Wetland wonders

Inanga are one of five species that in their juvenile stage are known as whitebait,” explains Stuart Slade, a 68-year-old potter who lives just outside Ohope, a small town east of Whakatane in the Bay of Plenty. “On the spring tide, they spawn in the flooded grass, where the fresh and saline water mix. The eggs sit in the grass for a month. Then on the next spring tide they hatch and the tiny inanga swim out to sea.”

Such are the hidden secrets of saltmarshes – an important kind of habitat that is often overlooked in this country. These coastal wetlands provide protection for all kinds of treasured wildlife, including the much-sought after delicacy whitebait. They improve water quality by acting as giant filters and help prevent flooding – yet in New Zealand over 90 per cent of these complex ecosystems have been drained or filled.

The natural value of these areas isn’t lost on Stuart and his wife Margaret, however. Their home and business, Cheddar Valley Pottery, overlooks the Nukuhou Saltmarsh – a 60 hectare area of rushes at the back of the Ohiwa Harbour. The area was once a mess of weeds and rife with pests, but thanks to the pair’s efforts – and the work of a volunteer group they helped start – the saltmarsh is now recognised as a wetland of national importance and echoes to the sound of birdsong.

It also echoes, in season, to the sound of happy whitebaiters. Three years ago Stuart, Margaret and their Nukuhou Saltmarsh Care Group planted inanga spawning sites along the Nukuhou River, which feeds into the marsh. Three years on, the flaxes, sedges, manuka and cabbage trees are thriving, and a walkway wiggles along the riverbank. The whitebaiters love the ready access to their favourite spots, and last season many experienced their best catches in years, Stuart says.

Small beginnings

Currently the group has about 20 active members including two retired teachers, a retired builder, a retired timber engineer, a hydrology engineer, a financial advisor, an enviro-educator, and a farmer. Typically about six to 12 members turn out for a working session on one Sunday each month, clearing weeds, planting, or bird monitoring. As Margaret points out, these are also really positive social occasions. Caring for the saltmarsh brings the small community together.

It all began in 2003 when locals wanted to find a way to protect the rare birds living in the saltmarsh. “We all knew there were fernbirds and banded rail, and probably bittern. But locals had observed stoats crossing the road, and the fringes were being invaded by pampas, gorse, wattle, and briar,” recalls Stuart.

One of the residents, Nareena Olliver, arranged for a meeting with locals, the Department of Conservation (DoC), and Tim Senior, who is a Bay of Plenty Regional Council land management officer. This meeting showed that while the local community was small, there was a commitment to take action.

Bay of Plenty Regional Council confirmed their support, and the fledgling group was soon registered with the council as a Care Group. From there, it was all go. DoC provided 30 tracking tunnels to track mustelids (weasels and stoats) and rodents (rats and mice), and helped the group to set up monthly bird monitoring. Tim reported on invasive plant species and provided the means to control them. Before long, Opotiki and Whakatane councils were also on board, setting in motion a partnership approach that continues today.

Pest attack

Those early tracking results confirmed that predators were rife. The first rat bait stations were set in 2004, and the first mustelid trapping followed in 2005, with over 40 stoats caught in the first year. Now there are 28 mustelid traps, supplied by regional council and DoC, and the running total is 193 stoats, 96 weasels, 265 rats, and 54 hedgehogs, which are known to eat the eggs of ground-nesting birds.

“Stoats have a home territory of up to about 10km radius, so we’re always going to have to trap animals moving into the vacuum. But rats only have an area of about 50sq m, so we have a much better chance of eliminating them from the saltmarsh,” says Stuart.

As the marauders were hammered, native birds began to recover. The care group continues quarterly bird monitoring, and from a first count of 35, fernbirds have steadily increased to over 100. More importantly, it seems that the 40ha saltmarsh now holds all the fernbirds it can. They’re starting to move out to other areas of the 28sq km Ohiwa Harbour.

“On many mornings, we cycle into Ohope [11km away] and we hear fernbirds along the way. It’s common for us to hear fernbirds at home and we’ve had them around the vege garden,” says Margaret.

The couple’s bike rides take them past another of the group’s successful initiatives. About seven years ago, native shrubs and trees were planted along about 800m of the main road, which divides the saltmarsh from paddocks. The trees are now about 4m high and looking great — but looks weren’t the reason for planting them. From 2003 to 2005, five bitterns were killed by vehicles, because as they lifted off from their saltmarsh home, they flew low over the road. Bitterns are heron-like birds that are seriously endangered, thanks to their reliance on wetlands, with fewer than 1000 left alive. The Nukuhou birds are doing better though – the trees have forced the large birds to fly higher, in safety. It’s a simple, natural conservation solution. (See ‘Just 1000 left’ below.)

A little further up the road, the main public face to the saltmarsh is a lookout area, initially cleared by Opotiki council, and now maintained by the care group. As well as a boardwalk into the saltmarsh, and a walkway along the edge, the lookout has large rocks on which there are sculpted ceramic tiles showing a fernbird, marsh crake, kingfisher, bittern, banded rail, and more. Stuart and Margaret made the tiles in 2004, supported by a (now defunct) DoC Artists in Conservation grant.

“Since roadside signs were put up [by Whakatane council] a lot of people stop at the lookout. There are lots of groups, lots of schools. I think it’s had a huge educational effect,” says Margaret.

In the last year the group has also pushed 3km north of the saltmarsh to Uretara island. “The aim is to reduce predator numbers and the infestation of weeds to the point it will provide a better habitat for birds, some of which are endangered,” says Stuart. With iwi, DoC and council consent, they’ve begun spraying and trapping. The group has several members who are registered to spray in public places, and handle poisons.

All such voluntary work is supported financially by an arrangement with regional council. Each hour of volunteer time is logged, and that time can be offset against the purchase of sprays and materials from the council. The group has also received a number of grants, which have been invaluable for projects like building the boardwalk.

Supporting the commitment

“It’s been a privilege to work with such a committed local group,” says Tim, Regional Council land management officer, who provides ongoing liaison between the council and care group.

“Right from the start the local residents had a vision for the saltmarsh, and how it could be restored. It’s my role to support that vision and to help them access technical expertise and resources. The group now has a formal management plan under our biodiversity programme. This includes biodiversity objectives and outcomes, and commits [regional council] funding for the next five years and beyond.”

“It’s a shining example of what can be achieved by the collaborative effort of the local community, regional and district councils, DoC and local iwi,” Tim says. “In the end, we’re all wanting the same outcome of doing the right thing for our local environments. The work of this group has been ground-breaking nationally. It has provided really important insights into saltmarsh ecology and restoration.”

As Tim points out, the sites are mostly DoC reserves, and “DoC don’t have the capacity to provide this kind of gilt-edged management.”

No surprise, there have been a number of awards. The highlight came in 2010, when Nukuhou Saltmarsh was voted Best Community Initiative in the Keep New Zealand Beautiful Awards. But the biggest rewards come daily.

“It gives me a lot of satisfaction to look out and not see the wattle, the briar. To look out and see the flax, the oioi, the marsh ribbonwood,” says Stuart. “The marsh ribbonwood is booming, probably due to fewer rats eating the seed, and that’s providing excellent habitat for the fernbirds. The oioi is a beautiful colour, a rich mustard-red.”

Margaret adds that the work is always wonderful exercise. “You use a lot of muscles dealing with weeds and things. The hardest work is stumbling through scrub to deal with pampas.”

“The more we do, the more we realise how much we didn’t know when we started, and how much we’ve learned,” Stuart says. “And how much there is to do,” Margaret completes.

Out beyond the saltmarsh, beyond Uretara’s pohutukawa flanks, there’s a whole harbour of conservation work yet to be done. But things are rolling. “There’s a network of volunteer groups that are starting to meet up,” says Stuart. “My vision is that all the fringes of the harbour have someone who has taken ownership of helping to restore and keep them in better condition. The ultimate would be to have different care groups overlapping one another.”

There’s good news, too, for those tiny inanga. “Judging by the bait take from rat poison stations along the riverside, we have hit the mouse and rat population hard. That means more inanga eggs will survive this year, to be swept out to sea and come back as whitebait.”

Wetlands working for us

“Salt marshes and mudflats are very productive ecosystems,” says Karen Denyer, who is part-time executive officer of the National Wetlands Trust, as well as an ecological consultant. “The invertebrates [such as crabs, worms and cockles] that live in the mud can feed huge flocks of migratory birds. Many fish spend their juvenile years in the calm waters among estuary plants. Around 30 fish species are found in New Zealand estuaries, and others like eels and whitebait migrate through them.”

Karen explains that because salt marshes aren’t usually favoured by predators like cats and possums, they are one of the last refuges for rare bird species like banded rail, which were probably once found throughout the country. They also form an important buffer between water and land, with mangroves and salt marsh shrubs minimising storm and high wave damage. And all vegetated wetlands help to protect water quality by trapping sediment and nutrients.

“You can see this after floods, where plants are covered in a layer of sediment that would otherwise have ended up in the water downstream. Some nutrients are taken up by the roots but nitrogen is also removed from water and released to the atmosphere by bacteria that live on the stems of wetland plants.”

Unfortunately far too often the value of wetlands has been sorely underappreciated. “Since humans arrived in New Zealand we have lost 90 per cent of our freshwater wetlands. This year’s drought was tough enough on wetland species, but some landowners took advantage of the dry conditions to dig or deepen drains or clear wetland vegetation. Seagrass beds have also been disappearing; perhaps too much silt is smothering them.”

The website of the National Wetlands Trust offers excellent information, a directory of wetlands to visit, links, and a newsletter with features on wetland initiatives. Visit www.wetlandtrust.org.nz.

Just 1000 left

The Australasian bittern or matuku is found in New Zealand, Australia and New Caledonia and is endangered in each country. Our population is the healthiest, yet there are thought to be fewer than 1000 birds alive in this country.

Bitterns stand stock still with their heads pointed upwards when disturbed. This helps their striped feathers blend perfectly with the reeds and rushes that they live in, and makes them almost impossible to spot.

However, their unique camouflage means they are almost completely dependent on wetlands and swamps for survival. The drainage and destruction of these habitats for farming is thought to be the main reason for the rapid decline of this handsome bird.

Visit www.tinyurl.com/cem7pjs to find out how you can help save the bittern.