Greenhouse gas soaked up by forests expanding into deserts

Rising carbon dioxide levels may be helping forests to start reclaiming the world's deserts, scientists believe.

Rising carbon dioxide levels may be helping forests to start reclaiming the world's deserts, scientists believe.

The trend could explain why a forest planted on the edge of the Negev desert in Israel 35 years ago is expanding much faster than expected. It could also help account for the estimated seven billion tons of carbon dioxide that goes missing from the atmosphere each year.

Scientists believe vegetation creeping back into arid lands could be soaking up the greenhouse gas.

Professor Dan Yakir, from the Weizmann Institute in Rehovot, Israel, led a team of experts who made the discovery. Their findings were published in the journal Global Change Biology. They were surprised to find the Yatir forest on the edge of the desert was a substantial carbon dioxide "sink".

It was absorbing carbon dioxide as efficiently as vegetation in more fertile areas and it was also expanding quickly into the desert. Seeing the forest, planted 35 years ago, flourish so well contradicted all expectations.

"It wouldn't have even been planted there had scientists been consulted," said Professor Yakir. The observation could indicate an unexpected consequence of man-made greenhouse gas pouring into the atmosphere. While contributing to global warming and turning parts of the world hotter and drier, it could be helping to make arid regions more green.

Plants need carbon dioxide for photosynthesis, and they absorb the gas through pores in their leaves. But the wider the pores open, the more water is lost through them.

Professor Yakir believes that when large amounts of carbon dioxide are present, plants do not need to open their pores so much to obtain the carbon dioxide they need. This allows them to conserve water, so that more is left in the ground. Forests are therefore able to grow in areas that previously would have been too dry for them.