From the redwood forests to the Gulf Stream waters, this land holds 10 regions of the world's most pristine wilderness.

Surprised by the results of his recent project to assess the state of conservation in America, biologist Eric Dinerstein couldn't help remarking, "It's as if North Americans won the biological lottery, but forgot to look at the ticket." Together with 11 other scientists, Dinerstein mapped North American ecosystems for the World Wildlife Fund and found a startling degree of biodiversity. In the United States alone, 22 regions were deemed "globally outstanding." And this even though we've lost 50 percent of our wetlands, more than 80 percent of our coastal habitats, and 95 percent of our old-growth forests. Of the 22 regions, most lie along the country's edges: in the southeast corner, on the Mexican border, on the West Coast, and across the top of Alaska. We've zeroed in on 10 that are pristine, accessible, even magical. Some are safeguarded by state or national parks and reserves; others are without protection. So claim a ticket while you can to the wonders in our own back yard.

Appalachian/Blue Ridge Forests
Of all the temperate forests that shed bright leaves in the fall, only those of central China are richer than Appalachia's. The Appalachian/Blue Ridge forests stretch from northern Alabama and Georgia through Tennessee, North Carolina, Virginia, and Maryland, and into Pennsylvania. Much of this land has been logged, mined, or seared by air pollution, but in the Great Smokies you can still find 1,400 species of spring-blooming plants. And it's salamander heaven. Second-growth forest is never as striking or complex, so look for the patches of old growth in Great Smoky Mountains National Park on the North Carolina­Tennessee border or Shenandoah National Park in Virginia. Best time to go: The wildflowers bloom in May.

Our only flooded-grassland habitat lies at the southern tip of the Florida Peninsula. The ponds, sloughs, and saw-grass marshes of the "River of Grass" support alligators, crocodiles, and spectacular wading birds. Unfortunately, encroaching agriculture and exploding population leave just 2 percent of the original Everglades intact, at Everglades National Park and Big Cypress National Preserve. Best time to go: In winter, when the mosquitoes retire.

Southeastern Conifer Forests
Longleaf pine forests once covered the entire Southeastern coastal plain—southern Louisiana, Mississippi, Alabama, Georgia, and much of northern Florida. These supported a diversity of trees, amphibians, reptiles, birds, mammals, and butterflies almost unmatched in North America. Though 98 percent of the forests have been replaced by farms and urban sprawl, large intact patches survive in Florida's Apalachicola and Osceola national forests. Best time to go: Spring, for the flora and fauna.

Flint Hills Tall Grasslands
The immense Central Tall Grasslands of Iowa and southern Minnesota became the nation's corn belt, but in Kansas the limestone base of the Flint Hills resisted the plow. Today the Flint Hills Tall Grasslands and the adjacent Osage Hills of Oklahoma are the last expanses of tallgrass prairie on the planet. You can see this country at the new Tallgrass Prairie National Preserve in Kansas, though some of the creatures that once called it home—bison, elk, and prairie wolves—are long gone. Best time to go: Early fall, for blue skies and yellow prairie.

Sierra Nevada Forests
Here ponderosas and groves of giant sequoias spread across a mountain range 400 miles long by 50 miles wide. Large predators (grizzlies, cougars, bobcats, wolverines) are rare. Cute natives, such as the heather vole and yellow-eared pocket mouse, proliferate. Though logging, mining, grazing, fire suppression, and railroad building have left only 25 percent of the Sierra Nevada forests intact, they're now protected by four national parks: Yosemite, Sequoia, Kings Canyon, and Lassen Volcanic. Best time to go: Just before the summer crowds arrive.

California Interior
Chaparral and Woodland

There are just five small Mediterranean climate zones around the globe, and this region falls within one of them. A mosaic of grasslands, oak savannas, and chaparral, it encircles California's Central Valley at elevations of 300 to 3,000 feet, washing over coast ranges to the Pacific, from Point Reyes to Santa Barbara. Ironically, fertile habitats like these are often preserved on big military bases and test ranges—such as Vandenberg in Lompoc and Hunter Liggett near King City. Best time to go: Spring, for hills blanketed in flowers.

Sonoran Desert
Bristling with trademark cacti—saguaro, cholla, organ-pipe—this desert stretches from southeastern California across the western two-thirds of southern Arizona and reaches deep into Mexico. Antelope and jaguars, once abundant, are now scarce, and the Mexican wolf is gone, but Gila monsters, rattlesnakes, and jackrabbits abound. And birds! Nearly half the terrestrial bird species of the United States can be seen here. Parts of the desert are badly degraded, but at Arizona's Organ Pipe Cactus National Monument and Cabeza Prieta National Wildlife Refuge, the region is protected. Best time to go: March through May, for the flowering paloverdes.

Hawaiian Moist Forests
On the windward sides of the large islands and on the mountaintops of some of the smaller ones, tropical forests flourish. There, in a medley of bogs, wet shrublands, and, at higher elevations, tropical rain forest, honeycreepers nest among lush tree ferns, mosses, and orchids. Development, recreation, and feral pigs have denuded the foothills, but the forests are still largely intact in the mountains of the larger islands—such as the Waianae Range of Oahu, Molokai's Eastern Mountain, and the West Maui Mountains. Best time to go: April through October, to dodge the rainy season.

North Pacific Coastal Forest
A broad band extending north along the Alaskan coast from the Alexander Archipelago to Prince William Sound encompasses one of the largest and most pristine temperate rain-forest and shoreline ecosystems in the world. It embraces thousands of mountainous islands, small and large, from Prince of Wales in the south to Kodiak in the north. Tongass and Chugach national forests and Glacier Bay National Park supposedly protect the region—prime habitat for bald eagles and brown bears—but nearly a quarter of the old-growth forest is scheduled for logging in the next 15 years. Best time to go: Before it disappears.

Arctic Coastal Tundra
The tundra sweeps across the north coast of Alaska into Canada's Yukon Territory and on to the Mackenzie River delta and Banks Island. The tussocky plain, shaggy with dwarf birch, willow, and Labrador tea, is critical breeding ground for many species: walrus, polar bear, caribou, porcupine, snowshoe and Arctic hare, red fox, musk ox, and a huge range of waterfowl—snow goose, brant, loon, and king eider. Still largely intact, the region is divided by the Trans-Alaska Pipeline and the Dalton Highway. Although tundra is extremely fragile, and slow to recover from any disturbance, the Arctic National Wildlife Refuge is a sizable protected area; caribou—the last great migratory herds of large animals in the country—still roam there. Best time to go: Summer, for constant daylight.

ANN JONES is a writer living in Arizona.