Biologists are trained to have a healthy respect for statistics and statisticians. It was disconcerting, therefore, to find that before even examining the extinction problem--and the numbers invoked to demonstrate that it is or is not a problem--Lomborg begins the chapter on biodiversity with a section questioning whether biodiversity is important. In less than a page, he discounts its value both as the library for the life sciences and as provider of ecosystem services (in part because of a general absence of markets for these services).

When he finally gets to extinction, he totally confounds the process by which a species is judged to be extinct with the estimates and projections of extinction rates. Highly conservative rules hold that to be declared officially extinct, not only does a species have to be known to science, it has to be observed going to extinction (as in the case of the passenger pigeon, the last individual of which perished in the Cincinnati Zoo in 1914). Or, in the absence of direct observation, it must not have been seen in nature for 50 years.

Projections of extinction rates, on the other hand, are generally based on the long-established relation between species number and area (which dates to 1921, not to the 1960s, as Lomborg maintains, and which demonstrates the rate at which species number increases with increase in area). Researchers then project what the reduction in a natural habitat will mean in terms of species loss. The disappearance of a species is not necessarily instantaneous, and thus some species that survive the initial reduction of the habitat are essentially "living dead"--they are not able to survive over the long term. The loss of species from habitat remnants is a widely documented phenomenon--in contrast to Lomborg's inclusion of an out-of-date assertion that no credible attempt has been made to pin down the underlying scientific assumptions.

As a consequence, a seemingly major contradiction that Lomborg then offers is no contradiction at all: the reduction of the Brazilian Atlantic Forest formation to something on the order of 10 percent of its original extent and the lack of large numbers of recorded extinctions. First, this is a region with very few field biologists to record either species or their extinction. Second, there is abundant evidence that if the Atlantic forest remains as reduced and fragmented as it is, it will lose a sizable fraction of the species that at the moment are able to hang on.

In another supposed example of species surviving habitat loss, he notes that few species went extinct when the eastern forests of the U.S. were reduced to 1 to 2 percent of their original area. But only the old-growth forests shrank that much; total forest cover never fell below roughly 50 percent--allowing much biodiversity to survive as forest returned to an even greater area. Consequently, the small number of bird extinctions does not contradict what species-area considerations predict but instead confirms them.

In presenting an analysis for Puerto Rico, Lomborg again cites apparently contradictory evidence that although 99 percent of the primary forest was lost, the island ended up with more birds than it supported before deforestation. First of all, total forest cover was never so dramatically reduced. More significant, he ignores that seven of the 60 species unique to Puerto Rico were lost, and the additional species are not only invasives from other parts of the world but live in a wide variety of habitats. He completely misses the point that the world's bird fauna was reduced by seven species.

Lomborg takes particular exception to projections of massive extinction that started with Norman Myers's 1979 estimate that 40,000 species are being lost from the globe every year. There is some justification for this objection: Myers did not specify the method of arriving at his estimate. Nevertheless, he deserves credit for being the first to say that the number was large and for doing so at a time when it was difficult to make more accurate calculations. Current estimates are usually given in terms of the increases over normal extinction rates, which is preferable in that it is not necessary to assume a figure for the total number of species on the earth. That science does not know the total number of species does not prevent an estimation of extinction rates. Lomborg cynically dismisses the use of multiples of normal rates as being done because it sounds more "ominous" rather than recognizing the altered approach as an improvement in the science.

Estimates of present extinction rates range from 100 to 1,000 times normal, with most estimates at 1,000. The percent of bird (12), mammal (18), fish (5) and flowering plant (8) species threatened with extinction is consistent with that estimate. And the rates are certain to rise--and to do so exponentially--as natural habitats continue to dwindle.

The consideration of acid rain in a separate chapter is equally poorly researched and presented. Indeed, the research is so shallow that almost no citation from the peer-reviewed literature appears. Lomborg asserts that big-city pollution has nothing to do with acid rain, when it is fact that nitrogen compounds (NO_x) from traffic are a major source. His reference to a study showing that acid rain had no effect on the seedlings of three tree species neglects to mention that the study did not include conifer species such as red spruce, which are very sensitive. There is no acknowledgment of the delayed effects from acid rain leaching soil nutrients, particularly key cations. He confounds tree damage from air pollution 30 to 60 years ago with subsequent acid rain damage and makes an Alice-in-Wonderland statement that the only reason we worry about foliage loss is "because we have started monitoring this loss." It is simply untrue that "there is no case of forest decline in which acidic deposition is known to be a predominant cause." Two clear-cut examples are red spruce in the Adirondacks and sugar maple in Pennsylvania.

The chapter on forests also suffers from superficial research and selective use of numbers. Lomborg starts by displaying Food and Agriculture Organization (FAO) data from 1948 to 2000. The FAO began by just reporting sums of "official data" furnished by governments (such data are notoriously uneven in quality and frequently overestimate forest stocks). Subsequently, the FAO adopted so many different definitions and methods that any statistician should know they could not be used for a valid time series.

Lomborg's discussion of the great fire in Indonesia in 1997 is still another instance of misleading readers with selective information. Yes, the WWF (World Wide Fund for Nature) first estimated the amount of forest burned at two million hectares, and Indonesia countered with official estimates of 165,000 to 219,000 hectares. But Lomborg fails to mention that the latter were not in the least credible and that in 1999 the Indonesian government and donor agencies, including the World Bank, signed off on a report that the real number was 4.6 million hectares.

From the very outset--his introductory chapter--Lomborg confuses forests and tree plantations. In criticizing a WWF estimate of loss of "natural wealth," he implies that the only value of forests is harvestable trees. That is analogous to valuing computer chips only for their silicon content. In fact, the metric the WWF used includes natural forests (because of their biodiversity) and omits plantations (because of their general lack thereof).

The central question of the book-Are things getting better?--is an important one. The reality is that significant progress has been made in abating acid rain, although much still needs to be done. And major efforts are under way to stem deforestation and to address the tsunami of extinction. But it is crucial to remember that whereas deforestation and acid rain are theoretically reversible (although there may be a threshold past which remedy is impossible), extinction is not. A dispassionate analysis, which Lomborg pretends to offer, of how far we have come and how far we have yet to go would have been a great contribution. Instead we see a pattern of denial.

The pattern is evident in the selective quoting. In trying to show that it is impossible to establish the extinction rate, he states: "Colinvaux admits in Scientific American that the rate is 'incalculable,'" when Paul A. Colinvaux's text, published in May 1989, is: "As human beings lay waste to massive tracts of vegetation, an incalculable and unprecedented number of species are rapidly becoming extinct." Why not show that Colinvaux thought the number is large? Biased language, such as "admits" in this instance, permeates the book.

In addition to errors of bias, the text is rife with careless mistakes. Time and again I sought to track references from the text to the footnotes to the bibliography to find but a mirage in the desert.

Far worse, Lomborg seems quite ignorant of how environmental science proceeds: researchers identify a potential problem, scientific examination tests the various hypotheses, understanding of the problem often becomes more complex, researchers suggest remedial policies--and then the situation improves. By choosing to highlight the initial step and skip to the outcome, he implies incorrectly that all environmentalists do is exaggerate. The point is that things improve because of the efforts of environmentalists to flag a particular problem, investigate it and suggest policies to remedy it. Sadly, the author seems not to reciprocate the respect biologists have for statisticians.

The Diversity of Life. E. O. Wilson. Belknap Press of Harvard University Press, 1992. [New edition. Penguin, 2001.}

Global Biodiversity Assessment. Edited by V. H. Heywood. Cambridge University Press, 1996.

Our Common Journey: A Transition toward Sustainability. National Research Council Board on Sustainable Development, Policy Division. National Academy Press, 1999.

Beyond Six Billion: Forecasting the World's Population. Edited by John Bongaarts and Rodolfo A. Bulatao. National Research Council, 2000.

Climate of Uncertainty. George Mussar in Scientific American, Vol. 285, No. 4, pages 14-15; October 2001.

Grand Challenges in Environmental Sciences, 2001. National Research Council. Available at www.nap.edu/catalog/9975.html

World Energy Assessment: Energy and the Challenge of Sustainability. United Nations Development Program, United Nations Department of Economic and Social Affairs, and World Energy Council, 2001. Available at www.undp.org/seed/eap/activities/wea/drafts-frame.html

The Intergovernmental Panel on Climate Change Web site is available at www.ipcc.ch/

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By Thomas Lovejoy

Thomas Lovejoy is chief biodiversity adviser to the president of the World Bank and senior adviser to the president of the United Nations Foundation. From 1973 to 1987 he directed the World Wildlife Fund-U.S., and from 1987 to 1998 he served as assistant secretary for environmental and external affairs for the Smithsonian Institution in Washington, D.C.