Weed management policy

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Executive summary

Introduction

On May 23 1997 Auckland City's combined Recreation & Community Services and Work & Services Committees resolved that a comprehensive investigation into weed management problems should be undertaken. The Committees further resolved that a strategic policy be developed from the information gathered throughout the investigation process. The impetus for these resolutions was adverse community reaction to a Works & Services recommendation to discontinue non-herbicide weed management on urban roadsides, that reaction being driven by health concerns. As a result a 6,519 signature petition was presented to a full Council meeting.
This policy is the result of the combined Committees' resolutions. It provides Auckland City with strategic direction in relation to weed management, plus a system for prioritising weed species and areas for priority control, together with proposed methods or practices to implement effective weed management. The policy also seeks to update the approach taken by Auckland City to its management of weeds, in line with recent statutory changes addressing issues of weed control methods. The policy relates to all land administered by Auckland City on the Auckland Isthmus and throughout the Hauraki Gulf Islands, with emphasis on council parks, reserves and roadsides.
The policy was prepared by three principal consultants. Additionally, a consultative group, named the Weed Management Consultative Group (WMCG), was established to contribute advice and provide comment and feedback throughout the process of preparing, drafting and finalising the policy. The process was facilitated by an officer from Auckland City's Community Planning Group. In addition a number of organisations and individuals were consulted during the preparation of the policy.

Principles, goals and objectives

The policy provides fundamental Principles, Goals and Objectives for Weed Management in Auckland City and identifies a three-step process for weed management:
- decision to intervene in weed management for a particular plant species or group of plant species and identifying the priority sites for weed management;
- target to be achieved in that intervention;
- evaluating and selecting management options, management approaches and control methods to be implemented to achieve target.
Within the policy the general goal given for weed management is:

To ensure Auckland City meets its legal and community obligations for weed management on land it administers, in a manner that is environmentally, socially and economically sustainable.
The policy provides specific weed management objectives that cover environmental and social issues, statutory obligations, consultation, selection of weed management sites and species, weed management options and approaches, and weed monitoring.

The weed problem

In ecological terms one of the most serious threats to Auckland's natural environment is the unchecked establishment and spread of invasive weeds which are destroying those few remaining bush remnants still existing throughout Auckland City. On the Isthmus invasive weeds are found in a wide range of situations. In most native bush remnants tree privet has replaced native canopy trees; exotic groundcover species such as wandering Jew, wild ginger and plectranthus more or less exclude native plant regeneration; exotic tree species such as monkeyapple, Chinese privet and ginger are replacing native shrubs in the understorey; and fast-growing climbers like moth plant, climbing asparagus and jasmine smother trees and shrubs from the ground to upper canopy level. Many former areas of native forest have been reduced to tree privet forests - for example Jaggers Bush (Westmere), Ayr Reserve (Newmarket), and Orakei Basin (Orakei).
This significant threat even extends to the few nationally and regionally important native forests located within the City boundaries. The rarest forest types in the region are native forests and shrublands growing on the volcanic areas and these, by unfortunate co-incidence, now represent some of the most weed infested natural areas in Auckland City. Additionally, along the Manukau Harbour the nationally-important native forests in Waikowhai and Captains Bush Reserves (and the adjoining reserves from Hillsborough to Blockhouse Bay) are being invaded by a host of weeds that primarily originate in planted areas of reserves and neighbours gardens, or are spread by birds from other reserves. These weeds include the tree species monkeyapple and tree privet, the climbers jasmine, moth plant and convolvulus, and the groundcover plants wild ginger, wandering Jew, plectranthus, African clubmoss and mist flower. The most significant native forest remnants on the Auckland Isthmus are in parks and reserves administered by Auckland City. These important natural areas require urgent action to be taken to control invasive weeds. Without appropriate, effective weed management these irreplaceable areas of natural heritage will, within a few years, be lost.
Similar significant weed infestation problems exist throughout the Hauraki Gulf Islands. On Waiheke Island, the invasion of significant native forest areas by climbing weeds is the predominant problem. Many of these native forest remnants are owned by Auckland City, often on land located immediately adjacent to Auckland Regional Council or Department of Conservation areas. Invasive weeds establish freely between adjoining lands. Inadequate levels of vegetation control undertaken by Auckland City in the past (and currently) have led to a significant increase in weeds proliferating in to neighbouring properties. Coastal forest reserves on Waiheke have a wide range of shrubby weeds that are steadily replacing the regenerating pohutukawa forests normally associated with the cliff-faces and hinterland. In rural areas of Waiheke, woolly nightshade, gorse, pampas, ginger and Japanese honeysuckle are major weeds of the roadsides. They are particularly prevalent where land adjoining the roadside is cleared pasture, or exotic tree or shrubland.
Invasive weeds are currently a relatively minor problem along the roadsides and throughout the native bush on Great Barrier Island. Many of the species listed in Appendix five - Weed species priorities in Auckland City (33kb PDF) have yet to reach this island. Adequate resources and ongoing vigilance are required, however, to ensure invasive weed species do not arrive in the first place, or having arrived, do not exceed manageable levels.
On urban roadsides in Auckland City all vegetation growing on road berms is mown and any vegetation overhanging or growing along kerbs, on footpaths and around street trees is regarded as a weed (with the exception of herbaceous or woody specimens deliberately planted for amenity purposes). The worst weed invasion occurs on asphalt or concrete paths and berm edges where surfaces are broken, or in cracks and crevices found along concrete or bluestone kerbs. Problem weeds are kikuyu grass, purple nut sedge and paspalum.
Weeds of sportsfields and lawns within parks consist of a range of flatweed species including catsear, perennial daisy, Onehunga weed and Cape daisy, plus the grasses paspalum, Poa annua, and kikuyu (although the latter is also deliberately used as a turf and lawn species in some parks). Cape daisy is a particularly bad problem because it spreads rapidly by airborne seed and out-competes most other turf species. Many large areas of lawn within parks have a high proportion of weed species, but this is not always seen as a significant problem in areas of low recreational use. In the Auckland Domain, for instance, plants such as onion weed, Freesia, Oxalis and other lawn weeds form an impressive wildflower display.

Current herbicide policy and use

Auckland City's current policy on herbicide is:

"Herbicides shall only be used where there is no practicable alternative control measure".

This statement is contained in The Code of Practice for the Use of Herbicides in Amenity Areas, developed by the Central Auckland District Noxious Plant Authority and adopted by Auckland City Council in 1989. No subsequent policy, plan or revision of the Code of Practice by Auckland City has altered that statement.

Auckland City also has a Chemical Reduction Programme operating in parks and reserves. Since its inception in 1995, a 77% reduction in the quantity of herbicides used in parks and reserves has been achieved. The programme has also brought about the elimination of the hazardous herbicide Pasma which was used on paspalum; paspalum is now removed by hand weeding.
This reduction approach developed over a period of time and has been influenced and guided by numerous factors, including mounting public opposition to the use of herbicides, initiatives by council officers to adopt non-chemical weed control methods and general political support. In 1988 the (then) Waiheke County Council declared a moratorium on herbicide spraying on council roadsides and reserves - a situation which still largely exists today. In 1993 Auckland City's Works & Services Committee resolved to support in principle the use of non-chemical methods wherever possible for weed control operations throughout the City. All eleven community boards resolved to support the reduction of chemical usage in Auckland City amenity areas. In 1994 Auckland City's Personnel Manger Health and Safety recommended the discontinuation of the following herbicides for health and environmental reasons: Tordon and other 'hormone' herbicides, amitrole, simazine, and paraquat.
Great Barrier Island Community Board has resolved that there be no herbicide use on roadsides, with the exception of that required to control environmentally damaging plants such as pampas and wild ginger, and with the exception of 'wand' application to control weeds on tarseal edges and around culverts. In Ellerslie, there is a ban on all herbicide use on roadsides and sportsfields.
The central issue that has driven the community's involvement in this issue is concern about human health, and in particular chemical sensitivity. Chemical sensitivity is a subject about which there is much dissension within scientific and medical literature. Comment was sought from 27 registered medical practitioners known to have a general understanding of chemical sensitivity and to have some experience in treating it. They were specifically requested to direct their attention to the likely effects of exposure to glyphosate (Roundup) such as may occur through roadside spraying operations. This in no way suggests that glyphosate is more toxic than other herbicides; it is simply that it is the most widely used herbicide and, therefore, the one to which people are most likely to be exposed. Of the 14 written replies received, 13 identified such exposure, in their medical experience, as posing a health risk to people who are sensitive to chemicals; the remaining reply stated the opinion that glyphosate was a safe spray when used sensibly. Details of the doctors views are contained in Section 8.3.
Currently herbicides are used for weed control on only half of Auckland City's urban roadsides. Approximately 2,000kg of glyphosate is used, accounting for 84% of all herbicide use by Auckland City. Of the remainder, 9% is used for road resurfacing operations (dichlorophen), and 7% is used in parks and reserves where glyphosate is the main herbicide (14 other herbicides are used in small quantities for specific problem weeds).

Other New Zealand and overseas approaches

Since the 1980's there has been a worldwide trend of reducing pesticide use. The reasons for this movement away from chemical use are essentially twofold: to reduce the risks of pesticides to the environment and to reduce reliance upon chemical methods of weed, disease and pest management which are increasingly seen as unsustainable. So far 30 countries have developed, or are in the process of developing, pesticide risk and use reduction policies. New Zealand has only comparatively recently embarked on this process, with the proposed development of a National Risk Reduction Strategy for Agricultural and Veterinary Chemicals.
Opposition to pesticide use has been evident in New Zealand for a number of years and community pressure has resulted in changes in the weed management practices of some territorial authorities. So far Tauranga is the only territorial authority that has come close to ceasing all herbicide use, as a result of public pressure. In 1992 a Citizens Initiated Referendum was held on the issue of Tauranga City Council's use of pesticides, as a result of a petition organised by the Tauranga Branch of Toxins Awareness Group (TTAG). Sixty two percent of voters endorsed the proposal that Tauranga City Council cease using "toxic chemical spraying as a means of vegetation control". The resultant policy involves on-going communication with TTAG and constant review of their vegetation management programme; they run a bus trip with councillors, staff and TTAG people every six months to view problem areas and trials. A number of exemptions to the policy have been negotiated between Tauranga City Council and TTAG.

Legislative requirements

A number of Auckland City statutory and non-statutory plans and legislation relevant to the management of weeds in Auckland City are reviewed. These revolve around the City's obligations regarding the removal of weeds and the methods used to remove them.
The key legislation for determining whether or not to intervene in the growth of a weed species is the Biosecurity Act 1993; under this Act the Auckland Regional Council's Regional Plant Pest Strategy provides a list of Biosecurity weeds which Auckland City is obliged to remove or control on its land.
Other legislation applies to methods used to manage weed problems. The key Act is the Health and Safety in Employment Act 1992. In January 1998 the Occupational Safety and Health Service provided Auckland City with the following interpretation of a council's responsibilities under this Act:

"The Health and Safety in Employment Act 1992 imposes an obligation on an employer to take all practicable steps to ensure the safety of employees on the one hand, and to ensure that no action or inaction of any employee while at work harms any other person, on the other hand.

Herbicide use does of course carry health risks, and will therefore constitute a hazard under the Act. These risks will vary from significant to nonsignificant depending on the herbicide type, conditions of exposure, and individual susceptibility of user or bystander. Some members of the public, for reasons not yet medically understood, can react to very small amounts of chemical.

The Act outlines a system of hazard identification and control. The first step in control is that of elimination of the hazard if practicable (section 8). In practical terms this means not using herbicides where nonherbicide methods can achieve the same ends. OSH will accept that in some situations herbicide use is necessary in order to fulfil the Council's weed control obligations as outlined in the policy. The test is that of "all practicable steps", specified in the Act."

Dr Evan Dryson, Occupational Safety and Health Service, Department of Labour.

Weed management

The report develops a process for evaluating the impact of weed species and the weediness of different types of sites found throughout Auckland City and developing priorities for management. The combined information from this assessment results in a programme of weed control for parks, reserves and natural areas on roadsides, targeting the highest impact weeds on the highest priority sites.
A range of herbicide and non-herbicide weed control methods were evaluated throughout the preparation phase of this policy. For street environments and intensively managed areas of parks there are practical non-herbicide methods of vegetation control which can be used, although these methods need some refinement, especially where they are to be used effectively around specimen trees. Currently herbicides appear to be the only practical option for controlling a range of invasive weeds in natural areas, and a small range of these weeds cannot be effectively controlled with lower toxicity herbicides. Where herbicides are considered the only viable control method specific conditions regarding notification, approval, application and use are given.
A comparison of the various costs associated with herbicide and non-herbicide control is given, including a qualitative evaluation of external hidden costs of herbicide use on roadsides, and direct monetary costs. Increased budgets are primarily required to provide satisfactory standards of performance and customer service. Importantly, the implementation of practices which further reduce Auckland City's level of herbicide use would, it is considered, have positive benefits in decreasing the current level of community concern and resulting complaints. In turn it is envisaged officer efficiency would be enhanced, as a consequence of diminished 'downtime' normally due to resolving time-consuming disagreements, as well as the saving of $14,400 operational costs for servicing the No-Spray list.

Conclusion

Two main issues have emerged from this report:
- The issue that has involved the public in a protracted and sometimes heated debate is that of herbicide use in public places. Although the proposals contained in this report will not completely eliminate all possible herbicide exposure (resulting from Auckland City operations), they will vastly reduce it.
- The second, wider, issue is that regardless of the weed control methods used, whether herbicide or non-herbicide, this report confirms the critical need for significantly increased funding for weed and vegetation management across the board. The environmental threat to Auckland City's natural heritage posed by invasive weeds must be met. Effective actions based upon adequately resourced, well conceived weed management programmes, are essential to the conservation of Auckland City's unique ecology and landscape.

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Reviewed - October 2006