A new concept in environmental and human affairs was introduced with the Brundtland Declaration of 1987: "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs." Implicit in this often-quoted definition is the idea that the natural environment faces stress and overexploitation and will not be able to indefinitely meet escalating human demands.
By itself, the Brundtland definition is insufficient. How does one define "needs," as opposed to wants or even excessive luxury? Is a lowering of living standards acceptable? Is barely enough to eat and minimal shelter good enough? What about education and medical care? Does sustainability imply some equity in distribution of goods, or might an increasing gap between rich and poor meet the sustainability test (if environmental and population stability are achieved)? Is ecosystem health important for itself, or only as it sustains humans?
The Brundtland Declaration suggests some answers. Linking global
inequity to environmental degradation, it calls for a decrease
in consumption in the wealthy global north, together with development
for the impoverished global south.1
In this, it foreshadows today's environmental justice movement.
The implicit problem here is that the wealthy are often protected
from the environmental costs of their lifestyles, while the poor
often lack the means to care for their immediate environment.
If sustainability implies a linking of problems of consumption
and poverty with pollution, resource degradation, and conflict,
the solutions also require novel linkages. Regarding sustainability,
science cannot exist in a vacuum, but must interact with politics,
with policy, with governance issues that reach into people's daily
lives. Economic factors structure how, where, and how much the
environment will be exploited. Communication between different
sectorswhich too often exist as compartmentalized unitsis
crucial. Environmental scientists can no longer be content merely
with doing "good" science; discussion and persuasion become part
of the scientist's role.
How we proceed toward sustainable development depends upon perception. If people perceive resource depletion, they will recycle; if they perceive an unlimited amount of extractable resources, or forthcoming technological answers to all problems, they will not. Similarly, if people believe that automobile emissions are causing dangerous global warming they will buy more fuel-efficient cars, and seek other alternatives. However citizens must also feel empowered, must believe that their efforts and decisions have some meaning, in order to work toward sustainable lifestyles.
Individual perceptions extend to the collective social will,
and hence to political and policy operations, which can institutionalize
what may begin as lifestyle choices. Regarding automobiles, monetary
incentives often prompt people to 'do the right thing.' Prohibitions
are a more heavy-handed policy instruments, as in absolute limits
on gas mileage. Incentives and prohibitions are generated, and
need to be supported, by policy and government. In moving toward
sustainability, the beliefs of key policy-makers, the system of
governance, and the role of local, national, and international
organizations all play a part.
The overlapping roles of governance, social values, and economic
needs generate the interdisciplinary nature of sustainability
science. To break down barriers between disciplines that too often
remain discrete, and to encourage exploration of practical policy
options, CSA and the USGS's National Biological Information Infrastructure
have launched the e-journal Sustainability:
Science, Practice, and Policy. "This is an important
endavor as it aims at answering fundamental questions on what
prevents the wide replication of best known practices in sustainable
development," writes Klaus Töpfer, executive director
of the United Nations Environment Programme. "I hope that
the journal will catalyze debate between different disciplines
that include practitioners and policymakers."
Given its interdisciplinary nature, a question remains as to
whether "sustainability science" is more of a traditional science,
a social science, or something different and more improvisational,
more an art than a science. In the narrowest sense of experimentation
and replication it cannot be called a traditional science (although
many contributing fields are certainly traditional sciences).
In the ultimate sense, that empirically events are occurring in
our ecosystems, and that these will have definite effects, it
is a science, albeit one that affects every human being's daily
life. The eventual impact of today's decisions, then, provides
a final test of sustainability.
Economic and Historical Roots
The link between economics and the environment is crucial, particularly
in a globalizing world. Historically economics, dating back to
Adam Smith's The Wealth of Nations, has largely disregarded
True, Smith included "land" among his original
economic factors, but mainly as a resource to be exploited.2
Later economists downgraded the importance of land and other
environmental factors, assuming a virtually unlimited amount
of natural goods to be harvested and used by humans.
The problematic exception is Thomas Malthus, who in 1798 published An Essay on the Principle of Population, warning that while population increased exponentially food production increased
only incrementally.3 Population
was thus bound to vastly overshoot subsistence, leading to mass
poverty and starvation. This set the terms for an environmental
limit to ever-expanding human needs.
In terms of today's wealthier societies, Malthus was quite wrong, as technological advances have allowed food production, along with numerous other goods and services, to advance at an even faster rate than population. Yet elsewhere, local environment has proved unable to meet daily needs. One question for future sustainability is whether resource use will be able to continually shift as needed, or whether all resources will eventually be exhausted. A related question is how heavy a price increasing pollution, including hazardous wastes and such threshold effects as global climate change, will exact. Economists refer to these costs, which are not paid by those who harvest or produce goods, as externalities.
Meanwhile, Malthus has proved right in numerous local circumstances, as various groups of people have exceeded the carrying capacity of their environments and paid the price. A favorite example of environmentalists and sustainability scientists is Easter Island, discovered in 1722 by Europeans who were amazed by the enormous stone statues that confronted them on an otherwise barren landscape. Speculation on the mystery of who put them there would last for centuries.
Today we believe we know the answer. Leaders of the Polynesian civilization that settled the island erected these statues as enormous symbols of their prestige. The drive for status overrode ecological considerations, leading them to denude the island, cutting down ever-more trees upon which to drag ever-larger boulders, in the quest to make ever-larger statues. That the island was isolated, with a fragile ecosystem, made it particularly prone to environmental collapse.
Although environmentalists use Easter Island as a symbol of what may happen to our own society, global ecosystems are, of course, far more complex and resilient, while our technology and our ability to communicate and change give us much greater ability to adapt. Yet, as Jared Diamond documents in his book Collapse: How Societies Choose to Fail or Succeed, other societies have overexploited their available ecosystems, precipitating disasters similar to that predicted by Malthus.4
The Maya present one of the most dramatic cases; their civilization largely collapsed, probably during the ninth century AD, leaving vast ruins replete with abandoned temples and monuments. Diamond explains the collapse as "population growth outstripping available resources," along with deforestation, conflict, drought, and inaction by Mayan kings.5 The explanation goes beyond ecological determinism; despite difficult circumstances, Diamond believes that better decision-making by the Maya would have forestalled collapse.
Societies facing overpopulation and ecological stress have not always failed. Sometimes, Diamond explains, they have realized their situation and adapted environmental management strategies that allow long-term success. Japan is a prime example. In the 17th century the island nation faced a population explosion that threatened to overrun the resources available in its limited space. Deforestation was a particular threat. According to Diamond, a combination of forward-looking forestry practices and rather draconian population measures enabled Japan to avoid the Malthusian fate of the Maya, to move toward its dynamic role in recent world history.6
Where Are We Now?
Sustainability science, then, implicitly holds that what happened to Easter Island and the Maya may happen to us on a global scale, that we are in a condition of overshoot in which environmental systems will not sustain our collective lifestyle. Foresight, wisdom, and better decision-making are thus necessary for our global civilization to ultimately succeed.
That we may be facing environmental limits was a key point brought into consciousness by the Club of Rome's 1972 report The Limits to Growth, a crucial predecessor of the sustainability movement, that predicted an eventual crisis as the world ran out of critical goods. Using computer modeling, and extrapolating from statistics over the previous 70 years, the report concluded that, "if the present growth trends in world population, industrialization, pollution, food production, and resource depletion remain unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years." The report was not fatalistic, however, but argued that, " it is possible to alter these growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future."7 From its inception onward, the report has been harshly criticized, for instance for assuming exponential growth in population and resource use but only incremental change in technology.
A similar, but more cataclysmic, theory had been advanced in
1968 by Paul Ehrlich, whose The Population Bomb updated
Malthus, predicting that, "in the 1970's the world will undergo
famineshundreds of millions of people will starve to death."8
By contrast Ehrich's intellectual opponent, Julian Simon, believed
that human creativity and technological development would allow
substitution of resources to the point that an infinitely growing
population would be able to continue to improve standards of living
virtually forever: 'We have in our hands now - actually in our
libraries - the technology to feed, clothe, and supply energy
to an ever-growing population for the next 7 billion years."9
That both Simon and Ehrich made preposturous statements- Simon's made preposturous by a basic mathematical knowledge of exponential growth, Ehrlich's by time-provides a warning of the dangers of letting ideology transcend facts. Yet in their argument of a race between human invention and environmental capacity lies a basic understanding of the challenge of sustainability. It comes down to the idea that resource renewal and substitution, together with the creative use of endless new technology, will allow endless economic growth, versus the idea that population growth, per capita resource use growth, and threshold effects spell eventual doom.
Although specific societies have lost the race between growth and destruction, the overall global trend has been toward improved living standards, as measured by such key indicators as life expectancy, health, resource use, and technology. Yet past performance is no guarantee of the future. Given that the earth is finite, and given rising resource use by a rising population, without careful planning we will, at some point, lose on a global scale. Employing a much broader range of data than that employed by Ehrlich in 1968, sustainability scientists believe that we are somewhere near the tipping point and that we must begin to decrease our per capita resource use and must monitor and manage the environment far more wisely.
The recent devastation of New Orleans provides a dramatic example of how, even in a technologically advanced society that has shown long-term improvement of human welfare, environmental stresses plus a natural disaster may lead to a local collapse, one that better prior planning would have alleviated. Sitting well below sea level, with the Mississippi river folding around it, and near numerous lakes and the Gulf of Mexico, New Orleans has long been vulnerable to flooding. To protect itself, the city built an extensive levee system. When hurricane Katrina hit, however, the levees acted as a giant bowl, keeping water in, in turn drowning the pumps normally used to prevent flooding. Toxic and human wastes stirred up in this cesspool have added to the trouble. The prior destruction of wetlands, which had acted as a natural buffer absorbing water from hurricanes, was another factor increasing Katrina's impact. Ironically, the levees built to protect the city from flooding due to the river helped dry up these wetlands.10
At least prior to Katrina, in the United States, many of the worst environmental predictions had failed to occur. Forests have revived, local air is often cleaner, and notable species such as the Bald Eagle have been taken off the endangered species list. These facts, however, are not an argument that we can do nothing and human creativity will solve all problems. They show, rather, that an awareness of environmental problems can lead to good environmental management, and that such management can then make an impact. The Bald Eagle really was threatened, and earlier species such as the Passenger Pigeon did go extinct. California really was plagued by smog alerts, and Cleveland's Cuyahoga River actually was so polluted that it caught fire several times.11
Environmental management has certainly had its successes at
a national level, but voracious resource use has created a wider
threat. And poor countries often neglect basic environmental standards.
Environmental scientists warn that solutions to escalating global
threats require foresight and planning.
If the resources available today are far greater than those in the past, the threats we face are also far greater. Human population may be a key driver of unsustainability, yet due to a declining birth rate growth is expected to level off at around 9 billion (still an enormous number) by 2050. Population distribution is also important. In some industrialized societies, such as Japan and many European countries, the birth rate has fallen significantly below what is needed to sustain the current population and care for the growing numbers of elderly. Yet these same industrialized societies also consume a disproportionate amount of resources. Geographical distribution is also crucial. For instance, that some 50% or more of the world's population lives within about 50 miles of the coastline greatly stresses these locations. Resource depletion, pollution, ecosystem exhaustion, and such threshold effects as global climate change, constitute primary threats.
Resources facing depletion may be divided into renewable and nonrenewable. Renewable include agricultural and forestry products, while oil and metals are examples of nonrenewable. Both sources depend upon energy from the sun, known as primary production, albeit on different time-scales. Agriculture and forest products harvest this energy in ways usable by humans in a relatively short time frame, within the scope of a single lifetime and often much shorter. Such non-renewable resources as oil and coal depend upon millions of years of work absorbing the sun's energy; theoretically renewable in the extremely long run, they are nonrenewable in the time frame within which human societies exist.
Resource exhaustion may not be the final arbiter of economic development due to the phenomenon of substitutability, that other resources may replace their function. If wood is scarce for buildings, bricks made from mud may be used, or artificial substitutes may be developed. If oil runs out coal may be used, or nuclear power, or wind and solar power. Ultimately, however, too many humans demanding too much will lead to exhaustion of primary production, and even of space upon the earth's surface. Just what amount becomes too much is a source of great debate.
Water: Is It the Key Limiting Factor?
Water is one resource that has no substitute. Although water covers three quarters of the planet, 97% of the Earth's water is salt water, and thus useless for drinking (and many other purposes). While some desalination is currently used, this is limited by factors from the costs of desalination plants, to their limited capacity, to concerns over disposal of brines/wastes from the desalination process.
Less than 3% of water is freshwater (much of it groundwater that has accumulated over time and is virtually nonrenewable. Rainwater is thus critical; the "global water cycle accounts for the only naturally renewable source of fresh water, that is, precipitation that occurs over land."12 Aquifer pumping is reducing our water resources. People living in arid regions, and even some not so arid regions, have been relying heavily on groundwater resources that accumulated over thousands of years. Removing this water at such rapid rates spends this resource many times faster than it can be replaced, leads to the deterioration of what water is left, and also can cause collapse of aquifers.
Pollution of freshwater is a constant concern, making prevention measures and sewage treatment crucial. Despite all of this, there might be enough freshwater available for earth's growing population, but unfortunately not in the places where population chooses to settle. In the Southwestern United States, for instance, industrial and agricultural water use have lowered aquifers and are not sustainable, while consumers bring habits from areas with radically different conditions, such as lush lawns requiring frequent watering.13
Water resources increasingly drive economic and political decision-making. Anticipating an accelerating water shortage, corporations are buying and selling water rights; the ubiquity of brand-name bottled water is one indication that a resource once considered free and public is changing in status. Water is a source of conflict that is likely to accelerate in the future. In the Middle East, for instance, access to Jordan River water is contested between Israel and the Palestinians to the extent that the issue has been delayed until final status negotiations (placing it on a par with the holy city of Jerusalem).14 Barring a miracle breakthrough in desalination technology, water disputes are likely to become more common in the near future. Still, according to Lester Brown, with conservation and productive use, water resources can be stretched much further than is currently happening.15
Water resources are threatened in numerous other ways, often linked to other forms of ecosystem health. Coastal waters suffer eutrophication, while damming of rivers causes a number of problems, including changing habitat both above and below the dam, and decreasing sediment flow to the coastline leading to increasing rates of coastal erosion. Draining of wetlands destroys habitat and causes loss of such ecosystem functions as filtering water and recycling carbon. A macro look at the state of our water reveals the numerous, complex linkages between environmental categories.
Agricultural production, which uses an enormous amount of water, becomes limited as aquifers deplete. According to Brown, "policymakers are beginning to look at water as the limiting factor for food production."16 Soil erosion and impoverishment also limit crop production, while energy prices affect intensive farming. Still crops are a far more efficient means of feeding large numbers of people than meat, since an enormous amount of productivity is lost as animals eat crops and are themselves converted into products for human consumption.
Pollution is another driving factor that threatens not only human health, but also resources on which we depend, not only water but also biodiversity and renewable resources. Industry, energy, and automobiles are key sources of emissions that harm our air. Common air pollutants include ozone, nitrogen oxides, sulfur dioxide, carbon monoxide, lead, particles, and organic pollutants. Among the numerous affects on human health are headaches, skin rashes, asthma, bronchitis, blood poisoning, neurological impairment, birth defects, and cancer.17
Sulfur dioxide emissions produce acid rain, which ends up in our water, as do atmospheric depositions of numerous substances, such as nitrogen. Sewage runoff and factory wastes are direct sources of water pollution. In the U.S. Great Lakes, for instance, pollutants include polychlorinated biphenyl, dichlorodiphenyl trichloroethane, dieldrin, toxaphene, mirex, methylmercury, benzopyrene, hexachlorobenzene, furans, dioxins, and aklylated lead.18 Beyond their impact on human health, these substances threaten the food chain and impact ecosystem health.
Radioactive wastes are the key drawback to an energy source that might otherwise be a magic bullet for many of our problems: nuclear energy. Nuclear wastes remain hazardous for centuries or millennia (depending on the grade of uranium or plutonium). Current storage methods include reprocessing, storage, and eventual permanent disposal in deep geological repositories. Transportation and the possibility of terrorist hijacking are other controversial issues regarding nuclear wastes.
Air and water pollution are key ecosystem stress factors. Even more obvious direct threats to ecosystem health include the cutting down of forests and destruction of habitat. Alteration of the physical environment is multifold. Non-permeable surfaces, such as pavement and buildings, increase runoff of silt, sewage, garbage, and other harmful materials into lakes and rivers while preventing water from replenishing aquifers. Invasive species, displaced from their original environment, alter ecosystem functions; invasive vines, for instance, strangle and kill trees.19 Overall biodiversity is lowered, leading to a multitude of effects, many as yet unknown. Ecosystem services refers to the multifold ways the natural environment contributes to the human economy. These services include air and water purification, agricultural pollination, nutrient cycling, soil enrichment, climate stabilization, medicinal products and drought mitigation. Nature magazine has estimated the value of these global services at an average of US $33 trillion a year.20
On the Threshold of Disaster?
Pollution is a key factor in the final threat to sustainability, threshold effects, which refers to boundaries that, once crossed, may cause irrevocable environmental changes. The dwindling or extinction of keystone species is one threshold effect that leads to numerous consequences, often unknown. For instance pollinators, such as birds or bats, are crucial for the reproduction of numerous plants; exactly what level of pollinator destruction leads to what level of vegetation destruction is unknown. Removal of one humble species may have little effect on surrounding species, or it may begin a cascade of devastating effects. Scientists simply don't know enough about the complex web of interdependencies to make accurate predictions.
Another kind of threshold effect is that which affects atmospheric systems. In the 1980s, worries that chlorofluorocarbons were destroying the outer ozone layer that protects the earth from dangerous radiation led to international prohibition. In this case a scientific theory that correlated with measurable atmospheric effects led to effective global management.
Climate change is the threshold effect currently most discussed, and most controversial. Beginning in the 1980s, climate models predicted that Carbon Dioxide released into the atmosphere would build up and trap heat, leading to a gradual overall warming of the planet. In the years since climatologists and other scientists have systematically studied this theory, through developing different computer models, measuring surface temperatures around the planet, and studying historical temperature patterns through such devices as tree rings and ice core samples. Measurements of upper atmosphere temperature, however, contradict the rest of the evidence (and the reasons for this are contested). Nevertheless, the overwhelming consensus is that global warming is actually occurring.
The exact effects of global warming, however, are uncertain. Because temperature does not rise uniformly, and at certain times and places may actually cool, the term "global climate change" has come to be used. It is also likely that global climate change will alter overall climate patterns, and perhaps increase the number and intensity of such natural disasters as hurricanes. Although data are limited, and the cause cannot be ascertained, ocean water surface temperatures seems to be increasing globally, a phenomenon associated with decreased ocean productivity that also leads to such events as coral bleaching. Numerous unexpected consequences are also likely to follow from global climate change. For instance, one theory holds that global climate change will change deep water formation, eventually altering the Gulf Stream, leading to a cooling of Northern Europe and parts of North America. Indeed ocean and atmospheric effects are so interrelated that their effects need much more discussion in the public sphere.21
Managing climate change on a global level means lowering the amount of CO2 emission. Although automobile emissions are the most publicized source of global warming, the commercial and residential sectors each play a bigger role.22 In any case, since the time lag between CO2 emission and change in atmosphere is at least twenty years, managing climate change is an extraordinarily difficult global challenge. Climate change must be seen in the way it interacts with such other threats as water shortages, biodiversity loss, and disease, to create a complete picture of the threats we face.
One striking dissent to the consensus of environmentalists and sustainability scientists comes from Bjorn Lomberg, a former Greenpeace member. His The Skeptical Environmentalist claims that environmentalists have systematically picked the most extreme data supporting environmental problems, while ignoring contrary data, and that their alarmist predictions are pushing societies to commit their scarce resources on environmental problems 23 Lomberg's conclusions, however, have been rejected by numerous scientists, who accuse him of selective source use and misuse of statistics.
By contrast, the 2005 Millenium Ecosystem Assessment by the United Nations and the World Bank comes as close as any document to presenting the scientific consensus. Drawing upon the work of 1,360 experts worldwide, the document's Key Messages include that "Humans have made unprecedented changes to ecosystems," that have " weakened nature's ability to deliver … key services such as purification of air and water, protection from disasters, and the provision of medicines," and that we are on "the edge of a massive wave of species extinctions."24
Despite a clear environmental danger, and with the terms "sustainability" and "sustainable development" in ever-broader use, definitions remain contested. Critics contend that "sustainability" has become such an overused word as to lose much of its meaning. Julianne Lutz Newton and Eric T. Freyfogle, for instance, believe that "sustainability" has no clear goal, confusing sustaining natural systems with other human goals and values. They question sustainability's usefulness in synthesizing "three strands-the human health/social justice strand, the biodiversity/ecological process strand, and the agrarian strand."25
On the most basic level, Paul Reitan points out that, "surely no one would want simply to sustain the maximum number of humans organized into societies, knowing that that would mean existence at the barest, meanest survival level."26 Attempting to untangle and sharpen definitions, Julian Marshall and Michael Toffel discuss the great range of uses of "sustainability," from simply "a new term for responsible environmental and labor management practices" to "a vast, diverse set of goals, such as poverty elimination and fair and transparent governance."27 They then draw upon psychologist Abraham Maslow's Hierarchy of Needs, which ranges from basic physical survival, to social and individual needs, to artistic and spiritual values.
Transferring this to the realm of human and natural environment, Marshall and Toffel define four levels of sustainability, simplified as follows:
Marshall and Tofel suggest that a blurring of these meanings
has led to a devaluation of the term "Sustainability," and that
the top level needs to be dropped outright. Sorting out which
issues remain in the three highest levels, how to prioritize them,
and what policies will best address them remains a formidable
Sustainability, then, seems best defined beyond the barest survival limits, to include basic health and human rights, yet limited in prescribing values systems. This still leaves it an arguable and vexed termis democracy, for instance, a primary value from which sustainability flows, or might a more authoritarian system be better able to mandate sustainable practices (as with China's population control policies)? Yet it also seems as though, given its origins in international reports and conventions, sustainability seeks healthy human societies as its ultimate goal, but sees environmental health as crucial to achieving this goal.
Beyond a simple definition, the term "sustainability" exemplifies an awareness that environmental conservation alone is a problematic goal, since acting to enforce conservation always involves social and political issues. So Robert Paehlke defends the term: "as a social scientist, the concept is centered in economics, public policy, and ethics rather than in the biological sciences."28 Depending on one's perspective, then, sustainability may be an anthropomorphic enterprise in which the sciences serve as instruments toward larger social goals, or the environmental and social sciences may be seen as relatively equal partners.
With human society given a central role, it may be unrealistic to ask for the clarity of purpose associated with the natural sciences. One group of scientists, however, proposes "connecting ecosystems models (a relatively well developed field within ecology) with models of human system. . . . few scholars in either area have communicated actively with scholars in the other; however, it is this combination of disciplines that is necessary to fully analyze today's environmental problems."29 These model theories attempt connections, to simplify a fuzzy and astoundingly complex assemblage. It is a start. Sustainability issues, however, are likely to be played out in amorphous political realms in a process at least partly improvisational.
The challenge of sustainability, then, is one of doing good science, of collecting the best data and analyzing it in as many ways as possible, of never accepting any theory as final but continually testing, rethinking, and revising. It is also one of communication and connections, of acting within the social realm, of challenging people in their day-to-day lives and assumptions. It means that science cannot continue to operate in a pure realm removed from daily life, but must be intimately involved with politics and society.
Science, Practice, and Policy (a
joint project of CSA and the National Biological Information
Infrastructure) establishes a forum for cross-disciplinary
discussion of empirical and social sciences, practices, and
policies related to sustainability.
thanks to Carolyn Scearce for her invaluable help in writing this
overview, and to Bryan Flowers, Amy Forrester, Natasha Soderberg,
Fred Spangler, and Deborah Whitman.
Note: all internet citations were accessed on September 7, 2005
or September 9, 2005.
- World Commission on Environment
and Development. 1987. The Brundtland Report: Our Common Future.
Oxford University Press. See http://www.are.admin.ch/imperia/md/content/are/nachhaltige
795e0733fcc8db467b28f461d for an electronic version.
- Smith, Adam. 1776. An Inquiry into the Nature
and Causes of the Wealth of Nations. The Wealth of Nations.
London: Methuen and Company. 1904, 5th edition.
- Malthus, T. 1798. An Essay on the Principle
of Population, as it Affects the Future Improvement of Society
with Remarks on the Speculations of Mr. Godwin, M. Condorcet,
and Other Writers. London: Printed for J. Johnson, in St. Paul's
an electronic version.
- Diamond, J. 2005. Collapse: How Societies
Choose to Fail or Succeed. New York: Viking.
- Ibid, p. 176.
- Ibid, p. 304 ff.
- Club of Rome. 1972. The limits to growth.
Washington D.C.: Potomac Associates.
- Ehrlich. 1968. The Limits to Growth. New
York: Ballantine Books, p. 11.
- Simon, Julian. 1995. "The State of Humanity:
Steadily Improving." Cato Policy Report 17(5), September/October
1995: 131. See http://www.cato.org/pubs/policy_report/
pr-so-js.html for an electronic version. See http://en.wikipedia.org/wiki/Julian_Simon
for further discussion. See Ed Regis, 1997, The Doomslayer,
Wired Magazine 5(2) for an influential article on Julian Simon
(available at http://www.wired.com/wired/archive/5.02/ffsimon_pr.html).
- The following sources present good discussions
of New Orleans and its vulnerability to hurricanes:
Hurricane risk for New Orleans. 2002. American Radio Works.
Available at http://americanradioworks.publicradio.org/features/wetlands/hurricane1.html;
Sullivan B. 2005. Wetlands erosion raises hurricane risks. MSNBC.
- For more information see Susan Griffith,
2004, Myths surrounding Cuyahoga River fire 35 years ago, Eurekalert,
- Miller, J. Review of water resources and
desalination technologies. New Mexico: Sandia National Libraries.
- For a discussion of water conservation
methods see Bryan Flowers, 2004, Domestic water conservation:
Greywater, rainwater and other innovations, CSA http://www.csa.com/discoveryguides/water/overview.php.
- Waternet. 2002. Water, the blue gold of
the Middle East. Jerusalem: Palestinian Academic Society for
the Study of International Affairs.
- Brown, L. 2003. Plan B: Rescuing a Planet
under Stress and a Civilization in Trouble. New York: W.W. Norton
- Ibid, p. 117.
- Queensland Environmental Protection Agency.
2003. Air pollutants. http://www.epa.qld.gov.au/environmental_management/air/
- United States Environmental Protection
Agency. 2005. The effects of great lakes contaminants on human
- For discussions of invasive species see
Rob Hilton, 2002, Northern snakehead: An invasive fish species,
and Rob Hilton, 2000, Two invasive insect species from Asia,
- Costanza R., et al. 1997. The value of the
world's ecosystem services and natural capital. Nature 387(6230).
Available online at
- For discussions of ocean-atmospheric interactions
see Katina Bucher Norris, 2003, Dimethylsulfide emission: climate
control by marine algae?, CSA http://www.csa.com/discoveryguides/dimethyl/overview.php;
and Ben Fertig, 2004, Ocean gardening using iron fertilizer,
- Energy Information Administration. 2003.
Emissions of greenhouse gases in the United States, executive
- Lomberg, B. 2001 (1998 in Danish). The Skeptical
Environmentalist. Cambridge: Cambridge University Press.
- United Nations and World Bank. 2005. Millenium
Ecosystem Reports. See http://www.millenniumassessment.org/en/index.aspx
for complete information.
- Lutz Newton, J., Freyfogle, E. 2005. Conservation
forum: Sustainability: A dissent. Conservation Biology 19(1):
36-38, p. 29.
- Reitan, P. 2005. Sustainability science
- and what's needed beyond science. Sustainability: Science,
Practice, and Policy. CSA & the National Biological Information
- Marshall, J. & Toffel, M. 2005. Framing
the elusive concept of sustainability: a sustainability hierarchy.
Environmental Science and Technology 39(3): 673-82, p. 673.
- Paehlke, R. 2005. Conservation forum: Sustainability
as a bridging concept. Conservation Biology 19(1): 36-38, p.
- Costanza, R., Bobbi L., Ostrom, E., & Wilson,
J. 2001. Ecosystems and human systems: a framework for exploring
the linkages." In R. Costanza, B. Low, E. Ostrom, & J. Wilson
(Eds.), Institutions, Ecosystems, and Sustainability. pp. 3-20.
New York: Lewis Publishers.