World Wetland Day: Do you know a swamp from a dune slack?

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Dune slacks, ephemeral, seepages, swamps, tarns and frost hollows? No, these aren’t place names from a sci-fi fantasy movie but types of wetland.

A wetland is accurately titled – land that gets wet – however, many wetlands are only wet for part of the year while others have areas of shallow but permanent standing water such as a swamp or bog. They aren’t large or deep like a lake, though a lake may be surrounded by wetlands where the water seeps into the banks. Every wetland sits on a continuum depending on how much water it has, the state of the water (pH, nutrient levels), and the water condition (fresh or salt water). And wetlands can change over time – so it makes identification a challenge.

The Horizons rohe (region) is home to many different wetlands and they are places of huge significance. The Manawatū River Estuary, at the mouth of the Manawatū River near Foxton, was declared a Wetland of International Importance under the Ramsar Convention in July 2005, one of only six in New Zealand.

Aerial view of the Manawatū River EstuaryAerial view of part of the Manawatū Estuary near Foxton.

Wetlands in New Zealand form a crucial part of the natural landscape. Like kidneys or lungs of the environment, wetlands purify water and act as a sink for excess nutrients and pollution from land. They provide habitat and food for many native plants, fish (e.g. mudfish) and birds (e.g. the matuku). Once extensive, it is estimated New Zealand has lost 90% of its wetland areas over the last 150 years.

Plants that live in wetlands are highly adapted to their environment. Some quickly flower and produce fruit when it becomes dry enough, and others reproduce while still being covered by water. The variety of wetland types leads to a rich diversity of plant life.

The Horizons Region is the only place you will find certain wetland plants. This is due to either the plant being naturally rare or because of man-made threats to habitats. Working with NIWA, we know there are 30 species of nationally endangered freshwater-dependent plants in the rohe.

The bidibid, piripiri or Acaena rorida, an evergreen creeping plant, only exists in damp hollows within tussock land in the northern Ruahine Ranges. The small swamp sedge (Isolepis lenticularis) used to be found all over the North Island (from Northland to Manawatū) but now it is only found on the edges of tarns and streams in the Central Plateau. Pimelea actea or sand daphne, is now only found in one location in the world, and that’s right here at Himatangi Beach. [You might not identify sand dunes as a type of wetland. But hollows between dunes can retain fresh or brackish water for significant periods of time before drying out.]

Wetlands are threatened by several things. They are sensitive to weeds that compete with them for food, or starve them of sunlight. Climate change – changes in rainfall levels – affects survival.  Animals damage wetlands; this includes grazing stock, wild hoofed animals or humans who want to use the land differently or drain the water. Wetland plants are also highly sensitive to declining water quality.

Tokorima School planting around a wetland Tokirima School community learning about restoring wetlands.

So how can we protect our remaining wetlands? One key issue with wetland protection is identification. It is very difficult to locate and identify all wetlands in the region. Many wetlands are small and cannot be seen from the air using aerial photography (a common method of mapping habitats). Other wetlands dry out in summer making them difficult to find. Or simply, their importance is not recognised.

Many wetlands are protected under National Freshwater Legislation and by regulations in the One Plan (Horizons Regional Plan and Policy Statement). Horizons scientists work to protect wetlands by identifying and assessing the biodiversity present. Additionally our biodiversity and freshwater programmes see staff work alongside landowners to provide advice, funding and assistance on fencing, pest or predator control and native planting.

If you find yourself out and about, and your shoes get wet, think about all the specialised plants that live like that for most of the year. Wetland plants don’t have a face that lend themselves to mass campaigns to save them. They need you to value them.