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En riesgo, la preservación del maíz; baja la diversidad de granos que se cultivan

Fecha: 
Lun, 2014-09-08

La mayoría de los agricultores mexicanos sólo siembran un tipo, alerta investigador

Angélica Enciso L.
 
Periódico La Jornada
Lunes 8 de septiembre de 2014, p. 42

La diversidad en el cultivo de maíz en México se redujo en sólo cinco años, entre 2002 y 2007, y ello representa un riesgo para preservar esta semilla, de la cual México es centro de origen. Esto indica que la mayor parte de los agricultores cultivan sólo una variedad, y ello ocurre no sólo en las siembras comerciales, sino también en las de subsistencia, indica George Dyer, investigador que encabezó el equipo de autores del estudio El maíz mexicano en proceso de erosión genética.

Explica que no hay datos para lo ocurrido después de 2007, pero es posible que sea un fenómeno duradero, ya que sucede entre todo tipo de productores. En el estudio, publicado en la revista Proceedings of 

the National
 Academy of Science,de Estados Unidos, también participaron Alejandro López Feldman, del Centro de Investigación y Docencia Económicas; Antonio Yúnez, del Colegio de México, y Edward Taylor, de la Universidad de California.

 

En el reporte científico se plantea que los agricultores mexicanos tradicionalmente conservan la semilla de maíz de un año a otro, lo cual permite al cultivo adaptarse a cambios en el ambiente a través del proceso de selección natural.

Se analizaron los cambios en la diversidad de maíz cultivado por mil 725 agricultores entre 2002 y 2007, y se encontró una reducción en el número de variedades sembradas en cinco años. El promedio de diversidad en el cultivo era de 1.43, y cayó a 1.22, lo cual significa que prácticamente utilizan una variedad, y es lo más bajo en cuanto a biodiversidad, explica Dyer en entrevista telefónica.

Estos cambios ponen en riesgo la seguridad alimentaria y las estrategias de adaptación al cambio climático en zonas rurales del país; podrían propiciar la migración de los campesinos. Destaca que estos recursos genéticos son valorados en todo el mundo.

La pérdida de diversidad de cultivo de variedades de maíz es grave, es la herencia viva cultural de los mexicanos. Tiene consecuencias prácticas, como la vulnerabilidad de los agricultores ante el cambio climático, indica.

Considera que hubo estudios de caso sobre el maíz que dieron una idea equivocada del uso de la diversidad, porque los investigadores fueron a zonas donde sabían que ésta se daba, y cuando se iba perdiendo cambiaban de lugar, cuando en realidad lo que ocurre es que está desapareciendo.

Refiere que hay expertos que hablan de que se sigue conservando la diversidad maicera, pero ello es porque se basan en información errónea. La erosión genética ocurre a distintos niveles. Puede hablarse de ello con la pérdida de razas. También se puede referir a la pérdida de variedades, que son más especificas. Igualmente, puede ser a nivel de genes. El estudio se basa en la pérdida de variedades.

Recuerda que la Comisión Nacional para el Estudio y Conocimiento de la Biodiversidad encontró que se siembran en el país las 59 razas que se conocen, pero éstas no representan más de 3 por ciento de la diversidad genética de maíz.

Con la reducción en la siembra se puede perder más diversidad sin que sea evidente, porque las razas siguen ahí. Si ocurren caídas de rendimiento del maíz, esto hace probable que los campesinos abandonen sus milpas y migren, lo que ocasionaría una mayor disminución de diversidad.Podríamos ver un ciclo perverso, en el que se reduzcan la diversidad, la productividad y se abandonan tierras.

Apunta que la raza que más se cultiva es el maíz tuxpeño y en el valle de México se utiliza el chalqueño. que es parte de los cónicos. Considera que se debería establecer un sistema de monitoreo, el cual ponga especial atención al intercambio de semilla entre productores.