25 February 2025, Nuku’alofa, Tonga - A prioritisation workshop in Nuku’alofa brought together stakeholders and experts from across Tonga to enhance their invasive weeds management. Hosted by the Natural Enemies - Natural Solutions (NENS) programme and the Tonga Ministry of Meteorology, Energy, Information, Disaster Management, Environment, Climate Change & Communications (MEIDECC), the workshop held in February, aimed to identify priority invasive weeds for future NENS projects.
The NENS programme, part of the Pacific Regional Invasive Species Management Support Service (PRISMSS) and hosted by the Secretariat of the Pacific Regional Environment Programme (SPREP), supports Pacific Island Countries and Territories in restoring ecological balance using natural enemies from the weeds' native range.
The workshop was facilitated by experts from Manaaki Whenua - Landcare Research (MWLR), from New Zealand, the technical lead for the PRISMSS NENS programme. The NENS programme aims to lower the impact of widespread invasive plants by reducing their vigour through reuniting them with safe natural enemies from their original homeland. The NENS programme initiatives empowers Pacific communities by improving the health and well-being of all living things and ecosystems.
Stakeholders from several government organisations and NGOs, including the Ministry of Agriculture, Forestry and Farming (MAFF) and the Vava'u Environmental Protection Association (VEPA) participated in discussions during prioritisation workshop.
Participants of the workshop ranked invasive weeds that are present in Tonga, including air potato (Dioscorea bulbifera), cordia Cordia alliodora, mile-a-minute (Mikania micrantha) and ivy gourd (Coccinia grandis). Weeds were ranked according to their importance, environmental, economic, social and cultural impacts, likelihood of success and costs to carry out a NENS project in Tonga.
Mr Viliami Hakaumotu, the National Invasives Species Coordinator in Tonga, commented that the workshop was a success, bringing together multiple stakeholders with a shared interest in enhancing invasive weed management in Tonga.
"The workshop was a crucial step in ensuring we’re directing our efforts where they’re needed most and pinpointed several weed species that are widespread across Tonga and are causing significant issues”.
“By working together, we can make a real difference in protecting our environment and livelihoods”.
Weeds that ranked highly on the prioritisation list, like prickly solanum (Solanum torvum), which is a significant weed in parts of the Pacific, can cause major impacts to primary production because they smother pasture weeds and are not typically eaten by cattle.
Other weeds that ranked highly were Cordia alliodora (sometimes called Ecuador laurel or Spanish elm), ivy gourd (Coccinia grandis), mile-a-minute (Mikania micrantha) and hoi/air potato (Dioscorea bulbifera).
NENS Programme Coordinator, Ms. Indigo Michael, commented, "some of the weeds that ranked highly on the list of priority weeds in Tonga were those that were major crop weeds and are economically expensive to manage using conventional methods of control."
Some of the most expensive plants to control are those where manual eradication of the plant is ineffective due to the ecology and reproductive habits of the plant. However, some plants have become so widespread across Tonga that neither manual removal nor herbicide use are practical methods of control as they are too abundant.
Weeds like mile-a-minute, aggressively smothers native or important plants, therefore making herbicide use too risky. It is at this point that the use of natural enemies needs to be considered.
SPREP Invasive Species Adviser, Mr David Moverley, commented that, “the use of natural enemies continues to be a practical and low maintenance solution to reduce the impact of widespread weeds in the Pacific and is a key focus for further regional development and scaling up”.
“Greater involvement across the Pacific in the PRISMSS NENS programme is benefitting all Pacific states as solutions to regional scale problems are being developed. Improving the health of ecosystems at the landscape scale puts Pacific people in a better position to adapt to climate change and sustain their livelihoods and traditional way of life”.
The use of natural enemies to control invasive weeds is a long-term, landscape scale, environmentally friendly, cost-effective solution that provides a major opportunity to improve the resilience of Pacific communities to the impacts of widespread weeds and climate change.
Using natural enemies to manage invasive weeds is not a new tool in the Pacific and has been used for over 100 years. So far, 71 natural enemies have been released across 18 Pacific Islands and Territories, to help manage 30 invasive weeds.
MWLR will continue to work with local partners to implement priority PRISMSS NENS project activities in identified priority sites in Tonga.
-----------------------------------------------------------------------------------------------------------
About PRISMSS: The Pacific Regional Invasive Species Management Support Service (PRISMSS) is a coordinating mechanism designed to facilitate the scaling up of operational management of invasive species in the Pacific. PRISMSS brings together experts to provide support within the Pacific region with a focus on protection of indigenous biodiversity and ecosystem function. As a service provider, PRISMSS provides a comprehensive suite of support services in a cohesive, effective, efficient, and accessible manner to Pacific Island countries and territories.
Restoring Island Resilience (RIR): The PRISMSS - Restoring Island Resilience (RIR) is a New Zealand-PRISMSS collaboration project that aims to improve Pacific Island Countries and territories livelihoods and resilience to climate change by reducing the impact of invasive species on natural and agricultural ecosystems through the five PRISMSS programmes.
The GEF 6 Regional Invasives Project (RIP) is funded by the Global Environment Facility, implemented by the United Nations Environment Programme, and executed by the Secretariat of the Pacific Regional Environment Programme. The Project works primarily in the Marshall Islands, Niue, Tonga, and Tuvalu and has a regional component. Implementation of the GEF 6 RIP is supported by the Pacific Regional Invasive Species Management Support Services (PRISMSS).
For more information:
Mr Viliami Hakaumotu
National Invasives Species Coordinator - Tonga
viliamihakau@gmail.com
Ms. Indigo Michael
NENS Programme Coordinator – Manaaki Whenua Landcare Research
michaeli@landcareresearch.co.nz
For additional information please contact Mr Domnic Sadler, PRISMSS Manager on dominics@sprep.org or Mr Nitish Narayan, PRISMSS Communications & Liaison Officer on nitishn@sprep.org