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Monarch Butterflies: If GM doesn’t get them, Roundup will

Immediate release (25 Jun 2013)

Calls to Pete Riley 07903 341 065

The iconic US Monarch butterfly is suffering a serious drop in numbers as result of the widespread adoption of GM Roundup Ready (RR) soya and maize in the US Midwest, GM Freeze said today.

A new briefing summarises the science behind the 15-year decline in Monarch numbers and warms that the European Union needs to think carefully before approving any GM RR crops for cultivation. [1] Monsanto’s RR GM crops are genetically modified to be tolerant to the weedkiller glyphosate (brandname Roundup) so the fields can be blanket sprayed with weedkiller and the crop survives. This practice can harm wildlife habitats.

Entomologists in the US have charted a major decline in the number of Common Milkweed, the food plant of Monarch caterpillar, in maize and soya fields since the introduction of RR crops in the 1990s. Milkweed likes disturbed land and is more common in cultivated fields than in non-agricultural habitats. Detailed field research shows that Common Milkweed in fields fell by 90% in the decade to 2009. This affects the number of Monarch caterpillars surviving to adulthood, and scientists say it partly explains the worrying decline in Monarch adults found at wintering sites in central Mexico.

Other factors, such as forest destruction in Mexico and urban sprawl in the US, have also played a part in Monarch declines, but scientists are worried that the population loss could become a permanent if Milkweed losses are not addressed. Low Monarch populations are further vulnerable to extreme weather events at all stage of the Monarch’s lifecycle as they migrate, so the problem could escalate.

Earlier research highlighted concern that GM Bt maize crops, which are genetically modified to produce toxins that kill insect pests, could also impact on non-target species like the Monarch butterfly by exposing their larvae to Bt toxins in maize pollen falling on the leaves of Milkweed they eat. Toxicity of pollen varies between different Bt maize crops, and the impact of single Bt genes is thought to be low. However the trend is toward “stacking” multiple GM genes into single crops, and the new Monsanto/Dow SmartStax maize contains six Bt genes, three of which have the potential to harm Monarch caterpillars. GM Freeze is concerned that exposure to this pollen could produce sublethal effects and add to the Monarch’s problems.

EU acceptance of GM RR crop cultivation (which is not currently approved) is believed to form part of the US position in the ongoing negotiations to establish a US/EU free trade agreement. [2] The EU is currently reviewing the approval of glyphosate in Europe, but the approval process does not cover indirect effects such as loss of butterfly larvae food plants. [3]

Commenting Pete Riley of GM Freeze said:

The rapid expansion of GM crops in US fields has caused another major problem regulators have either ignored or missed. It is pretty obvious that the wholesale destruction of Monarch larvae food plants due to Roundup use affects the numbers surviving to adulthood and reduces populations. This major land use change leaves the whole population in the Eastern US more vulnerable if there is bad weather.

Although Monsanto and US regulators don’t appear to be concerned, Europe needs to take note and protect our butterflies and moths from a similar fate. Many of our farmland butterflies and moths are already in decline, and the last thing they need is for RR crops to get the go ahead.

Europe must not be bullied into accepting RR crops by the US and Monsanto. We need to make it very clear that they do not fit with our vision of a productive countryside rich in biodiversity. RR crops will take us in the opposite direction, and we should say ‘No!’



[1] GM Freeze, 25 June 2013. Monarch Butterflies: If GM Bt doesn’t get them, Roundup will

[2] Global Trade, undated. “White House calls EU GM crop rules ‘unnecessary’

[3] The German Federal Authorities are conducting the ongoing reassessment of glyphosate safety as part of the EU reapproval process. The final decision is due in 2015.