Greenhouse Gas Grows Greener Deserts

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In the early 20th century, the patriarch of climate change science, Svante Arrhenius, suggested that increased carbon dioxide gas in the air might actually be a boon for the world’s plants.

Arrhenius may have been at least partly right. Deserts and other arid regions have grown eleven percent greener over the past three decades, according to research published this month in Geophysical Research Letters.

However, greener doesn’t necessarily mean better. Plant communities are changing along with the rising greenhouse gas levels, which can stress the animals that depend on them and threaten the survival of some plant and animal species. For humans, changing plant communities can mean unfamiliar weeds popping up in farmers fields.

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“Trees are re-invading grass lands, and this could quite possibly be related to the CO2 effect,” said study co-author Randall Donohue of Australia’s Commonwealth Scientific and Industrial Research Organization in a press release. “Long lived woody plants are deep rooted and are likely to benefit more than grasses from an increase in CO2.”

Donohue and his colleagues used a computer model to predict vegetation change due solely to carbon dioxide increases from 1982 to 2010. They then cross-checked that model with satellite observations of arid lands in the southwest of North America, the Australian Outback, the Middle East and regions of Africa during that same time period.

The computer model was designed to prune out other effects of climate change such as temperature changes and rainfall variation. By observing deserts, the scientists reduced the influence of those other climatic variables on the plant cover in the satellites images.

“Satellites are very good at detecting changes in total leaf cover, and it is in warm, dry environments that the CO2 effect is expected to most influence leaf cover,” said Donohue.

IMAGE: Colorado National Monument (Rennett Stowe, Wikimedia Commons)