28 February 2025, Majuro, Republic of Marshall Islands - Effective invasive weed management is crucial for enhancing community resilience to climate change. Climate change can accelerate the spread of invasive species. Together, invasive species and climate change reduce ecosystem resilience, food security and negatively impacts biodiversity conservation efforts.
Climate change can facilitate invasive weeds by altering background environmental conditions, increasing disturbance through extreme climatic events and through human responses to climate change. While all plants, regardless of whether they are native or invasive, will likely be affected by environmental change, it is widely expected that climate change will favour invasive weeds at the expense of native plants.
Until 2024, the Republic of Marshall Islands (RMI) had not introduced a natural enemy to control a weed. This changed with the introduction of the chromolaena gall fly (Ceichidochares connexa) to manage chromolaena (Chromolaena odorata) on Bikini Island.
In late January this year, experts from the Manaaki Whenua – Landcare Research (MWLR) travelled from New Zealand to Majuro in RMI to run a capacity building and awareness raising workshop on the use of natural enemies to control weeds in the Pacific as part of the Natural Enemies – Natural Solutions (NENS) programme.
NENS is a programme of the Pacific Regional Invasive Species Management Support Service (PRISMSS), led by the Secretariat of the Pacific Regional Environment Programme (SPREP), which supports Pacific Island Countries and Territories in restoring ecological balance using natural enemies from the weeds' native range. MWLR is the technical lead for the NENS programme.
Hosted by the RMI Ministry for Natural Resources and Commerce, the workshop included 17 representatives from the Quarantine, Agriculture, and Forestry Departments. It focused on understanding how natural enemies can manage widespread weeds and identifying other weeds that might be controlled with NENS in the Marshall Islands.
Programme lead for the NENS programme from MWLR, Ms Lynley Hayes commented that “once invasive weeds have become widespread the only feasible and cost-effective way to manage them is through deploying their natural enemies to provide permanent suppression at the landscape level”.
“Currently information is lacking about what weeds are present in most of the Marshall Islands, which comprise 29 far flung low-lying coral atolls and five islands in the North Pacific, many of which are challenging to visit, but it is hoped that future capacity building activities and surveys will be able to address this information gap.
The workshop enabled participants to share their thoughts about the most problematic weeds for communities in RMI. Participants shared that, “coastal plants are highly valued for their essential role in stabilising shorelines and reducing erosion and therefore would not be controlled even if they exhibit weedy characteristics”.
Also that, “communities are likely to support the control of plants such as beggar’s tick (Bidens spp.), which require constant efforts to prevent them from overtaking gardens, and the vine marlap (Ipomaea violacea), which smothers food crops”.
SPREP Invasive Species Adviser, Mr David Moverley, commented that, “Natural enemies are a desirable means of managing weeds due to their potential impact at scale and the relatively small amount of effort required when compared with other management methods”.
“Hopefully this allows communities to focus their efforts on other duties rather than on continually managing the same weeds. On isolated islands it also means that return visits are not as necessary and the natural enemies can largely be left to their own devices”.
Discussions held during the workshop identified the need to enhance community awareness about the threat posed by some weeds present, that are still relatively low incidence, such as air potato (Dioscorea bulbifera), ivy gourd (Coccinia grandis), leucaena (Leucaena leucocephala) and taro vine (Epipremnum pinnatum cv aureum). These weeds may all need to be NENS targets in the future if they are allowed to continue to spread.
Participants expressed that they found the training valuable and were interested in more trainings in the future, including hands-on field activities. A common theme was that it was useful to learn more about weeds in RMI. One participant shared that the best thing about the workshop was getting to know the success stories from other countries and that NENS can be a very good solution for invasive weeds.
The recent training has enhanced the skills of invasive species battlers from the RMI Quarantine, Agriculture, and Forestry Departments, enabling them to identify and utilise natural enemies for more sustainable weed management.
A targeted community awareness campaign is also being planned to enhance the communities knowledge on why it is import to manage invasive species and the impact that it can have if not done properly or sustainably.
MWLR will continue working with local partners and coordinate with PRISMSS to implement priority NENS project activities in RMI.
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 PRISMSS NENS programme aims to lower the impact of widespread invasive plants. Led by Manaaki Whenua – Landcare Research, NENS reduces the vigour of widespread weeds 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.