Rising Global Temperatures Threatening Planet-wide Bird Extinction

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.

Comments

What a bunch of crap... In 1975 these self proclaimed experts said EXACTLY the same thing with the only notable exception being we were in the midst of "Global Cooling"...

This article from Newsday.
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By Peter Gwynne
28 April 1975

There are ominous signs that the Earth’s weather patterns have begun to change dramatically and that these changes may portend a drastic decline in food production — with serious political implications for just about every nation on Earth. The drop in food output could begin quite soon, perhaps only 10 years from now. The regions destined to feel its impact are the great wheat-producing lands of Canada and the U.S.S.R. in the North, along with a number of marginally self-sufficient tropical areas — parts of India, Pakistan, Bangladesh, Indochina and Indonesia — where the growing season is dependent upon the rains brought by the monsoon.

The evidence in support of these predictions has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it. In England, farmers have seen their growing season decline by about two weeks since 1950, with a resultant overall loss in grain production estimated at up to 100,000 tons annually.

During the same time, the average temperature around the equator has risen by a fraction of a degree — a fraction that in some areas can mean drought and desolation. Last April, in the most devastating outbreak of tornadoes ever recorded, 148 twisters killed more than 300 people and caused half a billion dollars’ worth of damage in 13 U.S. states.

To scientists, these seemingly disparate incidents represent the advance signs of fundamental changes in the world’s weather. Meteorologists disagree about the cause and extent of the trend, as well as over its specific impact on local weather conditions. But they are almost unanimous in the view that the trend will reduce agricultural productivity for the rest of the century. If the climatic change is as profound as some of the pessimists fear, the resulting famines could be catastrophic.

“A major climatic change would force economic and social adjustments on a worldwide scale,” warns a recent report by the National Academy of Sciences, “because the global patterns of food production and population that have evolved are implicitly dependent on the climate of the present century.”

A survey completed last year by Dr. Murray Mitchell of the National Oceanic and Atmospheric Administration reveals a drop of half a degree in average ground temperatures in the Northern Hemisphere between 1945 and 1968. According to George Kukla of Columbia University, satellite photos indicated a sudden, large increase in Northern Hemisphere snow cover in the winter of 1971-72. And a study released last month by two NOAA scientists notes that the amount of sunshine reaching the ground in the continental U.S. diminished by 1.3% between 1964 and 1972.

To the layman, the relatively small changes in temperature and sunshine can be highly misleading. Reid Bryson of the University of Wisconsin points out that the Earth’s average temperature during the great Ice Ages was only about seven degrees lower than during its warmest eras — and that the present decline has taken the planet about a sixth of the way toward the Ice Age average.

Others regard the cooling as a reversion to the “little ice age” conditions that brought bitter winters to much of Europe and northern America between 1600 and 1900 — years when the Thames used to freeze so solidly that Londoners roasted oxen on the ice and when iceboats sailed the Hudson River almost as far south as New York City.

Just what causes the onset of major and minor ice ages remains a mystery. “Our knowledge of the mechanisms of climatic change is at least as fragmentary as our data,” concedes the National Academy of Sciences report. “Not only are the basic scientific questions largely unanswered, but in many cases we do not yet know enough to pose the key questions.”

Meteorologists think that they can forecast the short-term results of the return to the norm of the last century. They begin by noting the slight drop in overall temperature that produces large numbers of pressure centers in the upper atmosphere. These break up the smooth flow of westerly winds over temperate areas. The stagnant air produced in this way causes an increase in extremes of local weather such as droughts, floods, extended dry spells, long freezes, delayed monsoons and even local temperature increases — all of which have a direct impact on food supplies.

“The world’s food-producing system,” warns Dr. James D. McQuigg of NOAA’s Center for Climatic and Environmental Assessment, “is much more sensitive to the weather variable than it was even five years ago.”

Furthermore, the growth of world population and creation of new national boundaries make it impossible for starving peoples to migrate from their devastated fields, as they did during past famines.

Climatologists are pessimistic that political leaders will take any positive action to compensate for the climatic change, or even to allay its effects.

They concede that some of the more spectacular solutions proposed, such as melting the Arctic ice cap by covering it with black soot or diverting arctic rivers, might create problems far greater than those they solve. But the scientists see few signs that government leaders anywhere are even prepared to take the simple measures of stockpiling food or of introducing the variables of climatic uncertainty into economic projections of future food supplies. The longer the planners delay, the more difficult will they find it to cope with climatic change once the results become grim reality.

Lest we forget just how wrong the climate experts can be.

It’s funny isn’t it?

Everyone complains about the weather, but only liberals try to legislate it.

Posted by: Mitch the Bitch | February 18, 2008 at 11:33 AM