[PDF]Can organic agriculture feed the world

Renewable Agriculture and Food Systems: 22(2); 80-85



doi : 1 0. 1 1 7/S 1 742 1 7050700 1 87 1



Preface



Renewable Agriculture and Food Systems is a multi-
disciplinary journal which focuses on the science that
underpins economically environmentally and socially
sustainable approaches to agriculture and food production.
The journal publishes original research and review articles
on the economic, ecological and environmental impacts
of agriculture; the effective use of renewable resources
and biodiversity in agro-ecosystems; and the technological
and sociological implications of sustainable food systems.



It also contains an open discussion Forum, which
presents lively discussions on new and provocative
topics. However, the opinions of the Forum and responses
are solely those of the authors and do not necessarily reflect
the opinions of Renewable Agriculture and Food Systems
or Cambridge University Press.

John W. Doran
Editor-in-Chief, RAF S



Can organic agriculture feed the world?



Catherine Badgley and Ivette Perfecto



Forum



The prospect that organic agriculture has the potential to
feed the world is welcome news in light of the contra-
dictions of modern agriculture 1 . These include the massive
productivity of green-revolution agriculture yet the stub-
born persistence of hunger and malnutrition, the loss of
small farms even though they are more productive and
contribute more to local economies than do large farms 2 ,
and the pervasive environmental destruction by agricultural
biocides and synthetic fertilizers even as more and more
ecological services of agricultural landscapes are being
recognized 3 . Organic agriculture per se cannot resolve all
of these contradictions, but its potential to provide enough
food to feed the entire world opens the door to the creation
of a new kind of food system based on agroecological
production principles. We (Badgley et al. in this issue) have
demonstrated two critical points. The first is that the
relative yields of organic versus non-organic methods
(green-revolution methods in the developed world, low-
intensive methods in the developing world) suffice to
provide enough calories to support the whole human
population eating as it does today. This conclusion is based
on a global dataset of 293 yield ratios for plant and animal
production. The second point concerns nitrogen fertility.
Data from 77 published studies suggest that nitrogen-fixing
legumes used as green manures can provide enough
biologically fixed nitrogen to replace the entire amount of
synthetic nitrogen fertilizer currently in use. Thus, the
principal arguments from critics of organic agriculture are
invalid. These results are controversial, partly from
prejudice and vested interests in the current agricultural



system and partly from disputed aspects of the analysis.
While this study claims that organic yields and nitrogen
fertility methods could feed the world, it does not forecast
yields for any particular crop or region, nor does it claim
that a global organic food system would necessarily
increase food security anywhere. Food security depends
on policies and prices as much as on yields.

Our study is not the only one to reach this conclusion.
In 1990, Stanhill 4 came to a similar conclusion about
organic production based on a compilation of data from
North America and Europe (his average yield ratio was the
same as ours for the developed world). More recently,
Halberg et al. 5 modeled scenarios of conversion to organic
agriculture in Europe, North America and sub-Saharan
Africa, using a globalized market model. They concluded
that large-scale conversion to organic agriculture would
not severely diminish either the global food supply or
food security in developing regions. They noted that food
policies favoring local food availability, rather than export
crops, would enhance the impact of conversion to organic
farming and increase food security in sub-Saharan Africa.

Reviewers raised issues that merit dialogue beyond the
context of the article. The first issue concerns the
differences in crop-rotation patterns between organic and
conventional grain agriculture. The second concerns the
reliability of different kinds of sources (i.e. peer-reviewed
versus gray literature) for agronomic data.

Rotation effect. Organic grain production frequently
uses a different rotation cycle than conventional product-
ion. This difference complicates the comparison of yields



© 2007 Cambridge University Press



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between organic and conventional systems without some
kind of time adjustment for grain that must be grown in a
longer rotation cycle by organic methods. Corn, wheat
and rice, the world's staple grains, are grown in approxi-
mately equal quantities (in megagrams) on a global
basis 6 ' 7 . In the US, corn and wheat are usually grown in
rotation 8 . Corn is typically grown in a longer rotation
under organic than conventional methods. For wheat, it is
not clear that organic and conventional rotations differ in
length. Most rice is grown in irrigated fields so tailored to
rice production that other plant crops are not usually
included (although green manures and animals can be
included); organic and conventional methods for rice do
not require different rotations.

Thus, corn is the main crop for which the rotation effect
is an issue. A survey of corn/other crop rotations from the
sources of yield data cited in Badgley et al. 1 (this issue)
reveals that conventional corn was grown 25-60% of the
time in rotations of 2-6 years, and organic corn was grown
25-50% of the time in rotations of 2-4 years. For the sake
of a quantitative example, we can determine the yield
adjustment for two widely used rotations of corn — a 2-year
rotation of corn-soybeans under conventional management
and a 3-year rotation of corn-soybeans-wheat + cover crop
under organic management. All other things being equal,
the organic system would produce only 67% as much
corn as the 2-year conventional system would. If we
multiply all of the individual yield ratios for corn in our
dataset for the developed world by 0.67 and then
recalculate the average yield ratio for grains, the result is
0.84 instead of 0.93. The reduction in caloric output from
the lower average yield ratio for grains in the developed
world results in a change from 2641 to 2523 total kcal
person - 'day - 1 in Model 1 (based on yield ratios from
developed countries) and from 4381 to 4358 total kcal
person - 'day - 1 in Model 2 (based on yield ratios from
developed and developing countries). Even with this time-
adjusted correction for corn, both models generate enough
calories (i.e. > 2500 kcal person - 1 day - ') to feed the
current population. These calculations are conservative
since many conventional rotations feature corn less than
50% of the time. Organic rotations are capable of sustained
production of grains rotated with other crops, as demon-
strated by the Rodale Farm Systems Trial 9 . A more
thorough evaluation of rotation effects requires quantitative
comparison of the plot-to-plot yield differences between
organic and conventional production and the rate of change
in both organic and conventional production methods as a
function of the rotation sequence.

Thus, the necessity for different rotation schedules
would decrease the production of corn. But since over-
production of corn has depressed the price of corn for
many years, this change could actually benefit farmers
economically.

Gray literature. A reviewer raised the concern that
our quantitative results were suspect because a number of
our yield ratios come from the gray literature. Actually,



74% of the studies included in our analysis are from
peer-reviewed journals. For a study of this sort, which
makes a global-scale analysis, it is important to include
as many studies as possible from as many regions as pos-
sible. We included studies of three kinds: controlled
experiments of two or more management methods,
paired-farm comparisons in regions with the same soils
and climate and comparisons on the same farm before
and after a change in management practices. All three
kinds of studies could be found in both peer-reviewed
and gray-literature sources. It is worth noting that some
gray-literature sources are quite reliable, such as the tech-
nical reports of respected agricultural experiment stations
(the Henry Wallace Experiment Station, Maryland; Kel-
logg Biological Station's Long-Term Ecological Research
Site, Michigan; the Organic Farming Research Found-
ation, California). Three published works that we con-
sulted for data also cited a mixture of peer-reviewed
publications, gray literature and personal communications.
Stanhill's 4 compilation is largely supportive of organic
farming, while McDonald et al. 10 (which focuses just on
the system of rice intensification) was skeptical. The third
source was the book by Lampkin and Padel 11 , which cites
a similar range of sources for yield information. The
point is that our compilation is not unusual in the kinds
of sources used for analysis.

The most problematic source from the reviewer's
standpoint was the report by Pretty and Hine 12 based on
survey data from 52 developing countries. Yields were
compared before and after farmers adopted specific
agroecological practices. An analysis based on data from
this report was subsequently published in Agriculture,
Ecosystems and Environment 13 . The main reason for
including many of the quantitative comparisons in this
report is that relatively few published studies are available
from farms in the developing world. In order to evaluate
whether the survey data biased our results for the
developing world, we performed a significance test on the
survey data compared to data from experiments and paired
farms. The test failed to reject the null hypothesis that the
means in yield ratios do not differ significantly. (This test is
explained in detail in Appendix 1 of Badgley et al. 1 .) We
concluded that the use of survey data from the report of
Pretty and Hine 12 did not unduly bias our results for the
developing world. We note, however, the need for more
quantitative, experimental comparisons in developing
countries.

One controversial management practice is the system of
rice intensification (SRI) in developing countries. Its
proponents claim that it boosts yields substantially, while
its critics argue that best-management conventional pract-
ices perform just as well. A reviewer commented that our
cited publications on SRI did not provide the minimum
information about soil and environmental conditions for the
sites where the studies were performed. This criticism
applied to some of the studies cited on both sides of the
debate. We tried to avoid bias by using data from both



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proponents and critics in the debate. Furthermore, global
estimates by definition involve generalities. Detailed
information about soils, climatic conditions and specific
management practices was not given for all the studies,
regardless of publication source. In principle, these
unmeasured variables would favor yields in the conven-
tional system in some instances, while in others they would
favor the organic system. There is no reason to think that
the lack of information about these variables would bias our
study in any particular direction.

In general, we recognize that the high yield ratios from
developing countries likely result from the fact that many
existing farming practices do not involve optimal amounts
of synthetic fertilizer, and may not be managed optimally in
numerous other ways. The adoption of organic methods in
these settings is a huge improvement. However, our aim is
not to demonstrate the superiority of organic farming over
conventional agriculture. Our aim is simply to investigate
whether organic agriculture can produce enough food to
feed the world's population — ours is a sufficiency argu-
ment. It is appropriate to use yields from suboptimal
existing systems in developing countries, because these
systems are representative of much of the developing world
and most of the world's farmers.

Going forward. Readers of this journal are well aware
of the achievements of alternative agricultural systems
both agronomically and economically. These achieve-
ments would multiply with additional research on locally
suitable cropping systems, fertility methods and pest man-
agement for different agricultural regions. Changes in
agricultural policy are essential and could foster changes
in farming and marketing practices within a few years.
As an example, the Cuban food system underwent mas-
sive reorganization of farming and marketing methods
after the fall of the Soviet Union in 1990 14 . After a few
years of crisis, exacerbated by the US economic blockade,
Cuba now has one of the most progressive food systems
in the world. A global food system based on agroecologi-
cal principles is possible and there are urgent reasons to
move in this direction.



References

1 Badgley, C, Moghtader, J., Quintero, E., Zakem, E.,
Chappell, M.J., Aviles- Vazquez, K., Samulon, A., and Perfecto,
I. 2007. Organic agriculture and the global food supply.
Renewable Agriculture and Food Systems 22(2):86-108.

2 Rosset, P. 1999. The multiple functions and benefits of small-
farm agriculture in the context of global trade negotiations.
Food First Policy Brief No. 4.



3 Daily, G.C., Alexander, S.E., Ehrlich, P.R., Goulder, L.H.,
Lubchenco, J., Matson, P.A., Mooney, H.A., Postel, S.,
Schneider, S.H., Tilman, D., and Woodwell, G.M. 1997.
Ecosystem services: benefits supplied to human societies by
natural ecosystems. Issues in Ecology 2:1-18.

4 Stanhill, G. 1990. The comparative productivity of organic
agriculture. Agriculture, Ecosystems and Environment
30:1-26.

5 Halberg, N., Alr0e, H.F., Knudsen, M.T., and Rristensen, E.S.
(eds) 2005. Global Development of Organic Agriculture:
Challenges and Promises. CAB International, Wallingford, UK.

6 Clay, I. 2004. World Agriculture and the Environment. Island
Press, Washington, DC.

7 Food and Agricultural Organization of the United Nations.
2003. FAO Statistical Database. Available at http://faostat.
fao.org/

8 Vesterby, M. and Krupa, K.S. 1997. Major land uses in the
United States. Economic Research Service, US Department of
Agriculture Statistical Bulletin No. 973.

9 Pimentel, D., Hepperly, P., Hanson, I., Douds, D., and Seidel,
R. 2005. Environmental, energetic and economic comparisons
of organic and conventional farming systems. Bioscience
55:573-582.

10 McDonald, A.I., Hobbs, P.R., and Riha, S.I. 2005. Does the
system of rice intensification outperform conventional best
management? A synopsis of the empirical record. Field Crops
Research 96:31-36.

11 Lampkin, N.H. and Padel, S. (eds) 1994. The Economics of
Organic Farming: An International Perspective. CAB Inter-
national, Wallingford, UK.

12 Pretty, I. and Hine, R. 2001. Reducing Food Poverty with
Sustainable Agriculture: A Summary of New Evidence.
Final report from the 'SAFE World' Research Project,
University of Essex. Available at http://www2.essex.ac.uk/
ces/ResearchProgrammes/S AFEWexecsummfinalreport.htm
(accessed 22 February 2007).

13 Pretty, I.N., Morison, J.I.L., and Hine, R.E. 2003. Reducing
food poverty by increasing agricultural sustainability in
developing countries. Agriculture, Ecosystems and Environ-
ment 95:217-234.

14 World Resources Institute. 2000. World Resources 2000-
2001. World Resources Institute, Washington, DC.

Catherine Badgley is a research scientist with the
Department of Geological Sciences and the Museum of
Paleontology at the University of Michigan, Ann Arbor, Ml.
Ivette Perfecto is a Professor in the School of Natural
Resources and Environment at the University of Michigan,
Ann Arbor, MI, USA.

Note: Catherine Badgley and Ivette Perfecto have not had
an opportunity to respond to the following comments by
Kenneth Cassman and lim Hendrix.



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83



Editorial response by Kenneth Cassman: can organic agriculture feed the
world — science to the rescue?



During the past 30 years there has been a steady decrease in
funding allocated to agricultural research in both developed
and developing countries because of the widespread view
that food insecurity is primarily caused by poverty and a
lack of purchasing power rather than the inability to
produce enough food 1 . However, these views are being
challenged by three global mega-trends: (1) a steady
decrease in arable land area suitable for intensive food
crop production as a result of farmland conversion to urban,
industrial and recreational uses, (2) a steady reduction in
the relative rate of yield gain for the major cereal crops —
yield gains that are falling below the projected rate of
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