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Obliterating rats in Tonga

By Pacific Island Times News Staff

Montreal— For the past four decades, Tonga has been trying to eradicate rats from the uninhabited Late Island, which supports a tropical broad-leaf forest ecosystem.

It is one of the most threatened ecosystem types in the world and one of the best remaining tracts of diverse native forests in Tonga.

Owing to its relatively unmodified forest communities, Late is also a global stronghold for two IUCN-listed species of bird, one native mammal, and six species of reptile. However, the biological integrity of Late is threatened by invasive Pacific rats that were historically introduced to the island.

“The direct and indirect impacts of this invasive species include habitat degradation; soil nutrient depletion, loss of floral diversity, seed predation, species extinctions and extirpations, predation of bird eggs, and chicks, and reduced bird, reptile, and invertebrate diversity and abundance,” states a report written by J. Bonham and R. Griffiths of Island Conservation for Tonga Ministry of Lands, Environment, Climate Change and Natural Resources.

Bonham said the effects of Pacific rats on ecosystems of the tropical Pacific remain relatively unstudied. “However, in Tongan forests, rats are a known seed predator.


In New Zealand and throughout the Pacific, Pacific rats have been implicated in the decline and local extinction of numerous forest trees and shrubs, palm and climber; species of invertebrates, frogs, reptiles; seabirds and forest birds,” Bonham stated in the report titled “Feasibility Assessment for the Removal of Pacific Rats (Rattus exulans) from Late Island.”

A major project to remove rats from Late Island will be the largest rat eradication initiative undertaken in the Pacific region.

This was highlighted at the 15th Conference of the Parties to the Convention on Biological Diversity (COP15) in Montreal Canada, as an example of Pacific countries taking the lead to restore island resilience.

The Late rat eradication project was spotlighted during a side event at COP15, where Pacific officials are working with delegates from 196 countries to seal the Post-2020 Global Biodiversity Framework to halt and reverse nature loss.

At the Partnership Pavilion, the SPREP Pacific Regional Invasive Species Management Support Service and the Global Environment Facility co-hosted the "Restoring Island Resilience" panel, which looked at how countries need to manage invasive species to increase the climate resilience of ecosystems and communities across the Pacific islands region.

“Tonga is a small country but a large ocean state,” said Atelaite Lupe Matoto, Tonga’s director of environment. “We have many uninhabited islands, and our ocean is very critical to our existence. The ocean is very important to us for the quality of life. Tonga being a group of islands in the Pacific, we face devastating impacts from climate change, especially sea level rise, as with many other Pacific countries. We also struggle with adverse health impacts from climate change.”

But with nature-based solutions, she said there is a number of approaches Tonga is using to mitigate many of the adverse impacts of the climate crisis. The Late rat eradication project is one of them.


“When you look at the guano of birds, there is a cycle where the runoff will provide nutrients to maintain coral health and in turn feed the fish, and then fish to the table, and so on. We have seen bird populations grow on our rat-free islands and we’ve even seen turtles returning to nest on islands that are rat-free.”

Matoto recalled that several years back, they translocated one of their endemic birds, the malau or the Tongan megapode, to one of their rat-free islands.

“Ten years after we found that there was a population that reproduced on the rat-free island, but on Late we didn’t find any birds left. We have to remember these birds lay their eggs on volcanic islands, so they depend on the warmth of the volcano to incubate. We have observed also that many of the rats are eating the eggs, so this is why we are very excited about the Late project and the promise it holds for conservation, and we are quite keen to see it through.” (Pacific Island Times News Staff/SPREP)

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