CHAPTER 3 THE STATISTICAL FLUMMERY ABOUT SPECIES LOSS Species extinction came to scientific prominence in 1979 with my debate opponent Norman Myers's book The Sinking Ark. It then was brought to an international public and onto the U. S. policy agenda by the 1980 Global 2000 Report to the President. These still are the canonical texts. Global 2000 forecast ex- traordinary losses of species between 1980 and 2000. "Extinc- tions of plant and animal species will increase dramatically. Hundreds of thousands of species -- perhaps as many as 20 percent of all species on earth -- will be irretrievably lost as their habitats vanish, especially in tropical forests," it said. The actual data on the observed rates of species extinction are wildly at variance with Myers's and following statements, and do not provide support for the various policies suggested to deal with the purported dangers. Furthermore, recent scientific and technical advances -- especially seed banks and genetic engineer- ing, and perhaps electronic mass-testing of new drugs -- have reduced the importance of maintaining a particular species of plant life in its natural habitat. But the bandwagon of the species extinction issue continues to roll with ever-increasing speed. Society properly is concerned about possible dangers to species. Individual species, and perhaps all species taken together, constitute a valuable endowment, and we should guard their survival just as we guard our other physical and esthetic assets. But we should strive for as clear and unbiased an under- standing as possible in order to make the best possible judgments about how much time and money to spend in guarding them, in a world in which this valuable activity must compete with guarding and supporting other valuable aspects of civilization. SPECIES LOSS ESTIMATES The standard forecast for loss of species comes from Lovejoy: What then is a reasonable estimate of global extinctions by 2000? In the low deforestation case, approximately l5 percent of the planet's species can be expected to be lost. In the high deforestation case, perhaps as much as 20 percent will be lost. This means that of the 3-l0 million species now present on the earth, at least 500,000-600,000 will be extinguished during the next two decades. (U.S., l980, II, p. 33l). The basis of any useful projection must be some body of experience collected under some range of conditions that encompass the expected conditions, or that can reasonably be extrapolated to the expected conditions. But none of Lovejoy's references contain any scientifically-impressive body of experience. The only published source given for his key table is Myers's 1979 book. This is Myers's summary: As a primitive hunter, man probably proved himself capable of eliminating species, albeit as a relatively rare occurrence. From the year A.D. l600, however, he became able, through advancing technology, to over-hunt animals to extinction in just a few years, and to disrupt extensive environments just as rapidly. Be- tween the years l600 and l900, man eliminated around seventy-five known species, almost all of them mammals and birds--virtually nothing has been established about how many reptiles, amphibians, fishes, invertebrates and plants disappeared. Since l900 man has eliminated around another seventy-five known species--again, almost all of them mammals and birds, with hardly anything known about how many other creatures have faded from the scene. The rate from the year l600 to l900, roughly one species every 4 years, and the rate during most of the present century, about one species per year, are to be compared with a rate of possibly one per l000 years during the "great dying" of the dinosaurs. Since l960, however, when growth in human numbers and human aspirations began to exert greater impact on natural environments, vast territories in several major regions of the world have become so modified as to be cleared of much of their main wildlife. The result is that the extinction rate has certainly soared, though the details mostly remain undocumented. In l974 a gathering of scientists concerned with the problem hazarded a guess that the overall extinction rate among all species, whether known to science or not, could now have reach l00 species per year... Let us suppose that, as a consequence of this man- handling of natural environments, the final one-quarter of this century witnesses the elimination of l million species--a far from unlikely prospect. This would work out, during the course of 25 years, at an average extinction rate of 40,000 species per year, or rather over l00 species per day. The greatest exploitation pressures will not be directed at tropical forests and other species-rich biomes until towards the end of the period. That is to say, the l990s could see many more species accounted for than the previous several dec- ades. But already the disruptive processes are well underway, and it is not unrealistic to suppose that, right now, at least one species is disappearing each day. By the late l980s we could be facing a situation where one species becomes extinct each hour (l979, pp. 4-5). We may extract these key points from the above summary quotation: (l) The estimated extinction rate of known species is about one every four years between the years from l600 to l900. (2) The estimated rate is about one a year from l900 to the present. (3) Some scientists (in Myers's words) have "hazarded a guess" that the extinction rate "could now have reached" l00 species per year. That is, this number is simply conjecture; it is not even a counter-point estimate but rather an upper bound. The source given for the "some scientists" statement is a staff- written news report. (It should be noted that the subject of this guess is different than the subject of the estimates in (l) and (2), because the former includes mainly or exclusively birds or mammals whereas the latter includes all species. While this difference implies that (l) and (2) may be too low a basis for estimating the present extinction rate of all species, it also implies that there is even less statistical basis for estimating the extinction rate for species other than birds and mammals than it might otherwise seem.) (4) This guessed upper limit in (3) is then increased and used by Myers, and then by Lovejoy, as the basis for the "projec- tions" quoted above. In Global 2000 the language became "are likely to lead" to the extinction of between l4% and 20% of all species before the year 2000. (U.S., l980, II, p. 328) So an upper limit for the present that is pure guesswork has become the basis of a forecast for the future which has been published in newspapers to be read by tens or hundreds of millions of people and understood as a scientific statement. The two historical rates stated by Myers, together with the yearly rates implied by Lovejoy's estimates, are plotted together in Figure 3-l. It is clear that the Lovejoy extrapolation has no better claim to belief than a rate that is, say, one hundredth as large. Indeed, looking only at the two data points alone, many forecasters would be likely to project a rate close to the past rate, nowhere near Lovejoy's estimate, on the basis of the common wisdom that in the absence of additional information, the best first approximation for a variable tomorrow is its value today, and the best second approximation is that the variable will change at the same rate in the future that it has in the past. Figure 3-1 -- Species Extinction Projected change in the amount of tropical forests implicitly underlies the differences between past and projected species-loss rates in Lovejoy's extrapolation. But to connect this element logically, there must be systematic evidence relat- ing an amount of tropical forest removed to a rate of species reduction. The only available evidence runs against this theory. Ariel Lugo details the situation in Puerto Rico, where "human activity reduced the area of primary forests by 99%, but, because of coffee shade and secondary forests, forest cover was never below 10 to 15%. This massive forest conversion did not lead to a correspondingly massive species extinction, certainly nowhere near the 50% alluded to by Myers" (1989, p. 28). During the 1980s there was increasing recognition that the rate of species loss really is not known. Indeed, as of 1989 Myers himself wrote, "Regrettably we have no way of knowing the actual current rate of extinction in tropical forests, nor can we even make an accurate guess" (p. 102). And Paul Colinvaux refers to the extinctions as "incalculable". One would think that this absence of knowledge would make anyone leery about estimating future extinctions. Nevertheless Myers continues, "But we can make substantive assessments by looking at species numbers before deforestation and then applying the analytical techniques of biogeography... According to the theory of island biogeography, we can realisti- cally reckon that when a habitat has lost 90% of its extent, it has lost half of its species." (p. 43) This is mere speculation, however. And as noted above, Lugo found disconfirming evidence in Puerto Rico. Yet the conservationists go right on pressing for expensive public policies on the unproven assumption that the number of species being extinguished is huge. Many biologists privately agree that the extinction numbers are quite uncertain. But they go on to say the numbers do not matter scientifically. The policy implications would be the same, they say, even if the numbers were different even by several orders of magnitude. But if so, why mention any numbers at all? The answer, quite clearly, is that these numbers do matter in one important way: they have the power to frighten the public in a fashion that smaller numbers would not. I find no scientific justification for such use of numbers. Some have said: But was not Rachel Carson's Silent Spring an important force for good even though it exaggerated? Maybe so. But the books are not yet closed on the indirect and long- run consequences of ill-founded concerns about environmental dangers. And it seems to me that, without some very special justification, there is a strong presumption in favor of stating the facts as best we know them, especially in a scientific con- text, rather than in any manipulation of the data no matter how well-intended. THE RISKS FROM SPECIES LOSS Let's look backwards and wonder: What kinds of species may have been extinguished when the settlers clear-cut the Middle West of the United States? Could we be much the poorer now for their loss? Obviously we do not know the answers. But it seems hard to even imagine that we would be enormously better off with the persistence of any such imagined species. This casts some doubt on the economic value of species that might be lost else- where. Still, the question exists: How should decisions be made, and sound policies formulated, with respect to the danger of species extinction? I do not offer a comprehensive answer. It is clear that we cannot simply save all species at any cost, any more than we can save all human lives at any cost. Certainly we must make some informed estimates about the present and future social value of species that might be lost, just as we must estimate the value of human life in order to choose rational policies about public health care services such as hospitals and surgery. And just as with human life, valuing species relative to other social goods will not be easy, especially because we must put values on some species that we do not even know about. But the job must be done somehow. We must also try to get more reliable information about the number of species that might be lost with various forest changes. This is a very tough task, too. Lastly, any policy analysis concerning species loss must explicitly evaluate the total cost of protective actions -- for example, the cost of cessation of foresting in an area. And such a total cost estimate must include the long-run indirect costs of reduction in economic growth to a community's education and general advancement. Maintaining the Amazon and other areas in a state of stability might even have counterproductive results for species diversity, according to a recent body of research. Natural disturbances, as long as they are not catastrophic, may lead to environmental disturbance and to consequent isolation of species that may "facilitate ever-increasing divergence," as Colinvaux tells us. Colinvaux goes on to suggest that "the highest species richness will be found not where the climate is stable but rather where environmental disturbance is frequent but not excessive". This is another subtle issue which must be taken into account. [DISCUSSING MATTERS WITH THE CONSERVATIONISTS [Why is there such an enormous gulf between what you hear from the conservationists and what you are reading here? [1. In the case of species extinction, as with many other public issues, there is a tendency to focus only upon the bad effects of human activities, and to exclude from consideration the possible good effects - for example, the increase in species due to human activities (Lugo, 1989, pp. 28-30) [2. Conservation biologists' goals with respect to species diversity are not clear. Sometimes they emphasize the supposed economic benefits of species diversity, and sometimes non-econom- ic goals. This vagueness of goals makes it very difficulty to compare the worth of a species-saving activity against another value. [3. Many biologists consider the interests of humans and of other species to be opposed. CONCLUSION There is now no prima facie case for any expensive species- safeguarding policy without more extensive analysis than has been done heretofore. The existing data on the observed rates of species extinction are almost ludicrously inconsistent with the doomsters' claims of rapid disappearance, and they do not support the various extensive and expensive programs they call for. Furthermore, recent scientific and technical advances -- espe- cially seed banks and genetic engineering -- have diminished the importance of maintaining species in their natural habitat. But the question deserves deeper thought, and more careful and wide ranging analysis, than has been given it until now. I do not suggest we ignore extinctions. Rather, we should be as informed as possible. We should separate the available facts from the guesswork and the purposeful misstatements, in order to improve the public decision-making process. And society should take into account -- but in a reasoned fashion -- the economic and non-economic worths of species, in light of our values for human and non-human aspects of nature and other as- pects of life on earth. It is important that we think as clearly as we can about this problem that is indeed difficult to think about sensibly. fn1 Drawn from work done with Aaron Wildavsky SOME ADDITIONAL MATERIAL PERTAINING TO THE SUBJECT OF THIS CHAPTER In response to the sort of questions raised in this section, the "official" IUCN commissioned a book edited by Whitmore and Sayer (1992) to inquire into the extent of extinctions that appeared after the first draft of this book. The results of that project must be considered amazing. All the authors are ecologists who express concern about the rate of extinction. Nevertheless, they all agree that the rate of known extinctions has been and continues to be very low. This is a sampling of quotations (with emphasis supplied), first on the subject of the estimated rates: ...60 birds and mammals are known to have become extinct between 1900 and 1950 (Reid, 1992,p. 55) [F]orests of the eastern United States were reduced over two centuries to fragments totalling 1-2% of their original extent...during this destruction, only three forest birds went extinct -- the Carolina parakeet (Conuropsis carolinensis), the ivory-billed woodpecker (Campephilus principalis principalis), and the passenger pigeon (Ectopistes migratorius). Although deforestation certainly contributed to the decline of all three species, it was probably not critical for the pigeon or the parakeet (Greenway, 1967). Why, then, would one predict massive extinction from similar destruction of tropical forest? (Simberloff, 1992, p. 85) IUCN, together with the World Conservation Monitoring Centre, has amassed large volumes of data from specialists around the world relating to species decline, and it would seem sensible to compare these more empirical data with the global extinction estimates. In fact, these and other data indicate that the number of recorded extinctions for both plants and animals is very small ...(Heywood and Stuart, 1992, p. 93) Known extinction rates are very low. Reasonably good data exist only for mammals and birds, and the current rate of extinction is about one species per year (Reid and Miller, 1989). If other taxa were to exhibit the same liability to extinction as mammals and birds (as some authors suggest, although others would dispute this), then, if the total number of species in the world is, say, 30 million, the annual rate of extinc- tion would be some 2300 species per year. This is a very significant and disturbing number, but it is much less than most estimates given over the last decade. (Heywood and Stuart, p. 94) ... if we assume that today's tropical forests occupy only about 80% of the area they did in the 1830s, it must be assumed that during this contraction, very large numbers of species have been lost in some areas. Yet surprisingly there is no clear-cut evidence for this.... Despite extensive enquiries we have been unable to obtain conclusive evidence to support the suggestion that massive extinctions have taken place in recent times as Myers and others have suggested. On the contrary, work on projects such as Flora Meso- Americana has, at least in some cases, revealed an increase in abundance in many species (Blackmore, pers. comm. 1991). An exceptional and much quoted situation is described by Gentry (1986) who reports the quite dramatic level of evolution in situ in the Centinela ridge in the foothills of the Ecuadorian Andes where he found that at least 38 and probably as many as 90 species (10% of the total flora of the ridge) were endemic to the `unprepossessing ridge'. However, the last patches of forest were cleared subsequent to his last visit and `its prospective 90 new species have already passed into botanical history', or so it was assumed. Subsequently, Dodson and Gentry (1991) modi- fied this to say that an undetermined number of species at Centinela are apparently extinct, following brief visits to other areas such as Lita where up to 11 of the species previously considered extinct were refound, and at Poza Honda near La Mana where six were rediscov- ered. (Heywood and Stuart, 1992, p. 96) ... actual extinctions remain low...As Greuter (1991) aptly comments, `Many endangered species appear to have either an almost miraculous capacity for survival, or a guardian angel is watching over their destiny! This means that it is not too late to attempt to protect the Mediterranean flora as a whole, while still identifying appropriate priorities with regard to the goals and means of conservation.'( Heywood and Stuart, p. 102) ... the group of zoologists could not find a single known animal species which could be properly declared as extinct, in spite of the massive reduction in area and fragmentation of their habitats in the past decades and centuries of intensive human activity. A second list of over 120 lesser-known animal species, some of which may later be included as threatened, show no species considered extinct; and the older Brazilian list of threatened plants, presently under revision, also indicated no species as extinct (Cavalcanti, 1981). (Brown and Brown, 1992, p. 127). Closer examination of the existing data on both well- and little-known groups, however, supports the affirma- tion that little or no species extinction has yet occurred (though some may be in very fragile persist- ence) in the Atlantic forests. Indeed, an appreciable number of species considered extinct 20 years ago, including several birds and six butterflies, have been rediscovered more recently. (Brown and Brown, 1992, p. 128) And here are some comments from that volume on the lack of any solid basis for estimation: ...How large is the loss of species likely to be? Although the loss of species may rank among the most significant environmental problems of our time, rela- tively few attempts have been made to rigorously assess its likely magnitude. (Reid, 1992, p. 55) It is impossible to estimate even approximately how many unrecorded species may have become extinct (Hey- wood and Stuart, p. 95) While better knowledge of extinction rates can clearly improve the design of public policies, it is equally apparent that estimates of global extinction rates are fraught with imprecision. We do not yet know how many species exist, even to within an order of magnitude. (Reid, 1992,p. 56) ...the literature addressing this phenomenon is relatively small... Efforts to clarifyify the magnitude of the extinction crisis and the steps that can be taken to defuse the crisis could considerably expand CONTINUE INSERT ON PAGE 5 OF SECTION 3 the financial and political support for actions to confront what is indisputably the most serious issue that the field of ecology faces, and arguably the most serious issue faced by humankind today. (Reid, 1992, p. 57) The best tool available to estimate species extinction rates is the use of species-area curves. ... This approach has formed the basis for almost all current estimates of species extinction rates. (Reid, 1992, p. 57) There are many reasons why recorded extinctions do not match the predictions and extrapolations that are frequently published...(Heywood and Stuart, 1992, p. 93) REFERENCE Whitmore, T. C., and J. A. Sayer (Editors), Tropical Deforestation and Species Extinction, (New York: Chapman and Hall, 1992).