Editor’s note
This post documents a recent exchange with the Department of Infrastructure regarding herbicide use within the Kingston and Arthur’s Vale Historic Area (KAVHA) catchment. It is published in the interest of transparency and environmental record-keeping, particularly given the proximity of these activities to Emily, Slaughter and Cemetery Bays, which are in the Norfolk Marine Park – a Commonwealth-protected marine area. All correspondence is reproduced verbatim, with staff names removed.
Back in 1990, Dr Malcolm Francis made the following observation in a Norfolk Island Fish Survey report:
Changing land use patterns and stream channelling may have increased the amount of freshwater runoff and sediment entering the Lagoon (mainly in the western corner of Emily Bay), and proposals have been made to spray aquatic weeds in the adjacent catchment with herbicides. The importance of Kingston Lagoon to Norfolk Islanders, and the preceived threats to its quality and health, have led to suggestions that it be protected as a marine reserve. (My emphasis.)
In the intervening years since this was written, we all know that herbicides have been used in the KAVHA catchment. The marine environment is now a protected area.
When exactly the practice of spraying herbicides began is something I have not yet uncovered. Having said that, I completely understand the temptation to use them. They are cheap – certainly cheaper than employing people to weed by hand – and quick to use. But in terms of reef health, particularly on an inshore reef, the impacts are disproportionate, and both insidious and cumulative.
On 29 July this year, I wrote to Department of Infrastructure staff on Norfolk Island expressing my concerns. I have reproduced my email, the Department’s response, and my subsquent reply here. This is for the sake of transparency, and so that my concerns are formally recorded.
29 July 2025
Good morning,
I’m writing in a personal capacity to ask a couple of questions about herbicide use along the foreshore.
I was told last night that KAVHA staff were spraying herbicide (assumed) along the shoreline on Monday, 28 July. I’m hoping you can confirm which chemical was being used and whether it is considered safe for use near coral reefs.
My concern relates to the timing. Rain had been forecast across multiple weather apps for that day – and indeed, it did rain quite heavily overnight. The channel into Emily Bay was already flowing from rainfall on 25 July and was running swiftly this morning, likely carrying any herbicide residue directly into the lagoon.
While I understand that scheduling work can be difficult, herbicide use in areas draining into coral reef environments needs to be handled with extreme care. As you know, all the science suggests that these chemicals are generally not considered safe for aquatic ecosystems, and application ahead of rain increases the risk of runoff. Best practice is to delay spraying for at least 24 hours after forecast rain, to allow time for absorption and reduce the likelihood of contamination.
When I visited the site this morning, the spraying was continuing. The smell was strong, and I noted the staff were appropriately using PPE.
I’d appreciate it if you could let me know what was used and whether environmental risks are routinely considered when planning this kind of work – especially in such close proximity to the reef.
Kind regards
Susan
Department response – reproduced verbatim
11 August 2025
Hi Susan
Thank you for comments around herbicide use along the foreshore.
A combination of herbicides is used across the site to manage the weeds/broadleaf effectively with consideration given to environmental sensitivity, heritage structures and operational requirements.
WeedPro Bio Aqua 360 - A Glyphosate-based, non-selective herbicide used around buildings particularly the heritage structures like the NMB Barrack walls etc., where mechanical methods like whipper snipping are not suitable due to risk of damage to the structures. This product is also used near waterways as its formulation is designed for this use. However, because it also kills grasses, its use is limited in areas where grass retention is required.
Bio Weed Organic- A non-Synthetic, clove oil-based product which is used around paths and in the Quality Row heritage precinct. It is generally utilized in high traffic areas and in the courtyards of occupied buildings due to its organic composition.
WeedPro Bio Aqua 360 and BioWeed Organic are both chosen for their lower aquatic toxicity and compatibility with sensitive locations.
Conrta M Duo- [sic] A selective Broadleaf herbicide used under strict protocols in areas where broadleaf weed control is required but the grass needs to be retained. Contra M Duo is used more selectively with attention to a buffer from waterways and environmental conditions.
The team adhere to standard operating procedures which focus on safe use of chemicals, buffer zones near waterways, low pressure spray equipment and the team places strict emphasis on avoiding spraying during windy conditions as the wind poses a greater and more immediate risk of herbicide drift to non-target areas and sensitive environments.
The golf course is adjacent to the Marine Park.
The chemicals have a rainfast period, the chemicals used around site range from 2 – 6 hours rain free. The KAVHA works team routinely check and refer to local weather forecasts before undertaking any spraying to minimize the risk of rainfall compromising the treatment or leading to runoff. As you know, while taking all reasonable precautions, island weather at the best of times can be extremely unpredictable sometimes arriving earlier than forecasted.
As you noted, the team wear appropriate PPE when using chemicals and am grateful for your interest and correspondence.
Regards
My response to the above email was, as follows:
12 August 2025
Hi,
Thank you for your detailed response outlining the herbicides used at KAVHA and the protocols your team follows. I’m sorry that I am persisting with this, as I do I appreciate the effort to balance weed control with heritage preservation, and I note the consideration given to aquatic toxicity and operational constraints. However, I remain concerned about the cumulative environmental risk – particularly to the reef – from herbicide use in areas where runoff into the lagoon is possible. Based on the three products you identified:
WeedPro Bio Aqua 360 (glyphosate IPA salt) – laboratory studies with Great Barrier Reef seawater show glyphosate can persist for weeks to months, depending on light and temperature, increasing the likelihood of exposure to reef biota after rainfall events. While ‘aquatic-safe’ formulations avoid some of the more toxic surfactants, other co-formulants can still be harmful.
Contra M Duo (MCPA + dicamba) – guideline data identify algae and diatoms as among the most sensitive taxa. These primary producers are fundamental to coral settlement and lagoon productivity. Marine-specific data are limited, but their mobility in water means residues could feasibly reach the lagoon.
Bio Weed Organic (clove oil/eugenol) – experimental work has shown clove oil can cause bleaching and growth reduction in corals, and eugenol has documented toxicity to aquatic invertebrates at low mg/L concentrations.
Rain events, especially when preceded by spraying, increase the likelihood that residues from any of these products reach the lagoon before they break down. In a reef-lagoon environment, prevention is always preferable to post-impact mitigation. The short distances between foreshore application sites and reef waters, combined with Norfolk Island’s unpredictable weather, mean even small miscalculations can have outsized consequences.
As you’ll be aware, the Norfolk Marine Park – which includes Emily Bay and Slaughter Bays – is an EPBC Act protected place. This status provides additional federal protections and reinforces the importance of applying the precautionary principle when planning works that may result in runoff into the lagoon.
In thinking about possible alternatives, I was struck by the fact that KAVHA is both a heritage precinct and an environmental asset. The reef itself is heritage – as much part of Norfolk Island’s story as the buildings and grounds. I understand that other heritage sites, for example Government House in Melbourne, have shifted to traditional or ‘heritage’ land management techniques in sensitive areas, avoiding herbicides entirely in favour of manual removal, mulching, selective planting, and low-impact mechanical methods. This approach aligns the care of built heritage with the care of living heritage, creating a unified stewardship message for the site.
I would like to suggest that KAVHA consider trialing a heritage management approach in the sensitive foreshore zones. This could include:
Prioritising manual or mechanical weed control in those areas.
Increasing planting of low-maintenance, historically appropriate groundcovers to reduce weed regrowth.
Reviewing spray schedules to ensure no applications are made within 48 hours of forecast rain, regardless of product rainfast times.
Monitoring runoff points for herbicide residues to build a local evidence base.
I believe this would strengthen KAVHA’s environmental credentials and demonstrate leadership in protecting both our cultural and natural heritage.
Thank you again for your openness to this discussion, and for the work your team does to care for the site. I’ve included relevant references, below.
Kind regards,
Susan
Bibliography
ANZG. (2024). MCPA freshwater default guideline value (DGV) technical brief. Australian and New Zealand Guidelines for Fresh and Marine Water Quality.
Boyer, S. E., Whitehead, R. F., & Franklin, E. C. (2009). Effects of clove oil on coral health and growth. Journal of Experimental Marine Biology and Ecology, 369(1), 53–57. https://doi.org/10.1016/j.jembe.2008.10.020
CCME. (2007). Canadian water quality guidelines for the protection of aquatic life: Dicamba. Canadian Council of Ministers of the Environment.
EFSA. (2024). Peer review of the pesticide risk assessment of the active substance clove oil. European Food Safety Authority.
Mercurio, P., Flores, F., Mueller, J. F., Carter, S., & Negri, A. P. (2014). Glyphosate persistence in seawater. Marine Pollution Bulletin, 85(2), 385–390. https://doi.org/10.1016/j.marpolbul.2014.01.021
Vione, D., Khanra, S., Das, R., Minero, C., Maurino, V., Brigante, M., & Mailhot, G. (2010). Effect of dissolved organic compounds on the photodegradation of the herbicide MCPA in aqueous solution. Water Research, 44(20), 6053–6062. https://doi.org/10.1016/j.watres.2010.07.079
Step from the beach into a shallow coral reef area in Cemetery Bay (September 2020), part of the Norfolk Marine Park and a protected inshore reef system.