looked at T.R.'s conservation, the saving of our national parks and forests, the creation of the U.S. Fish and Wildlife -- it's one of the biggest events in American history between the Civil War and World War I.

Roosevelt put aside hundreds of millions of acres of public lands, places like the Grand Canyon and Crater Lake, Wind Cave. He saved bird refugees all around Florida, places like Key West and the dry Tortugas.

In addition, repopulated the Great Plains, Greta, which were almost shot off. So if you go to places like Mount Rushmore in South Dakota, Wichita Mountains in Oklahoma, these are Theodore Roosevelt's buffalo. They actually were bred at the Bronx Zoo and brought repopulated.

So I was looking at T.R. and his friends that 100 years ago saved while the American. They thought that beneficiaries, who are our Taj Mahals and the great canyons and the Tetons were our equivalent of Westminster Abbey or the Louvre.

VAN SUSTEREN: In the book, even the influence of Charles Darwin -- it's extraordinary, the various influences in his life.

BRINKLEY: As a young boy -- he was born in 1858 in New York City. And he had asthma, and he was very sick in an industrial area. So he got healthy going out into the Catskills. He also would draw birds and write about bird. Then he went to Harvard and majored as a naturalist, which is equivalent of being a biologist today.

So he ended up writing books about the Dakota Badlands. Even when he fought for the Roughriders, he had animals around him. He had as a mascot a cougar named Josephine and a golden eagle and a little dog Cuba. Somebody who loved animals and the Dr. Doolittle fashion, but also was a hunter, and he believed in keeping America while, having patches of parklands.

And so we all want to what he did 100 years ago.

VAN SUSTEREN: What surprised me, I guess, regrettably is how little I know about him.

I always think it is Chase for, like during World War II, or even the Vietnam war. I had not realized how conservationist could sort of change the dynamics, could have such a profound impact on history and even where we are today.

BRINKLEY: Greta, for example, we all know about the teddy bear named after Teddy Roosevelt, and that came from him going on a hunt in Mississippi. And then we wouldn't shoot the bear because somebody had tied it and roped it up. And the toy became ubiquitous.

Roosevelt was sending a public message that hunting is fine, but we have to have hunting seasons and licenses, and you don't shoot a trapped animal. And so he was really kind of instructing us on how to save forest lands.

And so when many people are going around the country this summer, it's T.R.'s America, whether you're going to Mesa Verde in Colorado, or you're going up to Northern California and the giant strands of redwood trees, Roosevelt believed these were heirlooms, just as people passed along their watches or might have something onto your children.

You believe we needed our national parks and forests and refuges for the generations yet unborn.

VAN SUSTEREN: And he was only 42 when he became president. JFK was the youngest elected, but he became president after McKinley was shot. But it was interesting, he had a long, almost 10 or 15 years afterwards, post-presidency, died a young man.

BRINKLEY: And even in his post-presidency, effort, and explorations. He went to the Amazon and brought back specimens from the Museum of Natural History, Smithsonian Institution.

TR's great love nature and wilderness, and the belief that basically we needed some green zones around urban places, that if you're going to work in the city, yours won't have the option of the outdoor life. Many believe that's what made the American character special. He had climbed the Matterhorn in Switzerland and saw no game, no wildlife. He wanted to make sure the Cascades and the Rockies and the Sierra's state forever wild.

VAN SUSTEREN: Doug, this is one of the these book where I hadn't realized how almost little I knew about something until I read it and learn so much about a president I had sort of actually ignored in my travels.

But anyway, it's a great book, Doug. Thank you, as always. It's always nice to see you as well. And I should point out, it's going on sale tomorrow, in a matter of hours.

Thank you, Doug.

BRINKLEY: Thanks.