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Exotic Weeds A ‘silent Invasion’ – Expert Reaction

 

Invasive weeds could “transform our ecosystems beyond recognition” if left unchecked, according to a new report from the Parliamentary Commissioner for the Environment (PCE).

The report has a series of recommendations on how to manage New Zealand’s pesky weeds in a smarter way.

The SMC asked experts to comment on the report.

Associate Professor Margaret Stanley, Ecologist, School of Biological Sciences, University of Auckland, comments:

“The release of this report by the PCE is timely. While Predator Free NZ captures the conservation limelight with a focus on the threats to native birds, the threat that weeds pose to entire native ecosystems is largely in the shadows. The scale of the problem is enormous, so we must be strategic.

“A national policy direction with an emphasis on national coordination and prioritisation of weeds proposed by the PCE would be an excellent step forward, but needs to be to accompanied by funding. Lack of long-term funding (at an appropriate level) puts native ecosystems at risk. Weed management is a ‘long game’. Current weed management funding is not often committed for the long term and is hampered by local political and community pressures and agency restructures. MPI and DOC need vastly higher levels of funding to be able to provide leadership in national weed management with national biodiversity benefits.

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“For widespread weeds we have to take the focus off single species and tackle multiple species at the sites we value the most in a more holistic way. If we remove one weed species, then others can fill the gap. We can’t get rid of all the weeds – so we must protect our highest value sites from the worst suite of weeds.”

Conflict of interest statement: “Member of the Ministry for Primary Industries’ National Interest Pest Response programme Technical Advisory Group, and Auckland Council’s Best Practice Reference group for Weed Management. I was interviewed a few times by the PCE report authors, but I did not see any draft reports or review it.”

Professor Bruce Clarkson, Environmental Research Institute, University of Waikato, comments:

“The PCE’s report addresses a major issue in effective weed management in Aotearoa New Zealand – long standing lack of coordinated action and underfunding to control and manage an increasing number of environmental weeds threatening indigenous ecosystems.

“The current emphasis on removing mammalian predators will surely assist indigenous biodiversity but not if it results in weeds (and introduced herbivores) being overlooked. The PCE report highlights the magnitude and growing impacts of environmental weeds that capture ecosystems which become dominated by foreign species.

“The enhanced surveillance advocated in the report is welcomed as the invasion of particularly undesirable plants is ongoing and appears to be increasing due to a warming climate. Here in the Waikato, for example, I am aware of shining privet and palms (Chinese windmill palm, Bangalow palm and Phoenix palm) invading and compromising a good number of the restoration plantings in urban areas.

“There remains a systemic need to understand which environmental weeds most limit efforts to restore or reconstruct indigenous habitat in urban, periurban and rural zones and how to efficiently increase dominance by indigenous plants.

“Responsibilities for weed control will vary but land owners, industry, conservation agencies and suburban gardeners all have a role to play if we are to retain the special indigenous biotic character of Aotearoa.”

No conflict of interest.

Dr Ronny Groenteman, Senior Scientist – Weed Biocontrol, Manaaki Whenua – Landcare Research, comments:

“The risk weeds pose to native ecosystems has been long overlooked by most New Zealanders. This report shines a long-overdue light on this critical issue.

“The report mentions separation from natural enemies as a reason exotic plants become weeds. Biological control, where natural enemies from the native range of weeds are utilised, is a safe, self-sustaining management option that operates on a landscape scale, and does not rely on human inputs beyond the early stages. Weed biocontrol has a proven track record in New Zealand but is currently available for only a few species.

“New Zealand is recognised globally as a leader in weed biocontrol, especially for weeds of native ecosystems. For example, biocontrol of mist flower (Ageratina riparia) in North Island forests resulted in 98 per cent reduction of the weed, successful regeneration of indigenous species, and reduced threats to two rare endemic species. Equally, biological control of heather (Calluna vulgaris) is preventing Tongariro National Park from turning into an exotic monoculture of this weed. Biocontrol of tradescantia (Tradescantia fluminensis) is still in its early days but is already displaying spectacular collapse of thick mats at early release sites, giving lowland forest remnants a chance to regenerate.

“The report also highlights the gap in national co-ordination required to reduce the serious harm weeds inflict on native ecosystems. Weed biocontrol in New Zealand operates under a unique collaborative model. The National Biocontrol Collective (a consortium of regional and unitary authorities and DOC) sets national priorities, shares the costs of developing weed biocontrol agents and assists with implementation in the field. Manaaki Whenua – Landcare Research provides the research to deliver biocontrol solutions to the Collective. Nationwide collaboration is possible. More is needed.”

“I support all recommendations made in the report.”

Conflict of interest statement: “Ronny provided advice to this report at its earlier stage. Manaaki Whenua – Landcare Research has received funding from the PCE for another employee to work on this report.”

Dr Imogen Bassett, Principal Advisor Biosecurity at Auckland Council, and Honorary Research Associate at the University of Auckland, comments:

“It is great to see the Commissioner put a spotlight on the management of weeds in indigenous ecosystems. As the report acknowledges, weeds have not to date received the degree of public attention that initiatives such as Predator Free 2050 have brought to mammalian pests. The threat posed by weeds is immense, yet often underappreciated because of the timeframes involved. It can take 10s – 100s of years for plants to jump the fence into indigenous ecosystems. Climate change will undoubtedly further exacerbate weed problems. If weed management is not more effectively resourced, the potential consequences for indigenous ecosystems are dire.

“The report correctly puts considerable emphasis on early intervention and a precautionary approach, which is much cheaper and offers better protection to ecosystems than delaying management until weeds are already widespread. For example, I agree with the Commissioner that the National Pest Plant Accord, which regulates trade of pest plants, should include more species that are not yet widely problematic, informed by weed risk assessments, and be updated more regularly.

“The report has also highlighted significant frustrations around accessing information about the distribution and status of weed species in New Zealand. Suggested improvements to national information management would greatly aid weed management, but the key will be adequate and sustained resourcing to ensure information can be maintained up to date.

“The report has also identified that the Biosecurity Act is not agile, or well suited to weed management. This makes it difficult for regional and unitary councils to establish and maintain up to date, effective regulatory provisions to support their weed management. I hope the issues identified in the report will be considered in the forthcoming review of the Biosecurity Act.

“Notably the report makes only passing mention of biological control (biocontrol). However, this is another area that requires improvements in coordination, prioritization and resourcing across central and regional government. Biocontrol has high start-up costs, but is very cost effective and environmentally friendly long-term.”

Conflict of interest statement: “Imogen Bassett has shared information with the Parliamentary Commissioner for the Environment’s project team, to inform this report, and reviewed an earlier draft of the report.”

Paul Champion, Principal Scientist – Freshwater Ecology, NIWA, comments:

“NIWA endorse the report’s recommendations, given the issues of inconsistent management of weed species by national and regional management agencies and the need for a national overview of environmental weeds. Additionally, we endorse active surveillance for weed species, assessment of species and management risks, and maintenance of science capacity to support this.

“The PCE report focuses primarily on terrestrial weeds. While some freshwater weeds are included, the need for different management approaches for the ecological impacts of freshwater weeds is omitted. Freshwater weeds have different modes of incursion, different vectors for secondary spread (mostly human-mediated) and different impacts on native species, habitat quality and other ecological properties. Freshwater weed impacts can be immense, including the complete collapse of native lake vegetation and associated ecosystems, so proactive management is key.

“The discussion of secondary legislation in the PCE report (page 123), does not mention the National Policy Statement for Freshwater Management (2020) or the National Environmental Standards for Freshwater 2020. These require weed monitoring but impose limitations on weed control in wetlands and aquatic ecosystems. MfE were identified as being ‘surprisingly absent’ from weed issues, but invasive freshwater plants are included as a monitoring requirement for lakes. DOC also have responsibilities for aquatic pest management, including coordinating freshwater weed management.

“NIWA are actively engaged with national and regional agencies (including LINZ, MPI, DOC and most regional councils) in the identification, risk assessment, surveillance and control of freshwater weeds, and the restoration of habitats degraded by weed invasions. The biggest challenges ahead are:
· a collective approach to the exchange of biosecurity information
· responses to new freshwater weed incursions
· smarter surveillance and detection of freshwater weeds
· more environmentally friendly techniques for freshwater weed control and eradication
· tools to restore degraded freshwater systems.”

No conflict of interest declared.

Dr Chris Buddenhagen, Weed Ecologist, AgResearch, comments:

“It is encouraging to see the Space Invaders report focus on ‘internal biosecurity’, and addressing the spread and management of damaging weeds within New Zealand. Historically the focus has been on New Zealand’s border and preventing new incursions, which is also important, however as the reports notes, most of the weeds that will spread and threaten our native ecosystems already exist in New Zealand.

“Weeds that threaten our native ecosystems typically first establish in urban areas or on farmland. Many of these same species also impact or threaten urban and agricultural land. Therefore, farmers need to be supported as they are increasingly called upon to establish and manage patches of native vegetation (e.g. riparian plantings) within a sea of non-native vegetation. By focusing research and management efforts on the source areas for the weeds, we give ourselves the best opportunity to protect both our native and agricultural ecosystems.

“The report rightly notes the need to prioritise weed species for research and management. The recommendation to establish a publicly accessible database on exotic plants would be an important step forward. This database would ideally link to map records of species across all ecosystems.

“As a nation, the funding and efforts we put into the research and management of weeds should reflect the value we place on our native and agricultural ecosystems.”

Conflict of interest statement: “I am a member of a weed research team at AgResearch which does science funded by both government and industry.”

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