Most of its reef-rimmed islands rise fewer than three feet above the ocean, which makes the Maldives particularly vulnerable to climate change. No surprise, then, that Soneva Fushi, a collection of refined, castaway-style villas, has pledged to cut its greenhouse gas emissions in half by next year and achieve carbon neutrality by 2010. To meet this goal, it's capturing waste heat from power generators, encouraging guests to offset the emissions of their (long) flights, and transitioning to renewable energy sources. The big news this year: a deep-sea air-conditioning system that circulates cold water pumped up from 985 feet under the sea.
Kunfunadhoo Island, Baa Atoll; 011-960/660-0304; sixsenses.com; doubles from $605.

Carpeted in vegetation and hugging the side of a jungle hill, Heritance Kandalama, when viewed from afar, resembles an ancient temple grown wild with disuse. In fact, the vegetation and location have nothing to do with neglect (note the handwoven tapestries and stunning floor-to-ceiling windows in each room) and everything to do with ensuring that rainwater flowing from the hills collects in the hotel's reservoir below. Such environmentally conscious touches made Kandalama a shoo-in for LEED certification. They also make the area a favorite for a multitude of monkeys (including toque macaques and purple-faced langurs) and 170 species of birds.
Dambulla; 94-66/555-5000; heritancehotels.com; doubles from $114, including breakfast.

Flanking a sand dune near the border of Uluru-Kata Tjuta National Park in central Australia, Voyages Longitude 131 is like no campground you've ever seen. The retreat's elevated canopy tents have solar-heated showers, a switch that lets guests control the floor-to-ceiling window blinds from the comfort of their king-size beds, and expansive views of Ayers Rock. Natural landscaping helps limit water consumption, while Aborigine-led tours to the 20,000-year-old rock paintings at Cave Hill help boost local development.
Yulara, Northern Territory; 866/729-4329; longitude131.com.au; doubles from $1,980, including meals and activities.

This solar-powered 11-bungalow hideaway, set alongside a stretch of perfect alabaster sand on the largely undeveloped South Andros Island, uses less electricity per month than one average American household. It manages this feat with a host of ingenious touches, like wraparound porches that shield the cottages' colorful interiors from the sun, and a bank of small refrigerators instead of an energy-hungry walk-in. Other eco efforts include a ban on unsustainably harvested seafood (even local catches like conch) and a program to host visiting biologists.
South Andros Island; 954/889-7076; tiamoresorts.com; doubles from $830, including meals.

Set in the Swiss Alps near Aigle, the nine Buckminster Fuller–inspired geodesic domes at Whitepod's camp (which doubles as a base for both winter skiing and summer hiking) may be electricity-free, but they keep things cozy with plush organic bedding, sheepskin throws, and fireplaces fueled with sustainably harvested wood. A few steps away lies the main lodge, complete with dining room and spa. Since no roads lead to the camp, guests must walk or ski to get here. The reward for this exertion: a private ski run, miles of hiking and snowshoe trails, and nothing but oil lamps to interrupt the stars.
Les Cerniers; 41-24/471-3838; whitepod.com; doubles from $392, including some meals.

Across the American West, rising land prices and falling cattle profits are driving ranchers to sell their property to developers. Luckily, Devil's Thumb's current owners swooped in just in time to save its 5,000 acres. Instead of high-density (and -profit) single-family houses, they built only 16 airy timber cabins and a soon-to-open lodge—all of them heated and cooled entirely with fireplaces (the wood is harvested on the property, often from beetle-infested pine trees) and geothermal energy. Best yet, the owners have limited their development to only 1 percent of the land, leaving the rest free for guests—and elk, moose, bears, and beavers—to roam.
Tabernash; 800/933-4339; devilsthumbranch.com; doubles from $195.

Surrounded by 123,000 acres of protected forests, jagged limestone cliffs, and hidden lagoons, travelers to sister resorts El Nido Lagen Island and El Nido Miniloc Island can take their pick of daily activities: bird-watching, kayaking, rock climbing, or simply watching fish swim below one of the guest-cottages-on-stilts, which are set above the crystalline ocean. The resorts are active in both reef and island conservation, helping to protect giant-clam gardens and supporting the reintroduction of endangered Philippine cockatoos.
El Nido, Palawan; 63-2/894-5644; elnidoresorts.com; doubles from $210 (Miniloc Island) and $280 (Lagen Island).

In the 13 years since Chumbe Island Coral Park was designated Tanzania's first managed marine protected area, it has earned a reputation as one of Zanzibar's most diverse reefs. Thank the island's park rangers, who educate locals about marine ecology and prevent illegal fishing—and its sole resort, which helps to fund the ranger program. Chumbe's rooftop rainwater-collection system and solar-powered lights keep the resort in harmony with its surroundings, while its seven open-air bungalows, with their cavernous living rooms and African artwork, make it a favorite among honeymooners.
255-24/223-1040; chumbeisland.com; doubles from $440, including meals.

With walls built using rock salt and mud, doors and windows placed to catch the desert breeze, and oil lamps and candles lighting the corridors each night, the Adrère Amellal gives guests a taste of life in Siwa Oasis, a traditional Berber community in the Egyptian desert. But the hotel offers more than a romantic escape for travelers. As part of the Siwa Sustainable Development Initiative, it helps to fund and support numerous community projects. The gift shop carries jewelry handcrafted by local artisans. Meals, meanwhile, are prepared using organic ingredients purchased from farmers at fair market value­—a measure designed to encourage sustainable farming.
Siwa Oasis; 20-2/2736-7879; adrereamellal.net; doubles from $448, including meals.

The brainchild of an Italian expat with an economics degree, the Masai-owned Campi ya Kanzi is a brilliant model of how conservation can be a profitable local enterprise. Set on Masai land in southern Kenya, the lodge and its foundation employ 160 tribespeople and make a daily $40-per-guest donation to support new schools, merit scholarships, and compensation payments to Masai who've lost cattle to lions. Guests benefit, too. Not only do they get to stay in stylish solar-powered cottages, complete with oriental rugs and brass fixtures, but they can also take a walking safari with a Masai guide in the shadow of Mt. Kilimanjaro.
Chyulu Hills; 254-45/062-2516; maasai.com; doubles from $860, including meals.