www.biosciencemag.org March 2011 / Vol. 61 No. 3 • BioScience 183
Resilience in Agriculture through
Crop Diversification: Adaptive
Management for Environmental
Brenda B. Lin
Recognition that climate change could have negative consequences for agricultural production has generated a desire to build resilience into
agricultural systems. One rational and cost-effective method may be the implementation of increased agricultural crop diversification. Crop
diversification can improve resilience in a variety of ways: by engendering a greater ability to suppress pest outbreaks and dampen pathogen trans-
mission, which may worsen under future climate scenarios, as well as by buffering crop production from the effects of greater climate variability
and extreme events. Such benefits point toward the obvious value of adopting crop diversification to improve resilience, yet adoption has been
slow. Economic incentives encouraging production of a select few crops, the push for biotechnology strategies, and the belief that monocultures are
more productive than diversified systems have been hindrances in promoting this strategy. However, crop diversification can be implemented in a
variety of forms and at a variety of scales, allowing farmers to choose a strategy that both increases resilience and provides economic benefits.
Keywords: resilience, climate change, diversified agroecosystems, adaptation, trade-offs
and soil moisture, as well as shifts in pest occurrences and
plant diseases, all of which will greatly inﬂuence food pro-
duction and food security (Fuhrer 2003, Jones and Thorn-
ton 2003). These changes are expected to increase abiotic
and biotic stress, forcing agricultural systems to function
under greater levels of perturbation in the future.
Resilience is deﬁned as the propensity of a system to retain
its organizational structure and productivity following a
perturbation (Holling 1973). Thus, a resilient agroecosystem
will continue to provide a vital service such as food produc-
tion if challenged by severe drought or by a large reduction
in rainfall. In agricultural systems, crop biodiversity may
provide the link between stress and resilience because a
diversity of organisms is required for ecosystems to function
and provide services (Heal 2000). Removing whole func-
tional groups of species or removing entire trophic levels
can cause ecosystems to shift from a desired to less-desired
state, affecting their capacity to generate ecosystem services
(Folke et al. 2004). This effect highlights the possibility that
agricultural systems already may be in a less-desired state
for the continued delivery of ecosystem services.
Vandermeer and colleagues (1998) elucidated the main
issues linking the role of diversity in agroecosystems to func-
tional capacity and resilience. First, biodiversity enhances
ecosystem function because different species or geno-
types perform slightly different roles and therefore occupy
The observation that managed ecosystems often fail to
respond smoothly to external changes and pressures has
led to greater research on ecological regime shifts, thresholds,
and resilience (Folke et al. 2004). Although the idea of build-
ing resilience has been studied in a broad range of ecosystems,
from coral reefs to forests (Nyström et al. 2000, Chapin 2004),
this idea has not been well studied in an especially important
system to human society: the agroecosystem. The develop-
ment of resilient agricultural systems is an essential topic
of study because many communities greatly depend on the
provisioning ecosystem services of such systems (food, fodder,
fuel) for their livelihoods (Altieri 1999). Many agriculturel-
based economies have few other livelihood strategies (Tilman
et al. 2002), and small family farms have little capital to invest
in expensive adaptation strategies, which increases the vul-
nerability of rural, agricultural communities to a changing
environment. The challenge for the research community is to
develop resilient agricultural systems using rational, afford-
able strategies such that ecosystem functions and services can
be maintained and livelihoods can be protected.
Environmental changes may affect many different aspects
of agricultural production. With greater climate variability,
shifting temperature and precipitation patterns, and other
global change components, we expect to see a range of crop
and ecosystem responses that will affect integral agricultural
processes. Such effects include changes in nutrient cycling
BioScience 61: 183–193. ISSN 0006-3568, electronic ISSN 1525-3244. © 2011 by American Institute of Biological Sciences. All rights reserved. Request
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184 BioScience • March 2011 / Vol. 61 No. 3 www.biosciencemag.org
different niches. Second, biodiversity is neutral or negative
in that there are many more species than there are func-
tions; thus, redundancy is built into the system. Third,
biodiversity enhances ecosystem function because those
components that appear redundant at one point in time
may become important when some environmental change
occurs. The key here is that when environmental change
occurs, the redundancies of the system allow for continued
ecosystem functioning and provisioning of services. These
three hypotheses are not mutually exclusive and change over
time and space; therefore, all linkages between diversity and
function may be useful for the long-term maintenance of
sustainable agricultural systems.
Biodiversity—which allows for the coexistence of mul-
tiple species, fulﬁlling similar functions, but with different
responses to human landscape modiﬁcation—enhances
the resilience of ecosystems (Walker 1995). This concept is
linked to the insurance hypothesis (Yachi and Loreau 1999),
which proposes that biodiversity provides an insurance, or a
buffer, against environmental ﬂuctuations because different
species respond differently to change, leading to more pre-
dictable aggregate community or ecosystem properties. Such
diversity insures the maintenance of a system’s functional
capacity against potential human management failure that
may result from an incomplete understanding of the effects
of environmental change (Elmqvist et al. 2003).
The recognition that biodiversity is integral to the mainte-
nance of ecosystem functioning points to the utility of crop
diversiﬁcation as an important resilience strategy for agro-
ecosystems. There can be enormous diversity within agricul-
tural systems, and diversiﬁcation can occur in many forms
(genetic variety, species, structural) and over different scales
(within crop, within ﬁeld, landscape level), giving farmers
a wide variety of options and combinations for the imple-
mentation of this strategy. Diversiﬁcation at the within-crop
scale may refer to changes in crop structural diversity; for
example, using a mixture of crop varieties that have different
plant heights. Diversiﬁcation at the within-ﬁeld scale may be
represented by areas between and around ﬁelds where trap
crops or natural enemy habitat can be planted. At the land-
scape scale, diversiﬁcation may be achieved by integrating
multiple production systems, such as mixing agroforestry
management with cropping, livestock, and fallow to create a
highly diverse piece of agricultural land (table 1; Altieri 1999,
Gurr et al. 2003). It is important to recognize that diversity
can be created temporally as well as spatially, adding even
greater functional diversity and resilience to systems with
sensitivity to temporal ﬂuctuations in climate.
Because of the impacts that climate change may have on
agricultural production, the need to consider diversiﬁed agri-
cultural systems is ever more pressing. The following sections
review the current knowledge about agricultural diversity
and its ability to protect agriculture from the consequences
of climate change, as well as the barriers that remain for its
adoption as a climate change adaptation strategy. In the ﬁrst
section, I discuss the advantages of diversiﬁed agroecosystems
under a future climate by looking at pest, disease, and plant
physiological effects. The second section discusses the barri-
ers to the adoption of diversiﬁed agriculture as an adaptation
strategy, and the third section examines methods to help
farmers optimize diversiﬁcation strategies to improve resil-
ience and protect agricultural production.
Advantages of diversiﬁed agroecosystems
Current knowledge suggests that climate change will affect
both biotic (pest, pathogens) and abiotic (solar radiation,
water, temperature) factors in crop systems, threatening crop
sustainability and production. More diverse agroecosystems
with a broader range of traits and functions will be better
able to perform under changing environmental conditions
(Matson et al. 1997, Altieri 1999), which is important given
the expected changes to biotic and abiotic conditions. The
following are a few of the major ways that the greater func-
tional capacity of diverse agroecosystems has been found to
protect crop productivity against environmental change.
Pest suppression. Pest suppression is a perennial challenge
to farmers, and it is a very important ecosystem service. In
agricultural systems, as in natural ecosystems, herbivorous
insects can have signiﬁcant impacts on plant productivity.
The challenges of pest suppression may intensify in the
future as changes in climate affect pest ranges and poten-
tially bring new pests into agricultural systems. It is expected
that insect pests will generally become more abundant as
temperatures rise as a result of range extensions and phe-
nological changes. This abundance will be accompanied by
higher rates of population development, growth, migration,
and overwintering (Cannon 1998, Bale et al. 2002). Changes
in the distribution and abundance of species and communi-
ties are unlikely to occur at the same rates. Migrant pests are
expected to respond more quickly to climate change than
plants, and they may be able to colonize newly available
crops and habitats (Cannon 1998, Bale et al. 2002). However,
there are a variety of barriers to range expansions, including
such biotic factors as competition, predation, and parasitism
from other species (Patterson et al. 1999). Promoting such
barriers to range expansion and pest viability will have an
immediate negative impact on pest outbreaks and will help
protect agricultural production.
Farmers may be able to assist in creating biotic barriers
against new pests by increasing the plant diversity of their
farms in ways that promote natural enemy abundance. The
composition of the plant community, as determined by a
farmer, may be described as the planned diversity of the
system. Crop diversity is critical not only in terms of produc-
tion but also because it is an important determinant of the
total biodiversity in the system (Matson et al. 1997). With
greater plant species richness and diversity in spatial and
temporal distribution of crops, diversiﬁed agroecosystems
mimic more natural systems and are therefore able to main-
tain a greater diversity of animal species, many of which are
natural enemies of crop pests (Altieri 1999). Many examples
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of pest suppression have been shown within agricultural
systems possessing diversity and complexity, especially in
comparison with less-complex systems (Cannon 1998). For
example, in willow systems, insect pest outbreaks of the leaf
beetle Phratora vulgatissima have been shown to be greater
in willow monocultures than in natural willow habitats
(Dalin et al. 2009). However, in a review of specialist and
generalist natural enemy responses to agricultural diversiﬁ-
cation, it was found that diversiﬁcation may reduce natural
enemy searching efﬁciency. Moreover, pest control by spe-
cialist enemies may be less effective in a more diverse agro-
ecosystem because a lower concentration of host plants may
reduce attraction or retention of these specialist enemies
Table 1. Examples of diversiﬁcation in agricultural systems and the potential beneﬁts for farmers under climate change.
Type of diversiﬁcation Nature of diversiﬁcation Beneﬁt Examples
Makes crops within the ﬁeld more
Pest suppression Strip-cutting alfalfa during har vest allows natural enemies
to emigrate from har vested strips to adjacent nonharvest-
ed ones (Hossain et al. 2001)
Genetic diversity in
Growing mixed varieties of a
species in a monoculture
Disease suppression Genetic diversity of rice varieties reduces fungal blast
occurrence (Zhu et al. 2000)
Increased genetic diversity was positively related to mean
income and stability of income (Di Falco and Perrings 2003)
Diversify ﬁeld with
Growing weed strips or vegetation
banks in and alongside crops
Pest suppression Grassland or refugia planted at ﬁeld margins (beetle
banks) were used as overwintering habitat for natural
enemies (Thomas et al. 1991)
Pest suppression Using white and black mustard on the ﬁeld margins of
sweet corn crops trapped pests and prevented them from
entering the cornﬁeld (Rea et al. 2002)
Crop rotations Temporal diversity through crop
Disease suppression Alternating cereal crops with broadleaf crops and changing
stand densities disrupts the disease cycles (Kr upinsky et
Increased production Manipulating diversity through crop rotations of greater
cover crop and nitrogen-ﬁxing crops increased the yield of
the primary crop (Smith et al. 2008)
Polycultures Growing two or more crop species
and wild varieties within the ﬁeld;
spatial and temporal diversity of
Disease suppression Grassland ﬁelds planted with multiple species to decrease
disease transmission (Mitchell et al. 2002)
More ecologically complex systems with wild varieties and
temporal and spatial diversity of crops were able to grow
under climate stress (Tengö and Belfrage 2004)
Increased production Grassland plots with greater in-ﬁeld species diversity led
to more stable feed and fodder production (Tilman et al.
Increased production Grassland plots with greater in-ﬁeld species diversity led
to increased production (Picasso et al. 2008)
Agroforestry Growing crops and trees together ;
spatial and temporal diversity
Pest suppression Willow trees grown in natural willow habitats experience
lower rates of pest outbreak of the leaf beetle (Dalin et
Pest suppression Greater shade diversity increased bird natural enemy abun-
dance for larval control on crop plant (Perfecto et al. 2004)
Pest suppression Coffee berry borer control increased with greater ant
diversity and abundance in shade systems (Armbrecht and
Greater shade cover led to increased buffering of crop to
temperature and precipitation variation (Lin 2007)
Greater shade tree cover led to increased buffering from
storm events and decreased storm damage (Philpott
et al. 2008)
Mixed landscapes Development of larger-scale
diversiﬁed landscapes with
Pest suppression Complex landscapes that have areas of woodland and
hedgerows interspersed within ﬁelds had higher rates of
larval parasitism (Marino and Landis 1996)
Pest suppression Oilseed rape crops adjacent to complex, structurally rich,
and large old fallows had higher rates of parasitism by the
rape pollen beetle (Thies and Tscharntke 1999)
Increased production Mixed land use of organic cropland, crop rotations, and
intensive managed grazing led to optimal diversity and
proﬁtability strategies (Boody et al. 2009)
186 BioScience • March 2011 / Vol. 61 No. 3 www.biosciencemag.org
Habitat management is one method used within agricul-
tural systems to alter habitats to improve the availability of
the resources natural enemies require for optimal perfor-
mance (Landis et al. 2000). Such management techniques
have been developed for use at within-crop, within-farm,
or landscape scales, and some have been proven to be very
economical for farmers. In one review examining pest man-
agement in agriculture (Gurr et al. 2003), the authors found
that many degrees of complexity exist in increasing biodi-
versity for pest management. Simply diversifying the plant
age structure of a monoculture or strip-cutting ﬁelds such
that natural enemies have a temporal refuge can improve
in-ﬁeld habitats for natural enemies. Larger-scale changes,
such as integrating annual and perennial noncrop vegeta-
tion; increasing crop diversity within the ﬁeld; or increasing
farmwide diversiﬁcation with silvoculture, agroforestry, and
livestock may also provide a variety of other functions to the
system (table 1; Gurr et al. 2003).
In an example from a meta-analysis of the density
response of natural enemies (invertebrate predators and
parasitoids) to experimental changes in structural complex-
ity, Langellotto and Denno (2004) found that increasing
structural complexity led to a signiﬁcant rise in natural
enemy abundance at habitat and within-plant scales. Hunt-
ing and web-building spiders showed the strongest response
to structural complexity, followed by hemipterans, mites,
and parasitoids. Evidence of greater spider abundance in
response to diversiﬁcation has also been shown by Sunder-
land and Samu (2002), who found that abundance increased
with structural complexity in 63% of the studies they exam-
ined. The central conclusion of this review was that spiders
tend to concentrate in diversiﬁed patches, and greater diver-
siﬁcation throughout the whole crop would offer the best
prospect of improving pest control (Sunderland and Samu
One example of a perennial system that exhibits a rich
range of natural enemy pest control is the coffee agroforestry
system, where there is a wide variety of spatial and tempo-
ral diversity determined by the shade trees planted within
the cropping system. Greater natural enemy presence has
been observed in the more diverse and shaded agroforestry
systems, and increased bird diversity and density have been
shown to reduce herbivore plant damage through greater
insectivorous bird predation (Perfecto et al. 2004). It has
also been observed that predatory ground-dwelling ants are
attracted to and prey upon the coffee berry borer, a major
pest of coffee production, with greater efﬁciency in diversi-
ﬁed coffee systems when compared with unshaded mon-
ocultures (Armbrecht and Gallego 2007).
The integration of diversiﬁed systems into agriculture can
have ﬁnancial beneﬁts for the farmer, as well. One ﬁnancially
beneﬁcial type of habitat management that has been widely
adopted at the within-ﬁeld scale is the beetle bank, where
native grasslands and refugia are maintained at the ﬁeld mar-
gins to protect carabid beetle populations. In one analysis of
the costs and beneﬁts associated with pest suppression, the
cost of establishing a beetle bank in a 20-hectare (ha) wheat
ﬁeld, combined with yield loss resulting from land removed
from production, was calculated at $130 for the ﬁrst year with
subsequent costs and yield losses of $45 per year. However,
the ability to keep aphid populations below a spray threshold
through natural enemy suppression saved about $450 per
year in labor and pesticide costs, and the prevention of aphid-
induced yield loss saved about $1000 per year for the 20-ha
ﬁeld. These ﬁgures show that the loss in productive land for
the establishment of the beetle banks was more than offset
by the money saved from reduced pesticide use and aphid-
induced yield loss (Thomas et al. 1991).
Although climate change may produce a shift in pest and
natural enemy ranges, an agricultural system with greater
plant biodiversity improves the system’s resilience by har-
boring greater natural enemy biodiversity, thereby protect-
ing crops from a large variety of potential future pests.
Although natural enemies in a diverse system may be func-
tionally redundant at the present, they may no longer prove
redundant as future changes occur. The diversity of plant
species within the agroecosystem therefore provides long-
term pest suppression for agricultural systems by building
up a bank of potential natural enemies for any future pest
outbreaks in the system.
Disease suppression. Losses caused by pathogens can contrib-
ute signiﬁcantly to declines in crop production, and changes
in climate potentially could affect plant disease distribution
and viability in new agricultural regions. From 2001 to 2003,
10% of the global crop losses in wheat, rice, and maize were
shown to be a result of pathogens (Oerke 2006).
The diversity of crop species in an agroecosystem has a
much less predictable effect on microbial pathogens com-
pared with crop pests, as microclimatic conditions play an
important role in the development and severity of a disease
(Matson et al. 1997, Fuhrer 2003). The effect of climate
change on disease prevalence is therefore much less certain.
Climate change could have positive, negative, or no impact
on individual plant diseases (Chakraborty et al. 2000), but
it is suspected that milder winters may favor many crop
diseases, such as powdery mildew, brown leaf rust, and strip
rust, whereas warmer summers may provide optimal condi-
tions for other diseases, such as cercosporea lead spot disease
(Patterson et al. 1999). Global change is also predicted to
alter the distribution and abundance of arthropod vectors
that distribute viruses, thereby affecting the rates of and
chances for crop transmission (Anderson et al. 2004).
A central tenet of epidemiology is that both the number
of diseases and the incidence of disease should increase pro-
portionally to host abundance (Tilman et al. 2002). In one
grassland study, in which grassland plant species richness
and composition were manipulated, the pathogen load was
almost three times greater in the monoculture plots, where
host abundance was at a maximum, than in the polyculture
plots planted with 24 grassland species (an approximation
of natural diversity; Mitchell et al. 2002). Eleven diseases
www.biosciencemag.org March 2011 / Vol. 61 No. 3 • BioScience 187
were more severe at lower plant species richness, with
most of the diseases correlating with host abundance,
showing that the greater abundance of host species within
lower-species-diversity plots increased disease transmission.
The loss of genetic diversity in crop production has led
to a hypothesized increase in crop disease susceptibility as a
result of higher rates of disease transmission. Many mecha-
nisms reduce the spread of disease in agricultural systems
with greater varietal and species richness. Barrier and fre-
quency effects occur when other disease-resistant varieties
or species block the ability of a disease or virus to transmit
and infect a susceptible host (Finckh et al. 2000). These
effects increase with greater spatial and temporal diversity in
the agricultural system, and intentional crop system diversity
with greater barrier effects can signiﬁcantly reduce pathogen
impacts on crop production. Multiline cultivars and varietal
mixtures have been used to effectively retard the spread and
evolution of fungal pathogens in small grains and to control
some plant viruses (Matson et al. 1997).
One well-known example of barrier effects in rice pro-
duction showed that genetic variation within species and
within populations can increase the ability of an agricultural
system to respond to pathogen diseases. Zhu and colleagues
(2000) demonstrated that in-ﬁeld genetic crop heterogene-
ity suppresses disease in rice crops suffering from rice blast.
Disease-susceptible rice varieties, when planted in mixtures
with resistant varieties over large tracts of land, had 89%
greater yield and 94% reduced fungal blast occurrence than
when planted in monoculture. Because of this experiment’s
success, fungicidal sprays were no longer applied to these
ﬁelds after the trial. Rather, farmers grew rice in mixtures in
order to improve the resilience of the systems while reduc-
ing economic costs. There have been few such large-scale
experiments to study the efﬁcacy of genetic heterogeneity
to increase production, reduce chemical use, and potentially
stabilize or even reduce food prices for a region, but these
results do provide evidence that intraspeciﬁc crop diversiﬁ-
cation has the potential to effectively control fungal disease
spread and protect against crop loss.
Increasing diversiﬁcation of cereal cropping systems by
alternating crops, such as oilseed, pulse, and forage crops, is
another option for managing plant disease risk (Krupinsky
et al. 2002). Disease cycles could be interrupted through crop
rotation by interchanging cereal crops with broadleaf crops
that are not susceptible to the same diseases. Reduced tillage
could enhance soil biodiversity, leading to greater disease
suppression, and stand densities could be adjusted to allow
for better microclimatic adjustments to disease growth.
These examples show that farmers can take advantage of
greater crop diversiﬁcation to reduce disease susceptibility
in agricultural systems, thereby limiting the amount of pro-
duction loss as a result of crop diseases. Although changes
in disease spread and severity are uncertain under climate
change, greater genetic variation across space and time could
potentially reduce adverse disease transmission impacts that
may accompany climate change.
Climate variability buffering and mitigation. Diversiﬁed agro-
ecosystems have become more important for agriculture as
climate ﬂuctuations have increased. Research has shown that
crop yields are quite sensitive to changes in temperature and
precipitation, especially during ﬂower and fruit develop-
ment stages. Temperature maximums and minimums, as
well as seasonal shifts, can have large effects on crop growth
and production. Greater variability of precipitation, includ-
ing ﬂooding, drought, and more extreme rainfall events,
has affected food security in many parts of the world (Parry
et al. 2005).
Agricultural vulnerabilities have been found in a number
of important crop species. Observations of rice production
in the Philippines during an El Niño drought season showed
reductions in seed weight and overall production (Lansigan
et al. 2000). Studies of wheat have demonstrated that heat
pulses applied to wheat during anthesis reduced both grain
number and weight, highlighting the effect of temperature
spikes on grain ﬁll (Wollenweber et al. 2003). In maize,
researchers observed reduced pollen viability at tempera-
tures above 36 degrees Celsius, a threshold similar to those in
a number of other crops (Porter and Semenov 2005).
Such observed agricultural vulnerabilities to changes in
temperature and precipitation point to the need to develop
resilient systems that can buffer crops against climate vari-
ability and extreme climate events, especially during highly
important development periods such as anthesis. There
are a variety of ways that diversiﬁed agricultural systems
exemplify that more structurally complex systems are able to
mitigate the effects of climate change on crop production.
Agroforestry systems are examples of agricultural systems
with high structural complexity. Although the primary crop
of interest (e.g., coffee, cacao) is sometimes grown in more
intensively managed systems with little shade cover, the
more structurally complex systems have been shown to buf-
fer crops from large ﬂuctuations in temperature (Lin 2007),
thereby keeping crops in closer-to-optimal conditions. The
more shaded systems have also been shown to protect crops
from lower precipitation and reduced soil water availability
(Lin et al. 2008) because the overstory tree cover reduces soil
evaporation and improves soil water inﬁltration.
Agroforestry systems also protect crops from extreme
storm events (e.g., hurricanes, tropical storms) in which
high rainfall intensity and hurricane winds can cause land-
slides, ﬂooding, and premature fruit drop from crop plants.
In one example from Mexico, greater farming intensity of
coffee agroforestry systems was correlated with the percent-
age of farm area lost to landslides and the amount of cof-
fee production lost to premature fruit drop (Philpott et al.
2008). In another example of diverse agriculture systems
and hurricanes, a study of Nicaraguan farms following
Hurricane Mitch in 1998 showed that less intensively man-
aged land, which exhibited greater diversity and structural
complexity, suffered less erosion, had more vegetation, and
experienced lower economic losses from hurricane damage
(Holt-Giménez 2002). Resistance patterns became more
188 BioScience • March 2011 / Vol. 61 No. 3 www.biosciencemag.org
apparent in areas with high storm intensity, and complex
interactions and thresholds exist, but are difﬁcult to detect.
In a comparative study of farming systems in Sweden
and Tanzania, two locations where agriculture has suffered
from climate variation and extreme events, it was found that
agricultural diversity increased the resilience of the produc-
tion systems. Sweden suffered from cold-tolerance issues,
whereas Tanzania suffered from problems of heat tolerance
and irregular El Niño cycles. Both locations experienced
greater seasonal drought. In these cases, research showed
that successful management practices able to buffer systems
from climate variation and protect production were those
that were generally more ecologically complex, incorporat-
ing wild varieties into the agricultural system and increas-
ing the temporal and spatial diversity of crops (Tengö and
These examples present a potential long-term strategy
for farmers experiencing patterns of reduced rainfall and
growing temperature variability. Diversiﬁcation of agri-
cultural systems can signiﬁcantly reduce the vulnerability
of production systems to greater climate variability and
extreme events, thus protecting rural farmers and agricul-
Barriers and challenges to the increased adoption of
Although many recognize that diversity can improve the
resilience of agricultural systems to environmental change,
the adoption of increased diversiﬁcation has been slow for a
number of reasons. First, economic policy incentives for the
production of monoculture row crops under intensive man-
agement have outweighed the perceived incentives to imple-
ment diversiﬁed farming systems, although this may change
as climatic variations increase. Second, many of the efforts
to adapt agriculture to climate change have focused on
the development of biotech solutions to produce drought-
resistant crops, pushing agriculture toward more expensive
and intensive forms of management. Lastly, the mistaken
belief that biomass production is substantially greater in
monocropped systems than in multispecies systems has dis-
couraged the move toward more diversiﬁed systems. Such
barriers slow the rate of adoption of diversiﬁed agricultural
systems as adaptation options and must be addressed in or-
der to hasten the implementation of this strategy.
Farm price and income supports: A US example. In the United
States, the economic incentives to intensify production in
monoculture systems outweigh the incentives to diversify
agriculture systems. Agricultural subsidies select mainly
for ﬁve crops—corn, wheat, soybean, cotton, and rice—
thereby incentivizing greater production of these few crops.
Between 1995 and 2002, 89% of the $91.2 billion disbursed
in commodity payments went to these crops in order to
boost the income of crop and livestock farmers. Soybean
and corn farmers alone received 56% of that money (Boody
et al. 2009). The commodity payment system encourages
monocropping of select crops because payments are deter-
mined by acreage of crop produced, thereby incentivizing
the maximum production of one or a few crops over large
tracts of landscape. Such incentives favor greater production
of fewer species planted in space and time, at the expense
of ecosystem services and ecosystem function (Altieri 1999,
Tilman et al. 2002).
Incentives for the greater production of fewer crops have
also been supported by the mechanization of many agri-
cultural production practices (e.g., planting, harvesting).
Mechanization is now the status quo in the United States
and is necessary for this type of production system. The
mechanization of crop species for maximum production,
in general, is most efﬁcient when only one crop is planted
because management systems (e.g., planters, harvesters,
chemical inputs, irrigation systems) can be designed for one
crop type and one crop structure, thereby decreasing labor
time and costs (Pimentel et al. 2008). In this sense, an agri-
cultural system that selects mainly for one or two main crops
and is highly mechanized can be very efﬁcient and produc-
tive, and certainly this ability to scale up production and
increase yield has had many advantages for food production
and the maintenance of stable food prices in the past.
However, farm price and income supports were origi-
nally developed because farm households were ﬁnancially
disadvantaged compared with other US households, not
to increase the production of speciﬁc crops. Current data
show that farm household incomes have risen above those
of the average nonfarm household (Mishra and Sandretto
2002), and that much of the subsidy program does not
support small farmers; rather, the majority of the money
goes to large farms that own wide swaths of land (Riedl
2007), thereby negating the original intent of the price- and
income-support mechanisms. This brings into question the
true economic beneﬁt of subsidies for many small farmers,
who will be most vulnerable to climate change–induced
production losses in the future. Incentives that can increase
economic productivity of farms by permitting the selling
of ecosystem services, such as carbon sequestration, have
the potential to increase the adoption of diversiﬁed farm
systems such as terraces and agroforestry (Antle et al. 2007).
Developing policy that incentivizes the diversiﬁcation of
agricultural crops and landscapes may be a more rational
strategy for developing resilient agricultural systems and
protecting food production in the future under climate
change (Boody et al. 2009).
Biotech solutions. The recognition that agriculture will face
challenges under climate change has brought about a major
effort to adapt agriculture through technical means, primar-
ily the research and development of drought-resistant bio-
tech crops. The push for greater use of biotechnology that
focuses on sole-crop agriculture has made some headway
in protecting production yields for some farmers, but it has
not succeeded in many situations, especially in developing
nations (Herdt 2006). Yet biotech continues to be a major
www.biosciencemag.org March 2011 / Vol. 61 No. 3 • BioScience 189
focus in agricultural adaptation solutions to climate change.
According to assessments by the Australian government,
crops genetically engineered for drought tolerance have not
been found to outperform traditional varieties (Braidotti
2008), and in fact, many traits are most easily bred into crop
systems using conventional breeding through crop genetic
diversity (USDA 2008). The authors of an International
Water Management Institute report (IWMI 2007) concluded
that improvements in biotech products would have only
a moderate impact over the next 15 to 20 years in making
crops more efﬁcient in using water. They also concluded that
“greater, easier, and less contentious gains” could come from
managing water supplies better, rather than trying to develop
crops that can ﬂourish with less water (IWMI 2007).
Additionally, the speed of research and development of
new biotech crops must be assessed in comparison with
the speed of climate change effects on agriculture. A recent
New York Times article (Pollack 2008) that interviewed a
researcher on Monsanto drought-tolerant corn stated that
drought-tolerant varieties could reach American farmers
in four years, with a 10% increase in yield. Other varieties
could reach Africa by 2017 (Pollack 2008). The difﬁculty
with assessing such scenarios is the uncertainty in the rate
of change that farmers will have to contend with in the
next 5 to 10 years. Will the technology developed today be
sufﬁcient to protect farmers under the climate conditions
of the future when it is launched in 5 to 10 years? For how
long will the technology be useful? Such products may also
be prohibitively expensive, which will pose a challenge for
smallholder rural farmers who may want to pursue this
adaptation option under climate change.
If there is indeed a temporal scale mismatch in the rate of
development of adequate biotech lines and the rate and extent
of climate change effects on agriculture, farmers will have to
turn to other adaptation options to improve the resilience of
their systems to climate change. The need to develop options
for present and expected climate change and for those who
will have no access to such technology remains a great prob-
lem for agricultural development and food security ﬁelds.
Diversiﬁed agriculture in such cases remains a highly acces-
sible adaptation option for many farmers.
Biomass production. The belief that monocultures and inten-
sively managed systems are more productive than diversiﬁed
agricultural systems is another challenge to moving agricul-
tural systems toward more diversity. Maximizing biomass
production of one or two speciﬁc crops is essentially the
goal of the current modern agricultural paradigm. Although
ecosystem functioning of such systems persists at much
reduced capacity, outside infrastructure such as mechani-
zation, chemical inputs, and irrigation systems can help
replace the lost functionality (Altieri 1999) to enable high
production. However, the potential effects of climate change
on agriculture stability will further complicate our predic-
tions of production and pricing of goods from large-scale,
In many regions of the world, the ability to use intensiﬁed
production practices and products is limited by cost and
transportation. Petroleum for mechanization techniques
and chemical inputs can be prohibitively expensive. Even in
regions with access to mechanization and chemical inputs,
a lack of water resources can severely reduce production
capacity. In such cases, diversiﬁed agricultural systems that
are able to produce under extreme climate scenarios are
preferable because many of the ecosystem functions that
cannot be brought into the system through inputs and
mechanizations can be provided through natural means.
Such solutions support both biodiversity and community
resilience to climate change by taking advantage of ecosys-
tem functions and services, supporting high production
yields in potentially adverse environmental conditions.
A variety of research has shown that high plant diversity
within agricultural plots can yield higher production levels
than systems with low plant diversity. Grassland experiments
have shown that greater plant species diversity is correlated
with greater temporal stability in annual aboveground
plant production, demonstrating that a more efﬁcient and
sustainable supply of food, such as fodder, can be enhanced
by increasing biodiversity (Tilman et al. 2006). In a study
examining the effect of species diversity on crop and weed
biomass in perennial herbaceous polycultures, biomass
increased log linearly with species richness and polycultures
outyielded monocultures by an average of 73% (Picasso
et al. 2008). A growth in production has also been seen in
ﬁeld experiments manipulating diversity in crop rotations
(crops, cover crops, and chemical inputs), showing signiﬁ-
cantly greater corn grain yields with increased diversiﬁcation
over time (Smith et al. 2008). Such results demonstrate that
diverse polycultures can have higher and more stable yields
that lead to increased economic beneﬁts for farmers as well.
However, not all studies have shown that greater diversity
leads to increased production yield. In one study, biodiverse
rotational systems of three to six species produced 25%
lower yield versus integrated monocropped grain systems,
but the grain was of higher quality. The high-quality grain
from the more biodiverse system must be of greater value to
overcome the economic beneﬁt of higher production in the
lower-quality monoculture (Snapp et al. 2010).
Developing optimization strategies and win-win
solutions for diversiﬁcation
A major challenge for the implementation of diversiﬁed
agricultural systems for farmers is ﬁnding the appropriate
balance of diversiﬁcation within the farm system to satisfy
both production and protection values. Farmers and agri-
cultural managers must consider the variety of ways that
diversiﬁcation can occur within the system and develop
methods that best meet their speciﬁc needs of crop produc-
tion and resilience. Of course, as climate change variability
increases, the value of resilience will also increase, espe-
cially in production systems sensitive to climate variation.
However, a farmer’s decision to move toward diversiﬁed
190 BioScience • March 2011 / Vol. 61 No. 3 www.biosciencemag.org
adoption of diversiﬁed agricultural systems. In one model of
the potential of farmers to participate in carbon sequestra-
tion contracts and increase sequestration potential through
agroforestry and terracing of ﬁelds, analysis showed that at
prices higher than $50 per metric ton of carbon, adoption
would increase substantially, and at prices of $100 per metric
ton of carbon, terrace and agroforestry adoption for carbon
sequestration would have the potential to raise per capita
incomes by up to 15% (Antle et al. 2007). Such economic
models are also helpful for understanding whether price
incentives are effective for a particular goal. In a study by Wu
and colleagues (2004) of price incentives for agriculture con-
servation practices in order to reduce nutrient and soil pol-
lution of the Mississippi River, an economic model showed
that payments of $50 per acre for conservation tillage and
crop rotation increased the adoption of these conserva-
tion practices but were limited in their potential to reduce
hypoxia, the ultimate goal. Such results allowed policymak-
ers to concentrate on alternate conservation options and
incentives that would have a larger impact on the ultimate
goal of reducing hypoxia (Wu et al. 2004).
Development of larger-scale diversiﬁed landscapes that
support and improve ecological resilience in agricultural
systems requires a more in-depth analysis of the farm
business and landscape-level scenario modeling for on-farm
diversity possibilities. For example, Boody and colleagues
(2009) examined how two watersheds in Minnesota would
fare under a variety of future land-use scenarios including
(a) a continuation of current trends, (b) the application
of best management practices (BMPs) over the landscape,
(c) a mixture of agricultural uses that maximize diversity
and proﬁtability, and (d) a scenario increasing vegetative
cover over the landscape (Boody et al. 2009). The scenario
that maximized on-farm diversity and proﬁtability moved
beyond BMPs alone and included organic cropland, ﬁve-year
crop rotations, and intensive managed grazing. This diverse
system increased proﬁts and biodiversity while reducing
environmental externalities (e.g., water quality, greenhouse
gases, sedimentation, and ﬂooding), thereby creating a
win-win-win solution. Such scenario modeling of land-
scapes could be very useful for farmers making decisions
about large tracts of land or in systems where there is a
cooperative structure in land management. These types of
modeling scenarios may also assist decisionmakers in long-
term planning of landscapes.
Stakeholder involvement and participatory research. The adop-
tion of sustainable agricultural options under climate change
has been a challenge for many communities, as the idea of
climate change adaptation can seem overwhelming. The
ability and space to communicate adaptation options is very
important to implementation success; discussing the risk
and uncertainty of climate change is especially critical, as
sound climate science is required to implement rational and
useful strategies. Additionally, stakeholders must understand
that adaptation options become fewer as climate variability
agricultural systems will be highly inﬂuenced by the abil-
ity of the diversiﬁcation strategy to support the economic
resilience of farms. Cost-cutting examples, such as the use
of beetle banks to reduce pesticide costs (Thomas et al.
1991) or the reduction of fungicide use in integrated rice
systems (Zhu et al. 2000), illustrate the signiﬁcant possible
economic beneﬁts of greater biodiversity. Policy incentives
that strongly promote adaptation are also necessary for
transitioning agriculture to a long-term sustainable state.
Finding win-win solutions that account for farmers’ vari-
ous production and protection goals is necessary to develop
long-term, viable strategies.
Optimizing diversiﬁcation strategies at various scales. Develop-
ing tools that can help managers understand best practices
on a farm ﬁeld or landscape scale can signiﬁcantly enhance
diversity in agricultural systems while increasing the resil-
ience of systems to climate change and maintaining high
At the farm ﬁeld level, techniques such as crop modeling
(e.g., Decision Support System for Agrotechnology Transfer
[Jones et al. 2003], Agricultural Production Systems Simu-
lator [Keating et al. 2003]) allow researchers to simulate
crop mixtures within a speciﬁc regional setting in order
to model crop thresholds and production levels to climate
and management variables. Such systems can be very pow-
erful for modeling crop outcomes under climate change
scenarios, as climate data can be adjusted to mimic greater
climate variation as well as any accompanied changes in
agricultural farm management (e.g., crop mixtures and
rotations; Weiss et al. 2003). However, accurate modeling
of agricultural systems requires extensive knowledge of on-
the-ground parameters, such as soil proﬁles for water and
nutrient distribution, as well as a variety of crop-speciﬁc
physiological development data usually gained through
ﬁeld trials. This information can be difﬁcult to obtain, as
it requires labor and technical understanding to collect the
However, it will greatly beneﬁt future planning if there
is greater development of extension and on-the-ground
research staff who are able to assist in collecting relevant
soil and plant development data and in modeling cropping
strategies to speciﬁc location variables. Simulation analyses
conducted on speciﬁc production scenarios are especially
useful in improving decisionmaking (e.g., what crops should
be planted, and when), particularly when performed in con-
junction with local knowledge of potential environmental
and socioeconomic challenges. The use of interdisciplinary
research to consider the overall crop management system
will allow for better adaptation method development and
implementation (Stone and Meinke 2005).
Because farmers require economic incentives to be willing
and able to adopt new practices, economic models that can
predict threshold prices at which farmers begin to adopt
environmental land-use practices or payments for ecosys-
tem services can be highly effective in encouraging farmer
www.biosciencemag.org March 2011 / Vol. 61 No. 3 • BioScience 191
more complex systems could be used to protect farmers
from climatic change and improve food security.
Understanding the potential of increasing diversity within
farm systems is essential to helping farmers adapt to greater
climate variability of the future. By adopting farm systems
that promote ecosystem services for pest and disease control
and resilience to climate change variability, farmers are less
at risk to production loss and are more generally resilient to
I thank the Berkeley Environmental Institute, Claire Kre-
men, and Miguel Altieri for spurring me to develop this
topic. I also thank Ivette Perfecto, John Vandermeer, Miguel
Altieri, and three anonymous reviewers for their comments
in improving this manuscript.
This publication was developed under Cooperative Agree-
ment no. X3 83232801 awarded by the US Environmental
Protection Agency (EPA) to the American Association for
the Advancement of Science. It has not been formally
reviewed by the EPA. The views expressed in this document
are solely my own and do not necessarily reﬂect those of the
agency. The EPA does not endorse any products or commer-
cial services mentioned in this publication.
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Brenda B. Lin (email@example.com) is a fellow of the American Association for
the Advancement of Science and when this article was written was with the
Environmental Protection Agency. She is now with the Australian Common-
wealth Scientiﬁc and Industrial Research Organisation.
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