ISIS Report 06/09/07
Scientists Find Organic Agriculture Can Feed the World &
Comprehensive study gives the lie to claims that organic agriculture cannot
feed the world because it gives low yields and there is insufficient organic
fertilizer. Dr. Mae-Wan Ho
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Scientists refute common misconceptions about organic agriculture
Two usual objections are
levelled against the proposal that organic agriculture can feed the world.
Organic agriculture, opponents claim, gives low yields, and there isn’t enough
organic fertilizer to boost yields substantially.
A team of scientists
led by Catherine Badgley at the University of Michgan Ann Arbor in the United
States has now refuted those common misconceptions about organic agriculture.
Organic agriculture gives yields roughly comparable to conventional agriculture
in developed countries and much higher yields in developing countries; and
more than enough nitrogen can be fixed in the soil by using green manure alone
The research team
compared yields of organic and conventional agriculture (including low-intensive
food production) in 293 examples, and estimated the average yield ratio (organic
versus non-organic) of different
food categories for the developed and the developing world. With the average
yield ratios, they modelled the global food supply that could be grown organically
in the current agricultural land base. The results indicate that organic methods
could produce enough food to sustain the current human population, and potentially
an even larger population, without increasing the agricultural land base.
They also estimated
the amount of nitrogen potentially available from nitrogen fixation by legumes
as cover crops. Data from temperate and tropical agroecosystmes suggest that
they could fix enough nitrogen to replace all of the synthetic fertilizer currently
The report concluded:
“These results indicate that organic agriculture has the potential to contribute
quite substantially to the global food supply, while reducing the detrimental
environmental impacts of conventional agriculture.”
Price of the Green Revolution
The researchers are quick
to point out that the Green Revolution has been a stunning technological achievement;
for even with the doubling of the human population in the past 50 years, more
than enough food has been produced to meet the caloric requirements for all;
if food were distributed more equitably.
is great uncertainty about the future, given the projection of 9 to 10 billion
in the human population by 2050 and the global trends of increasing meat consumption
(requiring much more grain) while grain harvests are decreasing. They have
not mentioned the additional pressure on agricultural production from the
growing demand for biofuels  (Biofuels: Biodevastation,
Hunger & False Carbon Credits, SiS 33), which has already created “a looming
food crisis” worldwide, as John Vidal reports in detail in The Guardian . The climate extremes -
droughts and floods – brought on by climate change are almost certainly making
matters a great deal worse.
Much of the current
reduction in grain harvests is due to environmental degradation from decades
of unsustainable practices of the Green Revolution: massive soil erosion,
loss of soil fertility, loss of agricultural land through salination, depletion
of water tables and increased pest resistance. Other environmental costs of
the Green Revolution include surface and groundwater contamination, release
of greenhouse gases (especially through deforestation and conversion into
agricultural land), and loss of biodiversity.
Many have argued that more sustainable methods of food production are essential.
Notably, the Independent Science Panel consisting of dozens of scientists from
around the world have issued a report in 2003, calling for a comprehensive shift
to sustainable, organic agriculture  (The Case for A GM-Free
Sustainable World). It is no coincidence that those most opposed to organic
agriculture are also the strongest supporters of genetically modified crops,
and they see the recent rise in demand for biofuels as yet another opportunity
to promote a technology that has failed miserably to deliver its promises in
30 years, while evidence of serious health risks continue to emerge  (No to GMOs, No to GM Science,
Wide variety of organic agriculture
The organic agriculture
examples reviewed by the Michigan University team cover a wide spectrum of
farms that are agroecological, sustainable or ecological, but not necessarily
certified organic. They rely on natural nutrient-cycling processes, exclude
or rarely use synthetic pesticides, and sustain or regenerate soil quality.
Farming practices include cover crops, manure application, composting, crop
rotation, intercropping, and biological pest control.
The 293 studies
reviewed consist of 160 that compared organic with conventional methods and
133 cases comparing organic with low-intensive methods. Most studies are from
the peer-reviewed published literature, a minority from conference proceedings,
technical reports or website of an agricultural research station. They range
from a single growing season to over 20 years. Some examples are based on
yields before and after conversion to organic in the same farm.
global food supply from organic agriculture, the average ratios of the yields
of organic versus non-organic
are applied to current food production values minus post harvest losses from
the UN Food and Agriculture Organization (FAO) database for 2001.
Organic yields beat conventional
The yield ratios summarised in Table 1 are grouped into
10 categories covering the major plant and animal components of human diets.
Table 1. Yield ratios
of organic versus conventional agriculture
As can be seen, the
average yields of organic and non-organic produce are about the same in the
developed world, but it is in the developing world - where most food is needed
and where farmers can least afford to pay for expensive synthetic fertilizers
and pesticides - that the major gains in organic agriculture are most evident.
Yield ratios of organic versus
conventional range from about 1.6 to 4.0. The ratio averaged over all foodstuffs
for the world is 1.3.
More than enough organic food to feed the world
The team has worked out
two models of global food production. Model 1 is conservative, and applies
the yield ratios derived from studies in the developed countries to the entire
global agricultural land base; Model 2, more realistically, applies the yield
ratios determined for the developed and the developing countries back to the
respective regions. The calories per capita resulting from the models are
estimated by multiplying the average yields by FAO estimates of calorific
content in the food category.
The amount of
food available in Model 1 is about the same as currently available. The main
gain is in reducing energy and fossil fuel intensive inputs, and avoiding
all the collateral damages from conventional agriculture. Model 2 results
in real gains of 1.3 to 2.9-fold of various foods available in addition.
Both models show
that organic agriculture could sustain the current human population. In terms
of daily caloric intake, the current world food supply after losses provides
2786 kcal/per/day. The average requirement for a healthy adult is between
2200 and 2500. Model 1 yields 2641 kcal/day, above the recommended level (94.8
percent of current level). Model 2 yields 4381 kcal/day, 157.3 percent of
what is current available. Thus, organic production has the potential to support
a substantially larger human population than currently exists.
More than enough nitrate through biological nitrogen fixation
The main limiting macronutrient
for agricultural production is nitrogen in most areas. Nitrogen amendments
in organic farming derive from crop residues, animal manure, compost and biologically
fixed N from legumes (green manure). In the tropics, legumes grown between
plantings of other crops can fix substantial amounts of nitrogen in just 40
to 60 days.
The estimate of N
available globally is determined from the rates of N availability or N-fertilizer
equivalence reported in 77 studies, 33 for temperate regions and 44 for the
tropics, including three from arid regions and 18 of paddy rice.
of N in kg/ha are obtained from studies as either ‘fertilizer-replacement
value’ (i.e., the amount of N fertilizer needed to achieve equivalent yields
to those obtained using N from cover crops), or calculated as 66 percent of
N fixed by a cover crop becoming available for uptake by plants during the
growing seasons following the cover crop.
In 2001, the
global use of synthetic N fertilizers was 82 Mt. The estimated N fixed by
additional legume crops as fertilizer is 140 Mt, based on an average N availability
of 102.8 kg N/ha (the average N availability of temperate and tropical regions
are 95.1 kg N /ha and 108.6kg/ha respectively). This is 171 percent of current
synthetic N used globally, or 58 Mt more. Even in the US where conventional
agriculture predominates, the estimate shows a surplus of available N through
the additional use of leguminous cover crops between normal cropping periods.
regions, winter cover crops grow well in the autumn after harvest and in early
spring before the planting of main food crops. Research at the Rodale Institute
(Pennsylvania) showed that red clover and hairy vetch as winter covers in
an oat/wheat-corn-soybean rotation with no additional fertilizer achieved
yields comparable to those in conventional controls . The Farm System Trial
at the Rodale Institute uses legume cover crops grown between main crops every
third year as the only source of N fertility. Non-legume winter cover crops
are used in other years to maintain soil quality and fertility and to suppress
In arid and semi-arid
tropical regions, where water is limiting between periods of crop production,
drought-resistant green manures, such as pigeon peas or groundnuts, can be
used to fix N. Using cover crops in arid regions has been shown to increase
soil moisture retention.
These estimates of
N available do not include other practices for increasing biologically fixed
N, such as intercropping, alley cropping with leguminous tress, rotation of
livestock with annual crops, and inoculation of soil with free-living N-fixers.
In addition, rotation of food-crop legumes, such as pulses, soy, or groundnuts,
can contribute as much as 75 kgN/ha to the grains that follow the legumes.
Promises and remaining challenges
The implications of the
University of Michigan study are far reaching. The
results imply that even with rather conservative estimates, no additional
land area is required to grow enough food to feed the world if we were to
switch to organic, and enough biologically available N can be obtained to
entirely replace the current use of synthetic N fertilizers.
There are numerous other benefits of switching to organic agriculture not mentioned
in the paper that are documented in the Independent Science Panel Report 
and elsewhere. (See also  FAO
Promotes Organic Agriculture, SiS 36).
The largest gains from organic agriculture arise from the savings on the damages
to public health and the environment, estimated at more than US $59.6 billion
a year in the United States [6, 8] (Organic
Agriculture Enters Mainstream, Organic
Yields on Par with Conventional & Ahead during Drought Years, SiS
Another is the key
issue of food security. Findings from the Rodale Institute also confirm that
organic management retains more nutrients, organic carbon and moisture in
the soil, all of which make organic crops more able to withstand climatic
stress. So it is not surprising that while organic yields are comparable to
conventional during normal years, they are well ahead in drought years [6,
There are substantial
savings on carbon emissions and fossil fuels to mitigate climate change simply
from phasing out pesticides and synthetic fertilizers, not to mention the
extra carbon sequestered in organic soils.
The study has not
even considered all the existing options for renewable energies  (Which Energy?, ISIS Report)
or systems of farming that turns wastes into food and energy resources, thereby
potentially phasing out fossil fuels altogether  (How to Beat Climate
Change & Be Food and Energy Rich - Dream Farm 2, ISIS Report). Nor does it mention the many social,
economic, and health benefits from organic agriculture [4, 7].
The case for a global
shift to organic agriculture has never appeared more compelling and more urgent.
The Michigan University team see numerous challenges
for implementing a comprehensive shift to organic agriculture, however promising
it seems. The practice of organic agriculture on a large scale requires support
from research institutions dedicated to agroecological methods of soil fertility
and pest management, a strong extension system and a committed public.
Also needed are strong government commitment and support,
and policy changes that favour and encourage a globall shift to organic, sustainable
Most of all, it is time to put to rest the debate about
whether or not organic agriculture can make a substantial contribution to
the food supply. We should be debating instead the allocation of resources
for research on agroecological food production, the creation of incentives
for farmers and consumers; and the policies needed at the national and international
levels to promote and facilitate the global transition.