The growing popularity of ecotourism, a still-developing branch of travel that gives tourists an opportunity to help preserve the natural environment and interact with local people, has led to confusion among some consumers because of the sometimes misleading promotional material produced by travel companies eager to take advantage of a hot trend.

To counter this confusion, The Ecotourism Society, a nonprofit organization based in Alexandria, Va., whose motto is "Uniting Conservation and Travel Worldwide," is establishing a rating system based on consumer evaluations that will help future travelers make educated and accurate decisions on nature-sensitive excursions. The ratings are expected to be in place and available to consumers by the fall of 1994.

The Ecotourism Society, founded in 1990, currently claims more than 400 members, including tour operators, lodge owners, conservation specialists, park system officials and tour guides. Among those organizations listed by the society as "supporting institutions" (i.e., those that donate $1,000 in annual support) are: Conservation International, the National Audobon Society, Wildland Adventures and International Expeditions.

"It's a 'consumer beware' situation with use of the term ecotourism," said Megan Epler Wood, executive director of the society. "Consumers have no way of really interpreting that label.

"In every country where there is a large nature tourism industry, there are some tour operators trying to cash in on the ecotourism phenomenon by using the word 'ecotourism' without necessarily offering the important components of an ecotour. Companies pick up on the word, which sounds good, and use it in their marketing. There's no global standard for use of the term, and we're the first organization setting up much-needed standards."

Consumers will be asked to rate tour operators offering ecotourism-related trips. The survey will be comparable to the popular Zagat guides, where consumers rank restaurants and hotels according to a list of specific criteria supplied by the Zagat company. In the 1992 "Zagat Los Angeles/Southern California Restaurant Survey," for example, a total of 4,400 consumers participated in the rating process.

The first step in establishing a rating system took place last summer when The Ecotourism Society contacted ecotourism operators (according to one report, there are more than 300 U.S. tour operators now booking environmentally sensitive trips), conservation groups, lodge owners and others in the field about helping to devise a code of standards.