Minnesotans For Sustainability©
Sustainable: A society that balances the environment, other life forms, and human interactions over an indefinite time period.
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A Synopsis Limits to Growth, The 30‑Year Update
Donella Meadows, Jorgen Randers, Dennis Meadows*
The signs are everywhere around us: • Sea level has risen 10‑20 cm since 1900. Most non‑polar glaciers are retreating, and the extent and thickness of Arctic sea ice is decreasing in summer. • In 1998 more than 45 percent of the globe's people had to live on incomes averaging $2 a day or less. Meanwhile, the richest onefifth of the world's population has 85 percent of the global GNP. And the gap between rich and poor, is widening. • In 2002, the Food and Agriculture Organization of the UN estimated that 75 percent of the world's oceanic fisheries were fished at or beyond capacity. The North Atlantic cod fishery, fished sustainably for hundreds of years, has collapsed, and the species may have been pushed to biological extinction. • The first global assessment of soil loss, based on studies of hundreds of experts, found that 38 percent, or nearly 1.4 billion acres, of currently used agricultural land has been degraded. • Fifty‑four nations experienced declines in per capita GDP for more than a decade during the period 1990‑2001. These are symptoms of a world in overshoot, where we are drawing on the world's resources faster than they can be restored, and we are releasing wastes and pollutants faster than the Earth can absorb them or render them harmless. They are leading us toward global environmental and economic collapse —but there may still be time to address these problems and soften their impact. We've been warned before. More than 30 years ago, a book called The Limits to Growth created an international sensation. Commissioned by the Club of Rome, an international group of businessmen, statesmen, and scientists, The Limits to Growth was compiled by a team of experts from the U.S. and several foreign countries. Using system dynamics theory and a computer model called "World3," the book presented and analyzed 12 scenarios that showed different possible patterns —and environmental outcomes— of world development over two centuries from 1900 to 2100. The World3 scenarios showed how population growth and natural resource use interacted to impose limits to industrial growth, a novel and even controversial idea at the time. In 1972, however, the world's population and economy were still comfortably within the planet's carrying capacity. The team found that there was still room to grow safely while we could examine longer‑term options. In 1992, this was no longer true. On the 20th anniversary of the publication of Limits to Growth, the team updated Limits in a book called Beyond the Limits. Already in the 1990s there was compelling evidence that humanity was moving deeper into unsustainable territory. Beyond the Limits argued that in many areas we had "overshot" our limits, or expanded our demands on the planet's resources and sinks beyond what could be sustained over time.1 The main challenge identified in Beyond the Limits was how to move the world back into sustainable territory.
Now in a new study, Limits to Growth: The 30‑Year Update, the authors have produced a comprehensive update to the original Limits, in which they conclude that humanity is dangerously in a state of overshoot. While the past 30 years has
shown some progress, including new technologies, new institutions, and a new
awareness of environmental problems, the authors are far more pessimistic than
they were in 1972. Humanity has squandered the opportunity to correct our
current course over the last 30 years, they conclude, and much must change if
the world is to avoid the serious consequences of overshoot in the 21st
century. Ecological Footprint versus Carrying Capacity
On the contrary, as noted energy economist Matthew Simmons recently wrote, "The most amazing aspect of the book is how accurate many of the basic trend extrapolations ... still are some 30 years later." For example, the gap between rich and poor has only grown wider in the past three decades. Thirty years ago, it seemed unimaginable that humanity could expand its numbers and economy enough to alter the Earth's natural systems. But experience with the global climate system and the stratospheric ozone layer have proved them wrong. All the environmental and economic problems discussed in Limits to Growth have been treated at length before. There are hundreds of books on deforestation, global climate change, dwindling oil supplies, and species extinction. Since The Limits to Growth was first published 30 years ago, these problems have been the focus of conferences, scientific research, and media scrutiny. What makes Limits to Growth: The 30‑Year Update unique, however, is that it presents the underlying economic structure that leads to these problems. Moreover, Limits is a valuable reference and compilation of data. The authors include 80 tables and graphs that give a comprehensive, coherent view of many problems. The book will undoubtedly be used as a text in many courses at the college level, as its two earlier versions have been. The World3 computer model is complex, but its basic structure is not difficult to understand. It is based in system dynamics —a method for studying the world that deals with understanding how complex systems change over time. Internal feedback loops within the structure of the system influence the entire system behavior. World3 keeps track of stocks such as population, industrial capital, persistent pollution, and cultivated lands. In the model, those stocks change through flows such as births and deaths; investment and depreciation; pollution generation and pollution assimilation; land erosion, land development, and land removed for urban and industrial uses. The model accounts for positive and negative feedback loops that can radically affect the outcome of various scenarios. It also develops nonlinear relationships. For example, as more land is made arable, what's left is drier, or steeper, or has thinner soils. The cost of coping with these problems dramatically raises the cost of developing the land —a nonlinear relationship. Feedback loops and nonlinear relationships make the World3 dynamically complex, but the model is still a simplification of reality. World3 does not distinguish among different geographic parts of the world, nor does it represent separately the rich and poor. It keeps track of only two aggregate pollutants, which move through and affect the environment in ways that are typical of the hundreds of pollutants the economy actually emits. It omits the causes and consequences of violence. And there is no military capital or corruption explicitly represented in World3. Incorporating those many distinctions, however, would not necessarily make the model better. And it would make it very much harder to comprehend. This probably makes the World3 highly optimistic. It has no military sector to drain capital and resources from the productive economy. It has no wars to kill people, destroy capital, waste lands, or generate pollution. It has no ethnic strife, no corruption, no floods, earthquakes, nuclear accidents, or AIDS epidemics. The model represents the uppermost possibilities for the "real" world. Readers who want to reproduce the World 3 scenarios of the book can do so themselves, because the authors have prepared interactive World 3 CDs. To order disks, please see back of title page. [See below] The authors developed World3 to understand the broad sweep of the future —the possible behavior patterns, through which the human economy will interact with the carrying capacity of the planet over the coming century. World3's core question is, How may the expanding global population and materials economy interact with and adapt to the earth's limited carrying capacity over the coming decade? The model does not make predictions, but rather is a tool to understand the broad sweeps and the behavioral tendencies of the system. The most common criticisms of the original World3 model were that it underestimated the power of technology and that it did not represent adequately the adaptive resilience of the free market. Impressive —and even sufficient— technological advance is conceivable, but only as a consequence of determined societal decisions and willingness to follow up such decisions with action and money. Technological advance and the market are reflected in the model in many ways. The authors assume in World3 that markets function to allocate limited investment capital among competing needs, essentially without delay. Some technical improvements are built into the model, such as birth control, resource substitution, and the green revolution in agriculture. But even with the most effective technologies and the greatest economic resilience that seems possible, if those are the only changes, the model tends to generate scenarios of collapse. One reason technology and markets are unlikely to prevent overshoot and collapse is that technology and markets are merely tools to serve goals of society as a whole. If society's implicit goals are to exploit nature, enrich the elites, and ignore the long term, then society will develop technologies and markets that destroy the environment, widen the gap between rich and poor, and optimize for short‑term gain. In short, society develops technologies and markets that hasten a collapse instead of preventing it. The second reason for the vulnerability of technology is that adjustment mechanisms have costs. The costs of technology and the market are reckoned in resources, energy, money, labor, and capital.
For
more than a century, the world has been experiencing exponential growth in a
number of areas, including population and industrial production. Positive
feedback loops can reinforce and sustain exponential growth. In 1650, the
world's population had a doubling time of 240 years.
Moreover, in the current system, economic growth generally occurs in the already rich countries and flows disproportionately to the richest people within those countries. Thus, according to the United Nations Development Program, the 20 percent of the world's people who lived in the wealthiest nations had 30 times the per capita income of the 20 percent who lived in the poorest nations. By 1995 the average income ratio between the richest and poorest 20 percent had increased from 30:1 to 82:1. Only eight percent of the world's people own a car. Hundreds of millions of people live in inadequate houses or have no shelter at all —much less refrigerators or television sets. Social arrangements common in many cultures systematically reward the privileged, and it is easier for rich populations to save, invest, and multiply their capital. Limits to growth include both the material and energy that are extracted from the Earth, and the capacity of the planet to absorb the pollutants that are generated as those materials and energy are used. Streams of material and energy flow from the planetary sources through the economic system to the planetary sinks where wastes and pollutants end up. There are limits, however, to the rates at which sources can produce these materials and energy without harm to people, the economy, or the earth's processes of regeneration and regulation. Resources can be renewable, like agricultural soils, or nonrenewable, like the world's oil resources. Both have their limits. The most obvious limit on food production is land. Millions of acres of cultivated land are being degraded by processes such as soil erosion and salinization, while the cultivated area remains roughly constant. Higher yields have compensated somewhat for this loss, but yields cannot be expected to increase indefinitely. Per capita grain production peaked in 1985 and has been trending down slowly ever since. Exponential growth has moved the world from land abundance to land scarcity. Within the last 35 years, the limits, especially of areas with the best soils, have been approached. Another limit to food production is water. In many countries, both developing and developed, current water use is often not sustainable. In an increasing number of the world's watersheds, limits have already been reached. In the U.S. the Midwestern Ogallala aquifer in Kansas is overdrawn by 12 cubic kilometers each year. Its depletion has so far caused 2.46 million acres of farmland to be taken out of cultivation. In an increasing number of the world's watersheds, limits have already, indisputably, been exceeded. In some of the poorest and richest economies, per capita water withdrawals are going down because of environmental problems, rising costs, or scarcity. Another renewable resource is forests, which moderate climate, control floods, and harbor species, from rattan vines to dyes and sources of medicine. But today, only one‑fifth of the planet's original forest cover remains in large tracts of undisturbed natural forests. Although forest cover in temperate areas is stable, tropical forest area is plummeting. From 1990 to 2000, the FAO reports that more than 370 million acres of forest cover —an area the size of Mexico— was converted to other uses. At the same time that forests decline, demand for forest products is growing. If‑the loss of 49 million acres per year, typical in the 1990s, continues to increase at 2 percent per year, the unprotected forest will be gone before the end of the century.
A
prime example of a nonrenewable resource is fossil fuels, whose limits should
be obvious, although many people, including distinguished economists, are in
denial over this elementary fact. More
Nonetheless the stock of reserves is finite and nonrenewable. Moreover, fossil
fuels use is limited by the planet's capacity to absorb their byproducts after
burning, such as the greenhouse gas carbon dioxide. Fossil fuels may be
limited by both supply and sinks. Peak gas production will certainly occur in
the next 50 years; the peak for oil production will occur much sooner,
probably within the next decade. Energy efficiency and renewables offer the
best prospect for a sustainable future.
It is
important to distinguish between money and the real things money stands for.
This figure shows how the economy is represented in World3. The emphasis is on
the physical economy, the real things to which the earth's limits apply, not
the monetary economy, which is a social invention not constrained by the
physical laws of the planet. Industrial capital refers here to actual hardware
—the machines and factories
that produce manufactures products. The
production and allocation of industrial output are central to the behavior of
the simulated economy in World3. The amount of industrial capital determines
how much industrial output can be produced each year. This output is allocated
among five sectors in a way that depends on the goals and needs of the
population. Some industrial capital is consumed; some goes to the resource
sector to secure raw materials. Some goes to agriculture to develop land and
raise land yield. Some is invested in social services, and the rest is
invested in industry to offset depreciation and raise the industrial capital
stock further.
But if
an eventual nine billion people on earth all consumed materials at the rate of
the average American, world steel production would need to rise by a factor of
five, copper by a factor of eight, and aluminum by a factor of nine.
Such
materials flows are neither possible nor necessary. Fortunately, growth in
materials consumption has slowed, and the prospects for further slowing are
good. The possibilities for recycling, greater efficiency, increased product
lifetime, and source reduction in the world of materials are exciting. On a
global scale, however, they have not yet reduced the vast materials flow
through the economy. At best, they have slowed its rate of growth.
Another fundamental limit to growth is sinks —the capacity of the planet to
absorb the pollution and waste resulting from human economic activity. The
most intractable wastes are nuclear wastes, hazardous wastes (like human
synthesized chemicals), and greenhouse gases. They are chemically the hardest to sequester or
detoxify, and economically and politically the most difficult to regulate. Current atmospheric
concentrations of carbon dioxide and methane are far higher than they have
been in 160,000 years. It may take decades for the consequences of climate
change to be revealed in melting ice, rising seas, changing currents, greater
storms, shifting rainfall, and migrating insects, birds or mammals. It is also
plausible that climate may change rapidly. Using the World3 computer model, Limits to
Growth: The 30‑Year Update presents 10 different scenarios for the
future, through the year 2100. In each scenario a few numbers are changed to
test different estimates of "real world" parameters, or to incorporate
optimistic predictions about the development of technology, or to see what
happens if the world chooses different policies, ethics, or goals. Most of the
scenarios presented in Limits result in overshoot and collapse —through depletion of resources, food
shortages, industrial decline, or some combination of these or other factors. Under the "business as usual
scenario," world society proceeds in a traditional manner without major
deviation from the policies pursued during most of the 20th century. In this
scenario, society proceeds as long as possible without major policy change.
Population rises to more than seven billion by 2030. But a few decades into
the 21st century, growth of the economy stops and reverses abruptly. As natural
resources become harder to obtain, capital is diverted to extracting more of
them. This leaves less capital for investment in industrial output. The result
is industrial decline, which forces declines in the service and agricultural
sectors. About the year 2030, population peaks and begins to decrease as the
death rate is driven upward by lack of food and health services.
This
table postulates that advances in resource extraction technologies are capable
of postponing the onset of increasing extraction costs. Industry can grow 20
years longer. Population peaks at 8 billion in 2040, at much higher
consumption levels. But pollution levels soar (outside the graph!), depressing
land yields and requiring huge investments in agricultural recovery. The
population finally declines because of food shortages and negative health
effects from pollution. Other scenarios address the
problems of pollution and food shortages by assuming more effective pollution
control technologies, land enhancement (an increase in the food yield per unit
of land), and protections against soil erosion. Even a scenario with these
features however, results in overshoot and collapse. After 2070 the costs of
the various technologies, plus the rising costs of obtaining nonrenewable
resources from increasingly depleted mines, demand more capital than the
economy can provide. The result is rather abrupt decline. If to this scenario one adds
reductions in the amount of nonrenewable resources needed per unit of
industrial output (resource efficiency technology), in combination all these
features permit a fairly large and prosperous world, until the bliss starts
declining in response to the accumulated cost of the technologies. This technology program comes
online too late to avoid a gradual decline in human welfare throughout the
century. By the end of the 21st century, a stable population of less than
eight billion people is living in a high‑tech, low pollution world with a
human welfare index roughly equal to that of the world of 2000. But industrial output begins
to decline around 2040 because the rising expense of protecting the population
from starvation, pollution, erosion, and resource shortage cuts into the
capital available for growth. Ultimately this simulated world fails to sustain
its living standards as technology, social services, and new investment
simultaneously become too expensive.
Transitions to a Sustainable World The world can respond in three ways to signals that
resource use and pollution emissions have gone beyond their sustainable
limits. One way is to disguise, deny, or confuse the signals. Generally this
takes the form of efforts to shift costs to those who are far away in space
and time. An example would be to buy air conditioners for relief from a
warming climate, or to ship toxic wastes for disposal in a distant region. A second way is to alleviate
the pressures from limits by employing technical or economic fixes. For
example, reducing the amount of pollution generated per mile of driving or per
kilowatt of electricity generated. These approaches, however, will not
eliminate the causes of these pressures. The third way is to work on the
underlying causes, to recognize that the socioeconomic system has overshot its
limits, is headed toward collapse, and therefore seek to change the structure
of the system. World3 can be used to test some of the simplest changes that
might result from a society that decides to back down from overshoot and
pursue goals more satisfying and sustainable than perpetual material growth. Scenario 7 supposes that
after 2002, all couples decide to limit their family size to two children and
have access to effective birth control technologies. Because of age structure
momentum, the population continues to grow for another generation. But the
slower population growth permits industrial output to rise faster, until it is
stopped by rising pollution. Under this scenario, world
population peaks at 7.5 billion in 2040. A globally effective, two children
policy introduced in 2002 reduces the peak population less than 10 percent.
Because of slower population growth, consumer goods per capita, food per
capita, and life expectancy are all higher than in the scenario where the
world's endowment of natural resources was doubled. But industrial output peaks
in 2040 and declines. The larger capital plant emits more pollution, which
has negative effects on agricultural production. To sustain food production,
capital must be diverted to the agricultural sector. Later on, after 2050,
pollution levels are sufficiently high to have negative impacts on life
expectancies.
Nonlinear Costs of
Pollution Abatement The air pollutant NOx
can be removed from emissions to a significant degree at a low cost, but at
some level of required abatement the cost of further removal rises
precipitously. The marginal cost curve for NOx removal is
calculated for 2010 for OECD Europe and the former USSR in euros per ton.
(Source: J. R. Alcamo et al.) If the model society both
adopts a desired family size of two children and sets a fixed goal for
industrial output per capita, it can extend somewhat the "golden age" of
fairly high human welfare between 2020 and 2040 in the previous scenario. But
pollution increasingly stresses agricultural resources. Per capita food
production declines, eventually bringing down life expectancy and population. These changes cause a
considerable rise in consumer goods and services per capita in the first
decade after the year 2002. In fact, they rise higher and faster than they did
in the previous run, where industrial growth was not curtailed. But this economy is not
quite stabilized. It has an ecological footprint above the sustainable level,
and it is forced into a long decline after 2040. The world of Scenario 8 manages
to support more than seven billion people at an adequate standard of living
for almost 30 years, from 2010 to 2040, but during that time the environment
and soils steadily deteriorate. To remain sustainable, the world in this
scenario needs to lower its ecological footprint to a level below the carrying
capacity of the global environment. Scenario 9: World Seeks Stable
Population and Stable Industrial Output per Person, and Adds Pollution,
Resource and Agricultural Technologies from 2002. Moving in this direction, in
another scenario the world seeks stable population and stable industrial
output per person, and adds pollution, resource and agricultural technologies
starting in 2002. In this scenario, population
and industrial output are limited as in the previous run, and in addition
technologies are added to abate pollution, conserve resources, increase land
yield, and protect agricultural land. The resulting society is sustainable:
Nearly eight billion people live with high human welfare and a continuously
declining ecological footprint. Under this scenario, the world
decides on an average family size of two children and sets modest limits for
material production, as in the previous scenario. Further, starting in 2002 it
begins to develop, invest in, and employ the technologies that increase the
efficiency of resource use, decrease pollution emissions per unit of
industrial output, control land erosion, and increase land yields until food
per capita reaches its desired level. The society of this scenario
manages to begin reducing its total burden on the environment before the year
2020; from that point the total ecological footprint of humanity is actually
declining. The system brings itself down below its limits, avoids an
uncontrolled collapse, maintains its standard of living, and holds itself very
close to equilibrium. In a final
scenario, the sustainability policies of the previous scenario are introduced
20 years earlier, in 1982. Moving toward sustainability
20 years sooner would have meant a lower final population, less pollution,
more nonrenewable resources, and a slightly higher average welfare for all.
Under this scenario, population levels off just above six billion instead of
eight billion. Pollution peaks at a much lower level and 20 years sooner, and
interferes less with agriculture than it did in the previous scenario. Life
expectancy surpasses 80 years and remains high. Life expectancy, food per
capita, services per capita, and consumer goods per capita all end up at
higher levels than they did in the previous scenario.
Scenario 9: World Seeks Stable
Population and Stable Industrial Output per Person, and Adds Pollution,
Resource, and Agricultural technologies from 2002
In this scenario population and industrial output are limited,
and in addition technologies are added to abate pollution, conserve resources,
increase land yield, and protect agricultural land. The resulting society is
sustainable: Nearly 8 billion people live with high human welfare and a
continuously declining ecological footprint.
The final four scenarios also suggest some general
conclusions: • A global transition to a
sustainable society is probably possible without reductions in either population or
industrial output. • A
transition to sustainability will require an active decision to reduce the human
ecological footprint. •
There are many choices that can be made about numbers of people, living
standards, technological investment, and allocations among industrial goods,
services, food, and other material needs. •
There are many trade‑offs between the number of people the earth can sustain
and the material level at which each person can be supported. •
The longer the world takes to reduce its ecological footprint and move toward
sustainability, the lower the population and material standard that will be
ultimately supportable. •
The higher the targets for population and material standard of living are
set, the greater the risk of exceeding and eroding its limits. In 1987, the World Commission on Environment and
Development put the idea of sustainability into these words: A sustainable society is
one that "meets the needs of the present without compromising the
ability of future generations to meet their own needs." Such a society, with a
sustainable ecological footprint, would be almost unimaginably different from
the one in which most people now live. Before we can elaborate on what
sustainability could be, we need to start with what it need not be. Sustainability
does not mean zero growth. Rather, a sustainable society would
be interested in qualitative development, not physical expansion. It would use
material growth as a considered tool, not a perpetual mandate. Neither for nor
against growth, it would begin to discriminate among kinds of growth and
purposes for growth. It would ask what the growth is for, and who would
benefit, and what it would cost, and how long it would last, and whether the
growth could be accommodated by the sources and sinks of the earth. A sustainable
society would also not paralyze into permanence the current inequitable
patterns of distribution. For both practical and moral reasons,
a sustainable society must provide sufficiency and security for all. A
sustainable society would not be a society of despondency and stagnation,
unemployment and bankruptcy that current systems experience when their growth
is interrupted. A deliberate transition of sustainability would take place slowly enough, and with enough
forewarning, so that people and businesses could find their places in the new
economy. A
sustainable world would also not be a rigid one, with population or production
or anything else held pathologically constant. One of
the strangest assumptions of present‑day mental models is the idea that a
world of moderation must be one of strict, centralized government control. A
sustainable world would need rules, laws, standards, boundaries, social
agreements and social constraints, of course, but rules for sustainability
would be put into place not to destroy freedoms, but to create freedoms or
protect them.
Some people think that a sustainable society would have to stop using
nonrenewable resources. But that is an over‑rigid interpretation of what
it means to be sustainable. Certainly a sustainable society would use
nonrenewable gifts from the earth's crust more thoughtfully and efficiently.
The
authors do suggest a few general guidelines for what sustainability would look
like, and what steps we should take to get there:
•
Extend the planning horizon. Base the choice among current options much more on their long‑term costs and benefits.
•
Improve the signals. Learn more about the real welfare of human population and the real impact on the world ecosystem of human activity.
•
Speed up response time. Look actively for signals that indicate when the
environment or society is stressed. Decide in advance what to do if problems
appear.
•
Minimize the use of nonrenewable resources.
•
Prevent the erosion of renewable resources.
•
Use all resources with maximum efficiency.
•
Slow and eventually stop exponential growth of population and physical
capital. The necessity of
taking the industrial world to its next stage of evolution is not a disaster —it
is an amazing opportunity. How to seize the opportunity, how to bring
into being a world that is not only sustainable, functional, and equitable but
also deeply desirable is a question of leadership and ethics and vision and
courage, properties not of computer models but of the human heart and soul.
Donella Meadows,
who died unexpectedly in 2001, was a systems analyst and adjunct professor of
Environmental Studies at Dartmouth College. She wrote the nationally syndicated
newspaper column "The Global Citizen."
Jorgen Randers
is professor and former President of the Norwegian School of Management. He is
also former Deputy Director General of World Wildlife Fund International. He
lives in Oslo, Norway.
Dennis Meadows
has served on the faculties and directed research centers at MIT, Dartmouth
College, and the University of New Hampshire. He is President of the Laboratory
for Interactive Learning. He lives in Durham, New Hampshire. Publishers: |
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