At first glance, pine plantations look tidy, even reassuring — neat rows of trees rising from the hills.
But what you don’t see is what they’re actually being sprayed with. It’s not pure glyphosate — it’s high-strength 540 g/L forestry formulations like Roundup Transorb Bio or Weedmaster TS540, loaded with penetrants, surfactants, solvents, and “inert ingredients” hidden as trade secrets. In other words: it’s a chemical cocktail — not just herbicide.
This “hidden half” has largely escaped public scrutiny. Regulators focus on glyphosate itself, while what forests, workers, neighbours, and waterways actually get exposed to is a murkier—and potentially far more harmful—mix. The forestry industry depends on this cycle: spray the weeds before replanting; spray again to release young seedlings; carpet-spray blackberry, gorse, broom — anything that might outgrow pine.
Efficient? Sure, at least for the bottom line. But efficient for whom? The people mixing that brew under hot sun? The neighbours downwind? The streams where residues run off? And the forest floor, stripped of undergrowth that birds, insects, and mushrooms call home?
This is where forestry’s glyphosate problem intersects with what we’ve already exposed in Roundup® Exposed: The Chemical Cocktail Behind Glyphosate’s Mask — it’s not just what’s written on the label, it’s what’s left unsaid.
Where and Why Glyphosate is Used in Forestry
When foresters talk about “glyphosate use,” they’re not referring to the active molecule on its own. They’re talking about 540 g/L glyphosate forestry formulations — products like Roundup Transorb Bio or Weedmaster TS540 — mixed on-site with water, penetrants, adjuvants, and surfactants. These mixtures don’t just kill plants; they stick, they penetrate, and they move — which is exactly why they’re used in big blocks of forest being aerially sprayed.
After clear-felling, helicopters carpet these sites with this mix to wipe the slate clean — gorse, broom, invasive scrub, grass, native seedlings—all gone. Then, once new pine seedlings are planted, the same formulations are used for a follow-up “release spray” to stop any vegetation from winning the race.
From the industry’s viewpoint, this makes perfect sense: clean site, strong pine growth, predictable outcome. But the reality is deeper—and darker. What’s being sprayed is not simply glyphosate, but a chemical cocktail carefully engineered to deliver maximum kill, with often-unlisted ingredients that regulators and the public barely see.
Health Risks for Forestry Workers
For forestry crews, glyphosate isn’t just a name on a safety data sheet — it’s something they handle up close. Workers are mixing and spraying concentrated 540 g/L glyphosate products like Roundup Transorb Bio or Weedmaster TS540, often blended with surfactants and other additives that don’t appear on the label but are essential to how the product works. These mixes don’t just stick to leaves — they can stick to skin and clothing too.
Exposure happens in small ways, over and over. A splash when filling a tank. Fine droplets drifting back on the wind. Gloves that stay damp through a shift. Even with protective gear, the reality of forestry work — heat, long days, steep terrain — means workers can’t always follow textbook safety advice. It’s not unusual for residues to be carried home on clothing or boots, exposing families as well.
The health risks go beyond irritation and rashes. Surfactants that help glyphosate penetrate plant cells also make it easier for the mixture to pass through human skin.
Solvents added to keep the active ingredient stable bring their own toxic effects. Studies link these formulations to eye and respiratory damage in the short term, and to more serious conditions — including hormonal disruption and cancers such as non-Hodgkin’s lymphoma — after years of repeated contact.
Forestry workers are on the front line of this risk. Yet in most safety assessments, their daily exposure is reduced to a line item, while regulators continue to assess glyphosate as though it were ever used on its own — ignoring the chemical cocktails forestry workers are actually exposed to.
Impact on Neighbouring Properties and Communities
The forestry industry often talks about herbicide use as if it all stays neatly inside the boundaries of a plantation. But chemicals don’t behave like that in the real world. When a helicopter sprays a glyphosate-based weedkiller across a cut-over hillside, the mist doesn’t stop at the fenceline — it follows the wind. And once residues hit the ground, gravity takes over. Run-off moves downhill into streams, wetlands, and eventually into community water sources.
For people living next to plantation forests, this drift isn’t an abstract concern. It means spray clouds can pass over homes, stock paddocks, or school bus routes. Sometimes it’s obvious — the smell of chemicals in the air, droplets on windows, a sudden rash after being outdoors. Other times it’s invisible, leaving families unaware of what they’ve breathed in or what has settled on their gardens and rainwater tanks.
Neighbouring farmers often find themselves caught in the crossfire too. Stock can graze on sprayed pasture edges or drink from contaminated troughs fed by forestry catchments. Residues are known to linger in soil and water, even if industry insists they break down quickly. And the fact that these products are applied repeatedly, year after year, means the exposure is rarely a one-off.
Then there’s the issue of consent. Local residents don’t get to choose whether a helicopter sprays a cocktail of glyphosate and surfactants next door. At best, they might get a notice in the mailbox; at worst, no warning at all. Unlike food crops, where consumers at least have some awareness of residues, forestry spraying often happens out of sight, leaving rural communities to absorb the risk without a say.
For neighbours, as for workers, the real hazard isn’t glyphosate alone — it’s the entire formulation drifting beyond the forest edge. And yet again, regulators look only at glyphosate in isolation, as though the cocktail doesn’t exist.
Wildlife and Ecosystem Concerns
Forests aren’t just pine trees. They’re home to insects, birds, fungi, and the tangled web of life that grows in the understorey. When helicopters spread glyphosate-based sprays like Roundup Transorb Bio or Weedmaster TS540 across cut-over hillsides, they don’t just kill “weeds.” They strip out the very plants that provide food and shelter for wildlife.
That loss ripples out. Birds lose nesting habitat and seed sources. Invertebrates that feed on native shrubs or grasses disappear, and the predators that rely on them go too. A plantation may look green from a distance, but underneath, it’s a monoculture — and a quiet one at that.
Aquatic life pays a price as well. Spray drift and run-off carry residues into streams and wetlands that weave through forestry blocks. Surfactants in these formulations are particularly harmful to fish and amphibians, damaging gills, skin, and eggs at concentrations far below agricultural application rates. Despite industry claims that glyphosate “binds to soil,” both glyphosate and its breakdown product AMPA (aminomethylphosphonic acid) have been detected in waterways, showing they can and do move through the environment.
Soil ecosystems don’t escape either. Glyphosate disrupts the microbial and fungal communities that help recycle nutrients and support tree growth. Ironically, the very fungi that radiata pines depend on for strong root systems can be harmed by the repeated use of herbicide sprays designed to protect them from competition.
And just as with human health, the problem isn’t glyphosate alone. It’s the full brew: surfactants that strip protective layers off fish eggs, solvents that persist in soil, and adjuvants that magnify toxicity in ways never considered by regulators. Each spray may be justified as “necessary management,” but the cumulative effect is a slow erosion of biodiversity that no one is measuring.
Drift and Environmental Persistence
One of the biggest myths around glyphosate-based sprays is that they stay put and break down quickly. In forestry, neither claim holds up. Aerial spraying by helicopter means fine droplets can drift well beyond the target zone. Wind, slope, and even temperature shifts can carry those droplets kilometres away. What’s sold as a “precision tool” ends up more like a chemical fog than a precision spray.
Residues don’t vanish either. Glyphosate is marketed as binding tightly to soil particles, but that’s only part of the story. In steep forestry country, heavy rainfall washes soil — and whatever it holds — straight into streams and rivers. Once there, glyphosate and its main breakdown product, AMPA, can persist in water long enough to expose fish, frogs, and downstream communities. Surfactants and solvents mixed into products like Roundup Transorb Bio and Weedmaster TS540 can be even more mobile, slipping through soil and into groundwater.
Forestry’s repeated spray cycle compounds the problem. Clear-felled sites are treated before replanting, then sprayed again for seedling release. Over decades of plantation rotation, these applications stack up. Even if a single spray is below regulatory concern, the cumulative load on soils, waterways, and nearby farms tells a different story.
Drift doesn’t just mean droplets in the air; it also means residues moving through landscapes in ways regulators rarely track. From rainwater tanks on neighbouring properties to estuaries at the bottom of catchments, glyphosate-based sprays don’t stay politely where they’re put. They travel, they linger, and they accumulate.
The Regulatory Blind Spot
For all the talk of safety, forestry spraying is regulated on paper in a way that barely resembles reality on the ground. Risk assessments almost always focus on glyphosate as a single active ingredient — tested in isolation, under lab conditions, at doses that don’t reflect the way it’s actually used. The chemical cocktails sprayed from helicopters are rarely assessed as mixtures.
That blind spot has consequences. Regulators can claim the science shows glyphosate is “low risk,” while ignoring the surfactants that strip protective barriers from fish eggs or the solvents that make it easier for residues to slip into groundwater. They can point to breakdown times in ideal soil conditions, while overlooking how steep forestry slopes funnel those same residues into streams after heavy rain. And they can downplay worker exposure by assuming perfect protective gear in perfect conditions, while anyone who’s mixed spray in the field knows how far from reality that is.
Oversight is also thin once the spraying starts. Communities living next to forestry blocks are often given little or no notice of aerial applications. Monitoring of drift or run-off is sporadic at best, and when residues are detected, the results are folded into regulatory averages that hide the outliers. In practice, this means forestry can apply tonnes of glyphosate-based products each year with little independent scrutiny of where the chemicals end up or who gets exposed.
The end result is a gap between how glyphosate formulations are really used in forestry and how they’re officially assessed. It’s a gap wide enough for risks to workers, neighbours, and ecosystems to fall straight through.
Alternatives and Safer Pathways
Forestry often defends its use of glyphosate-based sprays by claiming there’s no viable alternative. But that’s less a fact than a mindset. When “efficient” is defined as killing everything quickly with chemicals, of course alternatives look harder. Shift the definition to long-term sustainability, and the picture changes.
Mechanical options exist. Mulching, cultivation, and soil scarification can suppress weeds before planting without dousing whole hillsides in herbicide. Some smaller forestry operations already use these methods, proving they’re not just theory.
Biological and ecological strategies are on the table too. Mixed plantings, cover crops, and ground covers can reduce the need for aggressive chemical control. Indigenous forestry models — including those explored in some Māori-led initiatives — show how integrating native species can suppress invasive weeds while restoring ecological balance.
Even where herbicides are used, safer choices are possible. Spot-spraying with less toxic products, applied with precision equipment, is a far cry from blanket aerial applications of glyphosate cocktails. It’s slower, yes, but it keeps the chemical footprint smaller and the risk to workers and neighbours lower.
The real obstacle isn’t a lack of options — it’s an industry locked into a chemical cycle. Helicopters, formulations, and fast rotation forestry are all geared toward quick fixes. Breaking out of that cycle will take pressure from outside the industry and a willingness to rethink what “sustainable forestry” should mean in New Zealand.
The Real Cost
From the outside, forestry looks like a clean green industry — rows of radiata pine rising on the hills, supplying timber and jobs. But underneath that image lies a chemical dependency the public rarely sees. Workers mix and spray cocktails sold under names like Roundup Transorb Bio or Weedmaster TS540. Neighbours live downwind of helicopters misting entire hillsides. Wildlife loses food and shelter when everything but pine is killed off. And regulators continue to sign off on glyphosate as if it were ever used on its own.
Forestry may argue this is efficient, even necessary. But efficient for whom? The companies that profit from faster rotations, or the communities and ecosystems left to carry the risks? Every spray event is more than a management tool — it’s a choice that trades short-term growth for long-term harm.
If New Zealand wants forestry to be part of a truly sustainable future, it can’t keep leaning on chemical crutches. Alternatives exist. The question is whether we demand them, or whether we let the industry keep telling the same old story while the hidden costs keep adding up.
The next time you’re driving a rural road — past a forestry block or farm paddock — and you see a helicopter spraying, don’t assume you know what’s in the mix. Wind your windows up, switch your air-con to recirculate (not fresh air intake), and get out of the area as quickly as you can. Because whatever is drifting out of that spray boom is almost certainly a chemical cocktail — and you were never meant to breathe it in.
Resources and References
AMPA: Glyphosate’s Forgotten Hazard
Glyphosate doesn’t just disappear after spraying — it breaks down into AMPA, a residue that lingers in soil and water with its own set of health and environmental risks.
A Survivor’s Story: When Glyphosate Took the Bees
First-hand testimony from a New Zealander who witnessed entire beehives collapse after glyphosate spraying — a stark reminder that the impacts aren’t theoretical.
Roundup’s Long-Term Effects on Soil
Examines how repeated glyphosate applications disrupt soil biology, affecting fungi, microbes, and the very systems trees rely on for healthy growth.
Roundup vs. Glyphosate: Why Formulations Are More Toxic
Breaks down the evidence showing that it’s not glyphosate alone, but the cocktail of surfactants and additives in Roundup formulations that drive toxicity.
Glyphosate in Waterways: A Contamination Crisis
Looks at how forestry run-off and spray drift carry residues into rivers, lakes, and estuaries, with harmful effects on fish, amphibians, and aquatic ecosystems.
Glyphosate Spray Drift and Rural Communities
Explores how drift affects rural residents — from contaminated rainwater tanks to health symptoms after spray events — and the lack of real protection for neighbours.
Indigenous Forestry in Aotearoa: A Māori‑Centred Approach
(Parliamentary Commissioner for the Environment, June 2023)
Highlights how Māori values and mātauranga (indigenous knowledge) are shaping forestry alternatives—like mixed native plantings, ecosystem-aligned management, and reduced reliance on herbicides.
Glyphosate in New Zealand Soils: What the Massey Research Reveals
A 2019-Massey University thesis shows that glyphosate isn’t always locked into soils in Aotearoa — under certain conditions it can migrate, affect clover and soil microbes, and challenge the assumption that “soil-bound = safe.”
Ignored PCE Warning: NZ Chemical Monitoring Mini-Series – Part 1
This article kicks off a three-part series exposing how the Parliamentary Commissioner for the Environment warned about chemical oversight gaps in New Zealand — a warning that’s still largely unaddressed.
NZ Chemical Monitoring: Consultant Findings – Mini-Series Part 2
The second part of the mini-series looks at how chemical monitoring varies wildly between regions, making it easy for high-use substances like glyphosate to slip through the cracks.
NZ Chemical Reform: A Missed Opportunity – Mini-Series Part 3
The final piece shows how reform recommendations from the PCE remain unimplemented — meaning the structural blind spots around chemical monitoring still persist.
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