Missing Carbon Dioxide Greens Up The Desert

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A Weizmann Institute study suggests that rising carbon dioxide levels in the world might help upgrade dry environments to valuable forests. In fact, the researchers think that 7 billion tons of unaccounted-for carbon dioxide, may be the explanation for the expansion of forests into dry areas. A group of scientists headed by Prof. Dan Yakir of Weizmann Institute's Environmental Sciences and Energy Department found that the Yatir Forest, planted at the edge of the Negev Desert 35 years ago, is expanding at an unexpected rate. Their findings, published in the current issue of Global Change Biology, suggest that forests in other parts of the globe could also be expanding into arid lands, absorbing carbon dioxide in the process.

What's the connection between carbon dioxide and forest growth? Yakir's team says that the answer might be found in the way plants address one of their eternal dilemmas. Plants need carbon dioxide for photosynthesis - but to obtain it, they must open pores in their leaves, consequently losing large quantities of water to evaporation. The plant must decide which it needs more: water or carbon dioxide. Yakir suggests that the 30% increase in atmospheric carbon dioxide since the start of the industrial revolution eases the plant's dilemma - because the plant need open its pores only slightly to receive the necessary amount of carbon dioxide, thus causing it to lose less water. This efficient water preservation technique keeps moisture in the ground, allowing forests to grow in areas that previously were too dry.

The scientists hope the study will help identify new arable lands and counter desertification trends in vulnerable regions.