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Maize Landraces and Adaptation to Climate Change in Mexico



Mexico is the primary center of origin and diversity for maize (Zea mays L.). Farmers grow the crop largely under rain-fed conditions. Mexico is at considerable risk from climate change because of predicted rising temperatures, declining rainfall, and an increase in extreme weather events. Small-scale maize farmers are particularly vulnerable because of their geographical location as well as their limited adaptive capacity. Recommended climate change adaptation strategies include farmers’ increased use of heat and drought stress-tolerant maize. Farmer adoption of improved germplasm has been disappointing because of inefficient seed input chains and farmers’ preference for landraces for culinary, agronomic, and cultural reasons. Scientists have tended to overlook the fact that maize landraces have a critical role to play in climate change adaptation. Landraces may already exist that are appropriate for predicted climates. Furthermore, within the primary gene pool of maize and its wild relatives there exists unexploited genetic diversity for novel traits and alleles that can be used for breeding new high yielding and stress-tolerant cultivars. The breeding component of adaptation strategies should focus more on improving farmers’ landraces. The desired result would be a segmented maize seed sector characterized by both (improved) landraces and improved maize varieties. The public and private sector could continue to provide farmers with improved maize varieties and different actors, including farmers themselves, would generate seed of improved landraces for sale and/or exchange.
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Maize Landraces and Adaptation to
Climate Change in Mexico
Jon Hellina, Mauricio R. Bellonb & Sarah J. Hearnea
a International Maize and Wheat Improvement Center (CIMMYT),
Texcoco, Mexico
b Bioversity International, Rome, Italy
Published online: 14 Jul 2014.
To cite this article: Jon Hellin, Mauricio R. Bellon & Sarah J. Hearne (2014) Maize Landraces
and Adaptation to Climate Change in Mexico, Journal of Crop Improvement, 28:4, 484-501, DOI:
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Journal of Crop Improvement, 28:484–501, 2014
Published with license by Taylor & Francis
ISSN: 1542-7528 print/1542-7536 online
DOI: 10.1080/15427528.2014.921800
Maize Landraces and Adaptation to Climate
Change in Mexico
1International Maize and Wheat Improvement Center (CIMMYT), Texcoco, Mexico
2Bioversity International, Rome, Italy
Mexico is the primary center of origin and diversity for maize ( Zea
mays L.). Farmers grow the crop largely under rain-fed conditions.
Mexico is at considerable risk from climate change because of pre-
dicted rising temperatures, declining rainfall, and an increase in
extreme weather events. Small-scale maize farmers are particularly
vulnerable because of their geographical location as well as their
limited adaptive capacity. Recommended climate change adapta-
tion strategies include farmers’ increased use of heat and drought
stress-tolerant maize. Farmer adoption of improved germplasm has
been disappointing because of inefficient seed input chains and
farmers’ preference for landraces for culinary, agronomic, and
cultural reasons. Scientists have tended to overlook the fact that
maize landraces have a critical role to play in climate change
adaptation. Landraces may already exist that are appropriate for
predicted climates. Furthermore, within the primary gene pool of
maize and its wild relatives there exists unexploited genetic diver-
sity for novel traits and alleles that can be used for breeding new
high yielding and stress-tolerant cultivars. The breeding component
of adaptation strategies should focus more on improving farmers’
landraces. The desired result would be a segmented maize seed
sector characterized by both (improved) landraces and improved
maize varieties. The public and private sector could continue to
provide farmers with improved maize varieties and different actors,
including farmers themselves, would generate seed of improved
landraces for sale and/or exchange.
Received 13 March 2014; accepted 2 May 2014.
© Jon Hellin, Mauricio R. Bellon, and Sarah J. Hearne
Address correspondence to Jon Hellin, International Maize and Wheat Improvement
Center (CIMMYT), Apartado Postal 6-641, Texcoco 06600, Mexico. E-mail:
Downloaded by [] at 23:05 26 August 2015
Maize Landraces and Adaptation to Climate Change in Mexico 485
KEYWORDS climate change adaptation, seed systems, small-scale
farmers, landraces, wild relatives
Climate change is likely to lead to increased water scarcity in the coming
decades (Hendrix et al. 2007; Lobell et al. 2008)andchangesinpatternsof
precipitation. Climate change is also likely to lead to an increase in tempera-
ture. Climate models show a high probability (>90%) that by the end of the
21st century, growing season temperatures will exceed the most extreme sea-
sonal temperatures recorded in the past century (Battisti and Naylor 2009).
While an increase in temperature of a few degrees is likely to increase crop
yields in temperate areas, in many tropical areas, even minimal increases in
temperature may be detrimental to food production (Lobell and Burke 2008).
High temperatures reduce crop yields by affecting an array of physiological,
biochemical, and molecular processes.
While it is true that farmers have a long record of adapting to the impacts
of climate variability, predicted climate change represents an enormous chal-
lenge that will test farmers’ ability to adapt and improve their livelihoods
(Adger et al. 2007). Scientific research points to the negative impacts of cli-
mate change on small-scale farmers. This is especially the case in developing
countries (Jones and Thornton 2003; Fischer et al. 2005; Morton 2007). A sce-
nario of rising temperatures, declining rainfall, increase in extreme weather
events, and shifting pest and disease patterns will lead to more short-term
crop failures and long-term production declines (Lobell et al. 2011;Kang
and Banga 2013; Chauhan et al. 2014). Until recently, the impacts of climate
change had largely been regarded as a problem for the future; however, a
key finding of The Fifth Assessment Report (AR5) of the Intergovernmental
Panel on Climate Change (IPCC) is that climate change impacts on food
security are happening now (Vermeulen 2014).
The resulting decline in global per capita food production will threaten
future food security (Brown and Funk 2008). There are also gloomy predic-
tions of how environmental crises will affect global security (e.g., Raleigh
and Urdal 2007). Through direct effects on livelihoods, climate change may
under certain circumstances increase the risk of violent conflict. The environ-
mental problems associated with climate change could also force a greater
number of people to migrate to more favorable areas (Adger et al. 2003;
Feng et al. 2010), leading in some cases to conflict in receiving areas; the
arrival of “environmental migrants or refugees” can burden the economic and
resource base of the receiving area, promoting native-migrant competition
over limited resources, such as cropland and freshwater (Warner 2010).
Mexico is expected to be among the most negatively affected coun-
tries. Small-scale maize farmers are particularly vulnerable because of their
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486 J. Hellin et al.
geographical location as well as their limited adaptive capacity. Climate
change models suggest a drying and warming trend for many parts of Mexico
during the main maize season (May-October), with this trend predicted to
strengthen with time. Predicted trends include: i) a drying of lowland envi-
ronments, ii) an expansion of lowland and mid-altitude environments up the
elevation gradient, and iii) a substantial reduction of the highland environ-
ment (through displacement by warmer mid-altitude type environments and
an expansion of areas too dry for optimal maize production). A large per-
centage of poor rural communities is located in the environments that may
experience the trends described above (Bellon et al. 2005), highlighting the
challenges that the rural poor—many of whom depend on maize for their
livelihoods—face with climate change. Agricultural output in Mexico could
decrease by 25.7% by 2080 as a result of climate change (Cline 2007)and
one of the most affected crops will be the basic staple, maize.
Crop varieties with increased tolerance to heat and drought stress and
resistance to pests and diseases are critical for managing current climatic
variability and for adaptation to progressive climate change. The challenge
is that improved maize germplasm (and other climate-smart technologies)
has not been readily adopted by Mexican smallholder farmers. In this paper,
we argue that in the case of Mexico, researchers and development practi-
tioners have tended to overlook the importance of farmers’ maize landraces
(local varieties) in climate change adaptation initiatives. We suggest that a
more strategic approach would entail giving greater prominence to maize
landraces. This has implications for policy makers, researchers, and develop-
ment practitioners, as they engage in climate change adaptation, the purpose
of which is to manage effectively potential climate risks during the coming
decades as climate changes (Howden et al. 2007).
The rest of this paper is structured as follows. In the next section we
present and discuss the theme of climate-smart agricultural technologies. This
is followed by Section 3, which details how farmer adoption of these tech-
nologies is often less than anticipated. In Section 4, we argue for a broaden-
ing of the focus of climate-adaptation strategies by directing more resources
at farmers’ landraces. Using maize in Mexico as an example, we demonstrate
the largely untapped potential that maize landraces have in helping maize
adapt to climate change. We outline new crop breeding initiatives that are
taking advantage of this potential. In Section 5, we emphasize that efforts
also need to be directed at enhancing adaptive capacity rather than the
promotion of specific adaptation options per se. In Section 6 we conclude.
Climate-smart agricultural technologies contribute to: i) an increase in global
food security, ii) an enhancement of farmers’ ability to adapt to a changing
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Maize Landraces and Adaptation to Climate Change in Mexico 487
climate, and iii) the mitigation of emissions of greenhouse gases. Key tech-
nologies and practices include climate-resilient germplasm and sustainable
land-management practices.
Improved crop varieties are a key output of agricultural research and
have contributed to significant increases in agricultural production and pro-
ductivity (Pingali 2012). Scientific crop breeding will continue to play a
critical role in meeting the challenge of increasing food production in the
face of climate change. The development and dissemination of improved
germplasm have the potential to offset some of the yield losses linked to
climate change. Crop varieties with increased tolerance to abiotic stresses,
including heat and drought stress, will play an important role in manag-
ing current climatic variability and adapting to progressive climate change
(Cooper et al. 2008; Fedoroff et al.2010). Research is required to iden-
tify traits associated with combined heat and drought tolerance, and the
development of improved germplasm for high-temperature, water-limited
environments. The development of climate-resilient germplasm is possi-
ble through a combination of conventional, molecular and, in some cases,
transgenic breeding approaches (Cairns et al. 2013).
Climate change will be especially detrimental to crop production in
cropping systems where soils have been degraded to an extent that they
no longer provide adequate water-holding capacity to buffer crops against
drought and heat stress. These effects will be most severe if irrigation
is not available to compensate for decreased rainfall or to mitigate the
effects of elevated temperatures. Improving genetic adaptation to heat or
drought stress alone will not address these problems; there is also a need
for complementary agronomic interventions (Hobbs and Govaerts 2010).
Agronomic practices involving reduced or zero tillage, enhanced surface
retention of crop residues (mulches), and economically viable crop rotations
and diversification, e.g., conservation agriculture can contribute to cropping
environments that maximize expression of crop genetic potential, buffer
crops against erratic weather, and contribute to climate change mitigation.
At the same time, trade-offs exist, for example because of the use of crop
residues for feed or fuel (Hellin et al. 2013). These trade-offs need to be
addressed and, if necessary, appropriate context-specific solutions must be
developed to be not only environmentally but also socially and economically
Climate-smart agricultural technologies are just the latest in a long list of
technologies that researchers and development practitioners have developed
during the past decades and subsequently promoted in rural areas. The
salutary truth is that the benefits from these technological innovations have
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488 J. Hellin et al.
often not reached the majority of resource-poor farmers cultivating marginal
lands because farmers have not readily adopted them. The reasons behind
farmer (non) adoption of technologies are complex, but previous research
on farmers’ reluctance to adopt soil and water technologies in the 1980s (see
Hudson 1991) and more recently conservation agriculture (Giller et al. 2009;
Erenstein et al. 2012; Andersson and D’Souza 2014) sheds much light on this
An important factor in the non-adoption of climate-smart technolo-
gies has been rural labor shortages (Zimmerer 1993). Many farmers depend
both upon production from their land and upon off-farm income-generating
activities. This is very much the case in many parts of Mexico. This has far-
reaching implications for the availability of labor at different times of year
and can determine farmers’ acceptance of practices such as conservation
agricultural systems, especially if farmers are unable to purchase labor-saving
technologies, such as herbicides to control weeds (Giller et al. 2009).
A major challenge to farmer acceptance of these technologies is that
they are knowledge-intensive. While agricultural extension, education, and
training can help many farmers maximize the potential of their productive
assets through adoption of these technologies, their promotion has coincided
with deep cuts to publicly funded extension services in the developing world
(Ajieh et al. 2008). The breakdown of classical publicly funded agricultural
research and extension services means that these services are now unable to
address the needs of farmers living in marginal environments. In the majority
of cases, the private sector has proven incapable of replacing previous state
services because of high transaction costs, dispersed clientele, and low (or
non-existent) profits (Muyanga and Jayne 2008). The absence of relevant and
competent extension provision leads to low technology adoption rates.
As for crop breeding, efforts have tended to focus on producing high-
yielding germplasm. Despite decades of maize breeding and the promotion
of improved maize varieties, however, the majority of smallholder maize
farmers in rain-fed areas of Mexico continue to use local maize varieties
(Barkin 2002). It is widely accepted that farmers maintain crop diversity for
social, economic, or cultural purposes, and/or when local varieties show
an agronomic performance superior to that of improved varieties (Bellon
2004). Market-related issues in both input and output chains can influence
farmers’ propensity to adopt improved maize varieties. On the input side,
bottlenecks exist in the value chains, which impede farmers’ access to seed.
On the output side, quality and scale-related barriers also exist, inhibiting
the acceptance of farmers’ maize in industrial maize markets (Keleman et al.
Farmers may prefer local maize varieties for culinary and cultural rea-
sons (Brush and Perales 2007; Bellon and Hellin 2011). Perales et al.
(2005) documented the importance of culture in determining maize diver-
sity in Mexico. The authors found a significant association between linguistic
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Maize Landraces and Adaptation to Climate Change in Mexico 489
differentiation and morphological differentiation of maize varieties among
Maya-speaking communities in the highlands of the southern Mexican state
of Chiapas. There are also differences in preferences between women and
men on account of their reproductive and productive roles; women set prior-
ities toward food security and thus tend to favor varieties that are palatable,
nutritious, and meet processing and storage requirements. Women can also
generate income from the artisanal processing and sale of traditional maize
products (Keleman and Hellin 2009).
Adoption studies related to smallholder production systems have shown
risk to be an important component in farmers’ decision making. From
a farmer’s perspective, it may well be too risky to purchase seed of an
unknown variety if there is a chance that drought and/or frosts are going to
have an adverse impact on crop yields. The result is that farmers often trust
local varieties, considering farmer-saved seed to be a “known quantity” while
fearing that unfamiliar seed would perform in unexpected ways (Arellano
Hernández and Arraiga Jordán 2001; Badstue et al. 2007). This may well
be a very rational decision; improved maize varieties, often developed on
research stations, do not necessarily perform well under farmers’ conditions.
For example, in Mexico, a study that examined the relationship between
maize research and rural poverty showed that maize production was largely
coincident with areas of rural poverty; however, it also found a disparity in
the locations of trials used for testing improved maize germplasm and where
the poor lived, suggesting that the potential for spillovers from germplasm
tested in those sites to poor farmers may be limited (Bellon et al. 2005).
Improved varieties that crop breeders identify as superior to landraces under
experimental conditions may actually yield substantially less under farm-
ers’ conditions because of genotype-by-environment interactions that remain
undetected in the data from experimental plots (Keleman et al. 2013).
Maize Landraces
Landraces have been defined as dynamic populations of a cultivated plant
with a historical origin, distinct identity, often genetically diverse and locally
adapted, and associated with a set of farmers’ practices of seed selection and
field management (Camacho Villa et al. 2005). The structure and dynam-
ics of these landraces are the result of both natural and human selection
(Bellon and van Etten 2013). Observers have posited that farmers’ varieties
will be lost in the face of technological change, with modern varieties eventu-
ally replacing landraces wholesale (c.f. Harlan 1975). Detailed, ground-level
studies (Brush et al. 1992; Chambers et al. 2007; Bellon and Hellin 2011)
have both highlighted the threats to farmers’ local varieties and also their
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490 J. Hellin et al.
resilience. In Mexico, 59 well-defined races (e.g., morphologically and genet-
ically distinct sub-populations) of maize have been described (Sanchez et al.
2000; Ureta et al. 2012) and countless varieties exist at the farmer level.
Farmers’ maintenance of local maize varieties may have a very impor-
tant role to play in climate change adaptation in Mexico (Bellon et al. 2011).
In many parts of Mexico, small-scale maize farmers recycle seed either by
saving their seed from the previous harvest and/or obtaining it from fellow
farmers (Badstue et al. 2007; Dyer and Taylor 2008). The vast majority of
these farmers operate under rain-fed conditions, and climate is one of the
most important risk factors in their agricultural systems. Maize landraces in
Mexico show remarkable diversity and climatic adaptability, growing from
arid to humid environments and from temperate to tropical environments.
Ruiz Corral et al. (2008) found a very high level of variation among and
within 41 Mexican maize races for climate adaptation and ecological descrip-
tors. The general overall climatic ranges for maize included 0 to 2900 m
altitude, 11.3to 26.6C annual mean temperature, 12.0to 29.1C growing
season mean temperature, and 426 to 4245 mm annual rainfall (Ruiz Corral
et al. 2008).
Bioclimatic modeling of the impact of climate change on the distribu-
tion of maize races in the future, while showing, on the aggregate, significant
reductions in their potential distribution, also point to contrasting responses
by race, showing no major shifts in areas with high race richness, highlight-
ing the important role of race diversity in buffering the effects of climate
change (Ureta et al. 2012). Providing farmers with access to more diversity
of landraces can, hence, be an important strategy to mitigate the negative
impacts of climate change on their livelihoods.
In some parts of Mexico, there may already exist crop germplasm in the
form of farmers’ local maize varieties that are appropriate for predicted cli-
mates (Bellon et al. 2011;Merceretal.2012). Farmers’ local maize varieties
should be part of the arsenal of climate-smart technologies and practices.
In some cases traditional seed systems may be able to provide farmers
with landraces suitable for agro-ecological conditions under predicted cli-
mate change, after all traditional seed systems are not closed or static but
open and dynamic with seed coming in and out of the systems, with farmers
experimenting and incorporating new seeds (Bellon and van Etten 2013).
However, if suitable germplasm does exist, those farmers who are going to
need it may not currently source it, suggesting that farmers are likely to need
to source seed from outside their traditional geographical ranges. This may
entail the development of new social networks (Bellon et al. 2011).
In practice, broadening the geographical reach of farmers’ seed net-
works could be achieved through exchange visits; linking farmer groups
in different locations; fostering the exchange of germplasm, knowledge,
and practices among them; and encouraging cross-community experimen-
tation with local and introduced crop varieties (Bellon and van Etten
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Maize Landraces and Adaptation to Climate Change in Mexico 491
2013). Landrace populations may also be able to ‘keep up’ with climate
change because of farmer selection of climate-adapted traits among landraces
(Mercer and Perales 2010;Merceretal.2012). Furthermore, maize’s wild rel-
atives, Tripsacum species and Teosinte species and subspecies, are expected
to respond differently to climate change because of different environments
that they currently inhabit (Ureta et al. 2012).
Furthermore, within the primary gene pool of maize and its wild rel-
atives there exists unexploited genetic diversity for novel traits and alleles
(Ortiz et al. 2009) that can be used for breeding new high-yielding and
stress-tolerant cultivars (Jarvis et al. 2008; Ruiz Corral et al. 2008; Chauhan
et al. 2014). Formal breeding efforts as part of climate change-adaptation
strategies will likely depend heavily on the diverse crop genetic resources
that farmers have helped develop across centuries (Burke et al. 2009).
Hence, along with farmers’ use of maize landraces, many farmers may
be able to acquire improved germplasm with new adaptive traits. Thus,
formal crop breeding still has a very important role to play in the devel-
opment and diffusion of improved varieties with appropriate traits to cope
with climate change. As Bellon (2009) notes, having a diversity of ‘winning’
(adaptive) combinations of genes and traits that are constantly being updated
in response to changing situations and new knowledge should allow us to
cope and adapt better to change. This is precisely the idea of the option
value of the evolutionary services that on-farm conservation delivers (Bellon
and van Etten 2013) and is likely to be critical to climate change-adaptation
Small-scale maize farmers’ adoption of improved germplasm has been
minimal and, hence, public and private sector interventions are required to
foster a well-functioning seed system that links formal and informal seed
systems to enable farmers to access climate-adapted seed. The desired result
would be a segmented maize seed sector characterized by both (improved)
landraces and improved maize varieties. The public and private sector would
provide the latter and different actors, including farmers themselves, would
generate seed of landraces for sale and/or exchange.
Landraces as a Breeding Resource
In 1998, when the Food and Agriculture Organization (FAO) of the United
Nations published the State of the World Plant Genetic Resources, there were
261,584 accessions of maize held in gene banks around the world. Of these,
the number of unique landraces held in major collections worldwide ranged
from 58,000 to 80,000 (Taba and Goodman 2007). The international gene
bank at the International Maize and Wheat Improvement Center (CIMMYT)
in Mexico holds in excess of 27,500 accessions of maize, covering primarily
landraces (24,463; 97% of these from the Americas and Caribbean) but also
breeding lines, teosintes, Tripsacum sp., and some pools and pre-breeding
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492 J. Hellin et al.
populations. Within Mexico alone, approximately 18,000 further Mexican
maize accessions are held by regional gene banks, universities, and at the
new National Genetic Resource Centre within Mexico. These resources are
often called an “ark” representing a broad swath of maize genetic diversity,
which may offer a reserve of native alleles and genes of importance to crop
production now and in the future.
Even under the more moderate climate change scenarios, predicted cli-
mate shifts within Mexico are significant; during the past 100 years Mexico
has experienced between 0.5 to 0.9C of warming (Verhulst et al. 2012),
which represents 100 generations of maize or 0.009C per generation. The
moderate predicted changes in the next 50 years in Mexico equate to a
0.08C warming per generation in some maize-growing regions; nine times
that previously experienced.
Compared with hybrids, landrace populations have a wider plasticity in
the range of environments a particular population can successfully grow in
and still maintain yield. This is one of the reasons they are so valued by
farmers. This adaptive feature is a reflection of the heterogeneous nature of
the populations. However, the ability of landraces to adapt to the rapidly
changing climate, as suggested by climate models, is a point of concern. The
ex-situ landrace collections contain many materials that have evolved in envi-
ronments that have a propensity for stress, such as drought, heat, or frost,
during the growing season. For example, in the international maize collection
at CIMMYT, there are in excess of 3,900 landrace accessions (more than half
of which come from Mexico) that originate from locations where the monthly
average daily maximum temperature during the flowering period (based on
1901–2009 data) exceeds 30C. Such landraces offer a unique source of
germplasm, genes, and alleles for “climate change tolerance,” which may
be of benefit to crop improvement activities.
Existing breeding pools contain some genetic variation that can be and
is being harnessed. The continuing genetic gain seen in relatively closed
private-sector breeding programs is testament to this. However, many other
useful genetic characters present in landraces will not have passed through
the bottleneck of genetic selection. With increasing environmental variability,
heterogeneity in traits deployed for adaptation is important to ensure dura-
bility in the long term. The use of non-elite germplasm in plant breeding
is limited for very valid reasons, including issues such as linkage drag—
desirable traits may be associated with undesirable ones in this type of
germplasm; difficulty in making crosses; general adaptation difficulties—non-
elite germplasm may be locally adapted and may not perform well outside
very specific environmental niches; funding limitations—pre-breeding, the
process of making non-elite germplasm suitable for use in breeding, can
be costly and takes time; and the relatively short-term goals, from a breed-
ing perspective, of many breeding projects. Indeed, many races of maize
have been under-investigated as sources of beneficial genes with a focus
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Maize Landraces and Adaptation to Climate Change in Mexico 493
being placed on races more representative of an “ideal” plant type, e.g., the
Tuxpeño race in the case of maize.
Concerted efforts are now focusing on the characterization of landraces
at both genetic and phenotypic levels to better inform and enable selec-
tion and use of these important resources in plant breeding. Examples
include the Seeds of Discovery Initiative funded by Mexico’s Ministry of
Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA)
(, and the French Government and
industry-funded Amaizing Project (
While the most direct and simple approach to providing more climate
-resilient materials to resource-poor farmers may appear to be simply a re-
distribution of those landraces that may be tolerant to changing climates, this
may not be productive because of broad and local adaptation issues (Mercer
et al. 2012) and local culinary preferences. Indeed, it is not only farmers
cultivating landraces who face the challenge of increasing climate variability;
improvement of all germplasm, including hybrids, open-pollinated varieties
(OPVs), and landraces, for climate resilience is required as a tool in a suite
of climate-adaptation strategies.
Using conventional crossing, coupled with modern techniques, such as
genomics-assisted breeding and doubled-haploid technology, it is possible
to incorporate some important novel traits more rapidly, and, in a more
targeted manner (reducing linkage drag) from landraces into more breeder-
friendly germplasm. This process, termed pre-breeding, does not seek to
produce a finished product but rather a suite of easy-to-use donor materials
with associated information that can be deployed in the improvement of
all germplasm types from landraces to elite breeding lines. Multiple genetic
sources for adaptation characteristics of interest should be explored to enable
the development of landrace varieties (and panels of elite varieties) that have
(within landraces and across elite varieties) high degrees of heterozygosity
and heterogeneity for climate-resilience traits. Such materials better enable
buffering capacity in times of stress as demonstrated in studies of the climate-
durable crop pearl millet in Africa (Haussmann et al. 2012).
For those organizations involved in crop breeding, the challenge
remains of ensuring that beneficial genes and alleles are incorporated into
farmer-appropriate genetic backgrounds and that the resulting varieties are
evaluated in field trials that best represent farmer conditions and man-
agement practices. Resource-poor maize farmers in Mexico tend to grow
landraces for a number of reasons, including cultural and culinary pref-
erence, and limited access to improved materials. Bellon et al. (2005)
documented that in Mexico where formal CIMMYT maize trials had been
carried out, only 7 of the 158 sites used were actually in high probabil-
ity rural poverty areas and only 16 of the 158 were within extremely poor
municipalities. The disparity in the locations of the trials largely represents
the focus on managed stress trials, the ease of travel to trial locations, and
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494 J. Hellin et al.
most importantly the evaluation of lines, improved hybrids, and OPVs, which
are the mainstay of international breeding efforts at CIMMYT. The impor-
tance of improving the genetic resilience of landraces has, however, been
recognized and many national breeders in Mexico have components of their
breeding programs that look at landraces. Given the range and diversity of
landraces and farming niches, however, it is going to be a challenge to scale
out improved landraces in a similar way to what has been achieved with
OPVs and hybrids.
The development of suitable trait donor germplasm is an essential step
towards facilitating the development of climate-resilient germplasm across
the whole spectrum of variety types. Strategies, such as participatory plant
breeding, need to be discussed and formulated to identify the most effec-
tive way to enhance the incorporation of useful genetic variation into the
landraces currently used by farmers. These will involve trained plant breed-
ers and active farmer participation. Farmers have been practicing selection
for millennia and as long as they are provided suitable donor germplasm,
they should be quite capable of making effective selections in their own
fields for desired traits, including tolerance to climatic variability.
Considering more formal breeding approaches, while in many arenas
the notion is unpopular, some prioritization of landraces will need to be con-
sidered to ensure that some landraces are genetically protected against future
climatic variability. Irrespective of strategies developed for landrace improve-
ment, it remains that, as a follow up to the development of donor germplasm
and some improved varieties, breeders and extension agents should consider
re-emphasis on the evaluation of farmer-appropriate technologies and tech-
nology packages in locations where target farmers live and work to capitalize
on potential for spillovers from germplasm tested in those sites.
Adaptation Capacity
There also remains the challenge of enhancing adaptive capacity to cli-
mate change. Eakin and Lemos (2006) posit that the high uncertainties in
climate-change scenarios meant that there was growing interest in improv-
ing adaptive capacity as an alternative focus of policy efforts, rather than the
promotion of specific adaptation options per se. There is an expectation that
nation-states will improve their capacity and that of their citizens to adapt
to climate change (Eakin and Lemos 2006). Hence, while specific adaptation
technologies (such as climate-adapted germplasm) and practices are criti-
cal, there is a need to direct more attention at the institutional changes that
empower states to design and implement policy to increase adaptive capacity
of different actors, including farmers. As Thornton et al. (2009) write, in place
of defining large development domains for identifying and implementing
adaptation options, what is needed are localized, community-based efforts
to increase local adaptive capacity.
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Maize Landraces and Adaptation to Climate Change in Mexico 495
A systems approach is needed in which innovation is the result of a
process of networking, interactive learning, and negotiation among a het-
erogeneous set of actors (Klerkx et al. 2009). This very much applies to
climate-change adaptation because “the effectiveness of these adaptations
for mitigating future sensitivity to climatic risk will be strongly influenced by
the ways in which policy enables or inhibits households’ capacity to address
climatic challenges” (Eakin 2005). This is largely because a households’
management of climatic risk is a function of numerous factors, including
education, wealth, natural resources, social organization, and institutional
relationships (Eakin 2005). This calls for increased farmer participation in
stakeholder design of climate-adaptation strategies (Eakin et al. 2007)and
an increase in various dimensions of social capital, including peer groups,
networks, and collective action (Meinke et al. 2006). Strengthening the
social relations of maize production and seed exchange among farmers are
fundamental to a successful adaptation strategy (Mercer et al. 2012).
Public- and private-supported extension programs can play a key
role in the design of more appropriate adaptation strategies by transfer-
ring technology, facilitating interaction, building capacity among farmers,
and encouraging farmers to form their own networks. Extension services
that specifically address climate-change adaptation include disseminating
drought-resistant crop varieties; teaching improved management systems;
and gathering information to facilitate national research work. The breed-
ing and agronomic research work needs to be supported by other factors,
including complementary investments in climate-responsive information and
input-delivery systems; and strengthening of institutions to coordinate grain
marketing with seed, fertilizer, and credit delivery. The development of reli-
able seasonal weather forecast, record of reliable weather, and strengthening
of early warning system are also crucial for facilitating adaption to climate
The above can best be achieved via a judicious mix of public and pri-
vate service provision in the agricultural sector that also addresses multiple
market and government failures in the delivery of technologies, inputs, and
services (Cooper et al. 2008). This requires new institutional arrangements
and policy instruments to enhance local capacity and stimulate the adoption
of improved technologies for adaptation, managing risks, and protection of
vulnerable livelihoods. This requires novel, flexible research and extension
approaches that differ from those more commonly used by policy makers,
donors, researchers, and extension agents (Ekboir et al. 2009). Enhancing the
productivity and profitability in marginal areas will require approaches that
promote the translation of innovations in plant science into concrete bene-
fits for poor farmers and in ways that support the emergence of agricultural
innovation systems as well as respecting and supporting farmers’ preferences
for landraces; there is much emphasis on the importance of breeding crops
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496 J. Hellin et al.
for future climatic conditions even though much of the world’s farming pop-
ulation still relies on landrace populations rather than the products of formal
breeding networks (Mercer and Perales 2010). Production is clearly impor-
tant, but food distribution and exchange also determine food availability
while access to food and food utilization are other important components of
food security (Ingram et al. 2008).
Climate change threatens current agricultural output and, hence, there is a
greater need to enhance agricultural yields and resilience of agro-ecosystems
as well as to improve the livelihoods of farmers. Despite some uncertainties
on the spatially differentiated impact of climate change on agricultural pro-
duction, there is little doubt that germplasm, more suited to future climates,
is critical along with improved agronomic and crop-management practices.
Mesoamerica is the center of origin and diversity for maize, and landraces
may already exist that possess traits that enable adaptation to predicted
Formal crop breeding using landrace resources has a key role to play
in climate change-adaption strategies. Complementary adaptation strategies
would include farmers’ increased use of climate-adapted maize varieties
(with improved tolerance to heat stress, and combined heat and drought
stress), coupled with effective soil moisture-conservation techniques. The
development and dissemination of climate-responsive germplasm may take
several years because the process consists of several steps, including breed-
ing, on-farm testing, release of varieties, and germplasm dissemination.
Research efforts need to be directed at facilitating the development of pre-
breeding germplasm, germplasm (landrace, OPV, and hybrid) enhancement
and varietal release, training seed entrepreneurs, and increasing the provision
of foundation seed. Furthermore, widespread farmer uptake of improved
climate-adapted maize varieties relies on a functioning and efficient seed
The authors are grateful to an anonymous reviewer and the Reviewing Editor
for invaluable comments on an earlier version of this paper. The views
expressed in this paper do not necessarily reflect the views of the authors’
institution or the donors.
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Maize Landraces and Adaptation to Climate Change in Mexico 497
We acknowledge support provided by the CGIAR Research Program on
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... We further suggest that this is more likely to happen if aquaculture smallholders participate in genetic exchange networks, variously called "community-based breeding programs" (CBBP) (Mueller et al., 2015), "participatory plant breeding" (Ceccarelli et al., 2010) or "on-farm dynamic management" (Thomas et al., 2015), that allow concurrent rapid adaptation to local climate change threats and opportunities in a range of environments. CBBP enable the dynamic change that characterizes terrestrial crop "landrace" systems -open, decentralized genetic systems that are constantly evolving (Bellon et al., 2015;Hellin et al., 2014;Loeuille et al., 2013;Poudel and Sthapit, 2015;Sthapit, Padulosi and Mal, 2010;Thomas et al., 2015) -while avoiding inbreeding and genetic erosion (Doyle, 2016). Developing aquaculture CBBP networks will have challenges; however the basic social frameworks for CBBP already exist in many places (Bellon et al., 2015;Frison, 2016;Pautasso et al., 2013;Szuster, 2006). ...
... Technical help from local and regional government organizations and institutions, as well as non-government organizations, will be required (Mueller et al., 2015;Sthapit, Padulosi and Mal, 2010). A recent review and analysis of CBBP in Latin America, Africa and Asia highlights this high dependence of CBBP on external organizational, technical and financial support (Hellin et al., 2014;Mueller et al., 2015). ...
... Networked breeders and farmers exert on-farm selection pressures that change from location to location and over time in the face of climate change stressors and emerging pathogens (Hellin et al., 2014;Loeuille et al., 2013). The key aspect of CPPB is that, whereas local strains are continuously developed for cultivation, the networked, global meta-population continues to evolve indefinitely as a sustainable source of continuously better-adapted genetic material for industrial aquaculture as well as smallholders (Ceccarelli et al., 2010). ...
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... Sin embargo, y a nivel de toda la península, la mayoría de la superficie de maíz es cultivada por pequeños productores minifundistas (hasta 5 hectáreas), quienes conforman la mayor parte del universo de maiceros. Estos utilizan tanto variedades de maíz híbridas, como criollas o nativas, las cuales han sido comúnmente referidas como variedades "locales" o de los "productores", a diferencia de las variedades modernas (híbridas), que son desarrolladas en espacios de investigación por criadores de semillas (HELLIN et al., 2014). Estos maíces criollos, cultivados mayoritariamente por pequeños productores, se destinan sobre todo al autoconsumo familiar, al igual que en el resto de México (BOUÉ et al., 2018;EAKIN et al., 2014 2014; KELEMAN et al., 2013). ...
... Esto, debido a que constituye un insumo de calidad, usado para producir tanto tortillas, como una gran variedad de alimentos típicos o "antojitos" (tamales, atoles, pozole, etc.), beneficiando tanto a la economía familiar como a la seguridad alimentaria a nivel local. Sin embargo, los maíces criollos no solo son cultivados por preferencias culinarias y culturales, sino que conforman una parte relevante de las estrategias de adaptación a las condiciones del clima local y al cambio climático en general (HELLIN et al., 2014;BELLON y VAN ETTEN, 2013;EAKIN, 2005). El maíz criollo se produce bajo el régimen de monocultivo, o como parte de la "milpa", un sistema agroecológico diverso, donde el maíz comparte espacio con diversos cultivos (frijol, calabaza, chile, jitomate, cacahuate, etc.), muy común en regiones como la península de Yucatán. ...
... Los productores que han podido mantener su milpa es por porque han diversificado sus actividades e ingresos, entre los que destacan los trabajos extra-agrícolas y la recepción de remesas enviadas desde Estados Unidos (RADEL et al., 2010;MARDERO et al., 2018). Pero independientemente del régimen de cultivo, la producción de maíces criollos se ha venido reduciendo, tanto en la península como en el resto del país, como ha sido demostrado en diversos estudios (MCLEAN et al., 2019;HELLIN et al., 2014;BELLON et al., 2011;BELLON y HELLIN, 2010). ...
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... Across Mexico, these native races, and the hundreds of locally developed traditional maize varieties selected by farmers from them, provide multiple benefits: agroecological (e.g., adaptation to local environmental stresses [45]), crop diversity conservation [8], cultural [46], culinary, and economic [47]. As with other genetically diverse crop populations [48], the diversity present within traditional maize populations has the potential to make them better able to respond to ongoing environmental changes, including anthropogenic climate change [49], requiring fewer external inputs that are themselves often harmful to the climate and environment. A small but growing number of case studies (e.g., [50,51]) provide evidence that traditionally-based agriculture and the biological and social systems it supports can guide the transition to agricultural production that supports instead of undermines planetary health [52]. ...
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We are in the midst of an unprecedented public and planetary health crisis. A major driver of this crisis is the current nutrition transition—a product of globalization and powerful multinational food corporations promoting industrial agriculture and the consumption of environmentally destructive and unhealthy ultra-processed and other foods. This has led to unhealthy food environments and a pandemic of diet-related noncommunicable diseases, as well as negative impacts on the biophysical environment, biodiversity, climate, and economic equity. Among migrants from the global south to the global north, this nutrition transition is often visible as dietary acculturation. Yet some communities are defying the transition through selective resistance to globalization by recreating their traditional foods in their new home, and seeking crop species and varieties customarily used in their preparation. These communities include Zapotec migrants from the Central Valleys of the southern Mexican state of Oaxaca living in greater Los Angeles, California. Focusing on the traditional and culturally emblematic beverage tejate, we review data from our research and the literature to outline key questions about the role of traditional foods in addressing the public and planetary health crisis. We conclude that to answer these questions, a transnational collaborative research partnership between community members and scientists is needed. This could reorient public and planetary health work to be more equitable, participatory, and effective by supporting a positive role for traditional foods and minimizing their harms.
... Cultural capital, especially in the form of Indigenous knowledge and local knowledge, can guide adaptation practices in North America (Akpinar Ferrand and Cecunjanin, 2014), preserving Indigenous cultures and enhancing future adaptation and resilience (see Box 14.1;Pearce et al., 2012;Audefroy and Cabrera Sánchez, 2017). In Mexico, rainwater harvesting (practised by some Mayan communities) and the use of local-traditional varieties of maize have assisted in the adaptation to climate impacts and promoted food security (Akpinar Ferrand and Cecunjanin, 2014;Hellin et al., 2014). Funding and support for these social adaptation strategies have been uneven (Barbier, 2014;Romeo-Lankao et al., 2014). ...
Since AR5, climate-change impacts have become more frequent, intense and have affected many millions of people from every region and sector across North America (Canada, USA and Mexico). Accelerating climate-change hazards pose significant risks to the well-being of North American populations and the natural, managed and human systems on which they depend (high confidence1). Addressing these risks has been made more urgent by delays due to misinformation about climate science that has sowed uncertainty and impeded recognition of risk (high confidence). {14.2, 14.3} Without limiting warming to 1.5°C, key risks to North America are expected to intensify rapidly by mid-century (high confidence). These risks will result in irreversible changes to ecosystems, mounting damages to infrastructure and housing, stress on economic sectors, disruption of livelihoods, and issues with mental and physical health, leisure and safety. Immediate, widespread and coordinated implementation of adaptation measures aimed at reducing risks and focused on equity have the greatest potential to maintain and improve the quality of life for North Americans, ensure sustainable livelihoods and protect the long-term biodiversity, and ecological and economic productivity, in North America (high confidence). Enhanced sharing of resources and tools for adaptation across economic, social, cultural and national entities enables more effective short- and long-term responses to climate change. {14.2, 14.4, 14.5, 14.6, 14.7}
... Thus, a multidisciplinary characterization approach, combining morphological, genetic, biochemical, and stress response-related studies, has proven to be a more efficient method of exploring landrace diversity and identifying distinctive landrace traits [15,25,39,40]. This approach may provide a better understanding regarding the genetic resources best suited for use in managing the current climatic variability and adapting to progressive climate changes [41,42]. ...
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A prime role in matters of agrobiodiversity is held by landraces, which serve as a repository gene pool able to meet sustainable development goals and to face the ongoing challenges of climate change. However, many landraces are currently endangered due to environmental and socio-economic changes. Thus, effective characterization activities and conservation strategies should be undertaken to prevent their genetic and cultural erosion. In the current study, the morphological, genetic, and biochemical analyses were integrated with stress response-related studies to characterize the diversity of seven Italian autochthonous common bean landraces. The results showed that the morphological descriptors and the neutral molecular markers represent powerful tools to identify and distinguish diversity among landrace populations, but they cannot correlate with the stress tolerance pattern of genetically similar populations. The study also supported the use of proline as a biochemical marker to screen the most salt-sensitive bean landraces. Thus, to fully elucidate the future dynamics of agrobiodiversity and to establish the basis for safeguarding them while promoting their utilization, a multi-level approach should always be included in any local and national program for the characterization/conservation/use of genetic resources. This study should represent the basis for further joint research that effectively contributes to set/achieve Italian priorities towards sustainability in the framework of emerging environmental, societal, and economic challenges.
... Climate change is exacerbating the demand for new crop kinds. To keep up with constantly changing climate conditions, farmers must replace crop varieties with better-adapted kinds (Hellin et al., 2014) [9] . Where acceptable modern varieties do not exist, suitable farmer varieties are required ("variety" refers to all farmed materials in this context). ...
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During the main rainy season, seven maize genotypes were planted in RCBD with three replications each in a 5 meter by. 25 meter (row) plot to evaluate adaptation performance and identify high yielding and moisture stress tolerant genotypes adapted to Kumruk district in order to increase net national crop production in general and product diversification in maize benshangul gumuz in particular. The analysis of variance revealed that genotypes in the test differed significantly at the (p=0.05) probability level for all traits, and the maize grain yield mean value comparison or mean separation result revealed that genotype BH-549 is superior to others with 87.4qt/ha quintals grain yield per hectare value, followed by MHQ-138 and MH-140 genotypes with 70.1 and 62.7 quintals grain yield per hectare value. The superior genotype BH-549 outperformed the other genotypes by 142.78 percent and 74.8 percent, respectively, according to the productivity criterion.
... Yield of cereals is highly affected by stresses like high temperature and drought (Barnabás et al., 2008). A reduction of 25.7% is expected in agriculture production by 2080 due to a change in climate (Hellin et al., 2014). Zhao et al. (2017) reported a reduction of 6%, 7.4%, 3.2%, and 3.1% in wheat, rice, maize and soybean, respectively, due to climate change. ...
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Climate change is among the most crucial concerns of the world. It is a serious threat to the global agriculture and its overall impact on global agriculture is yet not clear. A rise of 2.5-4.5◦C is expected in the global temperature until the end of 21st century. The amount of greenhouse gases particularly CO2 is increasing at an alarming rate and is enhancing the plant photosynthesis and productivity. However, this increase in productivity is counteract by the more negative effects of climate change on agriculture like increased evapotranspiration, drought, floods, changes in the amount and distribution of rainfall, higher pest infestations and more irrigation demand. Climate change also affects the nutrients availability and efficiency by influencing microbial activities and population in the soil. Therefore, adaptation of agriculture sector to the changing climate is indispensable because of its sensitivity and size. This review is aimed to document the possible impacts of climate change on agriculture, its causes and future projections. Some strategies are also advised to mitigate the emission of greenhouse gases, to reduce the negative impacts of climate change on agriculture and to make new policies keeping in view their broader consequences on agriculture.
Maize is a highly important crop, not only because it is a staple crop for humans but also because it is a major source of feed for animals and has immense industrial potential. Existence of vast genetic diversity in maize germplasm makes it an ideal model plant for plant genetic studies. This diversity could play a vital role in maize breeding programmes aimed to enhance its agronomic performance under changing climate. Genome-wide association study takes advantage of such genetic diversity to reveal the genetics underlying a complex phenotypic trait. With the emergence of next-generation sequencing (NGS) and high-throughput phenotyping techniques, the significance of GWAS has been increased. In the last decade, a huge number of GWA studies have been performed in different crops for different phenotypic traits. Extensive natural variations, rapid linkage disequilibrium (LD) decay, wide climatic adaptability and availability of reference genome make maize an ideal crop for GWAS. GWAS in maize identified thousands of genomic regions associated with various phenotypic traits. In general, agronomic traits are polygenic and get affected by different types of stresses, which result in reduced yield and quality. Efforts have been made to improve agronomic traits in maize using traditional breeding and marker-assisted selection breeding. However, due to the low resolution of trait mapping, limited success has been achieved. In this chapter, we discuss how GWAS could take advantage of natural diversity and can play a chief role in improving the agronomic traits in maize. We also shed a light on the importance of functional validation of genes that are found to be associated with a specific trait using GWAS.
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Background Maize ( Zea mays L.) is a staple crop cultivated on a global scale. However, its ability to feed the rapidly growing human population may be impaired by climate change, especially if it has low climatic niche and range lability. One important question requiring clarification is therefore whether maize shows high niche and range lability. Methods We used the COUE scheme (a unified terminology representing niche centroid shift, overlap, unfilling and expansion) and species distribution models to study the niche and range changes between maize and its wild progenitors using occurrence records of maize, lowland teosinte ( Zea mays ssp. parviglumis ) and highland teosinte ( Zea mays ssp. mexicana ), respectively, as well as explore the mechanisms underlying the niche and range changes. Results In contrast to maize in Mexico, maize did not conserve its niche inherited from lowland and highland teosinte at the global scale. The niche breadth of maize at the global scale was wider than that of its wild progenitors (ca. 5.21 and 3.53 times wider compared with lowland and highland teosinte, respectively). Compared with its wild progenitors, maize at global scale can survive in regions with colder, wetter climatic conditions, as well as with wider ranges of climatic variables (ca. 4.51 and 2.40 times wider compared with lowland and highland teosinte, respectively). The niche changes of maize were largely driven by human introduction and cultivation, which have exposed maize to climatic conditions different from those experienced by its wild progenitors. Small changes in niche breadth had large effects on the magnitude of range shifts; changes in niche breadth thus merit increased attention. Discussion Our results demonstrate that maize shows wide climatic niche and range lability, and this substantially expanded its realized niche and potential range. Our findings also suggest that niche and range shifts probably triggered by natural and artificial selection in cultivation may enable maize to become a global staple crop to feed the growing population and adapting to changing climatic conditions. Future analyses are needed to determine the limits of the novel conditions that maize can tolerate, especially relative to projected climate change.
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This study examined the perception of constraints to privatization and commercialization ( P and C) of agricultural extension services by extension professionals and farmers. The study was carried out in Delta State, Nigeria. A sample size of 224 respondents comprising of 134 extension professionals and 90 farmers were involved in the study. Data for the study were collected through the use of structured questionnaire and structured interview schedule. The questionnaire was used for the extension professionals, while the interview schedule was used for the farmers. Data were collected between March and September, 2007. Trained field assistants selected in each location, in addition to the researchers collected the data. Data were analyzed using mean perception scores, standard deviations and t-test. Results show that all the 21 constraints examined by the study were perceived as being important. There was a general agreement between extension professionals and farmers regarding constraints to P and C of agricultural extension services. Differences were observed in only 6 constraints. The study concludes that the constraints identified by this study are serious issues to P and C and should therefore be given adequate consideration by policy makers, stakeholders in extension service delivery and the government of Delta State, Nigeria before final decision is taken on whether or not to privatize and commercialize agricultural extension services in the State.
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Progress has been significant in climate science and the direct and indirect influences of climate on agricultural productivity. With the likely growth of the world's population toward 10 billion by 2050, demand for food crops will grow faster than demand for other crops. The prospective climate change is global warming (with associated changes in hydrologic regimes and other climatic variables) induced by the increasing concentration of radiatively active greenhouse gases. Climate models project that global surface air temperatures may increase by 4.0-5.8 degrees C in the next few decades. These increases in temperature will probably offset the likely benefits of increasing atmospheric concentrations of carbon dioxide on crop plants. Climate change would create new environmental conditions over space and time and in the intensity and frequency of weather and climate processes. Therefore, climate change has the potential to influence the productivity of agriculture significantly. Climate variability has also become a reality in India. The increase in mean temperature by 0.3-0.6 degrees C per decade since the 1860s across India indicates significant warming due to climate change. This warming trend is comparable to global mean increases in temperature in the past 100 years. It is projected that rainfall patterns in India would change with the western and central areas witnessing as many as 15 more dry days each year, whereas the northern and northwestern areas could have 5 to 10 more days of rainfall annually. Thus, dry areas are expected to get drier and wet areas wetter. It is projected that India's population could reach 1.4 billion by 2025 and may exceed China's in the 2040s. If agricultural production is adversely affected by climate change, livelihood and food security in India would be at risk. Because the livelihood system in India is based on agriculture, climate change could cause increased crop failure and more frequent incidences of pests. Therefore, future challenges will be more complex and demanding. This chapter focuses on the variability of climate change and its probabilistic effects on agricultural productivity and adaptation and mitigation strategies that can help in managing the adverse effect of climate change on agricultural productivity, in particular for India.
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Climate change is expected to be a significant threat to biodiversity, including crop diversity at centers of origin and diversification. As a way to avoid food scarcity in the future, it is important to have a better understanding of the possible impacts of climate change on crops. We evaluated these impacts on maize, one of the most important crops worldwide, and its wild relatives Tripsacum and Teocintes. Maize is the staple crop in Mexico and Mesoamerica, and there are currently about 59 described races in Mexico, which is considered its center of origin . In this study, we modeled the distribution of maize races and its wild relatives in Mexico for the present and for two time periods in the future (2030 and 2050), to identify the potentially most vulnerable taxa and geographic regions in the face of climate change. Bioclimatic distribution of crops has seldom been modeled, probably because social and cultural factors play an important role on crop suitability. Nonetheless, rainfall and temperature still represent a major influence on crop distribution pattern, particularly in rainfed crop systems under traditional agrotechnology. Such is the case of Mexican maize races and consequently, climate change impacts can be expected. Our findings generally show significant reductions of potential distribution areas by 2030 and 2050 in most cases. However, future projections of each race show contrasting responses to climatic scenarios. Several evaluated races show new potential distribution areas in the future, suggesting that proper management may favor diversity conservation. Modeled distributions of Tripsacum species and Teocintes indicate more severe impacts compared with maize races. Our projections lead to in situ and ex situ conservation recommended actions to guarantee the preservation of the genetic diversity of Mexican maize.
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Climate change, caused by anthropogenic activities, is a universal phenomenon across the globe. There is general consensus that combating climate change will require a set of internationally coordinated policy interventions for reducing greenhouse gas (GHG) emissions besides addressing regional or global vulnerabilities, development patterns, equity distribution, and technology transfer. Agriculture is both a victim and an abettor of climate change. Serious attention is thus required, not only to enhance its adaptation capacity but also to exploit its mitigation potential as a carbon sink. A sustainable policy shift toward enhanced food security, preservation of freshwater resources, prevention of soil degradation, and maintenance of biological diversity and ecosystems remain the hallmark of mitigation strategies. Improved adaptive capacity relative to climate-resilient agriculture needs to be integrated with global developmental paths aimed at reducing social inequalities and alleviating poverty. The United Nations' Millennium Development Goals provide an excellent backdrop for integrating adaptation and sustenance into global development polity. World essentially requires a climate closest to which all forms of life have adapted during their evolution. Deceleration of carbon emissions and a shift to a long-term and sustainable growth paradigm are essential imperatives, notwithstanding the associated economic costs. Research has shown that benefits of reducing methane emissions alone would be to the tune of US$700–US$5000 per metric ton, whereas the abatement costs have been estimated to be less than US$250.
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Mixed crop–livestock farming systems prevail in Mexico – typically rain-fed and smallholder systems based on maize and ruminants and spanning diverse agro-ecologies. Maize grain is the key Mexican staple produced for home consumption and the market. Maize crop residues (stover) are an important by-product, primarily for feed use, often through in situ stubble grazing and/or as ex situ forage. This paper explores maize stover use along the agro-ecological gradient and the potential trade-offs, particularly the widespread use of maize stover as feed against its potential use as mulch (soil cover) to manage soil health within the context of conservation agriculture. The paper builds on three case study areas in Mexico in contrasting agro-ecologies: (semi-)arid, temperate highland and tropical sub-humid. Data were obtained through expert consultation and semi-structured farmer group/community surveys. Although in situ grazing is found in all three study sites, it represented the bulk of stover use in only one site (70% of stover in the sub-humid tropics), with ex situ feed dominating in the other two sites (>80%). Maize stover commercialization is limited and mainly restricted to households with no livestock and often within the local context. Farmers are generally hesitant to adopt conservation agricultural practices that require the retention of stover as mulch, as this competes with their livestock feed needs and purchased feed is expensive. To reduce trade-offs, a portfolio of options could be adapted to these mixed systems, including partial residue retention, cover and feed crops and sustainable intensification. Promising but yet to be explored, are investments in the genetic improvement of maize stover feed quality.
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This analysis of maize in Mexico reveals how technocratic prejudices and modernizing ideologies have had a devastating impact. The tenacity with which the peasantry continues to support traditional social and productive organizations with their own resources is evidence of the currency of their unique vision of society. This vision is leading them to inject new vigour into rural society by diversifying their productive strategies, an approach that has always been a central part of rural survival, but whose significance has been underestimated by social scientists who have largely focused on their productivity in the fields.
Agriculture contributes significantly to greenhouse gas (GHG) emissions: CO2, CH4 and N2O. Promoting agricultural practices that mitigate climate change by reducing GHG emissions is important; but those same practices also have to improve farmer production and income and buffer the production system against changes in climate. New agricultural practices also need to prevent further soil degradation and improve system resilience. Conservation agriculture (CA), based on minimal soil disturbance, permanent ground cover and crop rotations is a management system that achieves these goals; it results in improved soil physical and biological health, and better nutrient cycling and crop growth. CA also increases water infiltration and soil penetration by roots, which allows crops to better adapt to lower rainfall and make better use of irrigation water. Water and wind erosion are also reduced by CA since the soil surface is protected and water runoff is lowered as more water enters the soil profile. CA can also help to mitigate climate change. Growing rice with less water and adopting CA practices results in less CH4 emission. However, care has to be taken with fertilizer management to minimize N2O emissions that can increase under resulting aerobic conditions. CA can also substantially reduce CO2 emissions through reduced diesel use and increased sequestration of C in the soil. This chapter recommends that integrated research and participatory extension are needed to fine-tune CA to specific locations to convince farmers to adopt this technology.