The Hot Zone

Western weed offers glimpse into climate change

Posted by Alison Hawkes on June 2, 2011
Category : The man made climate

Invasive species are fending very well under higher temperatures and carbon dioxide conditions. And the yellow starthistle in the American West offers a glimpse of why.

A native to the Mediterranean, this thorny yellow-blossomed plant has become a bane to ranchers in the West as it outcompetes native grasses and degrades pasture quality. Cattle don’t want to eat it and it’s toxic to horses.

Photo: Patrick Berry

A Purdue University study found that yellow star thistle has some of the greatest response to elevated carbon dioxide every observed, and that makes it a stronger competitor to native grassland species. It’s been able to grow a more effective root system and it’s taken advantage of extra water in the soil that other grassland species are not using.

All this is bad news for Western farmers, who already contend with tens of millions of dollars a year in economic damage from the weed. In California, starthistle has already reduced the value of pastureland by 6 to 7 percent.

The study, published in the online journal Ecological Applications, is one of the first comparing invasive species to local competitors.

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