Population
growth, arable land and fresh water limits, and climate change have profound
implications for the ability of agriculture to meet this century’s demands for
food, feed, fiber, and fuel while reducing the environmental impact of their
production. Success depends on the acceptance and use of contemporary molecular
techniques, as well as the increasing development of farming systems that use
saline water and integrate nutrient flows.
Population experts anticipate the
addition of another roughly 3 billion people to the planet’s population by the
mid-21st century. However, the amount of arable land has not changed
appreciably in more than half a century. It is unlikely to increase much in the
future because we are losing it to urbanization, salinization, and
desertification as fast as or faster than we are adding it.Water scarcity is already a critical concern in parts of the world.
Climate change also has important
implications for agriculture. The European heat wave of 2003 killed some 30,000
to 50,000 people.
The average temperature that summer was only about 3.5°C above the average for
the last century. The 20 to 36% decrease in the yields of grains and fruits
that summer drew little attention. But if the climate scientists are right,
summers will be that hot on average by midcentury, and by 2090 much of the
world will be experiencing summers hotter than the hottest summer now on
record.
The yields of our most important
food, feed, and fiber crops decline precipitously at temperatures much above
30°C .
Among other reasons, this is because photosynthesis has a temperature optimum
in the range of 20° to 25°C for our major temperate crops, and plants develop
faster as temperature increases, leaving less time to accumulate the
carbohydrates, fats, and proteins that constitute the bulk of fruits and grains .
Widespread adoption of more effective and sustainable agronomic practices can
help buffer crops against warmer and drier environments,but it will be increasingly difficult to maintain, much less increase, yields
of our current major crops as temperatures rise and drylands expand.
Climate change will further affect
agriculture as the sea level rises, submerging low-lying cropland, and as
glaciers melt, causing river systems to experience shorter and more intense
seasonal flows, as well as more flooding .
Recent reports on food security
emphasize the gains that can be made by bringing existing agronomic and food
science technology and know-how to people who do not yet have it ,
as well as by exploring the genetic variability in our existing food crops and
developing more ecologically sound farming practices .
This requires building local educational, technical, and research capacity,
food processing capability, storage capacity, and other aspects of
agribusiness, as well as rural transportation and water and communications
infrastructure. It also necessitates addressing the many trade, subsidy,
intellectual property, and regulatory issues that interfere with trade and
inhibit the use of technology.
What people are talking about today,
both in the private and public research sectors, is the use and improvement of
conventional and molecular breeding, as well as molecular genetic modification
(GM), to adapt our existing food crops to increasing temperatures, decreased
water availability in some places and flooding in others, rising salinity ,
and changing pathogen and insect threats .
Another important goal of such research is increasing crops’ nitrogen uptake
and use efficiency, because nitrogenous compounds in fertilizers are major
contributors to waterway eutrophication and greenhouse gas emissions.
There is a critical need to get
beyond popular biases against the use of agricultural biotechnology and develop
forward-looking regulatory frameworks based on scientific evidence. In 2008,
the most recent year for which statistics are available, GM crops were grown on
almost 300 million acres in 25 countries, of which 15 were developing countries.
The world has consumed GM crops for 13 years without incident. The first few GM
crops that have been grown very widely, including insect-resistant and
herbicide-tolerant corn, cotton, canola, and soybeans, have increased
agricultural productivity and farmers’ incomes. They have also had
environmental and health benefits, such as decreased use of pesticides and
herbicides and increased use of no-till farming .
Despite the excellent safety and
efficacy record of GM crops, regulatory policies remain almost as restrictive
as they were when GM crops were first introduced. In the United States,
case-by-case review by at least two and sometimes three regulatory agencies (USDA,
EPA, and FDA) is still commonly the rule rather than the exception. Perhaps the
most detrimental effect of this complex, costly, and time-intensive regulatory
apparatus is the virtual exclusion of public-sector researchers from the use of
molecular methods to improve crops for farmers. As a result, there are still
only a few GM crops, primarily those for which there is a large seed market and the benefits of biotechnology have not been realized for the vast majority
of food crops.
What is needed is a serious
reevaluation of the existing regulatory framework in the light of accumulated
evidence and experience. An authoritative assessment of existing data on GM
crop safety is timely and should encompass protein safety, gene stability,
acute toxicity, composition, nutritional value, allergenicity, gene flow, and
effects on nontarget organisms. This would establish a foundation for reducing
the complexity of the regulatory process without affecting the integrity of the
safety assessment. Such an evolution of the regulatory process in the United
States would be a welcome precedent globally.
It is also critically important to
develop a public facility within the USDA with the mission of conducting the
requisite safety testing of GM crops developed in the public sector. This would
make it possible for university and other public-sector researchers to use
contemporary molecular knowledge and techniques to improve local crops for
farmers.
However, it is not at all a foregone
conclusion that our current crops can be pushed to perform as well as they do
now at much higher temperatures and with much less water and other agricultural
inputs. It will take new approaches, new methods, new technology—indeed,
perhaps even new crops and new agricultural systems.
Aquaculture is part of the answer. A
kilogram of fish can be produced in as little as 50 liters of water ,
although the total water requirements depend on the feed source. Feed is now
commonly derived from wild-caught fish, increasing pressure on marine
fisheries. As well, much of the growing aquaculture industry is a source of
nutrient pollution of coastal waters, but self-contained and isolated systems
are increasingly used to buffer aquaculture from pathogens and minimize its
impact on the environment.
Another part of the answer is in the
scale-up of dryland and saline agriculture .
Among the research leaders are several centers of the Consultative Group on
International Agricultural Research, the International Center for Biosaline
Agriculture, and the Jacob Blaustein Institutes for Desert Research of the
Ben-Gurion University of the Negev.
Systems that integrate agriculture
and aquaculture are rapidly developing in scope and sophistication. A 2001
United Nations Food and Agriculture Organization report describes the development of such systems in many Asian countries. Today, such
systems increasingly integrate organisms from multiple trophic levels .
An approach particularly well suited for coastal deserts includes inland
seawater ponds that support aquaculture, the nutrient efflux from which
fertilizes the growth of halophytes, seaweed, salt-tolerant grasses, and
mangroves useful for animal feed, human food, and biofuels, and as carbon sinks. Such integrated systems can eliminate today’s flow of agricultural nutrients
from land to sea. If done on a sufficient scale, inland seawater systems could
also compensate for rising sea levels.
The heart of new agricultural
paradigms for a hotter and more populous world must be systems that close the
loop of nutrient flows from microorganisms and plants to animals and back,
powered and irrigated as much as possible by sunlight and seawater. This has
the potential to decrease the land, energy, and freshwater demands of
agriculture, while at the same time ameliorating the pollution currently
associated with agricultural chemicals and animal waste. The design and
large-scale implementation of farms based on nontraditional species in arid
places will undoubtedly pose new research, engineering, monitoring, and
regulatory challenges, with respect to food safety and ecological impacts as
well as control of pests and pathogens. But if we are to resume progress toward
eliminating hunger, we must scale up and further build on the innovative
approaches already under development, and we must do so immediately.
References
and Notes
The
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2009; www.landcommodities.com).
Water
for Food, Water for Life: A Comprehensive
Assessment of Water Management (International Water Management Institute,
Colombo, Sri Lanka, 2007).
- ↵
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- R. L. Naylor
,
Historical warnings of future food insecurity with unprecedented seasonal heat.
Science 323, 240 (2009).
- ↵
- W. Schlenker,
- M. J. Roberts
,
Nonlinear temperature effects indicate severe damages to U.S. crop yields under
climate change. Proc. Natl. Acad. Sci. U.S.A. 106, 15594 (2009).
M. M.
Qaderi, D. M. Reid, in Climate Change and Crops, S. N. Singh, Ed.
(Springer-Verlag, Berlin, 2009), pp. 1–9.
- ↵
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,
Improving water use in crop production. Philos. Trans. R. Soc. London Ser. B
363, 639 (2008).
↵
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Panel on Climate Change, Climate Change 2007: Impacts, Adaptation and
Vulnerability (Cambridge Univ. Press, Cambridge, 2007; www.ipcc.ch/publications_and_data/publications_ipcc_fourth_assessment_report_wg2_report_impacts_adaptation_and_vulnerability.htm).
Agriculture
for Development (World Bank, Washington, DC, 2008;
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the Benefits: Science and the Sustainable Intensification of Global Agriculture (Royal Society, London, 2009;
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The
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- ↵
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,
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The
State of World Fisheries and Aquaculture 2008
(United Nations Food and Agriculture Organization, Rome, 2009;
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- ↵
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,
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growing environments. Agric. Econ. 29, 353 (2003).
Integrated
Agriculture-Aquaculture (United
Nations Food and Agriculture Organization, Rome, 2001; www.fao.org/DOCREP/005/Y1187E/y1187e00.htm).
T. Chopin et
al., in Encyclopedia of Ecology, S. E. Jorgensen, B. Fath, Eds.
(Elsevier, Amsterdam, 2008), pp. 2463–2475.
The Seawater Foundation, www.seawaterfoundation.org
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