Salty farms for storing global carbon.

As a low-cost strategy for soaking up some of the excess carbon dioxide in the atmosphere, a number of researchers have proposed reforesting huge tracts of land across the globe (SN: 12/24/88, p.411). But the massive reforestation required to slow global warming would render large amounts of arable land unavailable for agriculture. A team of scientists is now investigating an alternative: trapping carbon in seaweed or in plantations of salt-tolerant desert brush.

An estimated 2.6 million square kilometers would be available for these "biomass farms," divided about equally between ocean waters on the continental shelf and the world's inland salt deserts, according to a February report by the Electric Power Research Institute (EPRI) in Palo Alto, Calif. To keep the carbon they've incorporated from returning to the atmosphere, mature plants must be harvested and buried in a way that largely prevents decay. Seaweeds might be stored in ocean sediments, though no one has yet devised a cost-effective way to do that, says Louis F. Pitelka, a plant ecologist with EPRI. As a result, he says, the report concludes that salt-tolerant plants, known as halophytes, "appear to be a more effective medium for carbon storage than seaweed." With funding from EPRI and a Southwest electric utility, researchers in Arizona have begun to investigate the uptake and storage of carbon by halophytes that are simply plowed into desert soil at maturity.