BOULDER, Colo., April 3 /PRNewswire/ -- Inconvenient maybe, but the truth is that travel-related activities contribute an estimated third of worldwide greenhouse emissions. Anxious to make summer travel plans without turning your back on Earth Day's April 22 planet-consciousness? The responsible travel experts at Boulder, Colorado-based ecotour outfitter Natural Habitat Adventures want to help you fight global warming while keeping your travel cool with 5 easy ways to avoid making your next vacation a guilt trip:

1) Stay Neutral: Going the group tour route? Check for green credentials. Increasingly, travel outfitters like Natural Habitat Adventures (http://www.NatHab.com) are bolstering an ongoing commitment to sustainable travel by going carbon neutral. Natural Habitat Adventures reduces its carbon emissions with programs that include recycling and renewable energy use, then buys offsets to make up the difference -- guaranteeing carbon neutral trips for its guests. Other carbon neutral outfitters include O.A.R.S., REI Adventure and Escape Adventure. Traveling on your own? Organizations like Sustainable Travel International (http://www.sustainabletravelinternational.org) will help you calculate and offset trip emissions; major online travel companies Travelocity and Expedia also offer travelers offsetting options when they make reservations.

2) Chart a green course: New eco-maps chart the natural and cultural environment to suggest low-impact activities and resources wherever you travel. Green Map System (http://www.greenmap.org) provides "green" maps of some 302 spots around the globe, with most recent offerings ranging from Missoula, Montana, to 17 new Taiwanese maps.

3) Train yourself: Europe isn't the only place worth traveling by train. Check into train or bus options wherever you travel; railroad shuttles up and down the U.S. Eastern Seaboard are particularly quick and convenient. And if you do end up driving, keep your car well-tuned and tires properly inflated to pollute less -- and cut gas costs up to 15 percent.

4) Fuel for Thought: Committed to a road trip? Try to buy gas from a more environmentally responsible oil company: The Sierra Club recently updated its "Pick Your Poison" guide to gasoline; two companies, BP and Sunoco, continue to receive its "top of the barrel" rating. Better yet, buy or rent a hybrid or bio-fuel car. While mainstream rental companies continue to increase eco-friendly offerings -- Hertz recently began offering its "Green Collection" -- the few truly green rental companies are prospering and expanding. EV Rental Cars (http://www.evrental.com) and Fox Rent A Car regularly offer hybrid rentals, and Bio-Beetle Eco Rental Cars offers bio-fueled vehicles. Or consider hybrid car-sharing through a service like Flexcar (http://www.flexcar.com). Whatever your vehicle choice, consider joining eco-friendly auto club Better World Club (http://www.betterworldclub.com), which offers discounts on hybrid cars and eco-travel -- and even roadside assistance for bicycles.

5) In transit: If you do fly, eschew individual cabs in favor of public transit or a hotel shuttle to and from the airport. Or try hailing a hybrid cab: San Francisco, New York and Chicago all have added hybrid taxis to their fleets, mainly Ford Escape Hybrids, while the Brits recently introduced the new lower-emission diesel TX4 taxi in London. And the first hybrid taxi service, PlanetTran (http://www.planettran.com), continues to serve airports in greater Boston and the Bay area by prior reservation. While you're visiting another city, remember to plan your day around walking destinations or the city's public transit options.

SOURCE Natural Habitat Adventures