Beyond Barrier

ENVIRONMENTAL NEWS FROM NEW ZEALAND & AROUND THE WORLD

Mōhua thriving in the Landsborough Valley

Mōhua were once widespread in the beech forests of the South Island but the impact of predators has reduced their numbers so severely that they are now listed as endangered on the International Red List of Threatened Species. However, intense predator control in the Landsborough Valley in Westland, has seen numbers bounce back with a population estimated to be at around 485 in the most recent survey by DOC, slightly up from the last count in 2018. Bird counts in this valley have been running for 15 years, which is now DOC’s longest-running study.

Predator free islands have richer sea life

While it is well known that seabird occupation of islands enriches the soil with nitrogen-rich guano little is known about the impact on the nearshore environment. A recent study by two American biologists has now shown that run off of this guano into the sea enriches nearshore sea life(1). In a study of four islands in the Mercury archipelago off the Coromandel, representing three eradication histories: never invaded, eradicated 30 years ago, and eradicated 2 years ago, they found macroalgal diversity was highest at never-invaded islands, followed by islands in order of eradication. 

Conservation partnerships in Tamatea/Dusky Sound 

Predator control at landscape levels requires lots of partners. One of the best examples of this collaborative approach is predator control in Tamatea/Dusky Sound where Real Journeys, Fiordland Conservation Trust, Peregrine Wines, Pure Salt charters and Fiordland Lobster Company are all working with DOC and mana whenua to remove predators from several of the islands in Tamatea. Fiordland Lobster Company partnered with DOC to eradicate stoats from Pigeon Island (73 Ha) and have since funded the reintroduction of mohua, kakaruai and tieke to the island. Pure Salt has established a major trapping network on 1900 Ha Long Island and Real Journeys has done the same on adjacent 1779 Ha Cooper Island. These efforts are enabling tawaki, kea and kākā to flourish. The success of this interconnected island network of predator control provides confidence for even bigger projects like Predator Free Rakiura (1.75 m Ha). For more insight into the remarkable story of conservation and history in Tamatea read Petra Carey’s book Tamatea/Dusky Sound, which was awarded the 2021 Mountain Book of the Year.

References:

1. Rankin LL & Jones HP (2021). Marine Ecology Progress Series 661: 83-96.