It seems that virtually every news organ in the English language has carried the story of new scientific claims published in Nature magazine that by 2050 over a million species will be doomed to extinction owing to the effects of global warming. Yet few of them realized how flimsy the story actually is. Writing on another claim of mass extinctions almost two years ago, I said, "This area of research is prone to wild exaggerations," and here we have another one.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
There are several reasons this claim should be laughed out of the court of public opinion. First, the research doesn't say what the researchers themselves claim. They have extrapolated to all species a model that looked at only 1,103 species in certain areas (243 of those species were South African proteaceae, a family of evergreen shrubs and trees). For one thing, we don't know how many species there are—estimates vary from 2 million to 80 million—and have only documented 1.6 million. However, assuming the 14 million figure widely used in the press reports is anywhere near accurate, the sample size is a mere 0.008 percent of the total species population of the planet, with certain species vastly over-represented (there are only 1,000 species of proteaceae on the planet). All the researchers have demonstrated is that, if their model is correct, certain species in certain habitats will run a risk of extinction. Extrapolating to the entire planet from this small, unrepresentative sample is simply invalid. So when the lead researcher told The <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Washington Post, "We're not talking about the occasional extinction—we're talking about 1.25 million species. It's a massive number," he was guilty at the very least of over-enthusiasm, if not outright exaggeration.
This problem would be devastating enough for the claims, if it wasn't the case that the model on which the calculations are made is itself suspect. It relies on the 'species-area relationship,' the idea that smaller areas support fewer species. A researcher at the evocatively titled Golden Toad Laboratory for Conservation in Puentoarenas, Costa Rica, writing a commentary on the study for Nature, called this "one of ecology's few ironclad laws.” The trouble is that there are many exceptions to this supposedly ironclad law. The wholesale deforestation of the Eastern United States, for example, seems only to have caused the extinction of one species of bird. While in Puerto Rico, the island's loss of 99 percent of its forest cover caused the loss of 7 out of 60 species, but after the deforestation, the number of bird species on the island actually increased to 97. The species-area relationship (plotted as a linear function in 1859) seems to be a poor model on which to base extinction rates.
So the model is suspect and the extrapolation invalid. What about the link to global warming? The researchers assume that global warming will reduce habitat. Yet this isn't the case. The earth is not shrinking. The reduction of one area of habitat does not mean that it is replaced by void. Other habitats expand. And so far, all the evidence we have points not to desertification or other changes to less hospitable climates because of global warming. Instead, the increase of carbon dioxide in the atmosphere seems to have led to a 6 percent increase in the amount of vegetation on the earth. The Amazon rain forests accounted for 42 percent of the growth. To model only reductions in habitats and not expansions accounted for by global warming stacks the deck. The researchers created a model that dictated that global warming will cause extinctions. Surprise, surprise! When they ran the model that's exactly the result they got.
Thank goodness for The New York Times, whose writer John Gorman was careful enough to note the limitations of the study. While others talked about millions of extinctions, he said, "By 2050, the scientists say, if current warming trends continue, 15 to 37 percent of the 1,103 species they studied will be doomed," which is precisely what the study found, free of exaggeration. He also quoted Daniel C. Botkin of the University of California at Santa Barbara, who noted the limitations of the model, saying "the analysis was based on 'a lot of steady state assumptions that lead it to the most pessimistic forecast,' including the notion that things will stay as they are in terms of the ways animals migrate and respond to temperature change.” Darwin would see the holes in that approach.
In a world that has seen a grand total of just over 1,000 documented extinctions since 1600, these wild predictions should be ignored as alarmist hyperbole. They belong in the same virtual world that predicts the North Korean economy overtaking the American and leading to 6° C. increases in temperature, when the satellite record suggests half a degree is as much as can be expected. With luck, one day such modeling with reckless disregard for actual events will be as dead as the Dodo.