Sustainable tourism used to be little more than a travel-industry buzz phrase. Now it stands for healthy, guilt-free, eco-friendly vacations. Consider one of these adventures when planning your next escape.

Cumberland Gap National Park, Kentucky

On a three-day backpacking trek through Kentucky's rugged backwoods, you can hike the same Wilderness Road that pioneers like Daniel Boone once followed. Green Earth Outdoors' lead guide and owner Douglas Wagoner instills the Leave No Trace ethic. "We try to show the clients what we're doing and why we're doing it," Wagoner says. "Most of our clients enjoy the outdoors as much as we do and are open to being taught ways to minimize their impact on the Earth."

Temperatures in the spring will be mild as you ascend to a ridgeline and take in panoramic views of Kentucky, Tennessee, and Virginia. Plus, you'll learn how to minimize campfire impact, respect wildlife, and properly dispose of waste.

Barkley Sound, British Columbia

See the sea with gray whale, sleep among thousand-year-old cedars, and explore the Broken Group Islands on a four-day adventure — all while learning about local sea life and sustainable camping techniques. Majestic Ocean Kayaking's mission of ecotourism stems from a respect for their surroundings: the town of Ucluelet, gateway to Barkley Sound on the west coast of Vancouver Island.

In a small group you'll set up a central camp then hop from island to island, paddling eight to 12 miles a day. You'll visit the ruins of ancient native villages and spot animals such as bald eagles and sea lions. Twenty thousand gray whales migrate through each spring, and whale sightings are a daily event.

Canyonlands National Park, Utah

Cover 120 miles by four-wheel vehicle, foot, bike, and raft as you go deep into the Maze and Cataract Canyon of Canyonlands national Park, Utah. Escape Adventures uses waste-vegetable-powered vehicles and solar- and wind-powered facilities. They even grow some of their own produce and compost what is left over after their treks. "If we're going to make changes we have to be a good example to others," says Jared Fisher, Escape Adventures director.

After your group is dropped off in the Maze region, you'll be left to scramble your way down canyons, view a 2,000-year-old Anasazi pictograph, mountain bike slickrock trails, and tackle rapids by raft in the Colorado River. Then, when evening rolls around, you'll camp under the desert stars and watch the sunset over stunning Chimney Rock.

Kauai, Hawaii

During REI Adventures' six-day Kauai Multisport tour, you'll be biking through old sugarcane plantations, sea kayak along the sheer cliffs walls of the Napali Coast, and hike a 10-mile-long loop through the 3,500-foot-deep Waimea Canyon. Learn the ancient history of Kauai as you trek to waterfalls, snorkel and camp on REI's private beach, and sample local cuisine. Hawaii is all about respect, and this multisport tour teaches responsible enjoyment of Kauai's tropical paradise.

Recognizing the importance of travel in understanding other cultures and environments, REI has implemented a program to reduce the negative effects of guests flying to Hawaii. "We offset the carbon footprint for every person who travels with us," says Cynthia Dunbar of REI Adventures. For each guest, this amounts to offsetting about 6.14 tons of carbon dioxide, the equivalent of taking an average car off the road for a full year.

Algarve, Portugal

Surf perfect beach breaks, and dine in sustainable style in Algarve, Portugal. Nomad Surfers' Vale Figueiras surf camp is in close distance to both the west and south coasts, guaranteeing prime conditions no matter which way the wind blows. And you'll learn about respect for the ocean environment while you're at it. "Most people who surf are connected to animals," says Nomad Surfers' rep Jose Gutierrez. "And we all know that pollution in the water is bad for the seals, the dolphins — all sea life."

After surfing, enjoy fresh veggies from the house farm plus homemade pizza and perceves (a local seafood) cooked by an instructor who is also a former chef. Even your morning OJ is local, and freshly squeezed. " The owners fish as a passion," says Gutierrez. "Living off the land, surfing, fishing — that's their life."