Thursday, September 23, 2010

Pesticide Use and Wild Butterfly Populations

Alexis Stupich 0721741

Is pesticide use as detrimental to butterfly wildlife as it is made out to be? In Pamela Ronald’s article titled Organic Farms Not Always Best For Butterflies, she argues against the fact that pesticide use deters wild butterflies from feeding on plants grown in farms. To back up the statements made in her article, she references a study published in the journal; Ecology Letters, titled; Comparing Organic Farming and Land Sparing: optimizing yield and butterfly populations at a landscape scale. This study was performed by Jenny A. Hodgson, a professor from the University of Leeds, as well as several other studies referenced at the bottom of the page. Ronald’s article goes on to discuss the merits and caveats of organic farming on butterfly wildlife versus traditional farming as well as on reserves.

Pamela Ronald’s article makes a generalized statement that organic farms support a higher density of butterfly wildlife than traditional pesticide-using farms. However, the butterfly wildlife density was highest in reserves. This was proven in the primary source, as they counted the number of butterflies at each of the locations. The article concluded that even though organic farms could support a higher density of butterflies than conventional farms, the difference in yield of conventional farms in contrast to that of organic farms is so much greater that unless we uncover new methods in which organic yield increases, it is better to farm conventionally. It continues to speak of the pitfalls of converting all conventional agricultural farms to organic farms. According to Pamela Ronald, were we to convert all farms into organic farms, it would be more harmful to wildlife. This is because to produce the same amount of yield with organic farms as there would normally be with conventional farms, the amount of farm area would have to be expanded. Consequently, natural wildlife habitats would have to be transformed into farming space, which would be detrimental to wildlife populations. Pamela Ronald backs up this argument with a study done by Tom Bruulsema titled Productivity of Organic and Conventional Cropping Systems. He studied various types of farms and calculated that, on average organic farms produced only 87% as much yield as conventional farms.

Although the majority of the author’s claims were backed by evidence done in the study, the author inferred that the results were representative of all wild butterfly populations, and spoke in very general sentences regarding the effects of pesticide use and farming on butterfly populations. However, the study was only done in very specific areas of England. The results could have been entirely different had the experiment been performed in a different geographic area. Had the author stated that only in certain areas of England were these results representative of the truth, the article would have proven more correct. Furthermore, the author uses the information about wild butterfly populations to draw conclusions about the effect of organic farming on all wildlife populations. The author opens with the statement: “The most devastating impact on biodiversity is caused by agriculture.”(Ronald, 2010). In none of the studies referenced was this statement ever proven as fact. The author exaggerated the information from the studies done to state this. To prove that the most devastating impact on biodiversity is caused by agriculture would be virtually impossible. Every factor possible must have been accounted for in experiments and studies done to prove this as truth. Furthermore, in the study it is stated that butterflies were used in the experiment since they are highly sensitive to small-scale habitat change (Hodgson, Kunin, Thomas, Benton, Gabriel. 2010) Therefore, the data collected from the study involving wild butterfly populations should not be extrapolated and used as data relevant to all animal species. The majority of animal species are not as sensitive to environmental and habitat changes as butterflies are, and therefore it is likely that whether or not farms are organic would have much less of an impact on their population densities. It is for this reason that the author should not have made the assumption that trends for all animal populations would follow those of the wild butterflies.

This image shows the wild butterfly species, Erynnis tages, one of the more common species of butterfly accounted for in the study. Other common species found included; Thymelicus syvestris, Ochlodes venata, and Pieris napi.

Overall, the majority of Pamela Ronald’s statements made in her article were very well supported by the evidence concluded in the studies referenced. She included several primary resources to back up her claims about the effects of pesticides and farming on butterfly populations. Furthermore, her background can be used as grounds for credibility in her article. Pamela Ronald is a professor of plant pathology and chair of the plant genomics program at the University of California. However, there were a few claims made in her article that either exaggerated the evidence found in the studies, or was never proven as truth in the experiments referenced. It is for this reason that one should acknowledge the primary sources referenced in an article before believing all “facts” stated as truth.
News Article:
Pamela Ronald, Organic Farming not Always Best for Butterflies, published: September 21, 2010.
1. Rhys E. Green, Stephen J. Cornell, Jorn P. W. Scharlemann, Andrew Balmford. “Farming and the Fate of Wild Nature” published: December 23, 2004 in Science Vol. 307, pp.550-555.
2. Tom Bruulsema, “Productivity of Organic and Conventional Cropping Systems.” ,2003.
3. Jenny A. Hodgson, Willaim E. Kunin, Chris D. Thomas, Tim G. Benton, Doreen Gabriel , “Comparing organic farming and land sparing: optimizing yield and butterfly populations at a landscape scale”. Published in: Ecology Letters, September 6, 2010.

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