Is Mother Nature the perfect housekeeper? One of the most controversial theories in modern science gained some credibility last week with new evidence that sea life may help regulate the Earth's temperature. For two decades, that has been a key tenet of the "Gaia" hypothesis proposed by British climatologist James Lovelock and U.S. biologist Lynn Margulis, which contends that the planet and its life forms collectively constitute a self-regulating "super-organism."

According to the theory, named for the Greek Earth goddess, colonies of ocean plankton are part of a "feedback" process that controls both the air temperature and their population. Plankton excrete a gas with sulfur compounds that create "cloud condensation nuclei," the seeds of clouds. When the temperature rises, plankton growth increases, and more gas is emitted into the atmosphere. Sulfates from the gas help form more clouds that block sunlight, reducing the temperature, restricting plankton and thus maintaining an equilibrium.

In the current issue of the journal Nature, three Australian scientists report that 20 months of readings at Cape Grim in the South Pacific confirm a connection between plankton gas emissions and cloud-seeding sulfur compounds. Other correlations remain unproved, but the results lend weight to the idea that Gaia knows best.