Eco-tourism is a relatively new concept to the Virgin Islands. Many of the islands were clear-cut in the 1700s to make way for sugar plantations, destroying much of the natural landscape. All through the 1900s, while real estate developments on St. Thomas continued to grow, little concern was given to preserving and sustaining the natural resources of the U.S.V.I. Today, there is a very different attitude toward the ecosystem of the Virgin Islands among permanent residents and visitors alike.
While the eco-tourism infrastructure is still underdeveloped, and the terms "eco-friendly" and "sustainable" can be misused, it is still possible to find truly eco-friendly lodgings on the islands. Camping is always an option. St. John, which is almost entirely a national park, has numerous campsites. Aside from those run by the National Park Service, there is the Maho Bay Camp, which is an umbrella name for two different campsites with several types of eco-friendly lodgings ranging from bare cottages to comfortable studios. On St. Croix, there is Mount Victory Camp, which relies on renewable energy to power its cottages. The British Virgin Islands are less developed than their American cousins, so lodgings tend to be more eco-friendly by nature. You don't have to camp out to stay in eco-sensitive lodging. The Cooper Island Beach Club meets the middle ground between luxury and roughing it. Guana Island is a private island with only one hotel. The entire island is a wildlife sanctuary watched over by the attentive owners.
Low-impact activities like hiking, snorkeling, and kayaking abound in the Virgin Islands. While on St. Croix, contact the St. Croix Environmental Association, which hosts hikes, tours of research facilities, and events based around the hatching of baby sea turtles. Aside from the many companies that offer tours, the St. Thomas-based Virgin Islands Ecotours/Mangrove Adventures offers tours with professional naturalists of the mangrove lagoon and nature reserve at Cas Cay.
St. Thomas, with all its development and modern conveniences, faces the biggest challenges in regard to sustainable development.
Because of the decline of local species, such as Caribbean lobster and conch, you may want to eschew ordering reef fish, such as grouper, snapper, and grunt, and opt for equally tasty and more sustainable alternatives that live out in open water such as dorado, wahoo, and barracuda.