From: Andy Soos, ENN
Published June 4, 2012 05:07 PM
Tundra to Forest
As global warming proceeds the frozen arctic tundra will turn into
forest or grass lands. In just a few decades shrubs in the Arctic tundra
have turned into trees as a result of the warming Arctic climate,
creating patches of forest which, if replicated across the tundra, might
accelerate global warming. Scientists from Finland and Oxford University
investigated an area of around 100,000 square kilometers, known as the
northwestern Eurasian tundra, stretching from western Siberia to
Finland. Surveys of the vegetation, using data from satellite imaging,
fieldwork, and expert observations from indigenous reindeer herders,
showed that in 8-15% of the area willow (Salix) and alder (Alnus) plants
have grown into trees over 2 meters in height in the last 30-40 years.
In physical geography, tundra is a biome where the tree growth is
hindered by low temperatures and short growing seasons. In tundra, the
vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and
lichens. Scattered trees grow in some tundra. The ecological boundary
region between the tundra and the forest is known as the tree line or
timberline.
Previous models assessing the potential impact of forestation have
suggested that the advance of forest into Arctic tundra could increase
Arctic warming by an extra 1-2 degrees Celsius by the late 21st Century.
A report of the research is published in the journal Nature Climate
Change.
"It's a big surprise that these plants are reacting in this way," said
Dr Marc Macias-Fauria of Oxford University’s Department of Zoology and
the Oxford Martin School, first author of the paper. "Previously people
had thought that the tundra might be colonized by trees from the boreal
forest to the south as the Arctic climate warms, a process that would
take centuries. But what we've found is that the shrubs that are already
there are transforming into trees in just a few decades."
"The speed and magnitude of the observed change is far greater than we
expected," said Professor Bruce Forbes of the Arctic Centre, University
of Lapland, corresponding author of the paper.
The change from shrubs to forest is important as it alters the albedo
effect — the amount of sunlight reflected by the surface of the Earth.
With more forest, more heat will be absorbed.
In the Arctic spring and autumn much of the time shrubs are covered
under a blanket of white, light-reflecting snow. In contrast, trees are
tall enough to rise above the snowfall, presenting a dark,
light-absorbing surface. This increased absorption of the Sun's
radiation, combined with microclimates created by forested areas, adds
to global warming: making an already-warming climate warm even more
rapidly.
"Of course this is just one small part of the vast Arctic tundra and an
area that is already warmer than the rest of the Arctic, probably due to
the influence of warm air from the Gulf Stream," said Dr Macias-Fauria.
"However, this area does seem to be a bellwether for the rest of the
region, it can show us what is likely to happen to the rest of the
Arctic in the near future if these warming trends continue."
For further information see
Tundra
into Forest.
Ural
Mountains by BC Forbes via University of Oxford.
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