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The maximum global sea-level rise from the collapse of the rap-idly warming West Antarctic ice sheet may be 3.2 meters—not fi ve meters or more as predicted in the past. The revision comes from a new model suggesting that only parts of the ice sheet will collapse—namely, those that are grounded below sea level or

sloping downward. Areas of the sheet grounded above sea level or on upward-sloping bedrock would remain in place. The re-sults, in the May 15 Science, say nothing about disappearing ice sheets elsewhere, however. Greenland, for instance, holds enough ice to raise sea levels by seven meters. —David Biello

ENVIRONMENT

A Lower High-Water Mark

ATMOSPHERIC SCIENCE

Do Rain Forests Make Rain?Long-standing assumption: rain forests are a consequence of heavy rainfall. New hypothesis: some forested regions may produce conditions that lead to heavy rainfall. This “biotic pump” model con-tends that a vast forest such as the Ama-zon draws in large amounts of water va-por. Evaporation and condensation of the acquired water lead to a local atmo-spheric pressure drop. That decrease causes rain and attracts more water va-por to the forest, in a continuous positive feedback loop. “This theory could ex-plain why continental interiors with huge rain forests remain so moist,” says Wild-life Conservation Society researcher Douglas Sheil, who in an April Biosci-ence paper revived the biotic pump mod-el, originally proposed in 2006 by Anas-tassia Makarieva and Victor Gorshkov, both at the Petersburg Nuclear Physics Institute in Russia. “It could also under-line the dangers of widespread deforesta-tion.” Though promising, the model needs more data regarding air circula-tion patterns and vegetation types to support it, Sheil notes. —Steve Mirsky

RAIN FORESTS may pull in water vapor, which lowers the local atmospheric pres-sure, thus attracting even more moisture.

ENTOMOLOGY

Ants: “I’m Not Dead Yet” Ants are notoriously effi cient undertakers, carrying off dead nestmates before the corps-es can infect the colony with their pathogens. Some researchers had hypothesized that ants detected breakdown products in decomposing bodies, but a new study undermines that theory. Entomologists from the University of California, Riverside, found that Ar-gentine ants could detect dead nestmates before decomposition could have taken hold. More telling, the team found that living ants produce two “I’m not dead yet” chemicals, called dolichodial and iridomyrmecin. The compounds curb necrophoresis, the removal of dead colony members by fellow workers. Both chemicals dissipate quickly after death, plummeting to below half strength in just 10 minutes, the researchers write in a paper published in the May 19 Proceedings of the National Academy of Sciences USA. —John Matson