Getting into the weeds of the glyphosate debate

The herbicide glyphosate has polarised opinions for decades. And there are enough different ways to weigh the various evidence around its safety that make reaching any kind of unambiguous consensus hugely challenging. Those seeking to restrict use of the herbicide tend to lean on the assessment from the World Health Organization’s International Agency for Research on Cancer (IARC), which classifies glyphosate as ‘probably carcinogenic to humans’. Whereas parties seeking to retain commercial uses give more weight to decisions by national regulators and the European Chemicals Association (Echa) that suggest the available evidence does not support removing the products from the market.

Critics of IARC’s assessment say that it focuses solely on the intrinsic hazards posed by glyphosate, rather than the overall assessment of the risk posed by that hazard under real-world exposure conditions. Conversely, Echa’s decision, and those of various national regulators to renew approvals for glyphosate, are criticised as being biased by over-reliance on data from manufacturers (who have an enormous commercial interest in keeping the product on the market).

But while the lawyers battle back-and-forth over whether Bayer-Monsanto can be held responsible for thousands of US farmers’ and horticulturalists’ cancers, the body of knowledge around some more indirect effects of glyphosate continues to grow.

Beyond that, there are indications that the herbicide may affect the ability of bumblebees and other pollinators to withstand environmental stressors – they are less able to cope when food is scarce, for example. This kind of sublethal effect is difficult to pick up in conventional laboratory studies and field trials, but can have significant detrimental effects on insect populations.

While some countries have begun to restrict glyphosate use – particularly in domestic settings – it seems unlikely that broader bans will be implemented anytime soon. And while there are alternative strategies farmers could use to deal with weeds, it is inexpensive and effective. However, there is recognition within the farming community that its over-reliance on a single herbicide is not an ideal situation. Resistant weed species are emerging and spreading, adding weight to arguments for exploring alternative weed control strategies. But such strategies are almost inevitably more expensive. Hence, without restrictions on glyphosate, and/or support and incentives to investigate alternative approaches, it’s difficult for farmers on narrow profit margins to justify the required investment.