17 A Moment..., p. 559: "In 1993 two authorities on biodiversity, Michael Bean and David Wilcove of the Environmental Defense Fund, tallied 27 extinctions of North American fish species and subspecies since the year 1950. The BeanWilcove estimate is double the rate for the first half of the century, again a clear danger sign. But it's also a fish loss of about one per year, a figure impossibly low if pessimists... are right about their projections of annual losses by the many thousands."

Correction: Easterbrook ignores that rates of extinction for particular types of species in this case fish - may not be the same as rates for other types. Nor does he acknowledge that rates in one region may not be comparable to rates in other regions.

Moreover, Bean and Wilcove, the authors of the cited letter, are pessimistic about the overall rate of species loss in the United States. The number of species identified by the U.S. Fish and Wildlife Service as threatened or endangered continues to grow, as many natural areas in the United States that contain rare and localized species are developed.

A Moment..., p. 562: "... as Ariel Lugo, a Forest Service official in Puerto Rico, pointed out in a 1991 issue of Science, when pristine forests are cut they do not vanish; rather, the next step is usually new second-growth forests. Many species from the pristine forest adapt to the second-growth habitat and continue living.." Correction: First, forests don't always regenerate after being cut. Tropical rain forests, for example, are among the most fragile of ecosystems, containing thin soils, whose nutrients and minerals are washed away quickly by rain after deforestation. There are large areas throughout the American tropics where forests have been converted to cattle pastures, sugar cane fields, and other nonforested habitat. Many of these altered habitats will be very difficult if not impossible to restore to their previous, ecologically diverse conditions (33).

Second, many species are unable to adapt to second- growth habitat. An example from the United States is the now-extinct ivory-billed woodpecker (34).

S.L. Pimm As already discussed, the species losses following the forest clearings in the eastern U.S.A. are almost exactly what ecologists would predict.

A Moment..., p. 562: "Most troubling is a fundamental inconsistency in the work of Wilson.... It cannot be that a human-caused mass extinction occurred just 11,000 years ago, that ten million years must pass for nature to recover naturally from mass extinctions, and that today biological diversity is the highest ever."

Correction: These three points are not related to each other as if in mathematical equilibrium. Measured over millions of years, global biodiversity has increased, as demonstrated by the fossil record (35). Yet 11,000 years ago, roughly three

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quarters of the large mammals in the Americas were hunted to extinction (victims included long-horned bison, sabertooth cats, dire wolves, and ground sloths). The mammalian biodiversity in the Americas has not recovered (36). But because mammals are only a small proportion of the world's species- less than 0.3 percent, as currently described — the demise of some of them does not significantly change the numbers on species abundance (37).

The fossil record also indicates that it commonly takes millions of years for affected groups to regain their diversity following major extinction events.

S.L. Pimm First, the impact of Stone Age cultures is more dramatic than EDF contend. In the last 1000-4000 years, across the Pacific, Polynesian colonists eliminated about 2000 species of birds - or about 15% of the planet's total. There is no evidence that biodiversity is increasing following this slaughter. Indeed, it continues to decline. Second, we know from previous extinction catastrophes (like that at the end of the Cretaceous), that recovery times are on the order of tens of millions of years.

A Moment..., pp. 562-568: On these pages, Easterbrook presents what he calls "An Endangered Species Scorecard." He refers to the Endangered Species Act and says, "Let's take a look at what is happening on the list." He then proceeds to examine superficially 24 species or species groups for the trend in their numbers.

Correction: Of the 24, only 13 of his examples are unequivocally correct. In several cases he refers inaccurately to a group of animals as a single species — the kangaroo rat, for example (p. 563). There are many species of kangaroo rats, only some of which are on the endangered species list. Six times or 25% of his examples - he is simply wrong about whether a species or group of species is represented on the endangered species list: Mute swans, harp seals, tuna, sharks, wild turkeys, and mustangs have never made the list. He makes other errors within his inventory:

A Moment..., p. 563: "... political sentiment has run strongly against returning the wolf to Yellowstone, for fear that someday a child touring the park may be snatched and killed."

Correction: Though some people may have expressed this fear, the opposition to the reintroduction of wolves was and continues to be driven primarily by the fears of ranchers that it will lead to loss of livestock (38).

A Moment..., p. 567: "Mountain lions, also called cougars, were extensively bounty-hunted in the nineteenth century, and by the 1960s were believed extinct in North America... Oddly enough, the Fish and Wildlife Service still classifies the eastern cougar as extinct, yet nevertheless also classifies it as an endangered

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Correction: Mountain lions were never believed to be extinct in North America. The species has always been seen in the West (as well as throughout Central and South America). The eastern cougar, a particular subspecies of the mountain lion, is widely believed to be extinct, but unconfirmed sightings are reported from time to time (39).

A Moment. , p. 567: "...the steller [sic] sea lion... was listed as threatened in 1990 in response to a lawsuit by environmental groups, though about 65,000 steller sea lions are estimated to exist."

Correction: The Steller sea lion was listed because of sudden and severe population declines throughout its range, with an overall decline of 78% between the 1950's and 1990. The greatest loss occurred in the eastern Aleutians, where 10,802 sea lions were counted in 1985 but only 3,145 in 1989 (40). Declines of this magnitude and rate, by any calculation, justify protection.

A Moment..., pp. 567-568: "In the last decade environmental litigators have pressured the Fish and Wildlife Service to list creatures at any sign of population decline, regardless of whether the decline appears to engage a threat of extinction. This means a common invocation of doomsday cant — that `more and more creatures are being listed as endangered every day' is deceptive, since the listings are based on increasingly lenient criteria and now may be registered even when a creature is numerous."

Correction: The reality is really the reverse of what Easterbrook asserts. Most species are listed too late rather than too early to ensure their survival. According to a recent study, the median population size of an animal species at time of listing was just under 1,000 - well below the level generally considered viable; for plant species the median population size was fewer than 120 individuals, and 39 of these species were listed with ten or fewer known members. (41).

A Moment..., p. 570: "In the Western world at least, if most imperiled species could make it through the period from the 1940s to the late 1970s — when gross pollution was everywhere, development was unrestricted, and the Endangered Species Act did not yet exist - then those species have already passed the worst test that will be administered by man."

Correction: First of all, imperilment is a site-specific phenomenon, and over most of the globe, including major portions of the Western world, there are few laws to protect endangered species. Moreover, in much of the world, including many developed nations, habitat destruction continues unabated. Species whose habitats have been partly or entirely spared in the past, but are now finding themselves increasingly squeezed, will find little comfort in Easterbrook's

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Finally, in the future, human-caused climate change stands as one of the greatest threats to the survival of species, a prospect which, so far, the world has made little effort to forestall (42).

A Moment..., p. 571: "In Monterey County, California, the bush lupine, a native plant, is protected under the Endangered Species Act. About 200 miles away at the Lanphere Christensen Dunes Preserve in Humbolt [sic] County, California, where the bush lupine is not native, the Nature Conservancy has been trying to eradicate the same plant. It's hard to get your head around the notion that a plant can be so wonderful in one place that it deserves federal protection yet so horrible 200 miles away that it must be destroyed."

Correction: Easterbrook confuses two strikingly different species of lupine - one highly endangered, the other not. The endangered species is Lupinus tidestromii, or Tidestrom's lupine, which is not a bush lupine but a creeping perennial found in only three dune systems in California. The other species, which the Nature Conservancy is trying to eradicate from the Christensen Preserve in Humboldt County, is the Lupinus arboreus, or yellow bush lupine, a much more common plant (43).

S.L. Pimm One hopes that Mr. Easterbrook is more careful with his taxonomy of micro-organisms. Species in the genus, Salmonella can be both fatal and an essential ingredient of brie and camembert cheeses.

A Moment..., p. 572: "... species arriving from someplace else do not possess mystical superpowers. They are just different, and the local ecology needs time to react to the difference."

Correction: The fact remains that the introduction by humans of exotic species into ecosystems often leads to the imperilment and/or extinction of native species (as Easterbrook himself has pointed out, one paragraph earlier, with his example of the loss of several bird species on Guam after the accidental introduction of the brown tree snake). Indeed, of the known causes of animal extinctions since 1600, introduction of exotics ranks with habitat destruction as the most important (44).

A recent study found that the introduction of new species was a major cause for the listing of 41 species as threatened or endangered in the United States, and a contributing factor in the listing of 160 more, since the establishment of the Endangered Species Act (45). Another study found that over the past century, the introduction of new species has been a contributing factor in 68% of the extinctions of North American fish (46).

S.L. Pimm EDF has again been more conservative in their criticism than I would have been. Our summaries show that introduced species have been the single leading cause of extinction historically. Their economic impact is enormous.

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"The loss of several bird species on Guam" misses the point. The brown tree snake exterminated all Guam's land birds. Moreover, a local physician has told me that he estimates that about 50 people a year seek medical attention for snake bites. We ignore these warning signs at our peril. If this snake were to reach the Hawaiian islands its ecological and economic impacts would be devastating.

A Moment..., p. 573: "... many environmental groups, including the normally clearheaded Environmental Defense Fund, have succeeded in pressuring some states to outlaw possession of `exotic' species — animals endangered in other nations, but not in the U.S.—and have asked Congress for national legislation to that effect, depicting the notion of private U.S. stocks of endangered species from other shores as an odious hoarding. Yet... on a Texas ranch [there are] more representatives of the endangered scimitar-horned oryx than can be found in the species' native Africa.... It's hard to imagine how outlawing [this] collection will aid the survival prospects of the scimitar-horned oryx."

Correction: First of all, EDF has never tried to pressure any state to outlaw possession of exotics. Secondly, he defines "exotic" erroneously. Exotic species are plants or animals that have been introduced, deliberately or accidentally, into countries or areas where they do not normally occur; whether they are endangered or not is irrelevant. Thirdly, his suggestion that the rationale for such restrictions, to prevent "odious hoarding" by private collectors, is wrong. The motivation of states that have imposed restrictions on exotic-game ranching has been to prevent the transmission of diseases and parasites to native wildlife (47).

A Moment..., p. 575: "One looming absurdity is beetle protection [by the Endangered Species Act]... If beetles start receiving the instant-doomsday treatment, species protection will have veered into nonsense."

Correction: Would Easterbrook have the Act specifically exclude beetles from its protection just because there are thousands of species of beetles? Or because beetles are small? What could be the logic behind this statement, especially if he believes that, as he writes on the very next page (p. 576), "every animal on Earth may be vital to the cosmic enterprise"? Indeed, obscure creatures often yield things of value; witness the derivation of penicillin from a bread mold or an antileukemia drug from the rosy periwinkle.

S.L. Pimm Australian pastures were being seriously degraded because cow dung was not broken up by beetles (as it is elsewhere). The vegetation that grew in the nitrogen-rich dung was unsuitable and perhaps poisonous to the cattle. The solution was to introduce the appropriate species of beetle. Mr. Easterbrook should try telling Australian cattle ranchers that beetles are "nonsense."

An ecologically equivalent beetle is the subject of the first chapter of Mann and Plummer's Noah's Choice (see below). In pitting a beetle against the needs of