Scientists yesterday provided a global quantification of one of the
most pervasive, but least recognised, ways that humans are marring the
coherence of the natural world - by building endless numbers of roads.
Roads
fragment natural habitats, and the more of them there are, the smaller
and more compromised those habitats become. At the same time, roads give
humans access to remote, once pristine regions, where they can begin
logging, mining, accidentally (or intentionally) starting fires and much
else.
In the Amazon rain forest, for instance, the fragmentation
of the landscape that occurs because of deforestation - to which roads
also contribute - upends the entire nature of the ecosystem. Once
sunlight can penetrate into the rain forest from a cleared area to its
side, rather than being mostly blocked out by the lush canopy from
above, the forest floor dries out, the forest itself heats up, trees
collapse more easily, there isn't enough range for many key species, and
on and on.
The
new study, published in the journal Science by a team of 10
conservation scientists at institutions in Germany, Greece, Poland, the
United Kingdom, Brazil and the United States, used an open-source,
citizen science database of global roads. The researchers then combined
this with an assessment from the research literature of the size of
areas alongside roads that are compromised ecologically by them. This
allowed them to count up the world's remaining truly untrammeled areas
and assess their number and size.
They defined these areas as
starting 1 kilometre away from any road. "There are some effects that go
far beyond 1km actually. It's a gradient of course, of impacts fading
out, but the majority of problems is occurring in this belt or buffer of
1 kilometre," said Pierre Ibisch, the study's first author and a
researcher at the Eberswalde University for Sustainable Development in
Germany.
Using this metric, the study found that the Earth's land
areas (excluding Antarctica and Greenland) were 80 percent roadless,
which may sound like a good thing - but peering in closer, the
researchers found that roads had divided that land area into some
600,000 pieces. More than half of these were less than a square
kilometre in area.
Only 7 per cent of the fragments were very
large - more than 100 square kilometres in area. Some of the largest
untrammeled areas were in the Amazon rain forest, northern or boreal
forests, and in Africa.
http://www.nzherald.co.nz/world/news/article.cfm?c_id=2&objectid=11768201
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