Corn planting is increasing dramatically in the United States, due to a push for biofuels. Legitimate concerns regarding this trend include an increasing demand for fertilizer (pollution) and food prices.
Douglas Landis and coworkers (Michigan State University and Wageningen University) have addressed an underreported cause for further concern. They have shown that increasing corn production hinders natural pest control.
The pest and its environment.
The scientists focused on the soybean aphid, Aphis glycines Matsumura. It is the most destructive pest for soybean producers in the United States.
The soybean aphid is preyed upon by a wide array of natural enemies. However, these natural enemies need a diverse landscape (on a local scale) to thrive.
Diverse landscapes are common in small-scale agriculture. They are the exception in large-scale agriculture, such as "factory farms" for vast corn production.
Consequently, it is likely that dramatically increasing corn production, and decreasing landscape diversity, will be costly for farmers, especially those who heavily rely on natural pest control. The scientists set out to test this possibility.
Natural pest control.
The agricultural landscape of Iowa, Michigan, Minnesota, and Wisconsin is dominated by annual crop production. Corn production has increased dramatically here, primarily at the expense of soybean production.
Both corn and soybean production negatively impact landscape diversity. The difference between the two is their impact on natural pest control.
The proportional decrease in aphid population growth in the presence of natural enemies declined when more corn was produced in the place of soybeans, when considered on the 1.5 kilometer scale. A simple increase in soybean production did not give this effect.
In other words, when soybeans were replaced with corn, natural predators were less able to eliminate the aphid pests.
Economic impact.
The scientists next sought to quantify the economic impact of this loss of natural pest control.
For farmers who heavily rely on natural pest control, the value of natural pest control declines by roughly 50% due to increased corn production. For those who rely on a more integrated pest management strategy, the loss in value is roughly 25%.
In addition to the loss of value all around from natural pest control, this means that farmers will most likely tend to rely less on natural pest control in the future, if corn continues to be planted in the place of soybeans.
What can we do?
The scientists are not suggesting that we abandon biofuels. They are saying that simply planting loads of corn will not do us as much good as some people believe, and that communication between scientists, farmers, and policymakers is critical in order to adopt the most effective biofuel plans possible.
The scientists propose that we switch to other sources of biofuels in addition to corn, such as switchgrass, in order to create a more diverse agricultural landscape. This will enhance the capability of natural predators to control pest levels.
for more information:
Landis, D. A.; Gardiner, M. M.; van der Werf, W.; Swinton, S. M.
Increasing corn for biofuel production reduces biocontrol services
in agricultural landscapes.
Proc. Natl. Acad. Sci. USA 2008, 105, 20552-20557.