Trees are man’s best friend

Photo credit: AAAS

LEANDER ANDEREGG

Forests in the U.S. Southwest are showing the stress of drought.

Drought is preventing trees from fighting climate change

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In terms of curbing climate change, trees are man’s best friend. As they grow, they pull carbon dioxide out of the air and convert it into sugars that add bulk to their trunks. This carbon storage ability is so well-known it has spurred an international tree-planting movement to slow global warming.

But drought could compromise the ability of trees to protect us from climate change, according to a new study. Scientists have shown that drought slows tree growth for many years beyond the initial dry spells, creating what researchers call a “drought legacy.” And scientists trying to predict climate change “could be really missing the boat,” if they are not including the effects in their computer models, says Melinda Smith, a community ecologist at Colorado State University, Fort Collins, who was not involved with the work.

To determine the true toll of droughts, Princeton University ecophysiologist William Anderegg and colleagues turned to the International Tree-Ring Data Bank, which stores 100 years or more of tree-ring data from more than 1500 nontropical areas of the world. In these temperate zones, trees lay down new trunk each summer but go dormant in winter, creating a pattern of rings that track the intensity of annual growth. The broader the area between two rings, the more productive the tree and the more carbon it stores.

Examining tree-ring data from Europe, North America, and parts of Asia between 1940 and 2008 (a time with reliable weather data), researchers discovered that, in trees with at least 25 years’ worth of rings, these layers were thinner than usual not just in years of droughts, but on average for 3 or 4 years afterward. Scientists had known droughts could damage tree tissues, leaving a drought legacy, but they didn’t know how long the legacy lasts. As they report online today in Science, trees growing in drier climates, such as the U.S. Southwest, fared the worst.

Read the full article: SCIENCE MAG.

Great Green Wall in China ? (Google / The Washington Post)

Read at : Google Alerts – desertification

http://www.washingtonpost.com/national/health-science/let-a-billion-trees-bloom-can-a-great-green-wall-of-trees-stop-chinas-spreading-desert/2013/11/22/12908e0e-2d13-11e3-b139-029811dbb57f_story.html

Let a billion trees bloom: Can a great green wall of trees stop China’s spreading desert?

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Kubuqi Desert, Inner Mongolia, China —We start walking up ridges as high as 10 staircases, slipping as the grains of sand tumble underfoot, grabbing a hand to keep from falling, pushing to get to the top of the next dune to see the sea of sand undulating in the distance.

“We are on the front line of a huge Chinese Dust Bowl advancing east,” says former South Korean ambassador to China Byong Hyon Kwon, an activist in the global fight against deserts on the move.

He is leading a group of volunteers across 21 / 2 miles of desert to a “green wall” of recently planted trees and shrubs aimed at blocking the march of sand and restoring the land. As recently as 50 years ago, this was grassland, Kwon says. People lived here and raised sheep.

But now the Kubuqi Desert is sucking away life. Windstorms threaten the air 800 miles away in Beijing and send plumes all the way across the Pacific to the West Coast of the United States.

Kwon founded Future Forest, a nonprofit organization, to combat desertification in 2001. As ambassador to China from 1998 to 2001, he had experienced firsthand the sandstorms known as the Yellow Dragon, which thicken the skies over Beijing with dust and send people with asthmatic lungs and weak hearts to the hospital. He became convinced then that if action weren’t taken, the march of sand would threaten the viability of the Asian continent.

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