Responsible tourism is conscientious travel. It means being careful with the environments you explore and respecting the communities you visit. You can find some eco-friendly travel tips and statistics, as well as touring companies and associations -- listed by destination under "Your Travel Choice" -- at www.ecotourism.org.
Greater Los Angeles is the smoggiest region of the U.S. So if you're concerned about the size of your carbon footprint during your vacation to L.A., the single best effort you can make is to use L.A.'s public transportation system. Granted, it's an inferior and often a frustrating experience for anyone who's used to getting around via public transport in NYC, London, or Paris, but it's slowly getting better.
A more realistic alternative is to rent a hybrid car (such as a Toyota Prius). Not only will you save money on gas, but you'll be doing the local air a favor as well. In L.A., a local company called Simply Hybrid Rental Cars (tel. 888/359-0055; www.simplyhybrid.com) rents a wide range of environmentally friendly vehicles ranging from the sensible Toyota Prius to the luxurious Mercedes E320 BlueTEC. As an added bonus, it offers free vehicle delivery and pickup to and from Los Angeles International Airport, Bob Hope Airport (Burbank), Santa Monica, Brentwood, Bel Air, Westwood, Century City, Beverly Hills, West Hollywood, Hollywood, Downtown Los Angeles, Culver City, and Studio City.
Other suggestions for low-impact travel to L.A. include renting a bike to explore the beach communities, staying at eco-friendly inns such as the Ambrose hotel in Santa Monica, the Beverly Hilton, or Hotel Angeleno; and dining at restaurants with an emphasis on organic and sustainability, such as Rustic Canyon, and Inn of the Seventh Ray.