ONE of the world鈥檚 great landscapes could soon disappear. The cold, barren Arctic tundra, home to not much more than a sweeping velvety carpet of moss and lichen, could become dominated by bush and forests within decades. And global warming will be to blame.
A 10-year study across eight countries reveals that rising temperatures will kill off lichen and moss across up to 40 per cent of the tundra, while encouraging woody plant species to grow in their place. The trees and shrubs will then accelerate warming because dark vegetation absorbs more solar radiation.
An international team of researchers studied Arctic sites from Alaska and Canada to Iceland and the Norwegian territory of Svalbard, as well as three mountainous tundra regions further south, including the Tibetan plateau. To mimic the effects of global warming they surrounded patches of tundra with transparent open-topped enclosures and warmed them by 1 to 3 掳C (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0503198103).
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鈥淭he response was rapid and detected in whole plant communities after only two growing seasons,鈥� says lead researcher Marilyn Walker of the Boreal Ecology Cooperative Research Unit at the University of Alaska in Fairbanks. Trees, shrubs and grasses invaded and crowded out mosses and lichens. She says the findings echo what researchers are already seeing in the field, and 鈥減rovide rigorous experimental evidence鈥� that climate change is the cause.
Stuart Chapin of the Institute of Arctic Biology in Fairbanks says trees and shrubs are advancing north in many places. Because snow quickly slips off their branches, they provide a dark surface that absorbs heat from the sun for much longer each year than treeless tundra. Trees and shrubs will also absorb carbon dioxide from the air, but Richard Betts at the Hadley Centre for Climate Research in Exeter, UK, says the warming effect of a forested landscape will far outweigh any cooling from CO2 uptake.
鈥淟ichen and moss across up to 40 per cent of the tundra will die off, and woody species will grow in their place鈥�
A big surprise from the study, says Walker, is that biodiversity in the region will plummet as the temperature rises and local plant species disappear faster than others can invade. This loss in biodiversity might only be temporary, however.
Uncertainty over the potential for species loss in the Arctic is highlighted by a further study suggesting taxonomists have underestimated numbers of tundra species. Hanne Hegre Grundt of the National Centre for Biosystematics at the University of Oslo, Norway, found that three species of Arctic brassicas of the genus Draba are far more genetically diverse than first thought. Each could be subdivided into several different species (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0510270103). Whether this could be said of other Arctic plants and animals 鈥渞emains an unanswered question鈥�, says Grundt.
