Death Warmed Over

Global warming could wipe out a million-plus species, says a new study.

Fri Jan. 9, 2004 4:00 AM EST

A study published Thursday in the scientific journal Nature says that global warming at currently predicted rates will doom 15 to 37 percent of living species to extinction by 2050. The team of scientists behind the study called for "rapid implementation of technologies" to reduce emissions of greenhouse gases and reverse global warming trends that could doom upwards of a million species by midcentury.

The study, titled "Extinction Risk From Climate Change," was done by a 19-member international team and is the first to produce a global analysis with concrete estimates of the effect of climate change on habitat. The researchers surveyed habitat decline for 1,103 plant and animal species in six bio-diverse regions covering about 20 percent of the world’s land mass -- Europe; Queensland, Australia; Mexico's Chihuahuan Desert; the Brazilian Amazon; and the Cape Floristic Region at South Africa's southern tip -- and used computer models to simulate how the species, plants, mammals, birds, reptiles, frogs, butterflies and other invertebrates, are expected to move in response to changing temperatures and climate.

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The lead researcher on the study, Chris Thomas of Britain’s University of Leeds, had this to say:

"The midrange estimate is that 24 percent of plants and animals will be committed to extinction by 2050. We're not talking about the occasional extinction -- we're talking about 1.25 million species. It's a massive number."

Each species needs a very particular climate to survive, though some can adapt to change, within limits, or move to more conducive climates. Scientists used maps of regions to correlate climate changes to the needs of the species that live there. If all species are able to disperse or move from regions of climate change, only 15 percent would be irrevocably headed for extinction by 2050. If no species were able to disperse, the extinction rate could rise as high as 37 percent.

The scientists say the only way to minimize the extinction rate is by reining in emissions: "A rapid shift to technologies that do not produce greenhouse gases, combined with carbon sequestration, could save 15–20% of species from extinction."

There are skeptics, of course. William O'Keefe, president of the George C. Marshall Institute, a conservative science policy organization said the research "ignored species' ability to adapt to higher temperatures" and assumed that technologies will not arise to reduce emissions.

News accounts generally take the study's findings at face value, a notable exception being Gregg Easterbrook of The New Republic. Easterbrook acknowledges that "species loss is indisputably a problem--it's among the few environmental issues where trends are negative," and takes care to stipulate that he accepts most aspects of global-warming theory and favors greenhouse-gas restrictions. But he thinks the study is way off base because computer simulation is a notoriously speculative method of prediction:

"[The study is] nothing but computer modeling … computer models can be trained to produce any desired result. Computer models are also notorious for becoming more unreliable the farther out they project, as estimates get multiplied by estimates. This is a 50-year projection, and everything beyond the first few years should be treated as meaningless statistically, given that tiny alterations in initial assumptions can lead to huge swings at the end of a 50-year simulation."

Easterbrook also notes that other instances of climate change throughout history have not produced the massive species loss predicted by this one:

"Past episodes of global warming have not produced the mass-extinction that the Thomas computer models project. Global average temperatures have risen one degree Fahrenheit in the past century… without any significant effect on species… European temperatures rose naturally by one or two degrees at the end of the "Little Ice Age" of the fourteenth through nineteenth centuries. This rise did not cause a mass extinction in the region; in fact, it appears to have caused few or no extinctions. Why would the same level of temperature increase suddenly trigger a mass extinction now?"

The study partly addresses this objection, warning that the scale of extinctions this time around could climb much higher because of mutually reinforcing interactions between climate change and habitat destruction caused by uniquely modern factors.

"The risk of extinction increases as global warming interacts with other factors — such as landscape modification, species invasions and build-up of carbon dioxide — to disrupt communities and ecological interactions."

And London's Independent notes that the global warming currently occurring might be more usefully compared with other natural disasters that have caused mass extinction, rather than with other periods of climate change:

"Five times in the past half-billion years, the fossil record shows us, living things have been wiped out over much of the earth. Catastrophic changes in climate, or the impact of an asteroid or a comet, are the likeliest causes for the five great extinctions which geologists and palaeobiologists have identified, ranging from the Ordovician-Silurian extinction, of about 439 million years ago, to the Cretaceous-Tertiary extinction of 65 million years ago, when the dinosaurs disappeared. And it is not an asteroid that will have caused this, of course: it is us. The Sixth Great Extinction will be an entirely human achievement. To our widespread destruction of forests and other natural habitats, we are now adding the effect on the atmosphere of two centuries of burning coal, gas and oil on an ever-increasing scale."

Yet another reason, say many, to reduce fossil fuel emissions, spur conservation and invest in renewable energy sources. The Guardian says this:

"The only conservation response to climate change that makes any sense is to minimise the amount of warming that takes place. ...

Our estimates are only up to the year 2050, and most climate projections suggest that as much climate warming will take place between 2050 and 2100 as between now and 2050. These new climates are likely to make Earth hotter than it has been for 10m years. At that time, the bulk of species that now inhabit Earth had not evolved, and none of the currently observed biological communities (combinations of species) existed.

Serious conservation action means converting to progressively cleaner technologies rapidly and widely, and adhering to and tightening up international agreements. ...

Some species will actually be extinct by 2050, but probably most of the climate-threatened species will simply be in decline leading to their eventual extinction over the following decades. Reversing warming quickly may allow some, and possibly many, of these threatened species to hang on for long enough, until the climate improves for them again."

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