Global Temperatures Threatening Planet-wide Bird
Extinction
18 February, 2008.
http://www.dailygalaxy.com/my_weblog/2008/02/rising-global-t.html
Stanford scientists are warning that accelerating higher
global temperatures are driving plants and animals to shift
their habitats slowly to higher elevations, driven by rising
temperatures worldwide. As their habitats shrink to the
vanishing point, species will go extinct.
The Stanford team predicts that by 2100, climate change
could cause up to 30 percent of land-bird species -the vast
majority of all bird species- to go extinct worldwide, if the
worst-case scenario comes to pass. Sedentary,
non-migratory birds, will face even higher extinction risk.
Of the land-bird species predicted to go extinct, 79 percent
of them are not currently considered threatened with
extinction, but many will be if we cannot stop climate
change," said Cagan Sekercioglu, a senior research scientist
at Stanford and the lead author of a paper detailing the
research, which is scheduled to be published online in
Conservation Biology.
The study is one of the first analysis of extinction rates to
incorporate the most recent climate change scenarios set
forth earlier this year in the reports of the Intergovernmental
Panel on Climate Change (IPCC), which shared the Nobel
Peace Price with Al Gore.
The researchers modeled changes to the elevational limits of
the ranges of more than 8,400 species of land birds using 60
scenarios. The scenarios consisted of various combinations
of surface warming projections from the 2007 IPCC report,
habitat loss estimates from the 2005 Millennium Ecosystem
Assessment (an evaluation of the planet's ecosystems by
1,360 experts around the world), and several possibilities of
shifts in elevational range limits.
The worst-case scenario of 6.4 degrees Celsius surface
warming combined with extensive habitat loss produced the
estimate of 30 percent of land bird species going extinct by
2100. Increasing habitat loss exacerbates the effects of
climate change because organisms seeking more suitable
conditions will be less likely to find intact habitats. Even
with an intermediate 2.8 C warming, 400 to 550 land-bird
extinctions are expected.
"Vegetational shift is the key issue here," Sekercioglu said.
"Birds will follow the shift in habitat."
All plants have certain temperature and precipitation
requirements they need to flourish. As lowlands become too
warm for some species, higher slopes that were formerly too
cool become better suited to their needs, and the
distributions of plants slowly move upward. That shifting of
populations renders bird species vulnerable to a host of
complications.
Topography itself is a major issue. Each bird species is only
found between specific elevations, limits based mainly on
the temperatures at which it can survive and the presence of
the plants, insects and other animals on which it feeds.
Temperature decreases as one goes up a mountain, so as the
lowlands become warmer, plant and animal communities
need to move higher in order to remain in their required
microclimates.
Most bird species live in the tropics, mostly in lowland
environments. In many of these areas, there may be no
significantly higher slopes to which they can retreat. But
even the presence of hills or mountains does not guarantee
the survival of a species.
As one moves upslope, the extent of the area encompassed
by a given elevational range almost always decreases. It's a
matter of simple geometry. The circumference of a
mountain is typically smaller near the summit than at its
base, so a range of, say, a hundred vertical meters occupies
a far smaller band of area near the top than it does down at
the base.
And once the summit of a mountain becomes too hot for a
species or its preferred vegetation type, the habitable area is
reduced to nothing.
"It's like an escalator to extinction. As a species is forced
upwards and its elevational range narrows, the species
moves closer to extinction," Sekercioglu said.
In some instances, species can expand their ranges, which
the authors also considered in their models. If warming is
limited and a species adapts, only the upper limit of a
species' elevational range might rise. As warming continues,
however, the lower bound is likely to rise, as well.
Additional threats include interactions between the rising
temperatures and other environmental factors. For example,
as Hawaiian mountains get warmer, mosquitoes carrying
avian malaria, to which most native bird species have no
immunity, are moving upslope, invading the last refuges of
birds already on the brink of extinction. In Costa Rica,
toucans normally confined to lower elevations are colonizing
mountain forests, where they compete with resident species
for food and nesting holes, and prey on the eggs and
nestlings of other bird species.
In addition, plant species that currently share a habitat may
not all react the same way to temperature and moisture
changes. Some species may be forced upslope while others
are able to linger behind, tearing apart plant and animal
communities even if all the species survive. Differences in
soil composition can further disrupt plant communities. If
soils at higher elevations are inhospitable to some plant
species, those species will be wedged between a fixed upper
bound and a rising lower bound until they are squeezed out
of existence.
Until now, highland species have been less threatened by
habitat loss and hunting, simply because most people live in
flat lowlands instead of the steeper highlands. Compared to
lowland birds, however, highland species are not only more
sensitive to temperature changes, but their populations also
are more isolated from each other, as mountains effectively
constitute habitat islands surrounded by a sea of hotter
lowlands.
The study also has shown that sedentary birds, which
comprise over 80 percent of all bird species, are much more
likely to go extinct from climate change than are migratory
birds. That suggests that many sedentary mountain species
currently thought to be safe are actually jeopardized by
global warming. All in all, climate change is likely to be
especially hard on the hundreds of bird species endemic to
tropical mountains.
But in part because of the remoteness of the mountains and
in part due to a lack funding for ornithological studies in
most tropical countries, there are few data on these birds'
responses to climate change. Crucial remote sensing data are
also becoming less available, as government satellites like
Landsat age and as image distribution moves increasingly to
the relatively expensive private sector.
"To effectively monitor the rate of change as warming
progresses, especially in the species-rich tropics, we need a
lot more data on birds' distributions and on the speed and
extent of birds' elevational shifts in response to climate
change," Sekercioglu said.
Perhaps the most worrisome finding is that each additional
degree of warming will have increasingly devastating effects.
The authors estimate that an increase of 1 C from present
temperatures will trigger roughly 100 bird extinctions. But if
the global average temperature were to rise 5 C, from that
point on an additional degree of warming, to 6 C, would be
expected to cause 300 to 500 more bird extinctions.
"This emphasizes the importance of any measure that
reduces surface warming, even if we cannot stop it
altogether," Sekercioglu said. "Even a reduction of 1 degree
can make a huge difference."
"Giving up the fight against global warming would be the
true disaster," he added.
Posted by Casey Kazan.
Extinction
18 February, 2008.
http://www.dailygalaxy.com/my_weblog/2008/02/rising-global-t.html
Stanford scientists are warning that accelerating higher
global temperatures are driving plants and animals to shift
their habitats slowly to higher elevations, driven by rising
temperatures worldwide. As their habitats shrink to the
vanishing point, species will go extinct.
The Stanford team predicts that by 2100, climate change
could cause up to 30 percent of land-bird species -the vast
majority of all bird species- to go extinct worldwide, if the
worst-case scenario comes to pass. Sedentary,
non-migratory birds, will face even higher extinction risk.
Of the land-bird species predicted to go extinct, 79 percent
of them are not currently considered threatened with
extinction, but many will be if we cannot stop climate
change," said Cagan Sekercioglu, a senior research scientist
at Stanford and the lead author of a paper detailing the
research, which is scheduled to be published online in
Conservation Biology.
The study is one of the first analysis of extinction rates to
incorporate the most recent climate change scenarios set
forth earlier this year in the reports of the Intergovernmental
Panel on Climate Change (IPCC), which shared the Nobel
Peace Price with Al Gore.
The researchers modeled changes to the elevational limits of
the ranges of more than 8,400 species of land birds using 60
scenarios. The scenarios consisted of various combinations
of surface warming projections from the 2007 IPCC report,
habitat loss estimates from the 2005 Millennium Ecosystem
Assessment (an evaluation of the planet's ecosystems by
1,360 experts around the world), and several possibilities of
shifts in elevational range limits.
The worst-case scenario of 6.4 degrees Celsius surface
warming combined with extensive habitat loss produced the
estimate of 30 percent of land bird species going extinct by
2100. Increasing habitat loss exacerbates the effects of
climate change because organisms seeking more suitable
conditions will be less likely to find intact habitats. Even
with an intermediate 2.8 C warming, 400 to 550 land-bird
extinctions are expected.
"Vegetational shift is the key issue here," Sekercioglu said.
"Birds will follow the shift in habitat."
All plants have certain temperature and precipitation
requirements they need to flourish. As lowlands become too
warm for some species, higher slopes that were formerly too
cool become better suited to their needs, and the
distributions of plants slowly move upward. That shifting of
populations renders bird species vulnerable to a host of
complications.
Topography itself is a major issue. Each bird species is only
found between specific elevations, limits based mainly on
the temperatures at which it can survive and the presence of
the plants, insects and other animals on which it feeds.
Temperature decreases as one goes up a mountain, so as the
lowlands become warmer, plant and animal communities
need to move higher in order to remain in their required
microclimates.
Most bird species live in the tropics, mostly in lowland
environments. In many of these areas, there may be no
significantly higher slopes to which they can retreat. But
even the presence of hills or mountains does not guarantee
the survival of a species.
As one moves upslope, the extent of the area encompassed
by a given elevational range almost always decreases. It's a
matter of simple geometry. The circumference of a
mountain is typically smaller near the summit than at its
base, so a range of, say, a hundred vertical meters occupies
a far smaller band of area near the top than it does down at
the base.
And once the summit of a mountain becomes too hot for a
species or its preferred vegetation type, the habitable area is
reduced to nothing.
"It's like an escalator to extinction. As a species is forced
upwards and its elevational range narrows, the species
moves closer to extinction," Sekercioglu said.
In some instances, species can expand their ranges, which
the authors also considered in their models. If warming is
limited and a species adapts, only the upper limit of a
species' elevational range might rise. As warming continues,
however, the lower bound is likely to rise, as well.
Additional threats include interactions between the rising
temperatures and other environmental factors. For example,
as Hawaiian mountains get warmer, mosquitoes carrying
avian malaria, to which most native bird species have no
immunity, are moving upslope, invading the last refuges of
birds already on the brink of extinction. In Costa Rica,
toucans normally confined to lower elevations are colonizing
mountain forests, where they compete with resident species
for food and nesting holes, and prey on the eggs and
nestlings of other bird species.
In addition, plant species that currently share a habitat may
not all react the same way to temperature and moisture
changes. Some species may be forced upslope while others
are able to linger behind, tearing apart plant and animal
communities even if all the species survive. Differences in
soil composition can further disrupt plant communities. If
soils at higher elevations are inhospitable to some plant
species, those species will be wedged between a fixed upper
bound and a rising lower bound until they are squeezed out
of existence.
Until now, highland species have been less threatened by
habitat loss and hunting, simply because most people live in
flat lowlands instead of the steeper highlands. Compared to
lowland birds, however, highland species are not only more
sensitive to temperature changes, but their populations also
are more isolated from each other, as mountains effectively
constitute habitat islands surrounded by a sea of hotter
lowlands.
The study also has shown that sedentary birds, which
comprise over 80 percent of all bird species, are much more
likely to go extinct from climate change than are migratory
birds. That suggests that many sedentary mountain species
currently thought to be safe are actually jeopardized by
global warming. All in all, climate change is likely to be
especially hard on the hundreds of bird species endemic to
tropical mountains.
But in part because of the remoteness of the mountains and
in part due to a lack funding for ornithological studies in
most tropical countries, there are few data on these birds'
responses to climate change. Crucial remote sensing data are
also becoming less available, as government satellites like
Landsat age and as image distribution moves increasingly to
the relatively expensive private sector.
"To effectively monitor the rate of change as warming
progresses, especially in the species-rich tropics, we need a
lot more data on birds' distributions and on the speed and
extent of birds' elevational shifts in response to climate
change," Sekercioglu said.
Perhaps the most worrisome finding is that each additional
degree of warming will have increasingly devastating effects.
The authors estimate that an increase of 1 C from present
temperatures will trigger roughly 100 bird extinctions. But if
the global average temperature were to rise 5 C, from that
point on an additional degree of warming, to 6 C, would be
expected to cause 300 to 500 more bird extinctions.
"This emphasizes the importance of any measure that
reduces surface warming, even if we cannot stop it
altogether," Sekercioglu said. "Even a reduction of 1 degree
can make a huge difference."
"Giving up the fight against global warming would be the
true disaster," he added.
Posted by Casey Kazan.
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