22 Nov 2019 Story Ecosystems

Pacific countries confront a daunting invasion force

“You can often tell from afar which atolls are free of rats,” says Manoela Pessoa de Miranda, UN Environment Programme’s (UNEP) Programme Manager for the Pacific. “Nature is in abundance. Vegetation is healthy. The air is full of birds. The sea is teeming with fish. Coral is thriving.

“Seabird droppings wash into the ocean and fertilize the coral, which attracts the fish, which feed the seabirds, and so on. Rats break this natural cycle.”

In the Pacific, ecosystems hang in a delicate balance. The isolation of Pacific islands lends them a natural protection from invasive species that continental ecosystems don’t have. But when an alien species does alight on these remote shores, they can wreak havoc.

Invasive species are the number one cause of extinction of single-country endemic species in the Pacific. 5.8 per cent of the Pacific’s 2,189 single-country endemic species are already extinct. 45 per cent are at immediate risk.

The destruction takes its toll on nature but is just as dangerous for humans. Without significant industrial operations, economies in the Pacific are typically based on natural systems. Agriculture, fisheries and other ways of life depend on a healthy environment.

And as climate change increases the regularity and intensity of storms, invasive species not only exacerbate the impacts, they also benefit from extreme weather.

Take the example of Cyclone Evan, which caused over US$312 million in damage in Samoa, Fiji, Tonga and Wallis and Futuna in 2012. Native forests are deeply rooted in the soil, but invasive species like tamaligi trees that dominate the canopy in Samoa are not. It’s no wonder that the trees that dammed rivers—causing flash flooding, destroying buildings and bridges downstream—were almost all tamaligi trees. After, tamaligi and other invasive plants were the first to recolonize much of the land made bare by the cyclone.

For a sustainable future, the fight must be brought to the invaders.

That’s the goal of several ongoing projects supported by UNEP and the Secretariat of the Pacific Regional Environment Programme.

The Pacific Regional Invasive Species Management Support Service is approaching the fight on five fronts.

The first goal is to prevent new species from coming in, particularly through public education campaigns and technical training. While all countries have legislation on biosecurity, putting it into practice can be very difficult. Sailors can come in with boats full of rats or even carrying birds as pets, but if border agents or the public are unaware of the issue it can be difficult to deny entry or contain an outbreak.


A second goal is to remove predators that have already infiltrated the islands. In Niue, feral pigs were becoming a problem but local attempts to reduce their numbers were ineffectual. A professional pig hunter was brought in with proper hunting dogs and GPS trackers. By introducing proper hunting techniques, the island is now able to effectively manage its feral pig population.

Unlike eradicating larger animals, weeds pose additional challenges. Seeds can lie dormant in the soil for some time. And because plants don’t move around, considerable effort must be invested to go out and find them before they spread. However, certain biological agents can take out specific weeds without affecting native plant species. There are many opportunities to spread existing natural enemies present in the Pacific further.

This “natural enemy” approach to reducing the impact of widespread weeds is also being promoted by the Pacific Regional Invasive Species Management Support Service for new invasive plant species that don’t have natural enemies in the Pacific. But for this to work, extensive and expensive tests must be done to ensure native plants are unaffected.

Finally, the Pacific Regional Invasive Species Management Support Service is ensuring that whatever success they do realize is sustainable.

For David Moverley, Invasive Species Adviser at the Secretariat of the Pacific Regional Environment Programme, the community is key. “You can’t really do it without the community. The community has to value a site for anything to be effective. We can help set things up and get things going but at the end of the day it’s the community that has to sustain it.”

Moverley points to Tonga as an exemplar of bringing the community into the mix. “The King and Queen of Tonga themselves have been huge advocates of this work, particularly at Toloa Rainforest.”

Restoration projects at Toloa and Mt. Talau have seen a rat control programme and extensive replanting, at the former site, of native trees. The Queen of Tonga now presents national student prizes for restoration, alongside traditional awards for subjects like math and English.

“A key element of their success has been providing information to the public and getting them involved,” says Moverley.

It’s a success you can hear if you listen closely. “The endemic hengahenga, or Tongan whistler, are now common on Mt. Talau. Their song hasn’t been heard in over a generation.”

Pessoa de Miranda wants to see these achievements spread. “Healthy ecosystems are so important to Pacific countries and peoples. For the Pacific ecosystems to be truly resilient, we have no choice but to bring successes to every country in the region.”