Scientists modelling climate changes for the planet's northern regions may have to factor in the activities of large grazing animals.
Img: Caribou. Credit: alanwoo/flickr
Researchers previously thought woody plants would be the dominant plant across the north, taking over from grasses. Because woody plants absorb more carbon dioxide from the atmosphere than quickly decaying grasses, it was thought they would act as a mitigating factor against global warming.
However, climate modellers neglected to take into account the activities of large herbivores such as caribou and muskoxen.
"Woody plants suck carbon out of the atmosphere as they grow," said Eric Post from Penn State University in Pennsylvania, reports New Scientist. "But they get beaten back pretty severely by large animals."
To investigate how much effect these large animals would have on the woody plants, Post placed 25 squat, glass cones with open tops that allowed grazing in an area of West Greenland. The glass prevented cooling breezes, mimicking climate change with 12 of the 25 cones fenced off from the herbivores.
As expected, shrubs in warmed areas increased by 85 percent in the warmed areas over a five-year period compared with control regions; however, where areas weren't fenced off, large grazing animals had reduced this increase by 19 percent.
Post said it is difficult to extrapolate data towards predicting influence on atmospheric carbon dioxide on a global scale as his experiment was restricted to one area. However, he does believe that climate scientists have underestimated the activities of herbivores.
As a conservative estimate, Post offered that the global effect of the predominance of woody plants may have been artificially increased in climate models by as much as 10 percent.
Peter Convey, a climatologist from the British Antarctic Survey in Cambridge, told the New Scientist that it's difficult to estimate exactly what effect this could have on future climate simulations.
"As soon as you kick an ecosystem, it's difficult to know exactly how it will respond. But biological systems are poorly represented in climate models - anything that improves the accuracy is positive," he said.
The findings are published in the journal Proceedings of the National Academy of Science.
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