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The critters munch on fungi and other organic debris but are most easily spotted when there is snow on the ground, where they appear as brown specks that move.

Wondering why the bugs seem unfazed by frost, Laurie Graham and Peter Davies of Queen's University in Ontario analyzed compounds in snow fleas' bodies. They isolated two proteins that attach specifically to developing ice crystals, which stops the crystals from growing even when temperatures get as low as 21 degrees Fahrenheit -- 11 degrees below freezing.

The researchers also identified the snow flea genes that code for the two proteins. When they stuck those genes into bacteria, the bacteria produced the ice-inhibiting compounds.

Many organisms, including some bacteria, plants, fish, moths and beetles, produce antifreezes. Most are structurally unrelated to one another, suggesting they arose independently after those organisms diversified millions of years ago, the team concludes.

-- Rick Weiss

Measuring Amazon Logging

Human activities are degrading the Amazonian forest twice as fast as was previously thought, according to a new study that examines the impact of logging as well as clear-cutting for farming.

Until now, satellite technology detected only clear-cut land, where crews had removed all the trees to make room for farming and grazing. But working with his colleagues, Gregory Asner at the Carnegie Institution of Washington has developed a satellite imaging method that can identify where selective logging has thinned out trees.

The researchers -- who published their findings Friday in the journal Science -- were able to examine each pixel of a satellite image to determine what portion of an area had been deforested. They found that between 1999 and 2002, selective logging accounted for between 60 and 123 percent more damaged area in the Amazon than was reported when researchers were evaluating deforestation.

"This method gives us an incredible map of the ubiquitous but very diffuse types of disturbances that exist in Brazil or in any tropical forest," Asner said. "Logged forests are areas of extraordinary damage. . . . When you knock down a tree, it causes a lot of damage in the understory. It's a debris field down there."

Asner and his coauthors determined that the region's tree harvest is equal to removing between 10 metric tons and 15 metric tons of carbon from the ecosystem, which represents a 25 percent increase in the amount of carbon released into the atmosphere.

-- Juliet Eilperin

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