The irrelevant observations by Stuart Pimm and Jeff Harvey about Bjørn Lomborg's book The Skeptical Environmentalist (Nature 414, 149–50, 2001) exemplify the unfortunate tendency of some environmental activists, when challenged with well-founded objections to the scientific validity of their alarmist claims about the state of the planet, to respond with such diversionary tactics as counting the number of footnotes cited by their critics, disparaging their critics' credentials and misrepresenting their views — everything, in short, but dealing honestly with the evidence.

In his book, for example, Lomborg presents a detailed analysis, based on widely accepted United Nations (UN) data, to show how the alarmists have been consistently wrong about the global population and food supply. Contrary to the predictions of impending catastrophe by Paul Ehrlich, Lester Brown and Pimm himself (who in 1998 told a meeting at the American Museum of Natural History that the world population might reach 40 billion by the end of the twentieth-first century), the data actually show that, over the past four decades, per capita food production has increased substantially, even in the developing world, while population growth has slowed so that the world population will level off at about 9 billion by mid-century.

Lomborg shows with devastating effect how the alarmists have been able to generate their forecasts only by extrapolating from very short-term or local negative trends, while disregarding the larger positive trends. Yet, instead of discussing this evidence, Pimm and Harvey simply attack Lomborg's credentials by attempting to associate him with the absurd view that an ever-growing population could be sustained for the next 7 billion years. Lomborg says no such thing, nor anything like it.

Similarly, Pimm and Harvey dismiss Lomborg's detailed, well-founded critique of exaggerated extinction-rate predictions with the ugly charge that this is morally equivalent to denying the Holocaust. Yet far from denying that loss of biodiversity and other environmental threats are occurring, Lomborg plainly states that these are indeed serious problems. What he is criticizing is the habitual exaggeration and white lies that have become the common currency of environmentalist advocacy (see the Correspondence by A. Trewavas, Nature 414, 581–582; 2001).

It is thus particularly ironic that Pimm and Harvey level the supercilious charge that Lomborg's book (“like a bad term paper”, they say) cites secondary sources. Lomborg does indeed cite secondary sources — to provide examples of the exaggerations and distortions made by environmental activists. But to demonstrate the inaccuracy of these pronouncements, Lomborg cites primary sources such as UN data and articles in peer-reviewed scientific journals.

Lomborg's whole point is that the refusal of some environmental activists to deal honestly with the data harms the credibility of both environmental science and environmentalism. Pimm and Harvey in their review appear to have provided a further example in support of this thesis.