Sustainable tourism is conscientious travel. It means being careful with the environments you explore, and respecting the communities you visit. Two overlapping components of sustainable travel are eco-tourism and ethical tourism. The International Ecotourism Society (TIES) defines eco-tourism as responsible travel to natural areas that conserves the environment and improves the well-being of local people.

You can find some eco-friendly travel tips and statistics, as well as touring companies and associations -- listed by destination under "Travel Choice" -- at the TIES website, www.ecotourism.org. Also check out Ecotravel.com, which lets you search for sustainable touring companies in several categories (such as water or land based, or spiritually oriented).

While much of the focus of eco-tourism is about reducing impacts on the natural environment, ethical tourism concentrates on ways to preserve and enhance local economies and communities, regardless of location. You can embrace ethical tourism by staying at a locally owned hotel or shopping at a store that employs local workers and sells locally produced goods.

Responsible Travel (www.responsibletravel.com) is a great source of sustainable travel ideas; the site is run by a spokesperson for ethical tourism in the travel industry. Sustainable Travel International (www.sustainabletravelinternational.org) promotes ethical tourism practices, and manages an extensive directory of sustainable properties and tour operators around the world.

In the U.K., Tourism Concern (www.tourismconcern.org.uk) works to reduce social and environmental problems connected to tourism. The Association of Independent Tour Operators (AITO; www.aito.co.uk) is a group of specialist operators leading the field in making holidays sustainable.

Volunteer travel has become increasingly popular among those who want to venture beyond the standard group-tour experience. Some programs provide free housing and food, but many require volunteers to pay for travel expenses, which can add up quickly. For general info on volunteer travel, visit www.volunteerabroad.org and www.idealist.org. Volunteer International (www.volunteerinternational.org) has a helpful list of questions to ask to determine the intentions and the nature of a volunteer program before you commit.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.