Declining maize diversity: Understanding its drivers and analyzing policy options for in-situ conservation

Transcription

1 Declining maize diversity: Understanding its drivers and analyzing policy options for in-situ conservation Alejandro López-Feldman 1 George Dyer 2 1 CIDE (Econ Dpt.) / Fulbright visiting scholar (NSOE, Duke University) 2 DAS López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

2 What do we know? López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

3 What do we know? Genetic erosion in maize s center of origin George A. Dyer a,b,1, Alejandro López-Feldman c, Antonio Yúnez-Naude b,d, and J. Edward Taylor e a Abt Associates, Inc., Mexico D.F., Mexico; b Centro de Estudios Económicos, El Colegio de México, Mexico D.F., Mexico; c División de Economía, Centro de Investigación y Docencia Económicas, Mexico D.F., Mexico; d Desarrollo y Alimentación Sustentable, A.C., Mexico D.F., Mexico; and e Department of Agricultural and Resource Economics and Giannini Foundation of Agricultural Economics, University of California, Davis, CA Edited* by Major M. Goodman, North Carolina State University, Raleigh, NC, and approved August 4, 2014 (received for review April 16, 2014) Crop genetic diversity is an indispensable resource for farmers and varieties or landraces exerting an influence on maize s genetic professional breeders responding to changing climate, pests, and structure (12 14, 17). Seed exchange presumably explains why diseases. Anecdotal appraisals in centers of crop origin have 91% of isoenzymatic variation in maize landraces occurs within suggested serious threats to this diversity for over half a century. populations, whereas individual teosinte (wild Z. mays) populations remain genetically distinct (6, 18). The low genetic di- However, a nationwide inventory recently found all maize races previously described for Mexico, including some formerly considered nearly extinct. A flurry of social studies seems to confirm that versity of some accessions also has been attributed to human factors i.e., small field sizes (or few ears used for seed) for farmers maintain considerable diversity. Here, we compare estimates of maize diversity from case studies over the past 15 y with specialty varieties (1). In fact, most maize alleles are very rare nationally and regionally representative matched longitudinal (frequencies <0.01), and many are found in single accessions that data from farmers across rural Mexico. Our findings reveal an presumably correspond with farmer fields (1). Rather than segregated into discrete races, maize diversity may be spread con- increasing bias in inferences based on case study results and widespread loss of diversity. Cross-sectional, case study data suggest tinuously across thousands of populations (i.e., fields) in rural that farm-level richness has increased by 0.04 y 1 nationwide; however, direct estimates using matched longitudinal data reveal that structure is difficult because of farmers extensive control of crop Mexico (13, 14, 17, 18). Accounting for maize s metapopulation richness dropped 0.04 y 1 between 2002 and 2007, from 1.43 to population dynamics (11, 13). Although maize demography can 1.22 varieties per farm. Varietal losses occurred across regions and be modeled on management practices, the data required remain altitudinal zones, and regardless of farm turnover within the sector. critically scarce (11, 19). Numerous statistics have been reported, Extinction of local maize populations may not have resulted in an but only average varietal richness per farm is estimated consistently across studies. This is considered the key statistic for di- immediate loss of alleles, but low varietal richness and changes in maize s metapopulationdynamicsmaypreventfarmersfromaccessing germplasm suitable to a rapidly changing climate. Declining versity conservation in crops (10). We compare farm richness estimates based on cross-sectional yields could then lead farmers to leave the sector and result in a further loss of diversity. Similarities in research approaches across crops case study data and longitudinal survey data from a representative sample of rural farms to assess the state of maize conser- suggest that methodological biases could conceal a loss of diversity at other centers of crop origin. vation in Mexico. Our findings reveal significant changes in López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

4 What do we know? Genetic erosion in maize s center of origin George A. Dyer a,b,1, Alejandro López-Feldman c, Antonio Yúnez-Naude b,d, and J. Edward Taylor e a Abt Associates, Inc., Mexico D.F., Mexico; b Centro de Estudios Económicos, El Colegio de México, Mexico D.F., Mexico; c División de Economía, Centro de Investigación y Docencia Económicas, Mexico D.F., Mexico; d Desarrollo y Alimentación Sustentable, A.C., Mexico D.F., Mexico; and e Department of Agricultural and Resource Economics and Giannini Foundation of Agricultural Economics, University of California, Davis, CA Edited* by Major M. Goodman, North Carolina State University, Raleigh, NC, and approved August 4, 2014 (received for review April 16, 2014) Crop genetic diversity is an indispensable resource for farmers and professional breeders responding to changing climate, pests, and diseases. Anecdotal appraisals in centers of crop origin have suggested serious threats to this diversity for over half a century. However, a nationwide inventory recently found all maize races previously described for Mexico, including some formerly considered nearly extinct. A flurry of social studies seems to confirm that farmers maintain considerable diversity. Here, we compare estimates of maize diversity from case studies over the past 15 y with nationally and regionally representative matched longitudinal data from farmers across rural Mexico. Our findings reveal an increasing bias in inferences based on case study results and widespread loss of diversity. Cross-sectional, case study data suggest that farm-level richness has increased by 0.04 y 1 nationwide; however, direct estimates using matched longitudinal data reveal that richness dropped 0.04 y 1 between 2002 and 2007, from 1.43 to 1.22 varieties per farm. Varietal losses occurred across regions and altitudinal zones, and regardless of farm turnover within the sector. Extinction of local maize populations may not have resulted in an immediate loss of alleles, but low varietal richness and changes in maize s metapopulationdynamicsmaypreventfarmersfromaccessing germplasm suitable to a rapidly changing climate. Declining yields could then lead farmers to leave the sector and result in a further loss of diversity. Similarities in research approaches across crops suggest that methodological biases could conceal a loss of diversity at other centers of crop origin. varieties or landraces exerting an influence on maize s genetic structure (12 14, 17). Seed exchange presumably explains why 91% of isoenzymatic variation in maize landraces occurs within populations, whereas individual teosinte (wild Z. mays) populations remain genetically distinct (6, 18). The low genetic diversity of some accessions also has been attributed to human factors i.e., small field sizes (or few ears used for seed) for Contrary to previous assessments small farmers in Mexico are planting fewer maize varieties than before. First documented decline in a center of crop diversity. specialty varieties (1). In fact, most maize alleles are very rare (frequencies <0.01), and many are found in single accessions that presumably correspond with farmer fields (1). Rather than segregated into discrete races, maize diversity may be spread continuously across thousands of populations (i.e., fields) in rural Mexico (13, 14, 17, 18). Accounting for maize s metapopulation structure is difficult because of farmers extensive control of crop population dynamics (11, 13). Although maize demography can be modeled on management practices, the data required remain critically scarce (11, 19). Numerous statistics have been reported, but only average varietal richness per farm is estimated consistently across studies. This is considered the key statistic for diversity conservation in crops (10). We compare farm richness estimates based on cross-sectional case study data and longitudinal survey data from a representative sample of rural farms to assess the state of maize conservation in Mexico. Our findings reveal significant changes in López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

5 What do we know? Genetic erosion in maize s center of origin George A. Dyer a,b,1, Alejandro López-Feldman c, Antonio Yúnez-Naude b,d, and J. Edward Taylor e a Abt Associates, Inc., Mexico D.F., Mexico; b Centro de Estudios Económicos, El Colegio de México, Mexico D.F., Mexico; c División de Economía, Centro de Investigación y Docencia Económicas, Mexico D.F., Mexico; d Desarrollo y Alimentación Sustentable, A.C., Mexico D.F., Mexico; and e Department of Agricultural and Resource Economics and Giannini Foundation of Agricultural Economics, University of California, Davis, CA Edited* by Major M. Goodman, North Carolina State University, Raleigh, NC, and approved August 4, 2014 (received for review April 16, 2014) Crop genetic diversity is an indispensable resource for farmers and professional breeders responding to changing climate, pests, and diseases. Anecdotal appraisals in centers of crop origin have suggested serious threats to this diversity for over half a century. However, a nationwide inventory recently found all maize races previously described for Mexico, including some formerly considered nearly extinct. A flurry of social studies seems to confirm that farmers maintain considerable diversity. Here, we compare estimates of maize diversity from case studies over the past 15 y with nationally and regionally representative matched longitudinal data from farmers across rural Mexico. Our findings reveal an increasing bias in inferences based on case study results and widespread loss of diversity. Cross-sectional, case study data suggest that farm-level richness has increased by 0.04 y 1 nationwide; however, direct estimates using matched longitudinal data reveal that richness dropped 0.04 y 1 between 2002 and 2007, from 1.43 to 1.22 varieties per farm. Varietal losses occurred across regions and altitudinal zones, and regardless of farm turnover within the sector. Extinction of local maize populations may not have resulted in an immediate loss of alleles, but low varietal richness and changes in maize s metapopulationdynamicsmaypreventfarmersfromaccessing germplasm suitable to a rapidly changing climate. Declining yields could then lead farmers to leave the sector and result in a further loss of diversity. Similarities in research approaches across crops suggest that methodological biases could conceal a loss of diversity at other centers of crop origin. varieties or landraces exerting an influence on maize s genetic structure (12 14, 17). Seed exchange presumably explains why 91% of isoenzymatic variation in maize landraces occurs within populations, whereas individual teosinte (wild Z. mays) populations remain genetically distinct (6, 18). The low genetic diversity of some accessions also has been attributed to human factors i.e., small field sizes (or few ears used for seed) for Contrary to previous assessments small farmers in Mexico are planting fewer maize varieties than before. First documented decline in a center of crop diversity.... but we don t know why. specialty varieties (1). In fact, most maize alleles are very rare (frequencies <0.01), and many are found in single accessions that presumably correspond with farmer fields (1). Rather than segregated into discrete races, maize diversity may be spread continuously across thousands of populations (i.e., fields) in rural Mexico (13, 14, 17, 18). Accounting for maize s metapopulation structure is difficult because of farmers extensive control of crop population dynamics (11, 13). Although maize demography can be modeled on management practices, the data required remain critically scarce (11, 19). Numerous statistics have been reported, but only average varietal richness per farm is estimated consistently across studies. This is considered the key statistic for diversity conservation in crops (10). We compare farm richness estimates based on cross-sectional case study data and longitudinal survey data from a representative sample of rural farms to assess the state of maize conservation in Mexico. Our findings reveal significant changes in López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

6 What do we know? Genetic erosion in maize s center of origin George A. Dyer a,b,1, Alejandro López-Feldman c, Antonio Yúnez-Naude b,d, and J. Edward Taylor e a Abt Associates, Inc., Mexico D.F., Mexico; b Centro de Estudios Económicos, El Colegio de México, Mexico D.F., Mexico; c División de Economía, Centro de Investigación y Docencia Económicas, Mexico D.F., Mexico; d Desarrollo y Alimentación Sustentable, A.C., Mexico D.F., Mexico; and e Department of Agricultural and Resource Economics and Giannini Foundation of Agricultural Economics, University of California, Davis, CA Edited* by Major M. Goodman, North Carolina State University, Raleigh, NC, and approved August 4, 2014 (received for review April 16, 2014) Crop genetic diversity is an indispensable resource for farmers and professional breeders responding to changing climate, pests, and diseases. Anecdotal appraisals in centers of crop origin have suggested serious threats to this diversity for over half a century. However, a nationwide inventory recently found all maize races previously described for Mexico, including some formerly considered nearly extinct. A flurry of social studies seems to confirm that farmers maintain considerable diversity. Here, we compare estimates of maize diversity from case studies over the past 15 y with nationally and regionally representative matched longitudinal data from farmers across rural Mexico. Our findings reveal an increasing bias in inferences based on case study results and widespread loss of diversity. Cross-sectional, case study data suggest that farm-level richness has increased by 0.04 y 1 nationwide; however, direct estimates using matched longitudinal data reveal that richness dropped 0.04 y 1 between 2002 and 2007, from 1.43 to 1.22 varieties per farm. Varietal losses occurred across regions and altitudinal zones, and regardless of farm turnover within the sector. Extinction of local maize populations may not have resulted in an immediate loss of alleles, but low varietal richness and changes in maize s metapopulationdynamicsmaypreventfarmersfromaccessing germplasm suitable to a rapidly changing climate. Declining yields could then lead farmers to leave the sector and result in a further loss of diversity. Similarities in research approaches across crops suggest that methodological biases could conceal a loss of diversity at other centers of crop origin. varieties or landraces exerting an influence on maize s genetic structure (12 14, 17). Seed exchange presumably explains why 91% of isoenzymatic variation in maize landraces occurs within populations, whereas individual teosinte (wild Z. mays) populations remain genetically distinct (6, 18). The low genetic diversity of some accessions also has been attributed to human factors i.e., small field sizes (or few ears used for seed) for Contrary to previous assessments small farmers in Mexico are planting fewer maize varieties than before. First documented decline in a center of crop diversity.... but we don t know why. specialty varieties (1). In fact, most maize alleles are very rare (frequencies <0.01), and many are found in single accessions that presumably correspond with farmer fields (1). Rather than segregated into discrete races, maize diversity may be spread continuously across thousands of populations (i.e., fields) in rural Mexico (13, 14, 17, 18). Accounting for maize s metapopulation structure is difficult because of farmers extensive control of crop population dynamics (11, 13). Although maize demography can be modeled on management practices, the data required remain The first objective of this mid-term research agenda is to understand the socioeconomic drivers behind this decrease. critically scarce (11, 19). Numerous statistics have been reported, but only average varietal richness per farm is estimated consistently across studies. This is considered the key statistic for diversity conservation in crops (10). We compare farm richness estimates based on cross-sectional case study data and longitudinal survey data from a representative sample of rural farms to assess the state of maize conservation in Mexico. Our findings reveal significant changes in López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

7 But why do we care? López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

8 But why do we care? Crop genetic diversity: Climate change Pest Diseases López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

9 But why do we care? Crop genetic diversity: Climate change Pest Diseases In-situ conservation is increasingly regarded as a desirable way to conserve plant genetic resources (Di Falco, et al., 2010). On-farm conservation allows crops to evolve continuously in response to changing conditions. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

10 But why do we care? Crop genetic diversity: Climate change Pest Diseases In-situ conservation is increasingly regarded as a desirable way to conserve plant genetic resources (Di Falco, et al., 2010). On-farm conservation allows crops to evolve continuously in response to changing conditions. Public attributes of crop genetic resources (e.g., potential to reduce vulnerability to pests) versus private effects (e.g., on agricultural productivity) or attributes that have a private market (e.g., niche markets for taste or appearance of maize). López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

11 But why do we care? Crop genetic diversity: Climate change Pest Diseases In-situ conservation is increasingly regarded as a desirable way to conserve plant genetic resources (Di Falco, et al., 2010). On-farm conservation allows crops to evolve continuously in response to changing conditions. Public attributes of crop genetic resources (e.g., potential to reduce vulnerability to pests) versus private effects (e.g., on agricultural productivity) or attributes that have a private market (e.g., niche markets for taste or appearance of maize). Second objective of the research agenda is to evaluate policy alternatives that can effectively promote in-situ conservation of crops genetic diversity. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

12 Data and basic characteristics López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

13 Data and basic characteristics Data is representative of rural population of Mexico. Detailed household level data (1,500+ households). López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

14 Data and basic characteristics Data is representative of rural population of Mexico. Detailed household level data (1,500+ households). 2 rounds 2002 and A third round was applied in 2010 but smaller sample. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

15 Data and basic characteristics Data is representative of rural population of Mexico. Detailed household level data (1,500+ households). 2 rounds 2002 and A third round was applied in 2010 but smaller sample. How many rural households participate in farming? Is participation stable over time? López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

16 Participation dynamics López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

17 Participation dynamics No Yes No 875 Yes 57% of rural households in Mexico didn t farm during the period. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

18 Participation dynamics No Yes No 875 Yes % of rural households in Mexico didn t farm during the period. Only 27% of the households planted maize in both years. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

19 Participation dynamics No Yes No Yes % of rural households in Mexico didn t farm during the period. Only 27% of the households planted maize in both years. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

20 Where do we start? López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

21 Where do we start? Limited amount of data. Potential complex process behind decision to farm or not. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

22 Where do we start? Limited amount of data. Potential complex process behind decision to farm or not. Different possibilities to analyze the data. A preliminary and simple approach: Look at the factors behind the probability that a household planted more than one maize variety in a given year. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

23 Where do we start? Limited amount of data. Potential complex process behind decision to farm or not. Different possibilities to analyze the data. A preliminary and simple approach: Look at the factors behind the probability that a household planted more than one maize variety in a given year.a first look to one particular hypothesis. Diversification in maize is a way to self-insure: If there are other self-insurance mechanisms available households will be less likely to plant multiple varieties of maize. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

24 Where do we start? Limited amount of data. Potential complex process behind decision to farm or not. Different possibilities to analyze the data. A preliminary and simple approach: Look at the factors behind the probability that a household planted more than one maize variety in a given year.a first look to one particular hypothesis. Diversification in maize is a way to self-insure: If there are other self-insurance mechanisms available households will be less likely to plant multiple varieties of maize. Preliminary results (using instrumental variables to control for endogeneity of remittances) seem to support this. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

25 Remittances and diversity loss Similar hypothesis but for decrease in number of maize varieties. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

26 Remittances and diversity loss Similar hypothesis but for decrease in number of maize varieties.! Probit Education [0.018] Gender [0.184] Labor (adults in HH) [0.039] Land 0.017** [0.007] Remittances (000s pesos) * [0.005] _cons [0.215] * p<0.10, ** p<0.05, *** p<0.01 Robust standard errors in brackets López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

27 Remittances and diversity loss Similar hypothesis but for decrease in number of maize varieties. Probit IV-probit Education [0.018] [0.020] Gender [0.184] [0.145] Labor (adults in HH) [0.039] [0.029] Land 0.017** [0.007] [0.008] Remittances (000s pesos) * 0.050*** [0.005] [0.018] _cons [0.215] [0.176] * p<0.10, ** p<0.05, *** p<0.01 Robust standard errors in brackets López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

28 Remittances and declining diversity López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

29 Remittances and declining diversity Probability of decrease in diversity Remittances (thousands of pesos) Note: 95% robust confidence intervals are shown López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

30 Remittances and declining diversity Probability of decrease in diversity Remittances (thousands of pesos) Note: 95% robust confidence intervals are shown Not necessarily the best econometric model. Nevertheless, there might be something to the hypothesis of self-insurance. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

31 Remittances and declining diversity Probability of decrease in diversity Remittances (thousands of pesos) Note: 95% robust confidence intervals are shown Not necessarily the best econometric model. Nevertheless, there might be something to the hypothesis of self-insurance. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

32 Provision of in situ conservation López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

33 Provision of in situ conservation Very likely that some sort of compensation mechanism will be necessary if the government wants farmers to increase or even maintain the number of maize varieties hat they are actively farming. Maybe something along the lines of payments for ecosystem services. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

34 Provision of in situ conservation Very likely that some sort of compensation mechanism will be necessary if the government wants farmers to increase or even maintain the number of maize varieties hat they are actively farming. Maybe something along the lines of payments for ecosystem services. Once we have a better understanding of the determinants we will move to evaluate policy alternatives. Field Experiments seems a natural way to go about this. López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

35 Conclusions López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

36 Conclusions The only thing that we can conclude at this point is: López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10

37 Conclusions The only thing that we can conclude at this point is: we have a lot of work to do! Thanks! López-Feldman, Dyer (CIDE ; DAS) Declining maize October / 10