Why do Heinemann 2013 use the wrong year to obscure valid conclusions about improved yield growth from GM?

Veteran crop weed specialist Dr Chris Preston at the University of Adelaide has recently jumped into action analysing national crop yield growth data.

He has compared crop yield growth per year since the introduction of GM technology in North America with corresponding crop yield growth in the EU in same period, and kindly made his results available to the Pundit.

Chris’ interest in this topic was piqued by recent interesting and widely quoted claims by Jack Heinemann and colleagues (2013).

Chris notes correctly that GM technologies were introduced into North America in 1996. Using this start date for calculation of crop yield growth over time, he finds the following patterns shown in the figure:

(This were calculated  for GM (US and Canada data) and non GM (West Europe data) on corn and canola oilseed.  Note canola is called rapeseed in the EU)

From the above graphs covering the 1996-2011 period, corn yield growth in the US shows no evidence off falling behind corn yield growth in Western Europe. Note also that Canadian canola yield has marginally gained over time  on Western Europe’s rapeseed yield.

What does the Heinemann 2013 paper say?

They base their claims on their Table 1.

and say:

Starting with maize, how has the commitment to GM crops benefitted the US agroecosystem? Maize is a dominating crop for the US Midwest and a significant crop for W. Europe. Between 1961 and 1985 the United States produced on average approximately 5,700 hg/ha more maize per year than did W. Europe. By the mid-1980s, there was a significant change in yield in our comparison countries (Figure 1). Between 1986 and 2010, W. Europe’s yield averaged 82,899 hg/ha, just slightly above United States yields of 82,841 hg/ha (Table 1). Comparing W. Europe with the United States for the entire period 1961–2010 (Figure 1), the average yields were not significantly different (ANOVA:F_1,98 = 0.53;P = 0.47). These results suggest that yield benefits (or limitations) over time are due to breeding and not GM, as reported by others (Gurian-Sherman 2009), because W. Europe has benefitted from the same, or marginally greater, yield increases without GM. Furthermore, the difference between the estimated yield potential and actual yield or ‘yield-gap’ appears to be uniformly smaller in W. Europe than in the US Midwest (Lickeret al. 2010). Biotechnology choices in the form of breeding stock and/or management techniques used in Europe are as effective at maintaining yield as are germplasm/management combinations in the United States.

Citation: Jack A. Heinemann , Melanie Massaro , Dorien S. Coray , Sarah Zanon Agapito-Tenfen
& Jiajun Dale Wen (2013): Sustainability and innovation in staple crop production in the US Midwest, International Journal of Agricultural Sustainability, DOI:10.1080/14735903.2013.806408