Efecto de los pesticidas sobre las lombrices del Suelo

Rociando pesticidas, Fuente: AP Environmental Science Blog

Como todos vosotros sabéis, la ingente cantidad de pesticidas que demanda la agricultura intensiva actual contamina toda la biosfera, dañando el medioambiente. Finalmente somos los propios seres humanos los que padecemos tal envenenamiento derivado de tales prácticas. Muchos de estos tóxicos son dispersados en forma de espráis, aunque finalmente la mayor parte de los mismos termina en el suelo afectando a sus organismos y alterando negativamente el metabolismo de los ecosistemas. Ya os hemos comentado que, en ambientes templados húmedos y subhúmedos, los lumbrícidos, resultan ser  los ingenieros del suelo más relevantes, siendo su papel capital en la mejora de las propiedades físicas y químicas del medio edáfico. ¿Qué les ocurre a estas criaturas, cuando un campo de cultivo es rociado año tras año con pesticidas?. Simplemente el efecto de los últimos sobre las primeras es devastador. Un estudio reciente, cuyos resultados han sido publicitados por ScienceDaily muestra los estragos producidos. Los autores de la investigación que reproducimos hoy al final de esta entrega, muestran como las lombrices logran desintoxicarse, aunque el precio resultará ser muy alto, ya que gastan gran parte de su energía en tal proceso, en detrimento de otros esenciales para el buen funcionamiento de su metabolismo.

Los pesticidas incrementan el metabolismo de estos gusanos anillados expoliando sus reservas de glucógeno, aumentando también la cantidad de aminoácidos y proteínas como consecuencia de la desintoxicación. La respuesta varía según se trate de su primera exposición a estos tóxicos, o que ya sufrieran tal agresión en años previos. En cualquier caso, su tasa reproductiva disminuye dramáticamente  de tal manera que sus poblaciones se reducen dos o tres veces respecto a las que cabría esperar. Del mismo modo, este gasto energético requerido para la desintoxicación de sus cuerpos se traduce en que los individuos solo alcancen una masa corporal que equivalente a la mitad de los especímenes no afectados por el envenenamiento.

Resumiendo, menores tamaños y poblaciones se traducirán necesariamente en mermar la actividad de estos ingenieros del suelo, y como corolario,  tal proceso reducirá su rol en mantener la fertilidad de los suelos y el reciclado de nutrientes. Y así el agricultor se verá obligado a realizar nuevos desembolsos, algunos de los cuales, como las enmiendas químicas, aumentarán la fertilidad química y las producciones agrarias, aunque a costa de generar una nueva contaminación ambiental. Tal hecho no acaece en la denominada agricultura orgánica o ecológica.

Reiteramos por enésima vez que la agricultura industrial lo envenena  todo. El mejor pesticida sintético es el que no se produce.  Se han acumulado ya demasiadas evidencias científicas como para que la sociedad actual comprenda que la futura producción alimentaria debe basarse en otros principios, ya que de no ser así viviremos en un mundo más enfermo y polucionado, lo que ineludiblemente redundará negativamente en la salud de la población humana. Os dejo pues con la noticia (…)

  Juan José Ibáñez

Pesticides make the life of earthworms miserable

Date: March 25, 2014; Source: University of Southern Denmark

Summary: Pesticides are sprayed on crops to help them grow, but the effect on earthworms living in the soil under the plants is devastating, new research reveals. The worms only grow to half their normal weight and they do not reproduce as well as worms in fields that are not sprayed, a research team reports after having studied earthworms that were exposed to pesticides over generations.

Pesticides are sprayed on crops to help them grow, but the effect on earthworms living in the soil under the plants is devastating, new research reveals: The worms only grow to half their normal weight and they do not reproduce as well as worms in fields that are not sprayed.

Pesticides have a direct impact on the physiology and behavior of earthworms, a Danish/French research team reports after having studied earthworms that were exposed to pesticides over generations.

«We see that the worms have developed methods to detoxify themselves, so that they can live in soil sprayed with fungicide. They spend a lot of energy on detoxifying, and that comes with a cost: The worms do not reach the same size as other worms, and we see that there are fewer of them in sprayed soil. An explanation could be that they are less successful at reproducing, because they spend their energy on ridding themselves of the pesticide,» the researchers, Ph. D. student Nicolas Givaudan and associate professor, Claudia Wiegand, say.

Claudia Wiegand is from the Department of Biology at University of Southern Denmark, and she led the research together with Francoise Binet from University Rennes 1 in France. Nicolas Givaudan is doing his Ph. D. as a joint degree between University of Southern Denmark and University of Rennes 1 in France. They researchers reached their findings by metabolomic profiling and energetic parameters.

The researchers set up an experiment to study the behavior of the earthworm species Aporectodea caliginosa. They moved two portions of farmed soil with worms into the lab. One portion was taken from a local organic field, the other from a local conventionally cultivated field that had been sprayed with fungicide for 20 years. This soil had remnants of the internationally commonly used fungicide Opus® at a level common in fields. When crops are sprayed with fungicide, only a small part of the chemical is absorbed by the plant. The waste can be up to 70 per cent, and much of the fungicide ends up in the soil.

In the laboratory, the researchers could see how the fungicide-exposed worms adapted to the toxic environment. Over generations the worms have developed a method to detoxify themselves.

«The fungicide increased metabolism rate in the worms, both the adapted worms and the not adapted worms. In the not adapted worms we saw that their energy reserve of glycogen was used faster. Contrastingly, only in the adapted worms we saw that amino acids and protein contents increased, suggesting a detoxification mechanism. «They also increased their feeding activity, possibly to compensate for the increase in energy demand,» the researchers said.

Often there are 2 — 3 times more earthworms in unsprayed soil than in sprayed soil.

«The reason for this may be that earthworms in sprayed soil do not reproduce as successfully as worms in unsprayed soil, because they need to spend more energy on detoxifying,» the researchers say.

They also weighed the worms in the experiment and found that the worms exposed to fungicide weighed only half of the worms in organic soil. Worms in organic soil had an average weight of 0.6 grams, worms in conventionally cultivated soil had an average weight of 0.3 grams.

Story Source: The above story is based on materials provided by University of Southern Denmark. Note: Materials may be edited for content and length.

Journal Reference: Nicolas Givaudan, Claudia Wiegand, Barbara Le Bot, David Renault, Fredérique Pallois, Stéphanie Llopis, Françoise Binet. Acclimation of earthworms to chemicals in anthropogenic landscapes, physiological mechanisms and soil ecological implications. Soil Biology and Biochemistry, 2014; 73: 49 DOI: 10.1016/j.soilbio.2014.01.032

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University of Southern Denmark. «Pesticides make the life of earthworms miserable.» ScienceDaily. ScienceDaily, 25 March 2014. <www.sciencedaily.com/releases/2014/03/140325113232.htm>.

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