Despite the fact that the horror story that appeared in the London Times the beginning of this year, that a single Google search emits seven grams of CO², was summarily discounted because the Harvard physicist they used as source was proved to be grossly misquoted, the uneasy feeling still lingers about the all too careless misuse of the Internet required for a simple search -- a crime committed without bounds, thanks to netbooks and mobile devices.

Now 25-year-old Christian Kroll and his colleagues have developed a search engine, Forestle, that they hope will relieve some surfers' guilt feelings. The plan is to use ad revenue from the site to help The Nature Conservancy (TNC) buy tracts of rainforest for environmental protection, through the TNC's Adopt an Acre program. The ad money comes from Yahoo, which has sponsored links on the search pages. Each Forestle search should save 0.1 square meters of rainforest, which, averaged over a year for each user, would come to about the size of a large classroom of rainforest space. Just 10% of the ad revenue would go to administrative costs. But Forestle also has CO² in sight: as their FAQ site claims, the search engine is carbon-neutral in that it measures its CO² emissions and purchases renewable energy certificates.

Forestle estimates that 5 million users over a year can buy a rainforest area the size of New York City. Meanwhile they've already saved almost as much acreage so far from being slashed and burned; a counter on the search page keeps track. Recent news of a rainforest in the Osa Peninsula of Costa Rica being bought up (see slideshow) should be an encouragement for Kroll and his group.

Forestle advises against artificial ad clicks and searches in that they don't help the cause and threaten their entire business model. Word-of-mouth of the search engine would be most welcome for the project's small team in that the young company's advertising budget is still pretty limited.