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The Meaning of Biodiversity Loss.

Norman Myrs
Upper Meadow, Old Road, Headington, Oxford OX3 8SZ United Kingdom

Introduction

By the time we convene for the third National Forum on Biodiversity in 2007, we may have lost 1 million of Earth's putative 10 million species, counting all extinctions since the start of the biotic crisis a half-century ago. As with many other natural resources and their environmental services, we shall probably not understand the full consequences of biodiversity's decline until we, or rather our descendants, are obliged to learn by strictly empirical means. The loss could turn out to be greater than today's best theoretical models are likely to suggest. Meantime, we must peer into a clouded future and discern as best we can the “meaning” of this loss.

The world is increasingly subject to the dictates of the marketplace. Whether one likes this or not, it is a fact of biodiversity's life. So this paper deals largely with commercial and economic values of biodiversity as expressed through the marketplace or shadow prices. Many other values are at stake and are unamenable to even the most ingenious proxy pricing. It is surely the case, too, that there are many other values that we are simply not yet aware of. This paper's findings should be viewed strictly as a minimalist assessment.

The Role of Populations

Biodiversity is generally taken to comprise not only species but also units of species plus ecological processes. Those units, or populations, are more im-

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portant than is sometimes supposed. Earth's 10 million species feature a rough total of 2.2 billion populations, and we are losing these populations at a rate of 43,000 per day—proportionately far faster than we are losing species (Ehrlich and Daily 1993; Hughes and others 1997). That is important because it is populations rather than species that supply us with the myriad environmental services (known ecosystem services) that support our lifestyles, if not our very survival.

Key question: suppose that in the foreseeable future we lose 50% of all species and the surviving species lose 90% of their populations. Which will carry the greater consequences for the environmental stability of the biosphere? Which will be the most adverse for ecosystem services and environmental stability, whether at local, regional, or global levels?

Some evolutionary biologists believe that speciation and other forms of origination (plus novelty, innovation, and the like) often stem from core populations; other scientists think that they derive primarily from peripheral populations. In support of the second viewpoint is the notion that populations in border zones of a species's distribution often contain a greater amount of genetic variability and are therefore best able to respond to the environmental pressures that might well arise in greatest measure at the limit of the species's distribution. Is it not in this border zone, then, that speciation processes are most likely to arise and develop? Or are the populations that are most “productive” in an evolutionary sense more likely to lie in the heartland of a species's distribution? Is there any substantive evidence from the palaeontological past to indicate which has been the most frequent and productive response? Or is it a case of both together? Or conceivably neither? Could it be that the richest resources for natural selection occur in the heartland zone but that natural selection pressures are greatest in the peripheries?

However we view these uncertainties, it is certain that many species have already lost many of their populations. Consider the case of wheat. In 1996, the crop flourished across an expanse of more than 240 million hectares, with a rough average of 2 million stalks per hectare. Wheat plants totaled almost 500 trillion individuals—probably a record. (In comparison, consider that 1 trillion seconds equals about 32,000 years.) As a species, then, wheat is the opposite of endangered. But because of a protracted breeding trend toward genetic uniformity, the crop has lost the great bulk of its populations and most of its genetic variability. In extensive sectors of wheat's original range where wild strains have all but disappeared, there is virtual “wipeout” of endemic genetic diversity. Of Greece's native wheats, 95% have become extinct; and in Turkey and extensive sectors of the Middle East, wild progenitors find sanctuary from grazing animals only in graveyards and castle ruins. As for wheat germplasm collections, they were described more than a dozen years ago as “completely inadequate”—and that was without considering such future threats as macropollution in the form of acid rain and enhanced UV-B radiation.

In the rest of this paper, we consider species, these being the most recognizable components of biodiversity.

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Utilitarian Benefits of Species

Conservation biologists increasingly face the question, What is biodiversity good for? Naive as it might sound to some, it is a valid question. There is no longer enough room for a complete stock of biodiversity on an overcrowded planet with almost 6 billion humans and their multifarious activities, let alone a projected two-thirds increase in human numbers and a several-times increase in human activities within the next half-century. So biodiversity must stake its claims for living space in competition with other causes. Generally speaking, biodiversity must urge the merits of its cause through what it contributes to human welfare, preferably in the way that most appeals to political leaders and the general public, namely, in economic terms. This is a strictly anthropocentric approach, and limited as it might seem, it reflects how the world (although not the planet) works.

There are two categories of economic contributions: material goods and environmental services. The first has been frequently and widely (Baskin 1997; Daily 1997; Ehrlich 1992; Myers 1982) documented, principally in the form of new and improved foods, medicines, and raw materials for industry and sources of bioenergy. The second has been far less documented even though it was identified as unusually important 2 decades ago (Westman 1977) and even though its total value is far greater than that of the first (Bishop 1993; Ehrlich 1992; Risser 1995). The main reason for this lacuna is that scientists find it much harder to demonstrate the precise nature of the services, and it is still harder to quantify them economically. Whereas the benefits of material goods tend to accrue to individuals, often producers or consumers in the marketplace, the values of environmental services generally pertain to society; hence, they mostly remain unmarketed (Brown and others 1993).

Material Goods

From morning coffee to evening nightcap, we benefit in our daily lives from our fellow species. Without recognizing it, we use hundreds of products each day that owe their origin to wild plants and animals. Conservationists can well proclaim that by saving the lives of wild species, we might be saving our own. Yet we enjoy the manifold benefits of biodiversity's genetic library after scientists have intensively investigated only one in 100 of Earth's 250,000 plant species and a far smaller proportion of the millions of animal species.

Regrettably, there is not space here to do more than cite a few economic evaluations to demonstrate the utilitarian clout at issue. Consider crop-plant germplasm. Wheat andgermplasm collected in developing countries by the International Maize and Wheat Improvement Center near Mexico City benefits industrialized countries to the tune of $2.7 billion per year. In Italy, wheat germ pasta contributes $300 million per year to the pasta industry. In Australia, grain varieties have boosted annual harvests by as much as $2.2 billion between 1974 and 1990. One-fifth of the value of the billion-dollar US rice crop is attributed to genetic infusions (Evanson 1991). As for new foods, North American stores now feature all manner of exotic vegetables and fruits; from 1970 to 1985, the number of items available doubled to more than 130, and in some instances to as

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many as 250. By the middle-1980s, specialty produce, mostly from Asia and Latin America, had become a $200-million-a-year business in the United States alone (Vietmeyer 1986).

The cumulative commercial value of plant-based medicines in developed nations is estimated to amount to $500 billion1 during the 1990s (McNeely and others 1993; Principe 1997). Two anticancer drugs from the rosy periwinkle generate sales totaling more than $250 million per year in the United States alone, and all plant-derived anticancer drugs combined save around 30,000 lives in the United States each year (Principe 1997). According to the National Cancer Institute, tropical forests alone could well contain 20 plants with materials for several additional superstar anticancer drugs (Douros and Suffness 1980).

A number of analysts have attempted an economic assessment of tropical forest plants' overall potential worth, not just for anticancer purposes. Estimates range from $420 billion (Pearce and Puroshothaman 1993) to $900 billion (Gentry 1993; Mendelsohn and Balick 1995).

Suppose that until the year 2050 we will witness the extinction every 2 years of one plant species with medicinal potential. The cumulative retail-market loss from each such extinction will amount to $12 billion for the United States alone (Principe 1997).

Environmental Services

Species supply us with entire suites of environmental services, which can be defined as functional attributes of natural ecosystems that are beneficial to humankind (Baskin 1997; Daily 1997). They include generating and maintaining soils, converting solar energy into plant tissue, sustaining hydrological cycles, storing and cycling essential nutrients (notably through nitrogen fixation), supplying clean air and water, absorbing and detoxifying pollutants, decomposing wastes, pollinating crops and other plants, controlling pests, running biogeochemical cycles (of such vital elements as carbon, nitrogen, phosphorus, and sulfur), controlling the gaseous mix of the atmosphere (which helps to determine climate), and regulating weather and climates (both macroclimates and microclimates). In addition, biodiversity provides sites for research, recreation, tourism, and inspiration.

However, it is far from true that all forms of biodiversity can contribute to all environmental services or that similar forms of biodiversity can perform similar tasks with similar efficiency. How far do environmental services depend on biodiversity itself? Recent research suggests that they are highly resilient in the face of some loss of species, and they can keep on supplying their services even in highly modified states. A sugar cane plantation might be more efficient at producing organic material than the natural vegetation that it replaced, and a tree farm might be more capable of fixing atmospheric carbon than a natural forest. At the same time, many natural ecosystems with low biodiversity, such as tropical freshwater swamps, have a high capacity to fix carbon.

1 On the basis on an average of $50 billion per year ($15 billion in the United States alone).

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Similarly, the services supplied by one form of biodiversity in one locality might not necessarily be supplied by a similar form of biodiversity in another locality. Just because a wetland on the Louisiana coast performs a particular suite of functions, we cannot assume that a wetland on the Georgia coast will perform the same functions—still less an inland wetland in Massachusetts or California and even less a montane wetland in Sweden or a forest wetland in Thailand. Services tend to be site-specific. That makes it much more difficult for conservation biologists to demonstrate the intrinsic value of wetlands or any other biotopes.

Biodiversity plays two critical roles. It provides the biospheric medium for energy and material flows, which in turn provide ecosystems with their functional properties; and it supports and fosters ecosystem resilience (Ehrlich and Roughgarden 1987; Schulze and Mooney 1994). The latter attribute could turn out to be the leading service supplied by biodiversity insofar as all other services appear to depend on it to a sizable degree (Perring and others 1995). As biodiversity is depleted, there is often—not always—a decline in the integrity of ecosystem processes that supply environmental services.

Environmental services are so abundant and diverse that we cannot do more here than look at an illustrative selection. First, consider biotas as carbon sinks. The value of carbon storage in tropical forests as a counter to global warming is around $1,000–3,500/ha per year, depending on the type of forest (Brown and Pearce 1994). The value of the carbon-storage service supplied by Brazilian Amazonia is estimated to be some $46 billion (Guttierez and Pearce 1992). It has been further estimated that replacing the carbon-storage function of all tropical forests could well cost $3.7–25 trillion (Panayotou and Ashton 1992).

Next, note the role of biodiversity in protecting soil cover. Excessive runoff from denuded catchments causes soil erosion and siltation in valleyland water-courses. Siltation of only reservoirs costs the global economy some $6 billion per year in lost hydropower and irrigation water. In the last 200 years, the average topsoil depth in the United States has declined from 23 cm to 15 cm; this costs the average American consumer around $300 per year through loss of nutrients and water, with total annual costs (including degradation of watershed systems; pollution of soils, water, and air; and other off-farm problems) to the United States of $44 billion. Worldwide costs of soil erosion are around $400 billion per year (Pimentel and others 1995).

Consider, too, the important but little-recognized services performed by wetlands. These services include a supply of freshwater for household needs, sewage treatment, cleansing of industrial wastes, habitats for commercial and sport fisheries, recreation sites, and storm protection (Mitsch and Gosselink 1993). Their economic value can be sizable. Louisiana wetlands are estimated to be worth $6,000–16,000/ha with an 8% discount rate, or $22,500–42,500/ha with a 3% discount rate. At the lowest value, the current annual rate of loss of these wetlands is levying costs of about $600,000/km2 per year; at the largest value, $4.4 million/km2 (late 1980s values). Marshlands near Boston are valued at $72,000/ha per year solely on the basis of their role in reducing flood damage (Hair 1988).

About one-third of the human diet depends on insect-pollinated vegetables, legumes, and fruits. At least 40 crops in the U.S are completely dependent on in-

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sect pollination with a marketplace value of $30 billion (Pimentel and others 1992).

Finally, note the vital part played by biodiversity in the fast-growing sector of ecotourism. Each year, people taking nature-related trips contribute to the national incomes of the countries concerned a sum estimated to be at least $500 billion, perhaps twice as much (Eagles and others 1993). Much of these ecotourists' enjoyment reflects the animal life that they encounter. In the late 1970s, each individual lion in Kenya's Amboseli Park produced $27,000 per year in tourist revenues, and an elephant herd produced $610,000 per year (Western and Henry 1979); today's figures would be much higher with many more tourists in the park. In 1994, whale-watching in 65 countries and dependent territories attracted 5.4 million viewers and generated tourism revenues of $504 million, with annual rates of increase of over 10% and almost 17%, respectively. A pod of 16 Bryde's whales at Ogata in Japan would, according to conservative estimates, produce at least $41 million from whale-watchers over the next 15 years (and be left alive), whereas if killed (as a one-shot affair) they would generate only $4.3 million (Hoyt 1995). In 1970, ecotourism in Costa Rica's Monteverde Cloud Forest Reservegenerated revenues of $4.5 million, or $1,250/ha, to be compared with $30–100/ha for land outside the reserve (Tobias and Mendelshn 1991). Florida's coral reefs are estimated to generate $1.6 billion per year in tourism revenues (Adams 1995).

Overall Findings

A team of ecologists and economists has recently attempted a comprehensive evaluation of all the goods and services stemming from biodiversity. They offer a preliminary and exploratory total of $33 trillion per year (Constanza and others 1997), compared with a global GNP of $28 trillion. Thus, the world's gross natural product is in the same league as the world's gross national product and probably exceeds it.

Consider, too, Biosphere 2, the technosphere in the Arizona desert with its semisuccessful life-support systems for eight Biospherians over a period of 2 years. The cost was about $150 million, or $9 million per person per year. The same services are provided to the rest of us bynatural processes at no cost. But if we were charged at the rate levied by Biosphere 2, the total bill for all Earthospherians today would come to $3 quintillion (Avise 1994).

Conclusion

The biggest challenge of all is to determine a comprehensive answer to the question, What is biodiversity good for? At present lamentable rates of research and analysis, we might eventually find responses to that question only by discovering what has been lost after much biodiversity has been eliminated, with its goods and services.

Conservation biologists should feel more inclined to simply reject the question, What is biodiversity good for? We shall not have anywhere near a sufficient an-

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swer within a timeframe to persuade political leaders, policy-makers, and the public (let alone the professional skeptics). Rather, we should invoke the uniqueness and irreversibility arguments and throw the burden of proof on the doubters, requiring them to demonstrate that biodiversity is generally worth so little that it can be dispensed with if human welfare demands as much, through, for example, agricultural encroachment on wildland habitats. True, there is vast uncertainty about what biodiversity contributes to the human cause. But because of the asymmetry of evaluation, the doubters are effectively saying that they are completely certain that we, and our descendants for millions of years (until evolution restores the loss), can manage well enough without large quantities of biodiversity.

Acknowledgment

This paper was written with financial support from a Pew fellowship in conservation and environment.

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