Opinion: Glyphosate is the most commonly used herbicide in the world and also one of the most contentious. It’s the key ingredient in the weed killer Roundup and routinely used by councils and the agriculture and forestry sectors.

The Environmental Protection Authority recently released a report in response to a call for information on the costs, benefits and uses of glyphosate in Aotearoa New Zealand. This is the first step in a possible reassessment of the chemical’s use.

The authority should be commended for seeking more information on glyphosate and making this public. However, the report it’s published raises questions about the approach the authority will take.

Despite a disclaimer that the protection authority hasn’t verified the material provided and does not endorse submitters’ views, its report is open to criticism for presenting scientific information on a par with the opinions of industry.

Evidence of costs v benefits

In response to its call for information, the authority was provided with significant evidence about the environmental impacts of glyphosate. Much of the information in the Environmental Law Initiative’s submission, which I led, came directly from peer-reviewed scientific studies.

These studies add to a growing body of evidence on glyphosate’s toxic effects on ecosystems and species. For example, a recent study found worrying impacts on bumblebees – which are essential pollinators – from long-term exposure to glyphosate.

There is still little information available about glyphosate’s effects on the unique species and ecosystems found in Aotearoa. However, a 2014 review of the chemical’s impacts on freshwater environments tells us that effects can differ even between closely related species. This highlights the need for more research to gauge exactly what’s happening.

Surprisingly, the authority report references just one study on glyphosate’s adverse effects: a 2015 review by the World Health Organisation’s International Agency for Research on Cancer that classified glyphosate as a probable human carcinogen. The authority doesn’t reference a single peer-reviewed scientific study on the environmental costs of glyphosate. Why not? That remains unclear.

Information included in the Environmental Protection Authority report on glyphosate’s benefits is largely based on interviews with industry representatives and overseas data. There is a glaring absence of any scientific information on the contribution of glyphosate to the yield of target crops.

The protection authority also draws heavily on a recent report that the New Zealand Institute of Economic Research produced for Agcarm, an industry association representing agri-chemical companies. One could argue this group has a vested interest in ensuring the products used in the industry, including glyphosate, remain on sale here.

What the law requires

Under the Hazardous Substances and New Organisms Act, reassessment of a chemical can be triggered, if, among other things, “significant new information relating to the effects of the substance or the organism has become available”.

With growing evidence of the negative environmental effects of glyphosate, it’s hard to see why reassessment of this substance shouldn’t get the go-ahead.

A reassessment will require the Environmental Protection Authority to robustly determine the costs and benefits of glyphosate. But it can’t assess the latter simply by relying on industry perceptions, neither can it assume widespread usage equates to widespread benefit.

‘Benefits’ need to have some grounding in fact – they should be actual benefits rather than perceived benefits. Indeed, as Treasury’s guidance on cost-benefit analysis makes clear, only real costs and benefits should be taken into account.

This means the Environmental Protection Authority will have to commission independent research and not fall back solely on information provided by the industry.

Under the Hazardous Substances Act, it could only reapprove glyphosate if “the positive effects of the substance outweigh the adverse effects”. Peer-reviewed scientific evidence of these effects is crucial to a robust assessment that conforms with the law.

Reassessment will also need to consider the effects of glyphosate on our native ecosystems and species. Given this is an area where information is lacking, the authority will have to apply the precautionary principle contained in the act.

This principle requires the authority to “take into account the need for caution in managing adverse effects where there is scientific and technical uncertainty about those effects”. The toxic legacy of our agri-chemical use is testament to the importance of a precautionary approach.

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