Briefing note: 19 November 2009
Impact of genetically engineered crops on pesticide use: US Organic Center report evaluation by PG Economics
PG Economics welcomes the Organic Center (OC) latest release Impacts of genetically engineered crops on pesticide use: the first thirteen years by Charles Benbrook, which confirms the positive impact biotech crops have had on reducing insecticide use and associated environmental impacts. However, the OC’s assessment of the impact of biotech herbicide tolerant traits (HT) is disappointingly inaccurate, misleading and fails to acknowledge several of the benefits US farmers and citizens have derived from use of the technology.
For those reviewing the issues examined in the OC report, the following should be noted:
• Confirmation: of biotech insect resistant (IR) impact on insecticide use: the OC paper confirms the findings of other work that the use of IR technology has resulted in important reductions in
insecticide use on these crops that would otherwise have been used with conventional
technology;
• Failure to acknowledge the environmental benefits arising from use of HT technology. These include facilitation of no/reduced tillage production systems [2] which has resulted in important reductions in greenhouse gas emissions. For example, US HT biotech crops contributed, in
2007, to the equivalent of removing 9.48 billion pounds (4.3 billion kg) of carbon dioxide from
the atmosphere or equal to removing nearly 1.9 million cars from the road for one year. In
addition, whilst usage of broad spectrum herbicides, notably glyphosate (and to a lesser
extent glufosinate) has increased significantly, usage of less environmentally benign products
such as pendimethalin, metribuzin, fluazifop and metalochlor has fallen substantially, leading to net benefits to the environment [3];
• Inaccuracies: It uses assumptions relating to herbicide use on biotech crops in the US that do
not concur with actual practice. As a result, it overstates herbicide use on US biotech crops
significantly. For example, it overstates herbicide use on the HT crops of corn, cotton and
soybeans for the period between 1998 and 2008 by 63.4 million pounds (28.75 million kg) of
active ingredient;
• Misleading use of official data: The OC report states many times that the pesticide impact data
is based on official, government (USDA NASS) pesticide usage data. Whilst this dataset is
used, its limitations (namely not covering pesticide use on some of the most recent years and
not providing disaggregated breakdowns of use between conventional and biotech crops)
mean that the author’s analysis relied on own-estimates of usage and cannot reasonably claim
to be based on official sources. As a result, the herbicide usage assumptions on conventional
crops, if they replaced biotech HT traited crops, are significantly understated and unreliable.
Combined with the overstated use assumptions on HT biotech crops, it is therefore not surprising that the document concluded that biotech crops lead to an increase in US herbicide use. This contrasts sharply with the findings of PG Economics’ peer reviewed analysis [4] that estimated that biotech crop adoption in the US has reduced pesticide spraying in the US, eg, by 357 million lbs (162 million kg: -7.1% 1996-2007) relative to what might reasonably be expected if the crops were all planted to conventional varieties;
• Weak approach: the approach of the OC report author is based on personal assumptions of
herbicide use for biotech versus conventional crops and extrapolation of average trends in
total crop active ingredient use (from an incomplete dataset). It also does not present any
information about typical weed control regimes that might be expected in conventional
systems. Not surprisingly, this resulted in significant over estimation of herbicide use on
biotech HT crops (see above) and under estimation of usage on conventional alternatives. As
such, the approach delivers unreliable and unrepresentative outcomes. It is noted that the
OC author is critical of the approach used by other analysts5 to estimate the herbicide usage
regimes that might reasonably be expected on conventional crops if biotech HT traits were
not used in the US corn, cotton and soybean crops over the last thirteen years. The NCFAP/PG Economics approach, criticized by the OC report, is to present and estimate the conventional alternatives based on a survey of opinion from over 50 extension advisors in almost all states growing these three crops. Observers should note the key differences between the two approaches with the NCFAP & PG Economics approach being much more
reliable and representative.
Given the complexities of agricultural production systems and the nature of weed and pest control
systems, more detailed comment and critique of the OCS report is detailed below.(see linked PG Economics site for details).
For additional information: contact Graham Brookes, PG Economics on 00 44 1531 650123 or
[email protected]
Some earlier GMO Pundit posts on Dr Benbrook:
Commentary on Charles Benbrook’s anti-GM tour heats up
US Big picture at variance with Benbrook comments
