Be prepared: You'll get your hands dirty on each of these trips—and you just might help improve the planet.

Norway
The Book of the Living

Joining this Yarlung Tsangpo Gorge cultural preservation project is "like being one of the first groups to Mount Everest," says Richard D. Fisher, director of trip-outfitter Wilderness Research Expeditions. Substitute the world's deepest canyon, the 16,650-foot-deep Yarlung Tsangpo Gorge in eastern Tibet, for its tallest mountain and you realize that this is not hyperbole. Fisher, 48, was one of the first Americans to explore the center of the gorge—which is four times the size of the Grand Canyon—in 1992. This year he'll return with 12 clients to hike, jeep, and camp for 21 days on the canyon's floor, heading west from sand-dune desert to thick jungle. Along the way the team will collect historical documents and take photos for Fisher's book on the history of the gorge—which is believed to be the birthplace of Tibetan civilization. Outfitter: Wilderness Research Expeditions, 520-882-5341, www.canyonsworldwide.com When to Go: April–May Price: $5,500 Difficulty: Moderate —David Friedland

Spain: Mediterranean Marine Biology
Sail along the arid, deserted southern coast of Spain where the Mediterranean Sea meets the Atlantic for 12 days on a 91-year-old Norwegian fishing boat, helping University of Madrid biologists study the food-chain role of bottle-nosed and common dolphins, sperm and fin whales, and leatherback and loggerhead turtles. Plot positions, record behavior and sounds, and hoist sails as you attempt to identify critical habitats for future marine-protection areas. Outfitter: Earthwatch Institute, 800-776-0188, www.earthwatch.org When to Go: January, March, June–September Price: $1,995 Difficulty: Easy

Chile and Ecuador: Following Darwin's Footsteps
A 22-day exploratory trip to the major stops along Charles Darwin's 1834 Chilean route from Tierra del Fuego to Valdivia. The Nature Conservancy's local partner organization leads a hike through Torres del Paine National Park (a UNESCO World Biosphere Reserve), and environmentalists talk about their struggles against the wood-chip industry. You'll visit a TNC marine-otter conservation project an hour's flight from Santiago, Chile, before heading to the Galápagos's Rabida Island, home to nine of the 13 species of finches that inspired Darwin's natural selection theory. Outfitters: The Nature Conservancy, 703-841-8743, www.tnc.org; International Expeditions Inc., 800-633-4734, www.ietravel.com When to Go: November–December Price: $9,896 (includes international airfare) Difficulty: Easy

Russia: Investigating Lake Baikal's Pollution Levels
Help Russian scientists protect the deepest (more than a mile), largest by volume (14,000 cubic miles), oldest (20 million years) lake in the world and its 1,080 endemic species by taking water and fish samples from a motorized research vessel to measure chemicals and organic-waste levels. Then patrol the shorelines to observe sables and the world's biggest brown bears, and to scout potential nature-reserve sites. Hard work is rewarded with fresh salmon dinners and views of the 9,000-foot Sayan Mountains from lakeshore campsites. Outfitter: Earthwatch Institute, 800-776-0188, www.earthwatch.org When to Go: July–August Price: $1,695 Difficulty: Moderate

Kenya: Studying Bats and Elephants
Spend 12 days walking and jeep-riding in the flat, butte-fringed Taru Desert and Masai Mara Savanna, working with scientists to catch and count bats and identify and classify elephants by their tusk lengths and ear markings. With mist nets, headlamps, bat detectors, and microphones, you'll learn to distinguish the calls and wing shapes of horseshoe, free-tailed, and yellow-winged bats, which inhabit caves and acacia trees. Then you'll impart your newfound wisdom to local schoolchildren during nighttime field trips. Outfitter: Bat Conservation International, 520-743-0265, www.batcon.org When to Go: May Price: $4,145 (includes international airfare)Difficulty: Easy

And five more...

COUNTDOWN	TRAVEL NECESSITIES
	Tiny down pillow Soft enough to see you through a long night on hard ground; squishable enough to stash in the sparest of packs.