Native mangroves in Aotearoa are expanding, putting them in conflict with some local communities & councils. A wade into the research about the value of mangroves & how they are managed.

Unlike many of Aotearoa's native plant species, our mangroves are actually doing great. Is that a problem, with mangroves clogging some waterways and taking over estuaries? Or is it just nature adapting, providing a great habitat for some birds and protection for our coastlines? Are mangroves the bad guys or just misunderstood?

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Finding footprints

Jacques de Satgé has spent three field seasons surveying for banded rail in mangroves. He has learned how to trap and GPS tag these cryptic birds. He has learned how to mark out quadrats in dense mangrove growth to survey for footprints, banded rail prey and vegetation. And he has also learned about the different properties of mud!

Jacques is part of the Human-Wildlife Interaction Research Group at Massey University, led by Associate Professor Weihong Ji. His research work is aimed at starting to fill a knowledge gap about how native birds, such as the banded rail, use mangrove habitats.

While New Zealand's mangroves don't have any obligate bird species - that is, a bird that relies solely on mangrove habitat - there is evidence that some birds do use mangroves for foraging and resting.

With hundreds of footprint surveys conducted at his four mangrove sites, coupled with GPS data from tagged banded rails, Jacques can now add what he has learned to the bigger picture of what we know about how birds use Aotearoa's temperate mangroves.

Mangrove expansion

Aotearoa's native mangroves can be found in the north half of the North Island, on the shorelines and estuaries found between Ōhiwa on the east coast and Kawhia on the west.

Mangrove is actually a term for a collection of tree species - those who can survive a twice-a-day dunking of sea water. Globally, there are many different species of tropical mangrove, and near the equator there can be mixtures of 20 to 30 species in just one stretch of coast. Right at the southern latitude limit of where mangroves can survive, in Aotearoa there is just one species of temperate mangrove (Avicennia marina subspecies australasica, known as Manawa)…

Go to this episode on rnz.co.nz for more details