You Can Fool Climate Deniers, But You Can’t Fool Mother Nature. Plants Pack up and Move North.
March 10, 2013
You can fool a climate denier a lot easier than you can fool a fungus.
The Arctic is warming faster than many other parts of the planet, and plants are providing some of the clearest signs of the impacts, with vegetation now growing nearly 500 miles further north than it did a few decades ago.
LONDON, 10 March – The Arctic is on the move. The North Pole is in the same place, but Arctic conditions have begun to shift. A study of 30 years of satellite data confirms that the difference in temperatures between the seasons has diminished.
Conditions now have shifted the equivalent of four or five degrees of latitude southward. At the same time, vegetation has moved north, colonizing the thawing permafrost.
A team of 21 scientists from 17 institutions in seven nations reports in Nature Climate Change that as the cover of snow and ice has diminished and retreated in the Arctic Circle, the temperatures have begun to increase – at differing rates – during the four seasons. Although conditions differ from region to region, overall the growing season is beginning earlier, and the autumn freeze is starting later.
Conditions in northern latitudes now increasingly resemble those found several hundred miles further south 30 years ago. One of the authors, Bruce Forbes of the University of Lapland in Finland, told the Climate News Network that in his own research region of north-west Siberia “we are seeing more frequent and longer-lasting high pressure systems. In winter, the snow cover comes later, is deeper on average than in the 1960s, but is melting out earlier in spring.”
Climate is a complicated business, and there is always legitimate room for argument about the validity of one selected set of measurements, a potential bias in the observations, or the reliability of comparison data collected two generations earlier.
But vegetables can’t be fooled. Plants grow where they can. If deciduous shrubs are growing taller, and colonizing sites ever further north, then conditions must be getting warmer, and staying warmer.
Winners – and losers
Professor Forbes says that indigenous reindeer herders report that alder and willow, normally stunted by the polar winter, are growing taller: his own research team has confirmed this with dendrochronology, the science of tree ring measurement.
“In a few decades, if the current trends continue, much more of the existing low shrub tundra will start to resemble woodlands as the shrubs become tree-sized”, he says.
This enhanced warming over a longer ground-thaw season has changed the landscape: it has, says Compton Tucker of the Goddard Space Flight Center in the US, “created during the past 30 years large patches of vigorously productive vegetation, totaling more than a third of the northern landscape – over nine million km2, which is roughly about the area of the USA - resembling the vegetation that occurs further to the south.”
This warming of the high latitudes is not necessarily good news for all plants. As the tundra turns green at an accelerating rate, the growth of the boreal forests – those mighty stands of conifer species that cover northern Canada and northern Eurasia and enclose the Arctic Circle – may even be decelerating.
Boreal forest species are adapted to cold. “Some areas of boreal forest will be negatively impacted by warming temperatures, from increased drought stress as well as insect and fire disturbance”, says Scott Goetz of Woods Hole Research Center in the US, another of the co-authors.
Even as insect infestations and other factors accompanying warming have led to the “browning” of some stretches of boreal forest between temperate regions and the Arctic tundra, the tundra appears to be greening in a big way,various studies have shown. The newest such work, focused on scrubby windswept regions along Russia’s northwest Arctic coast, has found a particularly noteworthy shift is under way.
In this part of the Arctic, which could be a bellwether for changes to come elsewhere with greenhouse-driven warming, what might be called pop-up forests are forming. Low tundra shrubs, many of which are willow and alder species, have rapidly grown into small trees over the last 50 years, according to the study, led by scientists from the Biodiversity Institute at the University of Oxford and the Arctic Center of the University of Lapland. The researchers foresee a substantial additional local warming influence from this change in landscapes, with the darker foliage absorbing sunlight that would otherwise be reflected back to space. But the fast-motion shift to forests will likely absorb carbon dioxide, as well.
A particularly interesting aspect of this work, to my eye, is how it reveals the potential for fast-motion responses of ecosystems to environmental change in the far north. In work I covered in 2007, botanists found that Arctic plant species were extremely responsive to fairly rapid climate shifts in the past.