28 Jan 2019

Expert feature: New Zealand Wetlands

From Afternoons with Jesse Mulligan, 2:38 pm on 28 January 2019

This Saturday 2 February is World Wetlands Day. This year's theme is "wetlands and climate change". Wetlands are a little-known preventative for climate change and they have been described as the Earth's "kidneys".

Consultant ecologist and a trustee for the National Wetlands Trust, Melanie Dixon, said wetlands is a broad term that encompasses mangroves, swamps, salt marshes, mountain pools, bogs, shallow lakes, and some river edges. The key characteristic is water-logged soil that leads to a different kind of vegetation.

Dixon tells Afternoons that wetlands once made up around 10 percent of New Zealand’s land mass, but since settlement it’s down to around 1 percent. The big ones are in Waikato, the West Coast, and Southland.

She says there’s two things wetlands do for climate change. One is they are incredibly good sinks for carbon. “Because they’re so wet, when the plants grow, they can’t break down because its oxygen poor.” She says there are bogs in the Waikato that store carbon all year round.

The other aspect helps with the consequences of climate change. Weather events are become more extreme and more common and most involve water. “So if you’ve got something like a wetland that works as a sponge when it rains heavily, it’s going to soak up water, hold it, and let it out slowly. Coastal wetlands such as mangroves are going to slow wave action and break it down.”

Dixon says the 2004 Boxing Day Tsunami showed that areas where wetlands hadn’t been cleared provided a barrier to the incoming water which did not travel as far as areas without wetlands.

Wetlands can also provide a small measure of protection for water quality in dairy farming areas. Dixon says Fonterra and Dairy NZ have recognised the role wetlands can play in protecting water quality and have got on board.

While wetlands aren’t very beautiful in the traditional sense, Dixon says that you learn to appreciate them over time. They are host to bird and insect species rarely seen elsewhere.

Her advice for people heading out on World Wetlands Day this Saturday was to “keep your eyes and ears open.”

“Take a moment to be quiet and just observe and you’ll see and hear things. They’ve been described as New Zealand’s shy places – they take a little bit more to get to know than our beaches or mountains, but they have an appeal all of their own.”

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