Over 30 tonnes of glyphosate on Auckland roadsides and parks: Is our stormwater carrying a toxic load?

It started with a simple question to Auckland Council: how much glyphosate is actually being sprayed on our roadsides each year?

The answer was a shock. In 2024 alone, contractors working for the council applied more than 30 tonnes of concentrated herbicide across Auckland, says advocacy group NoMoreGlyphosate.nz.

That’s roughly equivalent to one and a half fully loaded 20-foot shipping containers worth of undiluted chemical concentrate, poured onto the verges, berms, gutters, and road edges of our largest city — all under the banner of weed control. Once diluted with water for spraying, the total volume of herbicide mix applied across Auckland is vastly greater.

The figures, obtained through an official information request by a concerned resident, confirm what many Aucklanders have suspected for years: that chemical weed control has become the default, rather than a last resort. While many expect trimming or manual weeding, what they’re getting instead is a chemical blanket covering entire streets, day after day, suburb after suburb.

Spraying at Dawn, in the Rain, Without Warning

Worse still, the spraying practices described are deeply worrying. Contractors have been observed spraying entire gutters — including leaf litter, kerb edges, and concrete channels — in darkness before dawn. Reports suggest spraying has occurred even on wet roads, or on mornings where rain was forecast later in the day.

Homeowners who registered for Auckland Council’s “no-spray” opt-out have sometimes found their berm edges still chemically treated, with no signage or public warning. Although neither the berms nor the gutters belong to homeowners, residents are generally expected to maintain these areas. Yet council contractors still carry out blanket spraying without signage or public warning, even in front of registered no-spray properties.

All of this matters because these gutters, which the council considers simple drainage structures, are in effect tiny waterways. When it rains, they funnel runoff directly into the stormwater system, which then flows untreated into the Hauraki Gulf, the Manukau Harbour, and the Kaipara Harbour.

If you think spraying a chemical designed to kill plants straight into our waterways sounds reckless, you are not alone.

In addition to roadside gutters and berms, glyphosate is also widely used around the base of trees — often to target weeds that barely exist — as well as for clearing land in Auckland Council reserves before replanting (a practice some residents see as more justifiable).

Contractors also apply glyphosate to control long grass, especially kikuyu, and to kill grass growing along fences. In parks such as Cornwall Park, entire pastures are reportedly sprayed annually with glyphosate to kill them off before replanting.

What Happens to Glyphosate After It Rains?

Glyphosate is marketed as breaking down rapidly in soil, but what about on hard surfaces like footpaths or concrete gutters? In those conditions, there is little opportunity for soil microbes to degrade the herbicide. Instead, it can wash away with the next rainfall. Studies in other parts of the world, such as Queensland’s Great Barrier Reef catchments, have documented herbicide residues travelling from land into sensitive marine environments, harming seagrass and coral ecosystems.

Locally, there has been minimal recent monitoring of herbicides in Auckland’s coastal sediments. The most relevant public study dates back to 2009, carried out for the Auckland Regional Council. That research did detect glyphosate in urban aquatic sediments, but the data is now over 15 years old and does not reflect current spraying intensities. That leaves a dangerous knowledge gap about what Auckland’s harbours might be accumulating today.

Given that Auckland Council is using more than 30 tonnes of glyphosate concentrate each year, there is an urgent need to investigate whether its repeated application along kerbs and stormwater pathways is putting marine life at risk.

Even the council’s Healthy Waters department, whose job is to protect our streams and harbours, has confirmed using glyphosate along waterways to manage weeds. That raises serious questions about the potential for herbicide runoff directly into aquatic environments.

The Loss of Roadside Biodiversity

Glyphosate doesn’t only end up in stormwater — it also wipes out the humble roadside weeds and grasses that, believe it or not, support urban biodiversity. Many residents have noticed that Auckland’s roadsides, once dotted with daisies, clovers, and other flowering plants, now look scorched and barren.

That loss of plant diversity has consequences. Flowering weeds, while unfashionable, are a vital food source for bees, butterflies, beetles, and other insects. These insects in turn support native birds, lizards, and wider ecological functions.

No published studies have yet investigated whether Auckland’s roadside spraying programme is driving insect or pollinator declines. But overseas evidence is clear: repeated herbicide spraying along roadsides is associated with reduced insect populations and a collapse of plant diversity, with wider ecological consequences affecting birds, reptiles, and other wildlife.

Auckland Council’s weed management strategy does not appear to monitor these impacts. Given the scale of chemical use, that’s a glaring omission.

What Alternatives Could Auckland Use?

Mechanical weed trimming, thermal (steam) weeding, foam weeding, and manual hand removal are all effective alternatives to herbicide-based sprays. Several European cities have abandoned routine glyphosate spraying on public land altogether, citing health and environmental risks.

New Zealand councils have the same options — and a growing number of communities are calling for them to be implemented. At the very least, Auckland residents should expect clear signage about when and where chemicals are being sprayed, genuine respect for “no-spray” opt-out requests, and robust testing of local sediments, stormwater, and marine environments.

Several cities overseas have already made the switch. For example, Dublin ended glyphosate spraying in its parks and streets in favour of safer, non-chemical methods (Dublin’s story here). And while councils sometimes argue chemical spraying is cheaper, a closer look shows that safer weed management can be far more cost-effective in the long run (explore the cost of convenience).

Where to From Here?

If you are as concerned as the resident who unearthed these figures, there are several steps you can take:

• Ask Auckland Council to release its weed control and spraying schedule publicly
• Demand independent water and sediment testing for glyphosate in Auckland’s coastal harbours
• Push for mechanical or thermal alternatives to routine chemical spraying
  Check if your property is registered for no-spray. Opt out of weed spraying on or near your property by calling Auckland Council on 09 301 0101, or by visiting this link.
• Raise public awareness by talking to your local board or sharing this article

Our city’s stormwater should not be a conveyor belt for chemicals into some of the country’s most precious marine environments. Aucklanders deserve a cleaner, healthier, more sustainable weed management solution — one that protects people, pets, insects, and the harbours we love.