“Leave it as it is. The ages have been at work on it and man can only mar it,” warned Theodore Roosevelt, president and environmental pioneer.

Environmentalists encourage travelers to take with them only their memories and leave behind only their footprints, but millions of travelers leave much more behind. They damage fragile ecosystems and decimate natural wildlife populations, reduce biodiversity, and contribute to climate change. In search of a “green” experience, tourists dine on haute cuisine and fine wine, seemingly unaware that their cruise ship is discharging thousands of gallons of toxic waste, polluting the pristine waters they came to revere. In Nepal, native sherpas haul away five tons of garbage left behind by “nature lovers” who came to climb Mount Everest.

Fortunately, many of the 842 million international travelers are beginning pack their conscience when they travel. Some are embracing ecotourism, which The International Ecotourism Society defines as “responsible travel to natural areas that conserves the environment and sustains the well-being of local people.”

Responsible choices do exist for tourists who thrive on rigorous outdoor adventures and for those who prefer pampering. Many resorts are adopting an environmental theme and some spas and retreats are recycling, using solar power, and purchasing produce from local farmers. Large environmental organizations like Sierra Club and World Wildlife Fund offer hikes and ecotours that support their larger conservation efforts.

Yet, despite our best intentions, ecotourism seems like an oxymoron. Although very small scale, locally produced programs can provide a special richness of experience and support local economies, traveling to these endangered areas seems a bit like the Hawthorne effect, whereby the mere fact of observation alters the experiment. We all know the horror stories about the immunological impact of “discovery” on native populations. In a recent editorial in the Los Angeles Times, Dan Neil beseeched us, “When it comes to the most delicate and imperiled places, resist the urge to see them before they, or you, are gone.”

Neil offers sage advice, but if you are not ready to limit your nature experience to IMAX or Animal Planet, there are some steps that you can take to reduce your impact. Travel in small groups and stay at locally owned accommodations. Don’t litter, don’t pollute and don’t disturb the natural habitat or buy products made from endangered species. Take public transportation, stay on trails and avoid sensitive areas. Use water sparingly. Show respect and support the local culture. Consider purchasing carbon offsets to help reduce greenhouse gas emissions.

When selecting a resort or ecotour operator, research their guides and their expertise. Request the operator’s guidelines for wildlife protection and sustainable travel. Ask about their policies for pollution prevention and energy conservation. Investigate how the organization deals with waste, pest management and toxic chemicals. Finally, inquire about their involvement with the local community and their donations to environmental organizations. You will return home with magnificent memories and a clear conscience.