http://www.eurekalert.org/pub_releases/2006-06/icl-fgb061906.php
Public release date: 19-Jun-2006
Imperial College London
First global bird map provides new clues to future extinctions
The first global survey of bird diversity could play a key role in
identifying species most vulnerable to extinction, researchers report
today in the journal PLoS Biology.
The study reveals a direct link, previously theorised but never proven
on a global scale, between the size of the geographical range that a
species inhabits and regional variations in extinction risk and
biodiversity. The international team hopes this new ability to plot
patterns on a global scale will enable conservationists to predict and
even slow or reverse future extinctions.
The new data provides the first strong evidence that species' range
areas are smallest in the tropics and larger in temperate and polar
regions. A smaller range area means that many different types of
creature can be accommodated in the same space, explaining why regions
such as the Amazon Basin contain such a rich variety of species.
Conversely, temperate areas contain a smaller number of different
species since large range areas mean fewer species can co-exist.
This in turn has important implications for extinction risks. The team
has shown that species with a smaller range size are at a greater risk
of extinction, probably due to their increased vulnerability to events
that could change or destroy their habitat. A larger range size, on the
other hand, means fewer species but larger populations of those that
exist, making it less likely that the whole population can be wiped out
by events such as tornados. Lead researcher Professor Ian Owens of
Imperial College London's Division of Biology says:
"There are marked variations in biodiversity and extinction rates in
different parts of the world, and why this should be has been a big
area of research and debate. Theories have pretty much all rested on
the core assumption that range size is the key, but until now tests
have proved inconclusive due to a lack of global data. This is really a
huge step forward in understanding ecology on a world-wide level and
hopefully will allow real results in protecting species that we are in
danger of losing."
Researchers have previously thought that range size varied on a
latitudinal basis, declining from the largest in the northern
hemisphere to the smallest in the southern. The team's work has
revealed a much more complex situation, says Professor Owens, with
different patterns emerging globally. He adds:
"We've found that the patterns seen in the well-studied northern
regions can't be assumed to apply to the rest of the world - a global
perspective is needed. This means that conservation can't be planned on
a one-size-fits-all basis and we will have to properly understand how
different micro-ecologies work in order to really make a difference.
Our next task is to test whether our findings in birds are replicated
in other types of organism."
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