|
Items in cart [4] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 5903
Proc. Natl. Acad. Sci. USA
Vol. 96, pp. 5903-5907, May 1999
Colloquium Paper
This paper is the introduction to the following papers, which were presented at the National Academy of Sciences
colloquium "Plants and Population: Is There Time?" held December 5-6, 1998, at the Arnold and Mabel
Beckman Center in Irvine, CA.
Plants and population: Is there time?
NINA V. FEDOROFF*l AND JOEL E. COHENT
*Biotechnology Institute, The Pennsylvania State University, University Park, PA 16802; and [Laboratory of Populations, Rockefeller University and
Columbia University, New York, NY 10021-6399
Historical Background
The year 1998 was the 200th anniversary of the publication of
Malthus's famous first essay on population (1~. Malthus argued
that agriculture could not increase production as fast as the lust
between the sexes would inevitably increase population size,
and therefore that humans were condemned to poverty, fam-
ine, pestilence, and vice. Malthusian worries have been echoed
by many since Malthus first wrote. Today discussions about the
future growth of food supply and population are increasingly
informed by the awareness that human activities impinge on
the Earth's ability to sustain them. There is concern about the
ecological and environmental consequences of expanding the
food supply further to feed the still rapidly growing numbers
of humans.
In 1968, a young Stanford biologist named Paul Ehrlich
published a short book called The Population Bomb (2~. This
widely read book warned of the dangers of continuing rapid
population growth, especially in the poor countries of the
world. In the same year, 1968, J. George Harrar, President of
the Rockefeller Foundation, gave a talk entitled "Plant Pa-
thology and World Food Problems" before the First Interna-
tional Congress of Plant Pathology in London (3~. Harrar
celebrated the cultural and material achievements of humans
but emphasized the need for scientists to help solve the
persistent problems of "wars, ..., hunger, poverty, disease,
ignorance, social and cultural deprivation, and overpopula-
tion." Harrar noted that there were then just under 3.5 billion
people in the world and anticipated 6 billion by the year 2000.
He urged the development of improved forms of contracep-
tion. "If there is evidence that birth rates can and will be
reduced, vast effort to augment world food supplies will then
become increasingly meaningful" (ref. 3, p. 587~.
Harrar described the past contributions of plant pathology
to the increase of crop production and the need to apply recent
progress in biology to increase food production. "Genetic
manipulation of plant species is as old as plant breeding, but
its modern aspects offer exciting new possibilities for disease
control as well as for greater productivity. It is becoming
increasingly possible to map and identify the genes controlling
a variety of functions and to introduce or extract genetic factors
for a variety of traits, including disease resistance, increased
yields, tolerance to heat, cold, and drought, photoperiod
insensitivity, and increased amino acid content of food prod-
ucts. Currently, efforts are also being made to collect, identify,
and store genes. Scientists can then draw on these 'germplasm
banks' as they are needed" (ref. 3, p. 593~.
After discussing "one highly interesting form of biological
engineering," the then new IR8 rice variety, "which has been
remarkably successful in most rice-producing regions," Harrar
noted public concern about problems of food and population.
PNAS is available online at www.pnas.org.
He concluded "with cautious optimism." His optimism was
limited by "the alarming fashion in which scientific and social
advances are changing the quality of our environment, tin-
cluding] the destruction of our soils and water courses, nega-
tive interference with the food cycle, and positive pollution of
Ella air Pn`~el~nP.
_~^ ~^ _A^~ if_ ~ ~ ~ Agriculture, too. complicates the ecolog-
ical pattern . . . " Thus "scientific and social advances" were
and are accompanied by negative as well as positive effects.
The challenge of finding a desirable balance among the
inevitable tradeoffs remains.
In retrospect, Harrar's assessment seems surprisingly pre-
scient and modern. The rice variety IR8 was a leading entry in
the Green Revolution. Complex changes in varieties planted,
farmer education, farm management, credit institutions, agri-
cultural extension, irrigation, and chemicals applied as biocides
and fertilizers combined to increase food production faster
than population grew in certain areas. Since 1968, despite
rising total numbers of people, increased food production and
changes in the distribution of access to food have reduced the
absolute number and the fraction of people estimated to be
chronically undernourished in every region of the world except
sub-Saharan Africa. Yet despite this remarkable progress, an
estimated three-quarters of a billion people still suffer from
undernutrition.
Demographic Situation and Prospect: The Challenge
The global population growth rate reached an all-time high of
2.1% per year just as Ehrlich and Harrar were writing. The
annual rate of increase has since declined by about one-third
to roughly 1.4% (4~. Global population size is expected to pass
6 billion in 1999. Apart from the catastrophic effects of AIDS
across the middle of Africa and the collapse of the economy
of the former Soviet Union, life expectancies have increased
almost everywhere, indicating overall better human health.
These increases in life expectancy are largely attributable to
improvements in sanitation, diet, reductions of environmental
hazards, behavior, and, to a limited extent, improvements in
medical care. The clouds that Harrar foresaw on the environ-
mental horizon have cleared in some places and darkened in
others. Although the quality of air and water have improved in
some developed countries, they have deteriorated in many less
developed countries. Moreover, in some areas, withdrawals of
water for agriculture are unsustainable; in many places, water
use in agriculture is both technically and economically ineffi-
cient. The adverse effects of treating common resources (such
as marine fisheries, water supplies, biological diversity, the
atmosphere, and some land and forest areas) as unlimited and
free have become more evident. Human interventions in
global geochemical cycles of water, nitrogen, carbon, methane,
iTo whom reprint requests should be addressed. e-mail: nvfl@
psu.edu.
5903
OCR for page 5904
5904 Colloquium Paper: Fedoroff and Cohen
and other compounds and elements have outpaced scientific
capacity to anticipate reliably the effects of these interventions.
Will the food supply keep up with human population growth
over the next half century, and if so, at what costs to other
aspects of the quality of life for present and future generations?
Answers will depend on economics, environments, and cul-
tures as much as on population sizes. Answers will differ
depending on whether the query is local, national, or global.
Nevertheless, it is helpful to start with a rough picture of
population sizes that can reasonably be anticipated, as well as
their distribution. Currently the global population of nearly 6
billion is increasing by about 80 million people per year. Were
growth to continue at this annual rate of 1.4%, the population
size would double to 12 billion in roughly 50 years. Most
demographers view this scenario as unlikely because the rate
of increase in population size has been declining for several
decades and the absolute number of people added annually to
the global population has been dropping since roughly 1990. It
now appears unlikely that 6 billion more people will be added
to today's 6 billion. At the opposite extreme, if the annual
increase in population were to drop linearly from today's 80
million to zero over SO years, then the average annual increase
would be 40 million per year for 50 years. Population would
increase by 2 billion people to give a population size of 8 billion
in the year 2050. This optimistic scenario requires continuing
and accelerating declines in fertility in presently poor countries
with high fertility rates. Between these extremes, it is plausible
to imagine a population size in 2050 of 9 or 10 billion (5, 6~.
Remembering that the human population numbered only 3
billion as recently as 1960, these numbers can only be viewed
with awe.
In 1998, roughly 1.2 billion people one person in five-
lived in the developed countries, defined as North America
north of the Rio Grande, Europe, Japan, Australia, and New
Zealand, and sometimes including some smaller Asian coun-
tries. Most of these countries have fertility rates below re-
placement levels (6) and little if any of the next half century's
population growth is expected to occur in these countries. But
unless the pace of economic and educational development
accelerates markedly, the fraction of people living in devel-
oping countries will increase from 4 in 5 at the end of the 20th
century to as many as 9 in 10 by 2050. The population density
in the developed countries is currently about 22 people per
km2, whereas that in the developing countries is roughly 55
people per km2. The latter number will roughly double to 100
people per km2 if global population grows to 10 billion, largely
as a result of increases in the developing countries. This is one
person per hectare. Attaining acceptable qualities of life in
developing countries at such population densities will be a
challenge of unprecedented proportions.
About 3 billion people presently live in the rural areas of
developing countries. According to some demographic pro-
jections, this number is not expected to change much over the
next half century, whereas the number of urban people in
developing countries is expected to grow enormously, by as
many as 3-5 billion (5 ). If these expectations are realized, then
in the developing world roughly the same number of rural
people will have to provide a very much larger number of
urban people with food and fiber or these products of agri-
culture will need to be acquired from the developed world by
trade or gift.
In 1998, the distinguished Australian plant physiologist
Lloyd T. Evans reviewed the intertwined history of human
population growth and agricultural development (7~. He
wrote: ". . . not only has agricultural evolution made increase
in population possible indeed it has been blamed for it but
also ... population growth has driven the development of
agriculture.... [Nevertheless,] the path to feeding the ten
billion in a sustainable way is still by no means clear."
Proc. Natl. Acad. Sci. USA 96 (1999)
Colloquium Goals and Structure
The National Academy of Sciences Colloquium titled "Plants
and Population: Is there time?" was organized to shed light on
how the world will feed its still expanding population in a
sustainable way while maintaining enough wildlands to sup-
port and preserve essential ecosystems services and biodiver-
sity. The magnitude and activities of the human population
make the task more complex than ever and more critical. The
Colloquium brought together economists, demographers and
other social scientists, as well as agronomists, biotechnologists,
geneticists, and ecologists.
Ismail Serageldin, the Vice President for Special Programs
of the World Bank, provided a forward-looking overview in his
after-dinner address. He emphasized that the currently rich
countries have agricultural and institutional needs that differ
importantly from those of the currently poor countries. The
responses of the rich countries will not automatically satisfy the
needs of the poor. He emphasized the need to design an
international system of intellectual property that balances the
private-property interests of the rich countries with the public-
good needs of the poor.
The four scientific sessions focused on: demographic and
economic projections of food demand and supply; limits on
land, water, energy, and biological resources in agriculture;
plant biotechnology; and biodiversity and multiple land use
demands. Dominated by representatives of a single discipline,
each session produced a markedly different vision of our
planetary future.
Insights from the Colloquium
Different disciplines approached the Colloquium's central
question from very different perspectives, made widely differ-
ent assumptions, and applied different yardsticks to measure
success. Participants' spirits were alternately lifted by projec-
tions of sustained expansion of productivity and of as yet barely
imaginable improvements in both the health and healthfulness
of crop plants, then dashed by predictions of the swiftly
approaching limits of plant productivity, constraints on the
availability of land, water, and other resources, and threats to
the sustainability of natural and anthropogenic ecological
processes and systems.
The first session, dominated by economists, examined the
forces that shape agricultural production today. Cereal pro-
duction per person world-wide peaked in the mid-1980s,
declined over the next decade, then began to grow again in the
mid-199Os, according to speaker Nikos Alexandratos. Histor-
ical economic analyses showed that the decline, far from being
a first harbinger of inadequate world food supply, was largely
the result both of deliberate efforts to decrease overproduction
in Europe and North America, where prices fell because
production capacity exceeded demand, and of the collapse of
the Soviet Union. Intentional cutbacks in production, despite
persistent undernutrition in some parts of the world, resulted
from the difference between effective demand cash exer-
cised in the market and the need for calories and nutrients
adequate for health, which does not depend on income.
Speaker Tim Dyson addressed the profound differences in
progress toward food self-sufficiency in different parts of the
world. Speaker Gale Johnson pointed out that low grain prices
on world markets have been a signal for some governments and
international donors to reduce support of agricultural re-
search, thereby hampering the capacity of the agricultural
system to respond to future changes. Dyson noted that much
agricultural research has bypassed Africa, where needs for
additional food are most acute.
Speakers Tim Dyson, Robert Evenson, Gale Johnson, and
Nikos Alexandratos all agreed that the growth in the world's
effective demand for food with increasing population could be
OCR for page 5905
Colloquium Paper: Fedoroff and Cohen
met by the world's agricultural system as a whole, although they
differed in the optimism of their projections. Alexandratos
reported projections that the average cereals yield of the
developing countries would grow at 1.5% per year until 2010,
down from 2.2~o per year in the past. Based on macroeconomic
projections that the currently poor countries will not achieve
the levels of income of the currently rich countries within the
next few decades, Alexandratos pointed out that a decline in
global cereal production per person will not necessarily mean
an equivalent decline in the average calories consumed per
person. This apparent paradox arises because population will
grow predominantly in the less developed countries where
people consume three to four times fewer primary plant
calories per day (as plant and animal products) than do people
in developed countries. These projections assume, therefore,
that current differences between countries in primary caloric
consumption rates will persist. All of the speakers in this
session acknowledged that population increases in some of the
least agriculturally productive countries were not likely to be
met by local increases in production and would require in-
creased transfer of agricultural products through trade. How
the less developed countries would become rich enough to buy
the food required to feed their people was not addressed.
However, speaker Robert Evenson emphasized that delaying
the development and use of biotechnology to increase local
grain yields would adversely affect poor countries far more
than rich.
Participants in the second session, drawn from agronomy,
plant breeding, agricultural economics, ecology, and other
disciplines, addressed what would be required for world agri-
culture to continue the yield increases of recent decades.
Speaker Vernon Ruttan pointed out that many of the gains in
yield that could easily be imagined half a century ago have now
been achieved. These gains were attributable to spectacular
increases in crop planting density made possible by changes in
plant architecture, marked jumps in harvest indices (the weight
of usable food product as a fraction of total plant weight),
transitions to harvesting multiple crops per year in many areas,
introduction of strains with greater responsiveness to fertilizer,
improvements in management practices, and expansion of
irrigated area. Many of these improvements cannot be re-
peated. Panelist Thomas Sinclair emphasized that plants'
ability to capture and fix energy is inherently limited by the
physics of intercepting photons and capturing carbon dioxide,
the biochemistry of photosynthesis, and the physiology of
nutrient uptake and utilization.
Although perhaps ultimately changeable, it is not clear that
these limits can be changed rapidly enough to keep food
production ahead of need and demand. The extraordinary
agronomic improvements of recent decades have moved
present agriculture closer to theoretical limits. Speaker Ken-
neth Cassman presented evidence that the yield potential of
two of the three most important cereal crops, rice and maize,
has changed little in response to plant breeding in the past
three decacles. die argued that the performance of cereals was
reaching 80% of-theoretical limits in some geographic areas
already, and that continuing increases in productivity per
hectare would occur only if average yields achieved by farmers
rose to comparable levels in the major cereal production
systems worldwide. He suggested that although this rise might
be attainable, it would require a profoundly deeper under-
standing of crop physiology and soil science than we now have.
Information-intensive management of inputs and natural re-
sources will be required to achieve these yield levels while
preserving environmental quality.
Speaker David Hoisington suggested that major gains in
productivity could still be made by accelerating the transfer of
plant genes from diverse sources by using the techniques of
molecular biology. Speaker Matthew Thomas argued that
productivity could be increased immediately and substantially
Proc. Natl. Acad. Sci. USA 96 (1999J 5905
by pest management that takes better account of all interac-
tions among plants, herbivorous insect pests, and natural
enemies of pests. Local ecological interactions need to be
understood better in the context of larger ecosystems. The
effects of biotechnology and gene manipulations on a single
plant or at one site are an inadequate basis for effective
area-wide prescriptions. Thomas and panelist William Mur-
doch noted that more analytical work could be done on past
biological control efforts to derive information that could
improve future ones.
Panelist Vaclav Smil pointed out that a large fraction of food
is still lost to spoilage and waste and suggested that significant
food gains could still come from improvements in postharvest
storage and distribution systems. Panelist Catherine Woteki
emphasized the need for more attention to the production of
a health-promoting mix of crops and to the safety of crops for
consumers. Overall, the second session brought the sobering
realization that future productivity gains would be more
difficult to achieve than past gains and would require more
basic knowledge, better institutional support, and increasingly
sophisticated management practices.
Optimistic presentations by molecular biologists in the third
session sought to dispel an earlier undertone of pessimism
about the potential of biotechnology. Speaker Ganesh Kishore
articulated a vision of a future for agriculture and human
health based on a combination of information technology and
biotechnology. He spoke of crops that will produce food better
suited to the nutritional needs of both humans and animals,
will remedy widespread nutrient deficiencies, will improve
human health, and will protect environmental quality. He
reported that unanticipated yield increases have already re-
sulted from the new weed management practices used with
genetically engineered herbicide-resistant soybeans. Speakers
Kishore and John Ryals noted that transgenic crops expressing
the insecticidal Bacillus thur~ngiensis endotoxin gene also
showed surprising increases in productivity, apparently be-
cause reduced insect damage indirectly increases disease re-
sistance.
Ryals sketched out the rapid progress in plant genomics that
promises to make available an unprecedented variety of indi-
vidual plant genes useful for improving crop plants. Speaker
Ilya Raskin described uses of plants to remediate environmen-
tal pollution and produce nonfood products. Plants can extract
and concentrate compounds from the soil to clean up land and
water contaminated with uranium and other heavy metals.
Plants also have the potential to become low-input biological
factories through their ability to secrete small molecules and
macromolecules into the surrounding medium. Panelist Rich-
ard Meagher described using bacterial genes to create trans-
genic plants that detoxify mercury-contaminated soils. Panel-
ist Brian Staskawicz discussed recent progress in identifying
plant disease-resistance genes. He expected that impending
understanding of underlying molecular mechanisms would
soon make it possible to enhance many different crop plants
with durable disease resistance very quickly by genetic engi-
neering techniques.
Speaker Luis Herrera-Estrella concluded the session with an
assessment of the disparate biotechnological needs of agricul-
ture in differently developed countries. He pointed out that,
compared with developed countries, the developing countries
have many more small farmers, a different interdependence of
culture and agricultural practices, and a variety of problems,
many of which are of little interest to the agronomic and
biotechnological sectors of developed countries. For example,
acid soils comprise 40~o of the world's arable land. A common
problem in the acid soils of many tropical countries is high
levels of aluminum. Herrera-Estrella described recent success
in making local crop plants that tolerate high soil aluminum
levels by introducing bacterial genes that enhance the plants'
ability to secrete small organic acid molecules to chelate the
OCR for page 5906
5906 Colloquium Paper: Fedoroff and Cohen
aluminum. He articulated the need to accelerate the transfer
of biotechnology from developed to less developed countries
by easing restrictions on intellectual property rights, which
increasingly limit the use of each component of a gene
construct. He argued that biotechnology could make a cultur-
ally acceptable contribution to the welfare of small farmers if
the yields of local varieties could be increased through genetic
engineering. Export taxes could pay back biotechnology com-
panies holding the patents if productivity increased enough for
farmers to export produce. Panelist Donald Roberts pointed
out that one-third of the world's food is not cereals. In West
Africa, cassava has replaced maize as the staple subsistence
crop. He suggested that noncereal crops deserve more atten-
tion from biotechnologists.
Herrera-Estrella's emphasis on improving food production
among poor farmers with small areas to cultivate reinforced a
point raised in earlier discussion. Several of the economists,
including panelist Kenneth Arrow, pointed out that today's
chronic widespread hunger results largely from inadequate
cash incomes among the poor, not from inadequate global
production of food. Given appropriate governmental policies,
increasing the capacity of poor farmers to grow food could
raise their incomes at the same time that it would increase the
local food supply. Apart from the effects of chronic poverty,
acute widespread hunger today often results from the break-
down of public order because of civil wars or other violent
political instability.
The fourth and final session, dominated by ecologists,
focused on the larger environment. The human population and
its activities bring different demands on natural resources into
conflict. Water management practices are inadequate to cope
with sometimes mutually exclusive demands from agriculture,
industry, and urban populations. Speaker Robert Socolow
identified a need to assess and manage the global nitrogen
cycle, just as ongoing efforts are devoted to assessing and
managing the global carbon cycle. Nitrogen from agriculture
and the burning of fossil fuels contributes to greenhouse gases,
stratospheric ozone depletion, and eutrophication and can
result in the effective sterilization of coastal waters through
oxygen depletion. Based on an analysis of trends in the past 35
years, speaker David Tilman suggested that another doubling
of agricultural production will have profound effects on non-
agricultural ecosystems because of massive inputs of nitrogen
and phosphorus, and because nonagricultural ecosystems will
have to be converted to agriculture. Panelist Ronald Sederoff
pointed out that current projections fail to take account of the
growing demand for wood and wood products, particularly
paper. The demand is likely to be met in the future only if trees
are domesticated and rapidly growing varieties are developed
and farmed.
Several participants, including speaker David Tilman and
panelist Wes Jackson, stressed the vulnerability of monocul-
tures, which dominate agricultural practices in developed
countries. Tilman and Jackson encouraged greater crop di-
versity to decrease the risk of crop failure. But speaker Daniel
Janzen pointed out that monocultures occur throughout na-
ture in a wide variety of circumstances, and Ruttan pointed to
examples of monocultural systems, such as east Asian wet rice
culture, that have been sustained over several centuries. Other
participants noted that in both natural plant communities and
agriculture, a mixed culture can produce more biomass per
unit area than a monoculture because of partitioning of
utilization of resources.
Panelist Dennis Avery emphasized that our future ability to
maintain current wildland area and meet the food needs of the
still growing human population depends on further increases
in the productivity of the land already under cultivation.
Indeed, the net area under cultivation worldwide has changed
very little over the past 30 years. Most of the best land is
already in cultivation, and additions are generally offset by
Proc. Natl. Acad. Sci. USA 96 (1999)
losses to urbanization, salinization, and desertification. Thus
the goal of increasing food production while preserving current
wildland area requires future crops and crop systems to be
more productive per unit of land area than are today's. The
alternative of major increases in the area under cultivation
would have significant social and economic costs, as well as
negative ecological impacts.
Speakers Arturo Gomez-Pompa and Daniel Janzen consid-
ered how to integrate conservation efforts throughout the
world with the support of local, national, and international
populations. Janzen warned that tropical wildlands would
survive only if tended as multipurpose "gardens." These
gardens should provide protective stewardship for and access
to biodiversity as well as essential ecological services and
should receive payment for the goods and services they
provide. Janzen proposed new mechanisms to generate in-
come from both biodiversity and ecological services and
stressed the importance of returning income to the local
stewards of the gardens.
There were profound and sobering differences of opinion
about humanity's future ability to feed the human population
while sustaining ecosystem services and preserving wildlands.
The question has changed and grown more complex as the
magnitude and impact of human activities have expanded.
Panelist Walter Reid pointed out that when the scale of
agriculture was small, and undisturbed ecosystems were vast,
the underlying ecosystems seemed limitless, and what has
recently come to be called their "services" could be freely
available to everyone. Humans concentrated on optimizing
food supply, often with little concern for the ecological con-
sequences. Now the competing demands of the human popu-
lation for ecosystem services and the direct and indirect
environmental costs of our activities are no longer negligible.
Yet efforts to value the planet's ecosystem services are rela-
tively new, controversial, and have as yet had little real impact.
Concluding Perspective
The Colloquium must be viewed as a step near the beginning,
not the end, of a journey. Both more knowledge and better
institutions will be required to continue the journey toward a
better fed world. The Colloquium focused on food production
and sustainability, leaving equity and other aspects of the
quality of life for future discussion.
We lack the knowledge to resolve the differences in per-
spective that startled many participants in the Colloquium.
Many questions raised during discussion went begging for
answers. How reliable are global statistics on the extent of
hunger, the extent of desertification, the amount of land used
for agriculture? How and how much does soil erosion impair
agriculture in various parts of the world? How much carbon
and nitrogen must farmers return to the land from crops to
maintain optimum soil fertility? How rapidly will resistance to
pesticidal proteins, such as the Bacillus thuringiensis endotoxin,
emerge in insect pests? How can intellectual property rights be
managed to optimize the balance between the interests of
biotechnology firms in developed countries and poor farmers
in developing countries? How extensive are postharvest losses
of food? How can the existing information about improved
farming practices and materials be diffused more effectively to
farmers in countries with very different levels of education and
technological sophistication? How important to food produc-
tion are regional variations in topography, climate, soil, biotic
environments, institutions, and individual behaviors? Which
are the best targets for intervention? If there are substantial
uncertainties about future climate change and about the
effects of each possible change on agricultural production,
what strategies of response make the most sense for national
governments and international organizations?
OCR for page 5907
Colloquium Paper: Fedoroff and Cohen
We also lack the human institutions required to define,
develop, integrate, and apply the requisite knowledge. Ruttan
wrote: "If the world fails to meet the challenge of a transition
to sustainable growth in agricultural production, the failure
will be at least as much in the area of institutional innovation
as in the area of resource and environmental constraints....
At our present stage of knowledge, institutional design is
analogous to driving down a four-lane highway looking out of
the rear-view mirror. We are better at making course correc-
tions when we start to run off the highway than using foresight
to navigate the transition to sustainability." Panelist Dennis
Ahlburg further pointed out that we do not know how to design
"better policies" like market reforms, as experience in Eastern
Europe attests. Where are useful models for developing the
institutions and knowledge needed to manage agricultural and
wildlands in a way that sustains global ecosystem services and
promotes human well-being?
Although the Earth's biogeochemical cycles ensure that
local practices have distant and even global impacts, our
thinking is far from integrative and global. Scientific models
are just beginning to grapple with the realization that complex
systems, whether geological, biological, or human, often ex-
hibit nonlinear responses. These include abrupt shifts in
oceanic circulation and climate, mutations that increase the
virulence of pathogens, extinctions of species, and rapid
changes in human fertility, mortality and migration. In addi-
tion, dilemmas of population, equity, food, and environmental
quality are local in many important respects, as panelist Billie
Lee Turner emphasized. These realizations must inform our
information-gathering, our institution-building, and our think-
ing about the kinds of changes that would lead to sustainable
practices in agriculture and all other spheres of human activity.
Our ability to gather local data on a global scale and to work
locally while integrating our activities across vast geographic
distances has never been better. It will continue to improve in
Proc. Natl. Acad. Sci. USA 96 (1999J 5907
the future as satellite imaging techniques develop and com-
puter networks expand. Molecular biology and biotechnology
open new vistas for understanding and altering the properties
of all organisms on which humans depend, including plants.
The potential pace of change could not even have been
imagined 30 years ago. Whether and how this potential is
realized and whether it is accepted by people cannot yet be
foreseen. Finding solutions will require collaborative efforts of
a broad array of disciplines and constituencies. Success will
depend profoundly on what we do now and in the immediate
future. What is very clear is that there is no time to lose.
A previous draft of this summary was sent for review to all speakers
and panelists in the Colloquium. We thank the following for helpful
comments: Dennis Ahlburg, Nikos Alexandratos, Kenneth Cassman,
Tim Dyson, Paul R. Ehrlich, Daniel Janzen, William Murdoch, Walter
Reid, Don Roberts, Vernon Ruttan, Robert Socolow, Matthew
Thomas, David Tilman, and Catherine Woteki. We thank the National
Academy of Sciences for sponsoring this Colloquium. J.E.C. acknowl-
edges support of National Science Foundation Grant DEB9207293.
1. Malthus, T. R. (1798/1970) An Essay on the Principle of Popula
tion, ed. Flew, A. (Penguin, London).
2. Ehrlich, P. R. (1968) The Population Bomb (Ballantine Books,
New York).
3. Harrar, J. G. (1970) Persp. Biol. Med. 13, 583-596.
Population Reference Bureau (1998) 1998 World Population Data
Sheet (Population Reference Bureau, Washington, DC).
5. United Nations, Population Division (1997) Urban and Rural
Areas 1996 (United Nations, New York), Publication ST/ESA/
SER. AI166.
6. United Nations, Population Division (1998) World Population
Estimates and Projections, 1998 Briefing Packet (United Nations,
New York).
7. Evans, L. T. (1998) Feeding the Ten Billion: Plants and Population
Growth (Cambridge Univ. Press, Cambridge, U.K.~.
\
\
Representative terms from entire chapter:
human population
