How Local is Local?
Assessing the Vulnerability of Traditional
Maize Seed Systems in Mexico to Climate
Change
Mauricio R. Bellon1, David Hodson2
and Jon Hellin2
1Bioversity International, 2CIMMYT

Maize and traditional seed systems
 Maize continues to be a fundamental crop for
millions of small-scale farmers in Mexico
 The vast majority rely on themselves or fellow
farmers to obtain seed to plant every season
 Sourcing of seed is not a random event but is
embedded in a well-structured system with rules
and expectations
 Traditional seed systems are based on family and
local social networks, regulated by ideas of
fairness, and of respect to the seed

Climate change and traditional seed
systems
 Climate change is predicted to have major
impacts on small scale farmers in the developing
world but these impact are likely be complex,
locally-specific and hard to predict (Morton 2007)
 Mexico and Central America are predicted to be a
region at considerable risk from climate change
 Given the importance of maize cultivation for the
wellbeing of small scale farmers and of the seed
systems that underpin it, it is fundamental to
explore the potential impacts of climate change on
traditional seed systems

Hypothesis and assumptions
 The hypothesis addressed here is that traditional maize
seed systems may not be able to provide small-scale
farmers with adapted landraces in the face of climate
change
 because they are “too local” relative to the spatial scope of
environmental shifts expected with climate change
 It is assumed that if predicted environments are similar to
current ones, the scope of the seed systems is adequate
 if not, farmers may need to get seed outside their traditional
ranges, in areas resembling the novel environment they will
face

Methods
 The spatial scope of traditional maize seed systems was studied in
transects across an altitudinal gradient from 10 to 2980 masl in five states
of eastern Mexico (Veracruz, Puebla, Tlaxcala, Hidalgo, Edo. de Mexico)
 A random sample of 20 communities in four transects were selected, with
20 households per community randomly chosen for a total sample of 400
households (survey carried out in 2003)
 An inventory of seed lots used by household was elicited with the specific
location where the seed was obtained and then mapped
 The spatial scope of the origin of seed lots was linked to maize agro-climate
environments as defined by CIMMYT (Setimela et al. 2005)
 Three major IPCC global circulation models were used, downscaled to
cover the study region for 2050
 To address some of the uncertainties from GCM’s and emission scenarios,
median values for the six alternative future climates in 2050 (3 GCM x 2
scenarios) were used to represent a likely future scenario and one extreme
one HadCM3, scenario A2 for 2050
 Potential environmental shifts in agro-climate environments were compared
to the current spatial scope of traditional seed systems

Transects 10 – 2980 masl in Eastern
Mexico
• 20 communities Marginality level Communities
• 20 households/ community (poverty) 2005
• 4 maize agro-climatic zones:
wet lowland, High 16
dry lowland, Medium 3
wet upper mid-altitude Low 1
highland Source: CONAPO

Farmers’ characteristics
Maize agro-climatic zone WL DL WUMA H Total Signif.
Indigenous households (%) 64.3 15.0 50.0 3.3 30.5 0.0000
Mean number of crops 2.8 2.3 2.8 3.9 3.2 0.0000
Mean number of fruit tree species 1.3 1.8 1.7 0.6 1.1 0.0000
Mean number of domestic animal species kept 1.9 1.1 2.2 2.8 2.3 0.0000
Households who perform off-farm labor 56.4 47.5 72.5 41.1 50.3 0.001
Mean number of non farm activities/hh 2.5 2.6 2.7 2.4 2.5 ns
Maize planted
Spring-Summer (mean area/hh) 1.8 1.9 1.3 3.0 2.3 0.0004
Autumn-Winter (mean area/hh) 1.8 1.9 1.1 0.0 1.7 ns
Type of maize producers (%)
deficit 27.1 32.5 52.5 36.1 34.3 0.08
equilibrium 12.9 7.5 12.5 11.7 11.7
surplus 60 60 35 52.2 54
Number of uses of maize 3.3 3.2 2.7 3.2 3.2 ns
Farmers who produce for self consumption 99.29 97.5 95 97.21 97.74 ns
Farmers who sell 60 42.5 50 42.2 49.3 0.013
Household with migrants within country 22.86 22.5 25 17.8 20.8 ns
Household with migrants outside country 5.7 17.5 10 17.8 12.75 0.006
WL: Wet Lowland; DL: Dry Lowland; WUMA: Wet Upper Mid-altitude; H: Highland

Characterizing traditional seed systems
Wet
Upper
Wet Dry Mid-
Maize mega-environment Lowland Lowland altitude Highland Total Signif.
No. of seed lots (SL) 177 47 62 318 604
SL of landraces (%) 98.3 97.9 98.4 97.5 97.9 ns
Average no SL/farmer 1.3 1.2 1.6 1.8 1.5 0.000
SL size 20.0 14.0 9.0 20.0 18.0 0.000
SL saved by farmer (%, 2003) 75.7 85.1 82.3 72.6 75.5 ns
If not saved, obtained from family, friends,
neighbors (%) 88.1 85.7 100.0 85.1 87.0 ns
Age of SL saved by farmer (median, years) 10.0 10.0 15.0 8.0 10.0 0.02
SL obtained outside community historical (%) 13.0 12.8 4.8 28.6 20.4 0.000
SL obtained outside community 2003 (%) 1.7 0 0 6.6 3.7 0.001
SL provided to other farmers 2002 (%) 25.4 23.4 29.0 18.2 21.9 ns
SL provided outside the community 2002 (%) 1.7 4.3 0 3.8 2.8 ns

Spatial reach of seed systems study
communities

Farmer experimentation
Wet
Upper
Wet Dry Mid-
Maize agro-climatic zone Lowland Lowland altitude Highland Total Signif.
Farmers who experimented (%) 19.3 22.5 12.5 34.1 25.6 0.003
Number of experimental SL 30 13 5 79 127
Experimental SL of improved varieties 10 4 1 4 19
Experimental SL retained 6 1 0 9 16
SL of improved varieties retained 2 1 0 0 3
•Farmers experiment with landraces and improved varieties
•Retention is low, particularly of improved varieties
•Improved varieties found wanting

The spatial scope of traditional seed
systems
Wet
Upper
Wet Dry Mid-
Maize agro-climatic zone (%) Lowland Lowland altitude Highland Total Signif.
SL obtained < 10 km historical 96.0 93.5 100 87.1 91.6 0.000
SL obtained < 10 km 2003 99.4 100 100 97.2 98.3 0.054
SL obtained altitude +/- 50 m historical 96.5 95.7 95.2 78.8 87.0 0.000
SL obtained altitude +/- 50 m 2003 99.4 100 100 95.2 97.3 0.01
SL distributed < 10 km 2002 97.6 100 100 100 99.2 ns
SL distributed to altitude +/- 50 m 2002 100 100 100 90.2 95.8 0.033
• more than 90% of seed lots originated and were distributed within a radius of less
than 10 km of where they were planted
• though with statistically significant differences across environments

Histogram of the distances from which seed lots
were acquired historically differentiated by maize
agro-climate environment

Predicted changes in maize agro-climate
environments current-2050
current Median of 6 futures HadCM3 model A2a scenario

Changes in the spatial scope of current
traditional seed systems under
predictions of climate change
% of pixels
covered by a Number of studied
10 km radius communities
Future climate
Maize mega- already within
environment Current 2050 Change Total the 10 Km
Wet Lowland 33.7 31.6 -2.1 7 7
Dry Lowland 12.0 18.3 2.7 2 2
Wet Lower Mid-
altitude 4.4 2.7 -1.7
Wet Upper Mid-
altitude 5.1 4.7 -0.4 2 2
Dry Mid-altitude 0.9 8.5 7.6
Highland 32.8 24.8 -8.0 8 6

Results
 Traditional seed systems are quite local
 90% of the seed lots are obtained within 10 km of
the community
 Most seed lots are saved and of landraces
 Seed not saved is mostly obtained from family,
friends and neighbors (local social networks)
 Highland agro-climate environment is the most
open and dynamic in terms of seed flows
 Significant changes in maize agro-climate
environments with climate change are expected
 Most dramatic in the highlands that almost disappears

Results (con’t)
 Except in the highland mega environment, all studied
communities already have access to predicted mega
environments within a 10 km radius
 Traditional seed systems may be able to cope with predicted
climate change, except in the highland mega environment
 Preliminary research indicates that highland landraces do
not appear to express the plasticity necessary to sustain
productivity under climate change (Mercer and Perales,
2010)
 Highland mega environment merits particular attention in
terms of adaptation measures to climate change for maize
farmers
 This may require increasing the spatial scope of the
highland seed systems and connecting farmers to others
outside their traditional range

Conclusions
 Traditional seed systems in study area have a
limited spatial scope—are quite local
 However, results indicate that they should be able
to continue to provide adapted landraces under
predicted climate change, except in the highlands
 These results apply to the study area, and may be
different for other parts of the country and for
other crops
 There is a need for further research on the spatial
scope of traditional seed systems and on the
evolutionary capacity of landrace populations to
climate change

Global relevance: the issue and the
approach
 Results presented here quite local, but
 Traditional seed systems important for millions of
small-scale farmers worldwide and will be affected
by climate change, hence the issue is of global
relevance
 Approached that can be replicated under diverse
conditions:
 Quantifying the spatial scope of the systems
 Relating this scope to potential climate shifts that would modify the
distribution of growing environments and hence the fit between the
current germplasm used and the future needed