Your travels can destroy habitats and accelerate global warming. They can also help heal the planet. This handbook shows you how simple decisions can make all the difference

Toward the Yucatán's northwestern tip, on a coastal bio-preserve that used to be a coconut plantation, sits a beachside resort that would satisfy the most hard-core environmentalist. Off the power grid and relying solely on two generators, the Hotel Eco Paraíso Xixim is all about the light footprint. Every cactus, bush, and flower on the grounds is native. Waste—from aluminum to shower water—is recycled or reused. The 15 thatched-roof bungalows are cooled by ceiling fans, and since guests share the setting with flamingos, foxes, iguanas, and monkeys, they're encouraged to minimize the use of lights to save energy and lessen the impact on the habitat. By and large, they comply.

Across the Yucatán, in the hotel jungle that is Cancún, Le Méridien Cancún Resort & Spa has a decidedly heavier environmental footprint. Giant swimming pools sparkle, saunas and Jacuzzis crank all day, and air-conditioning cools every corner of the hotel at all times. But surprises lie just beneath the surface: The resort has already reduced its energy consumption by about 15 percent and has done away with chlorine in the pools as part of its bid for Green Globe certification as an environmentally responsible facility. "In the coming years, I think the Green Globe designation will be an even more important distinction than being a five-diamond property," says Jorge Herrán, Le Méridien Cancún's manager (the hotel is a four-diamond property with loftier aspirations). "It's going to be a must."

The days when conservation was the priority only of ecolodges are over, as the environmental consequences facing the travel industry—and travelers themselves—are becoming ever more clear. After all, top destinations could be among the first to lose their luster in a warming world. "Carbon emissions is probably going to be the big issue for the leisure industry" and its clientele in the near future, says Daniel Sperling, director of the Institute of Transportation Studies at the University of California, Davis. "Ski resorts are going to be seeing less snow, and shorelines are going to be threatened."

Just how harmful is travel to the environment? In terms of greenhouse gas production, its impact is relatively small yet not insignificant. Sperling's data shows that tourism-related transportation generates only about 3 percent of all greenhouse gases in the United States. (By contrast, electricity generation accounts for 32 percent of emissions that cause global warming, according to data from the Environmental Protection Agency.) Nevertheless, experts say that travel puts a strain on Mother Earth in two key areas: resources and habitat. How travel companies—and travelers—can best reduce the damage remains a matter of some debate.