Study Shows Conventional Farming Increases Pest Pressure


(Beyond Pesticides, July 15, 2011)

A study conducted by researchers at Michigan State University and published in the Proceedings of the National Academy of Sciences has linked the growth of industrial farming systems to increased pest pressure and higher pesticide use, highlighting the importance of biodiversity in agriculture. The researchers found that “landscape simplification” in the form of conversion of natural areas to intensive monocultural crop production results in increased pest populations through the removal of natural habitat for pest predators. This in turn leads to higher rates of pesticide application by farmers in response to the increased pest pressure.

As wild areas providing natural habitat to a range of wildlife and beneficial insects are destroyed and converted to conventional crop production, pest populations in the area will be robbed of their natural predators. This leads to pest population booms and to a corresponding increase in pesticides in an attempt to control them. Monocultural crop production‚ growing a single crop on hundreds and often thousands of acres‚ presents a uniquely perfect breeding ground for pests as it provides acres upon acres of food and habitat with no natural checks or barriers.

The study lays out the problems in this way: “The link between landscape simplification, pest pressure, and insecticide use is expected on the basis of two lines of logic. First, conversion of diverse natural plant assemblages to monocultures, at both patch and landscape scales, is known to reduce the abundance and diversity of natural enemies of crop pests, which has been associated with reductions in natural pest-control services. Second, increases in the size, density, and connectivity of host crop patches are expected to facilitate movement and establishment of crop pests, leading to higher pest pressure regardless of natural enemy activity.

To obtain its results, the research team evaluated agricultural activity in 562 counties across seven states in the Midwestern U.S., Ohio, Michigan, Indiana, Illinois, Wisconsin, Iowa, and Minnesota. The researchers examined data showing rates of insecticide application, the percentage of land area in a county that is crop land compared to natural area, and what crops were grown on the cropland. The team uses the term “landscape simplification” as a way of describing conversion of natural areas with diverse populations of plants and animals to open areas of land where only a one or a small handful of plant species are intensively cultivated.

The findings show that, as land is cleared for crop production, insecticide use goes up. This is not surprising in itself, since insecticides would be unlikely to be used in great amounts in natural areas. However, the team noted that, since farmers are likely to want to minimize insecticide use owing to the financial costs, the fact that they are applying it in such large numbers likely betrays a disproportionately large insect population. This suspicion was verified by collecting data from aphid monitoring networks. As the team puts it, “We also found a positive relationship between aphid abundance and proportion cropland,” meaning the more farmland there was, the more aphids there were, and the more insecticide was being used to control them.

The team also examined the financial costs that farmers incur as a result of the increased pest pressure, in the form of insecticide costs as well as crop losses due to the pests. The results show that increased pest pressure due to landscape simplification cost farmers $48 per hectare, resulting in a total increase in the cost of farming of about $122,000 in the average Midwestern county, or $69 million across the region.

The paper also cites the indirect costs that result from the increased rates of pesticide application. These costs are more often borne by society at large rather than the producer and include “(i) health problems due to direct human exposure [to pesticides] or air and water pollution, (ii) development of insecticide resistance by crop pests, and (iii) mortality of beneficial organisms that perform services across agricultural landscapes.”

Biodiversity, the range of wildlife in an ecosystem and the unique roles fulfilled by each individual species‚ is an often neglected factor in food production. However, as this study shows, it is actually an integral factor in ensuring efficient and productive agricultural systems. Ignoring the important roles that it plays will lead only to more headaches and higher costs for farmers.

Organic agriculture is the embodiment of a food production system that nurtures biodiversity and encourages diverse cropping systems and integrated management of pests. Organic systems have been proven effective at reducing pests through harnessing the power of ecosystem services
such as growing a diversity of crops and maintaining wild areas on the farm to support populations of natural pest predators, pollinators, and other beneficial insects. For more information visit our page on organic food and farming.

Environmental News Network