[Population and related social issues]
[Resources]
[Food production]
[Environmental impacts]
[Poverty, inequity, and marginalization]
[Seeing the forest]
[Notes]

Nor is a comprehensive view of the connections among the major factors of the human predicament clearly presented by the educational system, whether at high school or college levels. More often its components are described in isolation from related issues. The academic structure of separate, compartmentalized disciplines creates artificial barriers to cross-disciplinary exploration and study of population-environmental problems, thus hindering understanding of connections between the various components. Accordingly, an explanatory guide to the human environmental predicament emphasizing the complex connections among its driving forces and undesirable results should prove useful for teachers, journalists, writers, and decision-makers in interpreting current events and trends.

The principal factors shaping the predicament are the human population's size and growth, its exploitation and consumption of resources and natural capital, the environmental characteristics of the technologies employed in mobilizing resources and producing commodities and manufactured goods to be consumed by that population, and the social, economic, and political arrangements that support the consumption. As the human enterprise continues to expand, these underlying factors have interacted to generate an array of impacts on the natural world at levels that threaten to destabilize the planet's long-evolved life-support systems. Although many people are wealthy on a previously unimagined scale, a sizable portion of the human population remains mired in poverty and a marginal existence. This marginalized population in turn is rendered increasingly insecure by human-caused environmental changes such as land degradation, deforestation, or exposure to toxic substances. Perhaps even more ominous, the income gaps between rich and poor, both within and between nations, are vast and growing. Such gross inequities, especially when combined with resource scarcities, also may give rise to conflict between groups.

The human population is now about 6 billion people, having nearly quadrupled in the twentieth century. The most recent reliable demographic projections indicate that it could expand by another 50 percent or more before growth ends (barring some huge disaster that drastically increases mortality rates). Although this prospect is less daunting than projections of only a decade or so ago, which predicted a doubling of the world population, it still poses critical challenges. Among them are the need to increase food production to meet rising demand; to prevent, mitigate, or cope with even greater environmental impacts; and satisfy the rising need for resources. A particular concern is meeting the growing demand for energy, just as world production of petroleum peaks and begins to decline, and as the environmental consequences of using fossil fuels mount to unmanageable levels.

This paper will outline some of the important connections between these major topic areas - population, resource use, environmental impacts, and equity - that are so frequently neglected in public media. Accompanying this essay, several recent events and their coverage in the press will serve as case histories illustrating both appropriate coverage of underlying connections and coverage that completely overlooked them. One is the disastrous consequences of hurricane Mitch to several small countries in Central America; a second is the heat wave of 1998 in Texas; and a third is the collapse of the salmon fishery in the Pacific Northwest of the United States and Canada. Although the studies were necessarily restricted to relatively short time-frames and narrow scopes, the surveys revealed cases in which important connections were overlooked by major newspapers and magazines as well as instances in which they were nicely drawn. Our goal here is to trace the most important connections and cause-and-effect relations among demographic changes, environmental degradation, social/economic inequity, and events such as "natural" disasters.

Following is a set of questions that this paper will try to address specifically, which can serve as a guide to the discussion of environmental problems by the media, educators and others.

· How does population growth help drive environmental impacts? · How do consumption levels affect environmental impacts? · Does population growth increase pressure on resources? · How does population growth affect the distribution of people and their vulnerability to "natural" disasters? · Could food production be a problem in the future? · What is natural capital, and why is it important? · Why is the loss of biodiversity important? · What is the significance of natural ecosystems and Nature's services? · How does the widening rich-poor gap affect the environment? · Why is global warming considered so serious a threat? · How does the conventional economic system fail to account for natural capital? · How can that failure be remedied?

We will attempt to illuminate the many connections among these elements of the global predicament, taking each major topic area in turn. Connections will be drawn within each general topic, as well as between them. The first is the population situation, which can be viewed as one of the principal driving forces underlying the proliferating problems faced by civilization today.

POPULATION AND RELATED SOCIAL ISSUES

Principal social connections

· Birth, death, and fertility rates and changes · Family planning, fertility control, contraception · Education and family health · Status of women · Age structure · Population distribution · Abortion · Migration · Urbanization · Epidemics and emergent diseases · Equity, distribution of wealth · Economic development

Connections to other major components of the predicament

· Resource consumption · Food security and production · Land use · Environmental deterioration

That the global population is now in the midst of a momentous shift from rapid growth toward an end to growth is not yet widely recognized. The global average rate of reproduction has dropped almost by half since the 1960s, with birthrate declines occurring in nearly every part of the world during the 1990s. Recent demographic projections indicate that the population is nonetheless likely to add another 2 to 5 billion before growth ends. If fertility continues to fall as it has been, the peak population size may be reached, followed by a gradual decline in size, before the end of the twenty-first century.

Population growth has ended or soon will end in most industrialized nations, except where immigration contributes to a higher growth rate, as in the United States. But in most developing nations, populations are still growing more or less rapidly, despite the recent decline in birthrates. Average family size in many African countries, for instance, is still as high as five or six children. It ranges from two to five in most of Asia and Latin America, where many countries have seen dramatic reductions in the last decade or two. Yet, because high fertility in the recent past produced a large proportion of young people who will be the next generation's parents, demographic momentum guarantees that growth will continue in most developing nations for at least several decades. Even where reproduction has reached "replacement" level (when parents just replace themselves in the next generation - an average of about two children per couple) growth persists as a result of past high fertility. Consequently, demographers project a 40 to 60 percent increase in the global population during the next half century, and a long lag time before growth stops.

The connections between population growth and rates of fertility and mortality are quite obvious. So are the links to the subjects of fertility control (through contraception), family planning programs (which facilitate fertility control by individuals), and maternal and child health. Family planning facilities are now available at some level in virtually every nation and have played a significant role in reducing population growth rates. In recent years, other factors that influence people to have fewer children have emerged: education, especially of women; adequate health care and sanitation (which increase the chances of children's survival); and opportunities for women to be active outside the home. These components of development have been shown to have strong influences on reproductive choices, and recent progress in those areas is considered to be a cause of today's falling fertility rates.

But in current discussions, these elements are mostly taking a back seat to concern about the prospect of an actual decline (shrinkage) in population size in industrial nations as fertility has fallen well below replacement and age structures change. Populations are now shrinking slightly in several European countries and are likely to do so soon in a number of others. Grave concern has been expressed about the rising proportion of older people in populations that have had low fertility for several decades -- an unavoidable consequence of ending population growth. But almost no connection is made to the countervailing circumstance of a far smaller proportion of children and youths to support and educate. Similarly, crime rates in an aging population are likely to be significantly reduced, since crimes are mostly committed by the young.

Almost forgotten in the mix of demographics is the subject of abortion, which in the United States has become ensnared in a polarized moral debate and largely separated in the public mind from questions of fertility control or the larger issue of population growth. Unfortunately, though, adamant opposition to abortion by conservative lawmakers has led to reductions and even denial of funds donated by the US to support international programs for family planning in developing countries, because of claims that the funds would be used to support abortion services.

Whether legal or illegal, abortion is nonetheless a significant method of birth control in many societies, including the United States where more than a million pregnancies are legally terminated each year despite the accessibility of contraceptives. Yet the widely differing circumstances in which abortion may be resorted to outside the United States, as well as differing views on the moral questions, are too often overlooked in domestic discussions of the issue. Approximately 50 million pregnancies are terminated each year worldwide, only about half of them safely and legally. Abortion is a leading form of birth control in many nations of the former Soviet Union, where availability of contraceptives can be problematic. It is widespread in many developing nations where it often is both illegal and dangerous, thereby causing a high toll in maternal injury and death.

While falling birthrates have been noted nearly everywhere, changes in death rates are usually ignored, with the exception of the AIDS epidemic, which has begun to reverse the trend of rising life expectancy in several African countries. Yet the global epidemiological environment in general is more and more worrisome, as sporadic outbreaks of new, unfamiliar diseases remind us. As the population expands and human groups invade previously unoccupied (by people) natural areas, they risk exposure to novel pathogens. As the population's density and mobility increase, the opportunities for new diseases to spread around the globe within hours also increase. The risk of a global pandemic is further enhanced by the growing resistance to antibiotics seen in older pathogens such as tuberculosis and malaria. The evolutionary roots of this phenomenon, which was both predictable and predicted by evolutionary biologists, are rarely mentioned in the popular press.

Poverty is an important connection to population growth and high fertility, in a complex cause and effect relationship. For decades, development specialists argued with population advocates over whether poverty caused high birthrates in less developed countries, or vice versa. The answer appears to be both; each feeds the other in a vicious cycle that includes illiteracy, poor health, undernutrition, and a marginal existence. Breaking the cycle of poverty and high birthrates (accompanied by high infant and child mortalities) has proven possible by targeting certain kinds of development: education, especially of girls; improvement of women's status (even by modest steps, such as providing small loans for education or starting small businesses); and provision of reproductive and family health services, including family planning. Much less frequently recognized is the importance of these same factors - women's education and participation in society and the improved health and well-being of families - to the progress of development as well. While this approach was emphasized in the 1994 UN Conference on Population and Development in Cairo, its program has yet to be fully funded in accordance with pledges made at the conference.

Migration and rapid urbanization are also important trends that have arisen from rapid population growth and the widening gap between rich and poor in the second half of the twentieth century. Hundreds of millions of young rural people, displaced from the land, have migrated to cities in search of jobs. Millions have gone further, to more prosperous countries where more and better paying jobs are available. In a few short decades, most developing countries have been transformed from predominantly rural to largely or even heavily urbanized societies. As the century turns, one of every two people in the world is a city dweller.

What are the environmental connections to all this? Rapid population growth and poverty are two forces that have helped to drive people off the land and into cities, abetted by development policies that have often promoted modern industrial farming for export crops over traditional subsistence food production. As agriculture has been intensified to increase production to feed the growing population, and poor farmers have often been relegated to marginal lands, land degradation has increased, natural areas have been invaded, and forests removed, all of which have led to an array of environmental problems. The expanding mobilization of resources, use of fossil fuels, and industrialization have generated another set of environmental problems that are multiplied by both population and economic growth and sometimes also exacerbated by technological changes. All of these connections will be described below as this paper explores other aspects of the environmental predicament.

The massive movement of millions of people to cities and elsewhere comprises another element in the rapid globalization of the human enterprise, which was initially led by technological advances in communications, transportation, and financial transactions. The increasingly multiethnic character of science, education, and business today could be a harbinger of a truly integrated global society in the twenty-first century. But such a profound transformation, especially given the prevailing inequities in wealth and development levels, could never proceed without social strains and reactions. The twentieth century has been marked not only by an enormous expansion of the human population and its technology, but also by an unprecedented level of conflict and suffering as the inequities have risen. Where the current globalization trends will lead is anyone's guess.

RESOURCES

Principal connections to the major factors shaping the human predicament

· Population size and growth · Mobilization and consumption of non-renewable resources · Depletion of non-renewable resources · Distribution of resources and wealth · Equity and poverty · Economic factors · Food production · Overexploitation of natural capital · Environmental impacts of resource mobilization and use

The rate and scale at which a society's resources are acquired and used are clearly connected to its population size. The world population's roughly fourfold expansion during the twentieth century has driven a rising demand for resources, and demand continues to rise. But resource consumption per person has also risen, catapulting total consumption up some eight- to fifteenfold, depending on the resource in question. Attending the enormous twentieth-century escalation in resource mobilization has been a parallel upsurge in pollution and other environmental impacts resulting from it.

Human exploitation of resources is a very broad topic that includes both non-renewable and renewable (natural capital) resources. Non-renewable resources include the fossil fuels, metals, and other materials extracted from Earth's crust that power civilization or are used to make tools, artifacts, or for building infrastructure. Renewable resources are those that are constantly replenished or recycled through natural processes: soil, fresh water, nutrients, and biodiversity -- organisms of every kind from bacteria and viruses to trees, fungi, and fishes to crops and livestock.

NON_RENEWABLE RESOURCES

Principal connections to population growth

· Depletion of mineral and fossil fuel deposits · Increasing consumption and demand

Principal connections to environmental problems

· Pollution of air and water

· Technology and efficiency · Impacts on human health · Impacts on ecosystems from extraction and use of minerals and fossil fuels · Releases of toxic substances · Acid deposition · Greenhouse gas emissions and global warming · Economic costs and benefits

The expanding extraction and use of metals and fossil fuels in the past century has generated concerns about depletion of accessible deposits and the environmental impacts connected with mining, refining or processing, transporting, and using these materials. The problems vary with the material, of course; however, many metals that are desirable for industrial purposes are highly toxic to human beings or other animals if inhaled or ingested: e.g., lead, copper, mercury, and cadmium. And many substances created, purposely or inadvertently, by industrial processes based on fossil fuels and released into the environment are also toxic, mutagenic, or carcinogenic: e.g., PCBs, pesticides, dioxins, furans, and a variety of common air pollutants.

In recent decades, fossil fuel byproducts (especially of petroleum) have increasingly been substituted for other resources (for instance, plastics and synthetic materials in place of metals, wood, and natural fibers). While these substitutions have helped to slow the depletion of metal deposits and ease pressures on forests and agricultural resources, they have come at a price. The manufacture or use of some petroleum-derived industrial chemicals and pesticides have caused some of the most serious environmental and public health problems, from pollution of air, soils, surface waters, and aquifers to poisoning of farm workers. Many have been implicated as hormone mimics in causing subtle developmental damage in wildlife and humans. And, as global petroleum reserves become depleted, pressure to find other substitutes can be expected to rise.

An additional factor is that of "technology" - how carefully, efficiently, or wastefully the resource in question is extracted and used. Careless handling of toxic materials results in their release into the environment, where they can contaminate drinking water, farmlands and crops, or the air people breathe, causing significant public health problems. Toxic substances can also damage crops, forests, and structures, or injure livestock, thus imposing economic costs on society. Such "external" costs are not customarily taken into account by companies in calculating their costs of doing business, although environmental regulation can penalize companies for them or enforce prevention or cleanup measures. Thus regulations have substantially reduced releases of many kinds of pollutants by requiring use of technologies that contain, recapture or chemically break down pollutants before they can be released into the environment. Examples include catalytic converters in automobile engines and scrubbers in smokestacks.

In the last decade or two, companies in industrialized nations involved in using or producing toxic substances have developed programs for recycling and reusing materials, or selling byproducts for other industrial uses, thereby reducing the environmental impacts per unit of resource exploited as well as production costs. More recently, some responsible companies have also begun seeking less potentially dangerous substances to use in their processes and products. Such efficiencies can allow increased mobilization and use of mineral resources to support the growing population without increasing impacts. Economic efficiencies can be achieved through a tradable permit system, which has helped reduce sulfur oxide emissions from coal-burning power plants in the U.S. since passage of the Clean Air Act of 1990.

Efficiency is particularly important with regard to using fossil fuels as energy sources; some technologies for their use are far more efficient than are others. A penalty is paid for inefficiency not only in unnecessarily rapid depletion of a limited resource but also in higher pollution emissions per unit of energy yield. Increased use of fossil fuels also inescapably increases emissions of the greenhouse gas carbon dioxide to the atmosphere, which is implicated in causing climate change. Substantial opportunities exist for increasing the efficiency of fossil-fuel use in all societies; but the costs of replacing power plants, vehicles, and heating and cooling systems, and of retrofitting buildings often stand as barriers to implementing efficiency changes, despite the self-evident longer-term gains in lower operating costs, pollution abatement, and reduced greenhouse gas emissions.

The need to reduce fossil energy consumption to abate global warming has become a recent item of controversy in the United States, but the public discussion has been too much divorced from the other important advantages of doing so - including reduction of dependence on imported oil and avoidance of likely shortages and higher prices in the near future. The price of petroleum in the U.S. in recent years has been low, thanks to relatively low production costs of domestic reserves and low taxes, combined with global overproduction and a low world market price. This situation has encouraged consumers, especially in the U.S., to continue using fuels wastefully. The United States, moreover, is the world's biggest consumer of fossil fuels, accounting for roughly 25 percent of global consumption. And the idea of reducing fossil fuel consumption is firmly resisted by corporate interests whose raison d'etre and profits are threatened by the scale of reduction that will ultimately be needed - especially coal, oil, and natural gas producers and distributors, auto makers, etc. Opponents of efforts to curb fossil fuel use to reduce the flux of greenhouse gases argue that measures to reduce consumption will inevitably cause draconian economic disruption and have blocked all governmental efforts to encourage greater efficiency and development of alternative energy sources.

RENEWABLE RESOURCES: Natural capital

Principal connections to population size, growth, and consumption

· Food production and security · Fisheries yields · Aquaculture · Freshwater supplies · Deforestation · Equity, distribution of food and resources · Land use conflicts · Economic accounting failures

Principal connections to environmental problems

· Land degradation, soil erosion · Technology, efficiency, and waste · Water quality · Ecosystem services · Desertification · Deforestation · Loss of biodiversity · Global warming

Natural capital includes productive lands and soils, surface and subterranean freshwater sources, and the vast diversity of life that has coevolved and shaped the biosphere over eons. These resources have customarily been considered renewable. The processes and functions of the biosphere arising from the activities of the planet's diverse biota and powered by sunlight, form the life-support system for all living things, including human beings. Without those life-support functions, humanity could have no agriculture or access to other biologically based materials (such as timber or fisheries) that we usually take for granted. Yet the vital importance of these renewal processes to human well-being and security are among the least understood and least valued by the general public or by business and political leaders. Consequently, natural capital too often has been exploited as though it was non-renewable, without accounting or compensating for depletion. In many cases, these resources have been abused as if of no value.

Land.Population growth, especially in the last century, has inevitably led to a great expansion in human exploitation of productive lands. Little unused land remains today that could be sustainably cultivated or used to graze livestock. In most regions of the world, productive land is already being intensively farmed or grazed. Since population growth will continue for several decades at least, food production must also be increased, and that will require further intensification of agricultural land.

But modern intensive agriculture is not necessarily sustainable; it depends heavily on abundant supplies of water and the use of agricultural chemicals and farm machines. Continuous cultivation of the same crop year after year results in soil erosion, nutrient depletion, offsite pollution problems from fertilizers and pesticides, diversion of water from natural ecosystems, and cumulative damage to the ecosystem in which the farm is embedded. A gradual loss of soil fertility eventually leads to falling yields when fertilizer inputs can no longer mask the process. In many areas where irrigation is used intensively, salts may build up in soils or rising water tables may cause waterlogging, causing a gradual deterioration in soil quality. A significant and growing portion of the world's agricultural land is already showing productivity declines; some land has been degraded to the point of being uneconomic to cultivate. Serious losses of productivity can lead to impoverishment of local populations, increased hunger, emigration, and continued deterioration.

Productive land is also increasingly subject to competing demands for its use. Growing populations require land for housing, commerce, transport, and industry. Millions of acres of good farmland are taken over each year for urban use in industrial countries, notably the United States, as well as in developing nations. In fast-expanding Asian economies, especially China, large tracts of farmland are being lost to urban development at a much more rapid rate than their populations are growing. Forests, grasslands, and other productive lands also are being fragmented and displaced by urban and industrial development, thus adding to the worldwide losses of habitat and biodiversity.

Fresh water. Sources of fresh water as well are under growing pressure and subject to competing demands. Irrigated croplands are among the most productive; in the past half-century, a great expansion of irrigation has played a major role in boosting food production. Because salt buildups and waterlogging can cause loss of soil quality and aquifers are being overdrawn in many parts of the world, irrigation often is a temporary game. Today new land put under irrigation barely replaces that being withdrawn because of damaged soil or lack of water. Furthermore, agriculture competes against domestic and industrial needs for water, and in water-short regions such as the Middle East, many parts of Africa, southwestern US, northern India, and northern China, severe shortages are emerging, with potential - sometimes actual -- links to conflict. Overall, it is estimated that humanity is already using some 50 percent of the world's dependable freshwater flows.

Pollution and degradation of freshwater sources by industry, agriculture, deforestation, and development are increasingly serious problems everywhere. Attempts to harness surface water flows and make supplies more reliable by building dams and reservoirs disrupt riverine ecosystems and damage or destroy important fisheries such as salmon. Further damage to stream systems is often incurred by careless development, overgrazing, and forest logging in watersheds. Diversion of surface water to supply farms and cities deprives riparian vegetation and wildlife of that essential resource, putting the human demand in competition with protection of biodiversity.

Fisheries. Overexploitation and depletion of natural capital is perhaps most obvious in the plight of oceanic fisheries. Two thirds of the world's major fisheries are depleted or being maximally exploited today. Many have experienced "economic extinction" - that is, the fish populations have been driven to such low levels that pursuing them doesn't pay. Fish and shellfish stocks have also been adversely affected by pollution of estuaries and destruction of coastal wetlands and mangroves, areas that serve as nurseries and breeding grounds for many oceanic species. Connections here include not only rising consumption and demand for seafood products, which drive the overexploitation and depletion of important fishery stocks, but also the same processes of land use, urbanization, and industrial pollution that are causing degradation and depletion of land-based natural capital.

While some of the gap from declining wild fisheries harvests is being filled by aquaculture (fish farming), the latter also contributes to coastal pollution and habitat destruction. This indirectly impacts wild populations of fish and shellfish, usually by degrading or occupying shoreline areas, including spawning grounds. Furthermore, fish farms are supported in part by exploiting for feed wild stocks that are not desired for human food, thereby further disrupting oceanic food webs. And, like intensively raised livestock on land, aquaculture fish are subsidized with both farm-produced feed (thus competing with livestock) and antibiotics to combat their susceptibility to disease outbreaks. In the latter case, as with intensive livestock production, the saturation with antibiotics hastens the day when pathogens develop resistance to them, increasing the risk of disease outbreaks either among the livestock or the human population itself. Unfortunately, the yield and environmental tradeoffs between fisheries production from overexploited wild stocks and fish farming with its expensive inputs and inherent instability are rarely noted.

As in other resource areas, inefficiency and waste also have roles in fisheries production. Waste and loss can occur at any stage: production, harvesting, processing, distribution, marketing, and consumption. Fisheries products are especially vulnerable to spoilage and loss at all stages of the process from water to dinner table. Of course, the societies least able to afford such losses usually suffer the most. And modern industrial fishing with lines and nets tens of miles long captures a huge portion of "by-catch" - fish species not sought for the market - which are killed and lost to the marine ecosystem and to local subsistence fishers.

Forests. More than half of the world's original forest cover has disappeared, either by clearing land for agriculture or for timber, or both. Most logging today is done by clearcutting, which degrades and fragments forest ecosystems, leading to impaired functioning, losses of biodiversity, and reductions in ecosystem services such as prevention or mitigation of droughts and floods. Usual consequences of large-scale clearcutting, especially on hillsides and in riparian areas, include severe soil erosion and degradation, silting of streams, and damage to stream fisheries. If the logged area is large, soils are fragile, and replanting is not quickly undertaken, recovery of the forest may be compromised. Moist tropical forests are especially vulnerable to irreversible destruction; the ultimate result within a few years can be an unproductive wasteland.

Much of the world's most valuable remaining forests are in the tropics, where populations are growing rapidly and forests are under rising pressure from loggers or farmers seeking land. Deforestation in the tropics has been proceeding at rates of 0.5 to 1.0 percent per year for several decades, reducing the extent of forested land by the mid-1990s by 30 (South America) to 64 percent (Africa). And much of the remaining forest has been subject to degradation from selective logging or from shifting cultivation as farmers enlarge their cleared patches and return to them sooner, as a consequence of population growth. Worldwide public awareness and concern about depletion of tropical forests have done little to abate tropical forest clearance. Often it is done illegally, and governments lack the power to prevent it. Indeed, governments in developing countries have customarily counted the unsustainable cutting and export of logs from their nations as augmenting their economic well-being when it actually is a loss of a valuable asset. Thus these activities are not only encouraged but subsidized, sometimes at a significant economic loss to domestic taxpayers.

In temperate regions, especially North America, forest area has been increasing in the late twentieth century through second-growth recovery. Only a tiny fraction of old-growth temperate forest survives in North America, and essentially none in Europe and Asia. Yet the rare old-growth forests of the United States, including some on public lands, are still being logged. Here, too, timber harvests and exports are considered an economic plus, with subsidies borne by taxpayers. A similar situation exists in Canada. Now, previously ignored subarctic boreal forests are under attack from wholesale logging in Canada and Siberia, with important implications for both ecosystem disruption and global warming.

As with other natural capital resources, waste and inefficiency are problems in today's forestry practices. While most timber and paper production are relatively efficient processes (although causing significant pollution), timber harvesting can be among the most wasteful, not only wasting roughly half of the biomass of each tree harvested, but often injuring or killing other trees in the process and disrupting the forest's functioning.

Biodiversity and ecosystem services. Biodiversity includes the diversity of all life on Earth, from the assemblages of species that make up ecosystems to species and populations to the genetic diversity in individual organisms. Many kinds of organisms are of direct utility to human beings, such as crops, livestock, forest trees, seafood, and wild sources of useful products such as foods, medicines, spices, oils, and fibers. Unfortunately, though, that perceived utility leads societies to regard useful species in isolation from their functions in natural ecosystems, simply as resources to be exploited. But all species and populations of organisms, including those with no direct economic value, are working parts of natural ecosystems, which supply civilization with vital ecosystem services. Because we have no way of knowing which components of ecosystems are essential for maintaining their integrity and functions, we must treat all species as potentially essential.

These natural services of ecosystems include maintaining the composition and quality of the atmosphere, moderating climate and weather, regulating the hydrologic cycle, replenishing soil fertility, cycling nutrients, disposing of wastes, pollinating plants (including crops), controlling pests and diseases, and generating and maintaining the vast genetic library of life. The importance of ecosystem services to human well-being is among the environmental connections most overlooked - until the services are impaired or lost. Even then, the consequences are often labeled "acts of God" and their roots in damage to ecosystems are ignored.

The loss of biodiversity and ecosystem damage and destruction (two sides of the same coin), occurring as they do virtually everywhere, hold enormous potential for undermining human security and destabilizing civilization. Yet this vital set of putatively renewable resources is almost universally ignored. Given that tropical forests, which cover only about 6 percent of the land surface, are deemed by biologists to harbor 50 percent or more of the world's species, their disappearance alone represents a grave assault on the world's biodiversity. But it is by no means the only assault; extinctions of populations and species of plants and animals have been documented from virtually every significant type of terrestrial ecosystem from the Arctic and Antarctica to forests, plains, deserts, and tropical islands, as well as from oceanic and freshwater systems. For each species of well known flora or fauna lost, several species of more obscure groups such as insects, mites, fungi, worms, or bacteria have also surely gone extinct.

When a large portion of an ecosystem is converted to a completely different type of system (i.e., plowing grassland to plant crops, or clearing forest for crops or pasture), local populations of a large array of organisms obviously are forced to extinction. These extinctions assume even greater importance when the last remaining fragment of a system disappears. Yet habitat loss or modification is only one avenue to extinction, albeit the most important. Another is introduction of species from other parts of the world, which outcompete or are predatory on native species, causing extinction of the latter. Such transfers are usually, but not always, inadvertent, as when ships' ballasts have brought predatory mollusks to North American waters, or packing materials have hosted a beetle whose larvae attack deciduous trees. Deliberate human introductions, too, have caused havoc in many areas, especially on islands. Examples include pigs, goats, mongooses, and cats. Extermination of perceived pests (such as wolves, beavers, and prairie dogs) can not only lead to regional extinction of the animal, but cause unexpected changes in the ecosystems from which they have been eliminated.

Since all these changes are occurring virtually everywhere in the world, it is evident that a mass extinction event is underway. But too often, political leaders and journalists alike assume that a given action of development that results in habitat destruction is an isolated, local event, not part of an uncoordinated, widespread assault on global biodiversity. Nor have losses of ecosystem services from each incremental change normally been considered, especially beforehand. Even comprehensive environmental impact statements, required before most major development projects are undertaken in the United States, may not assess the potential loss of ecosystem services. Yet these piecemeal losses eventually add up to a significant decline in the security and quality of life for human inhabitants, both locally and globally.

Recently, as severe storms have become more frequent and more destructive (a trend possibly related to mounting greenhouse gases in the atmosphere), connections to landscape changes and settlement patterns have begun to appear in news accounts. Thus the damage from disastrous floods, such as those along the Mississippi in the US in 1995, the Missouri in 1997, the Yangtze in China, and in Bangladesh, both in 1998 and 1999, has been connected to deforestation of watersheds and loss of natural wetlands. Such disasters have also highlighted the risks of building in floodplains, on steep hillsides, and in other marginal locations, a phenomenon commonly arising from poverty and population pressure.

Moderation of weather and climate and regulation of the hydrologic cycle are among the most readily perceptible ecosystem services; others are of comparable significance but seldom noted, let alone considered in social decision-making. Thus, although forests and wetlands have been recognized as helpful in flood prevention, their roles in buffering against drought and replenishing aquifers remain largely unappreciated. The value of maintaining even small patches of native woodland or brush interspersed in agricultural areas to help preserve soil fertility and nutrient-cycling ecosystem services is beginning to be realized; this was one purpose of "conservation set-asides" established by US agricultural legislation in 1985. Often, increased productivity of the crop fields more than compensates for the small loss of acreage to crops. These patches of natural vegetation also serve as habitat reservoirs for pollinators and bird and insect predators that help control crop pests, thus reducing the need for chemical pesticides. The woodland patches help to impede the spread of crop diseases as well.

Natural capital and humanity's future. The escalating losses of biodiversity and impoverishment of natural ecosystems are connected to myriad other problems and changes attending our expanding global civilization. The examples above, representing widespread and general trends, illustrate how humanity is using much of its natural capital not as a renewable resource but as if it were non-renewable, consuming and depleting it within a few generations. Not only is this rarely recognized in public information or public debate, but the foreseeable consequences of this aggregate behavior are mostly ignored. Cumulative land degradation amounts to a huge mortgage against future food production, as does the depletion of aquifers. Competition for both land and water resources poses threats to food production and to the well-being of urban populations. Aquaculture has the potential for making seafood more available, yet the practice causes drastic ecosystem modification, destruction of natural fishery "nurseries," and coastal pollution problems, while consuming additional agricultural and marine resources. Losses of biodiversity and natural habitats undermine efforts both to increase and sustain food production and to maintain the health and security of the human population. Yet the need for land to expand food production to feed and house the still-growing population suggests that the remaining natural systems may well be sacrificed to those ends, unless their importance for sustainability is recognized in time.

FOOD PRODUCTION

Principal connections to population growth

· Food distribution/equity · Food security · Livestock production

Principal connections to resources · Competition for land · Irrigation/water supplies · Energy inputs to intensive agriculture

Principal connections to environmental problems

· Green revolution · Land degradation · Loss of biodiversity/ ecosystem services · Pollution from agricultural chemicals · Pest problems · Climate change

The future of food production for the still-growing human population is on increasingly shaky ground, but this subject is greatly neglected by political leaders as well as by the news and information media. That land degradation, biodiversity loss, water shortages, and other negative trends are undermining efforts to increase food production is rarely considered. Instead, complacent assumptions prevail, even among some agricultural experts, that the green revolution, which doubled and tripled yields of major crops in the last half-century, will continue to boost food production substantially.

Modern intensive agriculture, however, depends on high inputs of manufactured fertilizers and pesticides, abundant water, and the use of machinery to produce the high yields of the green revolution. But the technologies of the green revolution account for both significant resource consumption and serious pollution problems, as well as accelerated soil erosion and land degradation. In many situations, high fertilizer inputs may mask a loss of nutrients and soil depth and quality for decades, but sooner or later yields will fall and productivity is compromised. The combination of high chemical inputs for widespread monocultures planted year after year creates an inherently unstable and unsustainable system in the long run. This instability is magnified in the humid tropics, where soils are characteristically thin and poor and pest problems are far greater. Yet plans to expand food production normally are based on assumptions that the green revolution will work in those still traditional settings.

Of course, preserving the productive capacity of agricultural land will be essential not only to maintain the gains of the twentieth century, but to expand production much further in the twenty-first simply to meet the needs of the growing population. Given that a substantial portion (a fifth or more) of the world population is nourished at minimal or inadequate levels today, most observers advocate increasing food production considerably more rapidly than the rate of population growth. Meanwhile a large portion of the population lives in countries that are experiencing rapid economic growth, and, as their incomes rise, so does their demand for food, especially for higher quality foods such as animal products.

Large-scale production of animals, however, commonly requires supplementary feeding of grains and other feeds (such as corn, soybeans, and alfalfa) which are farm-produced. In most regions, grazing lands are already under pressure, so a substantial increase in livestock production would inevitably require increased production of feed, in competition with food produced for direct human consumption. More than a third of the world's grain harvest goes to feed livestock, mainly in the industrialized nations. On average, three or more pounds of grain are needed to produce a pound of meat or dairy products from grain-fed animals. While feed crops might represent a potential reserve source of food in the event of a serious production shortfall (assuming that hungry people would accept foods normally considered inferior and the economic system allowed the transfer), they also represent a relatively inefficient use of food resources, especially in the case of feed-intensive beef.

Although per-capita grain production worldwide has failed to keep abreast of population growth since 1984, there has been no noticeable shortage of food supplies or rise in food prices on the world market. Apparently, the generally unappreciated tradeoff between feed and food grains has played a role in maintaining stability in the system. Demand for meat, especially beef, has dropped in some industrial nations for health reasons (the United States) or for economic reasons (the former Soviet Union and parts of eastern Asia), offsetting the rising demand in prospering low- and middle-income nations.

But this change in demand patterns does not compensate for the lack of security in the system, as demonstrated by the too-thin margin of reserves (no more than "pipeline" supplies) that has prevailed for the last several years. The world is highly vulnerable to a serious food shortage in the event of widespread crop failures. This vulnerability is heightened by the changes in climate and increasingly unpredictable adverse weather of recent decades, considered by scientists as at least in part related to global warming. The effects of climate change may themselves be intensified by human-caused changes in land use and vegetation, including deforestation and desertification, which have led to a diminution of the protective effects of ecosystem services.

ENVIRONMENTAL IMPACTS

Principal connections to the major factors shaping the human predicament

· Population growth · Human health impacts · Consumption · Resource mobilization and use · Depletion of natural capital · Technologies/efficiency · Food security · Development · Equity

Principal connections to ecosystems

· Loss of ecosystem services · Impacts on marine systems · Diversion of freshwater flows · Disruption of global biogeochemical cycles · Climate change

Many important environmental impacts have already been mentioned, but putting the spotlight on the environment may illuminate other connections and feedbacks that have not yet surfaced. Environmental impacts are the product of the size of the population and its consumption per capita of resources, modified by the technologies used to produce, process, and transport the goods and services used by the population. An analysis of environmental impacts is probably best served by focusing on the most serious environmental changes that are underway.

Global warming. Global warming is a short-hand term for the variety of consequences that are predicted to result from emissions of greenhouse gases to the atmosphere by human activities, principally the combustion of fossil fuels. These emissions augment the natural cycles of the same gases -- carbon dioxide, nitrous oxide, and methane - leading to buildups in the atmosphere. In addition, some novel chemicals created by industry, such as CFCs, have been released into the atmosphere. The chief result of accumulation in the atmosphere of all these gases is expected to be a gradual warming of the planet's surface and lower atmosphere due to the enhanced "greenhouse effect" they cause. Warming the atmosphere is likely to strengthen circulation patterns and thus may cause locally unpredictable changes in climate and more intense storms and severe weather. The warming also is expected to lead to a global sea level rise from the expansion of warmed seawater and from the melting of glaciers and polar ice.

The most important human-caused greenhouse gas is CO2, most of which is produced by fossil-fuel combustion. Deforestation and wood burning, however, account for a significant fraction, perhaps as much as one fourth of human-caused emissions. Methane, a potent but short-lived greenhouse gas, is released through a variety of means, including fossil fuel use. Other important sources are wetlands, including rice paddies, landfills, and flatulence of cattle. Nitrous oxide, a potent and long-lived gas, is a natural component of the complex global nitrogen cycle; its release is accelerated by land clearance, deforestation, and the use of nitrogen fertilizers. A variety of other gases, many produced in industrial processes also contribute to global warming. Among these are the CFCs that cause stratospheric ozone depletion, now being phased out, as well as some of the substitutes that are less of a threat to the ozone shield, but are still potent greenhouse gases. Not all sources and sinks of the principal gases - CO2, methane, and nitrous oxide -- are well understood, so effective approaches to abating their non-fossil-fuel related emissions have not yet been worked out. Since the latter two are closely tied to agriculture and land use, remedies for them will be difficult to apply.

Given the dependence of modern societies on the use of fossil fuels and the continuing increase in both population and per-capita consumption, stopping the human-caused emissions of greenhouse gases is not likely in the foreseeable future. Reducing the rate of increase that would otherwise take place is possible, however, but not easily achieved. It is in this context that the gross inequity in wealth and development level between the fully developed and less developed worlds emerges as a barrier to solutions. Developing nations look forward to increasing their levels of energy use substantially in the course of development; their leaders are not enthusiastic about curbing their future greenhouse gas emissions. Industrial nations, which contain a fifth of the world's population, are responsible for the great bulk of greenhouse gases emitted in past decades and still produce about half of current emissions (although their share is being overtaken by rising consumption in developing nations). Nevertheless, they are generally reluctant to change their energy-use habits. Since substantial reductions in greenhouse gas emissions will entail a major shift in economic and infrastructure arrangements, the needed changes are resisted by invested interests and will require many decades to implement.

Toxification. Every square inch of Earth's surface, land and sea, has been significantly altered by exposure to global toxification, including releases of persistent organochlorine compounds such as DDT and long-lived radioactive fallout from nuclear weapons tests. Until recently, toxic substances have been generally viewed as threats to individuals, not to societies, and certainly not posing the same sort of threat to the future as do essentially irreversible environmental impacts such as land degradation, the loss of biodiversity, and climate change. Nonetheless, globally distributed toxins (for instance, some chlorinated hydrocarbons such as DDT breakdown products, endosulfan, and PCBs) unquestionably can kill or injure many kinds of wildlife and seriously disrupt the functioning of natural ecosystems.

Now evidence is mounting of serious effects on wildlife and human health from the release of hormone-mimicking synthetic organic chemicals, although demonstrating the causal links is difficult. Some synthetic chemicals have molecular structures similar to naturally occurring hormones, and in ways both subtle and insidious may affect normal development in both animals and human beings. These hormone-mimicking chemicals may pose a major threat to humanity, both directly and indirectly. Directly, they may be causing or exacerbating developmental and reproductive disorders, including infertility, and triggering behavioral changes in some people, potentially causing a variety of social problems. The indirect threats arise from their disruptive effects on wildlife and consequently on ecosystems.

The epidemiological connection. Any changes associated with economic development and global change potentially could reduce health security. The human epidemiological environment is affected by population growth, nutritional status, increased mobility, and settlement of new areas. Land conversion and biodiversity loss, agricultural intensification, stratospheric ozone depletion, and climate change -- as well as processes of modernization, loss of indigenous medicinal knowledge, and microbial evolution of antibiotic resistance -- are all trends that may enhance human vulnerability to major epidemics of infectious diseases. And the resurgence of dreaded diseases such as tuberculosis and malaria as pathogens increasingly develop resistance to chemicals deployed against them is a real cause for worry.

The potential for a serious pandemic to destabilize social and political arrangements should be obvious. A case in point is AIDS. Population growth rates in several East and Central African nations are now being significantly slowed because of AIDS. Although its acute stages are delayed, its chief victims are people in their prime productive and reproductive years. The result can be a population dependent on aging adults struggling to support their orphaned grandchildren. Rapidly lethal diseases such as those caused by Marburg, Ebola, or Hanta viruses could wreak havoc in vulnerable populations, especially where good medical facilities are lacking. These diseases result from transfers from populations of wildlife into human groups, a phenomenon that occurs when people invade new environments and come in contact with animals and their pathogens to which they have had no previous exposure.

POVERTY, INEQUITY, AND MARGINALIZATION

Principal connections to population growth

· Population size, density, and growth · Urbanization · Development · Women's status · Culture and tradition · Health security

Principal connections to resources

· Consumption · Resource distribution · Agricultural development · Food security

Given the enormous scale and continuing expansion of the human enterprise today, and considering the evidence of deterioration in Earth's life support systems for human life, it is clear that civilization is increasingly unsustainable. The major factors in driving that expansion - population size and consumption per person - are still increasing. Most of the technologies behind the consumption are on the whole damaging, thus magnifying the impact of the consumption, although some progress has been made in increasing energy efficiency and substituting less damaging processes and products. But the magnitude of the entire enterprise continues to grow, as do the consequences of that growth for the biosphere. The predicament calls into question whether civilization can sustain itself in the long term.

Is the planet overpopulated? The key issue in assessing whether an area is overpopulated is not the number of people that can occupy any given space, but whether the population's requirements for food, water, materials, energy, and ecosystem services can be met on a sustainable basis. Most of the land perceived by urbanized individuals as "empty" either grows the food essential to people's well-being, or supplies forestry products, or, lacking water, good soil, and a suitable climate, cannot directly contribute much to the support of civilization. Thus the Netherlands, Singapore, Japan, and England can be affluent and crowded with people only because the rest of the world is not. The Netherlands imports large amounts of food, and extracts from other parts of the world much of the energy and virtually all of the materials it requires. It uses an estimated seventeen times more land for food and energy than exists within its borders.

In the increasingly interdependent world of today, most nations rely on trade with others for a growing list of important resources and products. So far, no acute shortages have appeared on a global scale, but regional deficits are not hard to find, although they are usually restricted to impoverished groups in underdeveloped areas. Given the human penchant for pushing any advantage, the pattern has been for the rich to get richer while the poor get left out of the action. The ever-widening income gap could be a recipe for disaster; it certainly has been at a local scale.

Equity thus enters the picture. The huge increase in per capita consumption of resources during the twentieth century has been concentrated mainly in the industrialized nations, although it is now spreading to previously less developed nations. More and more societies in Latin America and Asia are attaining levels of development roughly comparable with today's industrial nations in mid-century - often with similar levels of consumption and the inefficient technologies of that time. Yet the societies with inefficient technologies can little afford to waste resources or suffer the pollution that results; improving their technologies is becoming an imperative.

Meanwhile, some other nations, especially in Africa and some parts of Asia, seem bogged down in poverty, conflict, and chronic underdevelopment, while their populations continue to expand. Rapid population growth itself can significantly hinder the processes of modernization and economic development, just as poverty and illiteracy are known to hinder the adoption of family planning practices. The impacts of very poor societies on the environment may be negligible on a global scale (e.g., their contributions to global warming), but can be horrendous locally or regionally, undermining their efforts to improve well-being and escape poverty. Poverty itself can be a cause of land degradation, as poor farmers struggle to meet the needs of today but are unable to preserve resources for future years. The consequences, however, unlike those caused by industrial societies, are borne mostly by themselves and their families.

Energy use per person can be used as a rough surrogate for consumption generally, which is appropriate since energy use is involved in the production or utilization of most goods and services and also causes most of the environmental damage resulting from consumption. Using this index, reasonable comparisons can be made among societies. At the extreme, the average American uses 50 or more times as much energy as a citizen of a very poor country such as Mali or Bangladesh. Even comparably rich countries such as Japan, Germany, and Britain use only half to two-thirds as much energy per person as Americans.

Considering only average consumption rates of a society, however, neglects large differences that exist between rich and poor families or individuals within most nations. Many developing nations have a small elite class of families whose wealth is comparable to that of wealthy groups in rich countries and a small or almost non-existent middle class, while the majority of people remain in poverty. Even in the affluent United States, a significant fraction of its population lives in relative poverty, although the majority are comfortable or better off. Among developed nations, the largest discrepancy between rich and poor groups is in the United States. Gross inequities, as well as resource scarcities, surely undermine social stability both within and between societies, as witness the role of freshwater scarcity in generating tensions in the Middle East.

Any and all of the negative environmental trends described earlier in this paper can induce or be exacerbated by social disruption. Land degradation, combined with rapid population growth, poverty, and inequity, can lead to social problems as large portions of rural populations are forced off the land, sometimes generating major migrations. Hunger, poverty, and inequity are well-known destabilizing factors. Vulnerability to extreme weather events, as may be induced by global warming, can be enhanced by deforestation and desertification, as witness the tragic consequences of hurricane Mitch in Nicaragua and Honduras. No one knows how much of Mitch's intensity can be ascribed to global warming, although it may well have been significant. But there is no doubt that previous deforestation and marginalization of much of the population had left them highly vulnerable to such a disaster.

SEEING THE FOREST

Finding the forest beyond the trees can seem a daunting exercise - and somewhat discouraging. But understanding the connections may also lead to solutions to seemingly hopeless problems - and also lends itself to seeing things in a longer view. We cannot reverse population growth overnight, although a reduction in population size obviously would ease a great many pressures on our life-support system. Similarly, the combined catalysts of passing the peak in production of petroleum and the threat of global warming will surely force a major change in the management and uses of energy in all societies (regardless of resistance by interests vested in the status quo), but this will take decades to implement. Preserving and restoring degraded lands and depleted marine resources will take time, while the necessity of addressing these insidious trends grows more evident each day. And it daily becomes more apparent that many of civilization's 21st- -century problems are international or global in nature, and thus must be addressed in concert by all nations.

In this context, globalization has its benefits. As we see when the world community mobilizes to lend assistance in emergencies such as Turkey's devastating earthquake, or the results of hurricane Mitch, or the outpouring of Albanian refugees from Kosovo, diverse societies are discovering shared concerns and needs. Even as trade liberalization and financial globalization are leading towards greater inequity and exacerbating unwise consumption patterns, pressures toward democracy, modernization, and respect for human rights are exerting a counter influence. Both trends are facilitated by the explosive rise in global communications and information.

Yet analyses of the current situation and proposed policies are too often generated from narrow viewpoints that fail to take account of major portions of underlying trends. Economists and financial specialists overanalyze business and investment trends with no consideration of environmental factors that underlie their systems. If information on environmental conditions and trends were as carefully and exhaustively presented in the public media as are stocks and bonds prices or baseball statistics - information far less meaningful to people's futures - then many unwise decisions might be avoided. If citizens were aware that preserving productive land and natural ecosystems was essential for their future well-being and that of their children and grandchildren - not just an amenity - their attitudes toward some forms of development might be different. If people knew that wasting energy or depending on more damaging kinds was compromising climate stability and security of food production, they might make different choices as consumers. Above all, legislators and decision-makers (as well as their constituents) need to be informed of the implications and likely consequences of their actions, which too often are based on narrow, short-term economic or political concerns.

The world today appears to be in turmoil, with parts of the system out of control. In reality it is entering a profoundly important transition from a 20th-century process of industrialization and modernization, characterized by political nationalism and conflict, and shaped in large part by the population explosion, to a new global system, whose potential character we can now only dimly see. Will we continue the trends of today and bequeath a biotically impoverished, toxified, and climatically unstable world to future generations? Will today's social inequities be perpetuated and deepened? Will conflicts engendered by resource degradation and depletion and social injustice lead to destructive warfare and a downward spiral in human well-being? Or will people and nations realize their common humanity and the need for cooperation to create a sustainable, livable, and more equitable world? Will they overcome their differences and competitive urges and create that world? Whichever route is taken, information and news services will surely play a key role in shaping civilization's choices.

Notes

1 Ehrlich, P.R. and A.H. Ehrlich, 1991. Healing the Planet, Addison-Wesley, Reading MA; Ehrlich, P.R., A.H. Ehrlich, and G.C. Daily, 1995. The Stork and the Plow, Putnam, New York; see also World Resources Institute, United Nation Environmental Programme, United Nations Development Program, and The World Bank, 1998. World Resources 1998-99, Oxford University Press, New York. Homer-Dixon, T., 1999. Environment, Scarcity, and Violence, Princeton University Press, Princeton NJ;

2 Homer-Dixon, T. and J. Blitt (eds), 1998. Ecoviolence, Rowman & Littlefield, Lanham MD.

3 Population Reference Bureau, 1999. 1999 World Population Data Sheet , PRB, Washington DC; Gelbard, A., C. Haub, and M.M. Kent, 1999. World Population beyond Six Billion, PRB, Washington DC.

4 Gelbard et al., 1999.

5 Maartin, P. and E. Midgely, 1999. Immigration to the United States, Population Reference Bureau, Washington DC.

6 PRB, 1999, 1999 World Population Data Sheet.

7 Ehrlich, Ehrlich and Daily, 1995, and references therein; Gelbard et al., 1999.

8 E.g., Wattenberg, B., 1997, The population explosion is over. New York Times Magazine, Nov.23; Eberstadt, N. The population Implosion (op-ed). Wall St. Journal, Oct. 16.

9 Ehrlich, Ehrlich, and Daily, 1995; Population Reference Bureau, 1998. Global estimates of unsafe abortion, Population Today, November, pp. 1-3; Rahman, A., L. Katzive and S. K. Henshaw, 1998. A global review of laws on induced abortion, 1985-1997. International Family Planning Perspectives, June, pp.56-64.

10 Daily, G. and P. Ehrlich, 1996. Global change and the epidemiological environment, Environment and Development Economics, vol.1.

11 Riley, N.E. 1997. Gender, power, and population change. Population Bulletin (Population Reference Bureau) 52:1 (May); Ehrlich, Ehrlich, and Daily, 1996.

12 Martin, P. and J. Widgren, 1996. International migration: A global challenge, Population Bulletin 51:1 (April).

13 Ehrlich, P.R., A.H. Ehrlich, and J.P. Holdren, 1977. Ecoscience: Population, Resources, Environment. , San Francisco.

14 Harte, J., C. Holdren, R. Schneider, and C. Shirley, 1991. Toxics A to Z. University of California Press, Berkeley CA.

15 Intergovernmental Panel on Climate Change (IPCC), 1996. Climate Change 1995; Summary for Policymakers, Working Group I. Cambridge University Press, New York.

16 Ehrlich, P.R. and A. H. Ehrlich, 1996. Betrayal of Science and Reason, Island Press, Washington DC; Gelbspan, R., 1998. The Heat is On, Perseus Books, Reading MA.

17 Daily, G.C. (ed.) 1997. Nature's Services; Their Nature and Value, Island Press, Washington DC.

18 Vitousek, P. et al., 1997. Human domination of Earth's ecosystems, Science 277:494-499; Vitousek, P. P.R. Ehrlich, A.H. Ehrlich, and P. Matson, 1986. Human appropriation of the products of photosynthesis. BioScience 36:368-373.

19 Ehrlich, Ehrlich, and Daily, 1995, chapters 5-7.

20 Oldeman, L., V. Van Engelen, and J. Pulles, 1990. The extent of human-induced soil degradation, Annex 5 of Oldeman et al., World Map of the Status of Human-induced Soil Degradation: An Explanatory Note (rev. 2nd ed.), International Soil Reference and Information Centre (ISRIC), Waginengen, Netherlands; G. Daily, 1995. Restoring value to the world's degraded land, Science 269:350-354.

21 Postel, S., G. Daily, and P. Ehrlich, 1996. Human appropriation of renewable fresh water. Science 271:785-788; Gleick, P., 1993, Water in Crisis, Oxford University Press, New York.

22 Postel, S. 1999. Pillar of Sand: Can the Irrigation Miracle Last? W.W. Norton, New York.

23 Gleick, P. 1998. The World's Water, Island Press, Washington DC.

24 Pauly, D., 1998. Fishing down marine food webs, Science 279:494-499.

25 Naylor paper on aquaculture

26 Daily, 1997.

27 WRI et al, 1998, World Resources 1998-99; Myers, N., 1996. The world's forests; problems and potentials, Environmental Conservation 23:156-168.

28 Myers, N., 1979, The Sinking Ark, Pergamon Press, New York; Ehrlich, P.R. and A.H. Ehrlich, 1981. Extinction; The Causes and Consequences of the Disappearance of Species, Random House, New York; Wilson, E.O., 1992, The Diversity of Life, Harvard University Press, Cambridge MA; Daily, 1997.

29 Fowler, C. and H. Mooney, 1990. Shattering; Food, Politics, and the Loss of Genetic Diversity, University of Arizona Press, Tucson.

30 Ehrlich, Ehrlich, and Daily, 1995.

31 Ehlrich, Ehrlich, and Daily, 1995.

32 Brown, L.R., 1999, Feeding nine billion, in Brown, L.R., C. Flavin, H. French, et al., State of the World 1999, (Worldwatch Institute), W.W. Norton, New York.

33 Brown, L.R., M. Renner, and B. Halweil, et al., 1999. Vital Signs 1999 (Worldwatch Institute), W.W. Norton, New York.

34 Field, C. and E. Carpenter, 1999. Land Use Changes Cause Significant Carbon Loss. Paper presented at Ecological Society of America meeting, August 11. (see University Science News, August 11, 1999).

35 Holdren, J. and P. Ehrlich, 1974. Human population and the global environment, American Scientist, 62:282-292; Ehrlich and Ehrlich 1991.

36 IPCC, 1996.

37 Vitousek, P., H. Mooney, J. Lubchenko, and J. Melillo, 1997. Human alteration of the global nitrogen cycle: sources and consequences. Ecological Applications 7:737-750.

38 Ehrlich and Ehrlich, 1996; Gelbspan, 1998.

39 Simonich, S. and R. Hites, 1995. Global distribution of persistent organochlorine compounds. Science 269:1851-1854.

40 Simonich and Hites, 1995.

41 Edwards, C., 1993. The impact of pesticides on the environment, in D. Pimentel and H. Lehman (eds), The Pesticide Question: Environment, Ecnomics, and Ethics, Chapman & Hall, New York, pp. 13-46; T. Colborn and C. Clement (eds.), 1992, Chemically-induced Alterations in Sexual and Functional Development: The Wildlife/Human Connection, Princeton Scientific Publishing, Princeton, NJ, chapters 6-9; for more details and references, see Ehrlich, Ehrlich, and Holdren, 1977, chapters 10 and 11; and Ehrlich and Ehrlich, 1981.

42 Toppari, J., et al., Male reproductive health and environmental xenoestrogens. Environmental Health Perspectives 104 (suppl. 4):741-803.

43 T. Colborn, J. Myers, and D. Dumanoski, 1996. Our Stolen Future, Dutton, New York; see also Colborn and Clements, 1992, especially chapters 14-21.

44 WRI et al., 1998, World Resources 1998-99. The focus of this edition is on health and the environment.

45 Holdren and Ehrlich, 1974; Ehrlich and Ehrlich, 1991.

46 In 1989-91, the Netherlands had average net imports of more than 3 million metric tons of cereals and 800,000 metric tons of pulses (peas and beans, including soybeans); World Resources Institute, 1994. World Resources 1994-95, Oxford University Press, New York.

47 Wackernagel, M., 1993, How Big is our Ecological Footprint? A Handbook for Estimating a Community's Carrying Capacity, Discussion draft, Task Force on Planning Healthy and Sustainable Communities, University of British Columbia, Department of Family Practice, Mather Building, 5804 Fairview Avenue, Vancouver B.C., Canada, V6T 1Z3, 15 July. The Netherlands' "ecological footprint" or "appropriated carrying capacity" is defined as "the aggregate land (and water) area in various categories required by the people in a region a) to provide continuously all the resources they presently consume, and b) to absorb continuously all the waste they presently discharge, using current technology" (p. 10).

48 Holdren and Ehrlich, 1974; Ehrlich and Ehrlich, 1991.

49 Ehrlich, Ehrlich, and Daily, 1995; WRI, 1998.

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