Aviation is the fastest growing contributor to global warming, yet there are plenty of foreign trips sold as responsible holidays that involve flying, from tagging turtles in the Great Barrier Reef to community-based tours of Ethiopia. Can globetrotting green travellers square their holidays with the environmental cost of flying?
"No," says anti-air travel campaigner and Guardian columnist George Monbiot. "In almost all cases the atmospheric impact of the flight greatly outweighs any environmental savings during your holiday."
Yet there are significant advantages that tourism can bring to a destination, particularly in developing countries, through creating jobs, stimulating local economies, and ensuring the conservation of land and animals in protected areas.
Mark Ellingham, founder of Rough Guides, which has just published The Rough Guide to Climate Change (£9.99, roughguides.com), says: "I'm not convinced there is such a thing as a 'responsible' or 'ethical' holiday. But it is clearly a good thing if your holiday has a low environmental impact, or positive social or economic impact.
"But the overriding concern in green or ethical living is to reduce our carbon footprint, which must mean flying less often and less casually - maybe staying longer, opting for occasional 'travel' rather than constant 'short breaks'.
"Ultimately, though, we need government action to limit flights. I would like to see a significant carbon tax levied on all flight departures."
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