We're glad to hear that GMO Answers has been a helpful resource to your research on plant biotechnology. Janet Carpenter, an agricultural economist, gave her thoughts on this paper in two other responses posted to GMO Answers. In one of the responses she explains:
"While the yield benefits of currently commercialized GM crops in developed countries such as the U.S. may not be large, surveys of farmers in both developed and developing countries show that GM crop farmers in developing countries have achieved much greater yield increases. Currently commercialized technologies are intended to improve pest management and therefore reduce or eliminate losses for insect damage or weed competition. In developed countries, these technologies have substituted for other pest-management practices and have been adopted for reasons other than yield improvement, such as reduced costs and management time. In developing countries, these same technologies can improve yields substantially if farmers lack access to effective conventional pest-management tools, such as pesticides.
"With respect to the referenced paper, I believe the authors' 'conclusions' are better characterized as assertions. Regarding the impacts of GM crops on both yields and pesticide use, the study makes gross comparisons between yields and pesticide use in North America and Western Europe, drawing “conclusions” about the impact of GM crops, whereas of course there are many other factors that influence yields and pesticide use, such as climate, soils, topography, farming system and government subsidies."
She also discusses the paper's analysis of pesticide use:
"For pesticide use in particular, the analysis is extremely weak. The data that are used in the analysis are from FAO, which reports annual estimates of total pesticide use by country for all crops. Because the FAO data only present an aggregated estimate of pesticide use for all crops produced in a country, it would be extremely difficult to draw any conclusions based on these data alone. Further, despite the assertion by the authors that pesticide use reductions were observed in Switzerland and Germany (with no data shown in the paper), current FAO data show overall pesticide use increasing in both countries between 1995 and 2010. Perhaps most importantly though, simply comparing trends in the aggregate amount of pesticides used is problematic, as pesticides are applied at vastly different rates and are inherently different in their potential environmental and human health impacts.
"The other important point that the Heinemann paper ignores is about the current and potential impact of GM crops in developing countries, where observed yield increases for adopters of GM crops are much greater than in developed countries, and pipeline technologies offer solutions to some critical production and nutritional constraints."
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