Scholars of ecocide have identified at least a half-dozen major underlying causes for current declines in species and devastation of natural ecosystems. Most of them agree that population growth - which includes both global and local natural increase and migration - is one of these primary causes of ecocide.68 In short, gaining people means losing species. This truism has never been more consequential than in the modern era. Since farming economies first came into existence 480 generations ago, the human population has increased a thousand-fold, to more than 6 billion. Half of this increase has occurred in the last 30 years.69 The enormous increase in the planet's population is causing severe pressures on its ecosystems, resulting especially from activities associated with the production of food and the use of timber and fibers. Vast areas of the Earth's surface, especially in arid and semi-arid regions, have nearly ceased to be biologically productive. According to the United Nations Food and Agricultural Organization, if present rates of land degradation continue, there will not be a single fully productive hectare of arable land on this planet in less than 200 years.70
Perhaps two of the best illustrations of the demographic threats to biodiversity are the worldwide expansion of human and livestock biomass, which continues to increase at essentially exponential rates in a world of finite size, and the related human appropriation of Net Primary Production of Photosynthesis (NPP) on land. In 1850, humans and their livestock represented perhaps 5 per cent of total terrestrial animal biomass, a century later this value represented just over 10 per cent and currently is somewhat more than 25 per cent.71 Ten years from now it is sure to be in the neighborhood of 30 per cent. This increase in human and livestock biomass occurs at the expense of wildlife biomass, a loss that is measurable in both quantitative and qualitative terms - that is, both in loss of numbers of individuals within a species and in loss of numbers of species.72 In other words, these losses in biodiversity result largely from an arrogation of nature by the ever-expanding human population, an expansion that has been variously likened to a biospheric pathology or cancer.73 Indeed human demands on the environment have been growing even more rapidly than population increases suggest, as indicated by the even more rapid increases of productive and consumptive activities.74 By the late 1980s, humans worldwide were already consuming, diverting, or putting into reserve more than 40 per cent of all Net Primary Production of Photosynthesis generated on land.75
Traditional concerns about the relationship between population growth, environmental degradation, and ecocide have largely focused on aggregate population levels. However, the impact of humans on the world environment is as much a function of per capita consumption as overall population size.76 The exhaustion of biological diversity and natural resources is overwhelmingly due to over-consumption and technological application, not simply increased population growth. The US, for example, comprises only 5 to 6 per cent of the world's population but consumes 30 to 40 per cent of the world's resources. The vast majority of US over consumption is directed by and benefits only a small percentage of the US population.77 A significant proportion of consumption of natural resources in the global North, further, is sustained by resource flows from the southern to the northern hemisphere.78
Some indicators suggest that ecosystem and resource limits have already been reached. World fish harvests peaked at 100 million tons in 1989. By 1993, they had declined 7 per cent from 1989 levels. Growth in grain production has slowed since 1984, with per capita output falling 11 per cent by 1993. World economic growth has slowed from over 3 per cent annually in the decade 1950-60 to just over 1 per cent in the decade 1980-90 and less than 1 per cent from 1990 to 1993.79 The Worldwatch Institute, extrapolating from historical data, forecasts that if current trends in resource use continue and if world population grows as projected, by 2010 per capita availability of rangelands will drop by 22 per cent and the fish catch by 10 per cent. The per capita area of irrigated land, which now yields about a third of the global harvest, will drop by 12 per cent. And cropland area and forestland per person will shrink by 21 per cent and 30 per cent respectively.80
Rapid population growth, combined with unsustainable consumption patterns in a world where a small minority of 20 per cent of the world population consume over 80 per cent of its resources, have massively increased pressures on biodiversity habitats. Recent research suggests that species extinction during the past century have occurred at least 1,000 times more frequently than in pre-human eras. From projected habitat losses based on current trends, some biologists project that 2 to 13 per cent of the world's species could go extinct in the period between 1990 and 2015. More could disappear as a result of other causes, such as invasions of exotic species and diseases, pollution, over-harvesting, and human-induced climate change.81
Conversion of natural habitat to human use will further reduce the value of remaining wild areas for most wildlife. When development chops wild lands into fragments, native species often decline simply because the small remnants cannot meet their biological needs. For example, studies of US forest birds indicate that species that prefer to nest on forest interiors are more subject to predation and lay fewer eggs when habitat fragmentation forces them to nest along forest edges. A study in southern California indicated that most canyons lose about half the native bird species depending on chaparral habitat within 20 to 40 years after the canyons become isolated by development, even though the chaparral brush remains. Biologist William Newmark's 1987 study of 14 Canadian and US national parks showed that 13 of the parks had lost some of their mammal species, at least in part because the animals could not adapt to confinement within parks surrounded by developed land. The Breeding Bird Survey, a volunteer group that tabulates nesting birds each June, found that 70 per cent of neo-tropical migrant species monitored in the eastern United States declined from 1978 to 1987. So did 69 per cent of monitored neo-tropical migrants that nest in prairie regions. Declining species include such familiar songbirds as veeries, wood thrushes, blackpoll warblers, and rose-breasted grosbeaks. As human population growth continues to push development into wild areas, fragmentation will increase, and its overall negative effect on wildlife survival will intensify.82
The pressures on these rich natural resources and environmental systems, particularly on biodiversity-rich regions of the Asia-Pacific, have been continuously increasing over the past few decades. The world's current population of 6.1 billion is projected to hit 8 billion by 2025, with 97 per cent of that growth occurring in the global South.83 Perhaps most worrisome to conservation biologists is that some of the most rapid human population growth is taking place in the vicinity of some of the world's biologically richest yet most vulnerable habitats. High population growth rates in 25 "biodiversity hotspots" - identified by Conservation International as especially rich in endemic species - have already experienced dramatic reductions in the amount of original vegetation remaining within their boundaries.84
Nearly one-fifth of humanity lives within these already severely degraded 25 hotspots, despite the fact they enclose only one-eighth of the habitable land area of the planet. In addition, more than 75 million people, or 1.3 per cent of the world's population, now live within the remnants of the world's three major tropical wilderness areas: Upper Amazonia and the Guyana Shield in South America, the Congo River basin of central Africa, and New Guinea and adjacent Melanesia. Areas of rich biodiversity facing the greatest risk include south India's Western Ghats and Sri Lanka, the Philippines, the Caribbean, the Tropical Andes, and Madagascar.85
Unlike other natural resources, biodiversity is especially affected by both extensive means of acquiring food and shelter (farm expansion and suburban sprawl), and intensive means (intensive agriculture and urban concentration). Farm expansion and sprawl play an important role in the clearing of terrestrial and wetland habitat. At the same time, intensive solutions to food and shelter needs tend to overload aquatic and marine ecosystems with pollutants. Clearly, the additions to human population projected for at least the next half-century will require further appropriation of the Earth's ecosystems. Such growth, coupled with an expected growth of consumption, further globalization of trade, and much-needed improvements in the living standards of the world's poor, is likely to put at further risk much of the remaining biodiversity in the bioregions.
The twentieth century was marked by a profound historical development: an unwitting evolution of the power to seriously damage global ecosystems. Warfare represents one source of this power. Even the complexities of global arms control, however, are now dwarfed by the changes inherent in runaway population growth, a further source of modern ecocide. Diminishing the ecological threat posed by warfare involves relatively few parties, well-established international protocols, alternative strategies that carry easily assessed costs and benefits, and widespread recognition of the severity of the threat. In contrast, curbing the devastating global impact of population growth is more difficult, since it involves coordination of the most personal life decisions of every inhabitant of the planet, in a context in which socioeconomic incentives for sacrificing the future for the present are often overwhelming.86
Population growth seems to affect everything, but for a number of reasons, changes in population trends will come about only slowly.87 First, demographic change is inherently a gradual process, operating not in terms of months or years, but generations. In a world where policy makers are faced with short-term crises that demand immediate responses, tackling the thorny issues of population growth involves enormous practical obstacles. Second, the topic of population growth does not generate the continuous news coverage that might attract wider public attention. Third, international meetings on population and women's issues have met with staunch religious opposition, most notably, from the Vatican and some Muslim communities.88 Political and religious groups in many countries may seek to block the implementation of publicly supported programs that they see as eroding morals or promoting promiscuity. Even so, as little as $20 billion a year could provide contraceptives to every woman who wants them, allowing families throughout the globe to reduce births voluntarily.89 Third, tensions will inevitably arise over resource allocation, because the best strategy for addressing population growth calls for simultaneous investments in health, education, and the empowerment of women, in addition to contraceptive and reproductive health services. Some social scientists have expressed disappointment that the new focus on human development downplays the importance of lowering fertility.90
The moral of the story here is that globally we are procreating ourselves into a future of accelerating forest loss, fresh water depletion, and poverty. Global social and ecological deprivation has increased in absolute numbers. By 2025, most of the population of developing countries will face water shortages, two out of every three persons on Earth will live in "water-stressed" conditions, and rising seas could inundate large areas, displacing 70 million people in China alone.91 Clearly there are multiple causes, but efforts at alternative social development and global ecological restoration are, without a population program, like "mopping the floor with the water turned on."92 Zero population growth within the next generation is one of the critical prerequisites for reducing the progressive degradation of the global environment and the annihilation of species.
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