WAIRAU LAGOONS

Forest and Bird, Issue 267, 1 February 1993, Page 34

WAIRAU LAGOONS

Margaret Peace

important wetlands under threat

In 150 years New Zealand has lost ninety percent of its wetlands. Of those remaining, one of the most outstanding is the Wairau Lagoons and its associated estuaries in north-east Marlborough. Yet, as MARGARET PEACE reports, the area has never had protected status or a management plan. Only recently has local controversy over the lack of protection motivated the Department of Conservation to look at an appropriate management regime for the lagoons.

T THE SOUTHERN end of Cloudy Bay, just east of Blenheim and south of where the Wairau and Opawa river mouths flow into the bay, are a series of tidal wetlands known as the Wairau lagoons. They are famous for the diversity and abundance of their birdlife. These include the largest population of spoonbills in the country and a significant breeding population of Caspian terns. It is also an important staging area for golden plover, wrybill, knot and even the occasional black stilt in their migration from the South to the North Island. The area also has great cultural significance. The lagoon surrounds were used extensively by early Maori and there are numerous archaeological sites dating back a thousand years. Recent investigations on the Wairau Bar by Dr Roger Duff have changed archeological thinking on the evolution of Maori culture and society. The lagoons themselves cover 12 square kilometres; two times this if you include the fringing land under DoC stewardship. They average less than half a

metre deep and are separated from the sea only by a low boulder bank or spit formed of gravel from the Awatere River, swept up from the south by ocean currents. Tidal flow is maintained through a channel opposite the Wairau River mouth. The Wairau wetlands are now only a fraction of what they were 150 years ago. Since that time they have been continuously reduced by drainage canals on adjacent farmland and since 1963 by the opening of a major diversion canal north of the lagoons designed to take the major part of the Wairau River flow. Of the 90 species of birds recorded in the area some 60 are wholly or partly dependent on wetland resources. Some, like godwits, turnstones and knots are long-distance regular migrants, others are rare visitors. Shooting is popular and the western half of the lagoons is open for waterfowl hunting. Black swan, Canada geese, mallard, plus the native grey duck and paradise shelduck are regularly shot during the official hunting season (May and June) by about 60 hunters. The lagoons and estuary are also

important feeding and especially breeding areas for over 20 species of fish, mainly flounder, mullet, kahawai and inanga, and the extensive mudflats support a variety of tubeworms, molluscs and crabs which are a major source of food for wading birds. Historically the area was an important source of shellfish, with cockles and pipis and, on the outer coasts, sizeable mussel beds. There is little commercial fishing at present although flounder and kahawai were taken in the past and there have been limited attempts at aquaculture. Recreational fishing with nets and lines is popular at the mouth of the river diversion. EGETATION AROUND the lagoons has been severely modified in the past by Maori fires and, in European times, by stock grazing and burning accompanied by an invasion of introduced weeds, notably boxthorn and gorse. Only vestiges of native woody vegetation remain — scattered matagouri, manuka, shore ribbonwood and Hymenanthera. Saltmarsh areas are dominated by Salicornia, sea rush and introduced tall fescue, and there are extensive beds of horse’s mane between tide levels. Flax and raupo, once abundant, have been reduced considerably by cattle, and their freshwater habitats lost. Commercial exploitation became a threat in the 1970s with a proposal to extend the salt-harvesting activities of the Grassmere company into the Wairau lagoons. The Marlborough Catchment Board and Ministry of Works carried out preliminary research for some years but there was strong opposition from Forest and Bird and the Acclimatisation Society and the proposal never went ahead. An ongoing problem is the pollution from nearby operations. Sewage from Blenheim has for many years been partially treated in oxidation ponds on the edge of the lagoon system before being piped to an outfall on the lower Opawa River which takes it to the sea. Periodic failures in the sewerage system have resulted in raw sewage entering the river and ongoing complaints about unacceptable levels of pollution. A second oxidation pond is being built and the district council is looking at options for further treatment and the best location for ultimate disposal. In the early 1980s a large freezing works was built by Waitaki NZ at Riverlands on the outskirts of Blenheim to the west. Effluent from the works goes through aerobic and anaerobic ponds before being piped to an outfall where the lagoons open to the sea. To satisfy objectors at the time, the Planning Tribunal required baseline ecological investigations

which recommended ongoing regular monitoring. The Marlborough branch of Forest and Bird tried unsuccessfully for many years to get public recognition and protection for the lagoons as a wetland important for indigenous flora and fauna. But until the mid-1980s, the attempts came to nothing. One of the problems was the divided ownership of the wetlands. Known as Vernon lagoons, they were obtained by the Crown between 1844 and 1848. A number of tribes claim to be tangata whenua of the region and several claims have been filed with the Waitangi Tribunal covering the lagoons. Title was then divided for many years between the Department of Lands and Survey, the Marlborough Harbour Board and the Marlborough Hospital Board. In 1956 Big Lagoon was proclaimed a wildlife refuge — primarily, it seems, to ensure a continuing supply of gamebirds for

shooting. The Wildlife Service became responsible for the wildlife but not for their habitat. Lands and Survey finally took over full title to the lagoons and surrounding area in 1984. A draft Strategy Plan in 1985 recommending designation of the lagoons as a national reserve was overtaken by the changeover to Department of Conservation stewardship. DoC has not proceeded with the comprehensive management plan that was hoped for, and the department’s main activity in the area has been limited wildlife survey work and instalment of a public walkway to allow access to a restricted area. UBLIC CONCERN for the conservation of the lagoons came to the fore in February last year when a proposal was put to DoC and the Marlborough Conservation Board by the

Marlborough/Nelson Fish and Game Council (successor to the Acclimatisation Society) requesting the lifting of refuge status from Big Lagoon to enable shooting over it the following winter. Opposition to this came to a head at a well-attended public meeting. The proposal was resisted by Forest and Bird

members on the grounds that the disturbance caused by people, dogs and boats through the area would be very disruptive to birdlife. Some non-game birds would be killed or wounded by hunters and an accumulation of lead shot in the bed of the lagoons would pose an unacceptable threat to all wildlife. Local Maori also opposed any opening of Big Lagoon to shooters because of the area’s many ancient burial grounds. The strength of the opposition led to continuation of the current status while DoC agreed to prepare an "issues and options" report for the lagoons. My view is that the whole wetland and its immediate environs should be formally protected to provide optimum habitat for the indigenous plants and wildlife. Any management plan should exclude stock from access to the lagoons, extend the sewage outfall beyond the Boulder Bank, and exclude hunters. For the time being at least Big Lagoon remains undisturbed. "+

has been

actively involved in this conservation issue since first coming to live in Marlborough sixteen years ago.

DoC’s issues and options report on the lagoons was to have been available for public comment last Septem ber but has been delayed. DoC has consulted with Marlborough Forest and Bird and it is expected that the report will be available for public comment in April. However, it is not expected to make specific recom mendations about protective status or management regimes. The next step will be a period of public comment and consideration of the report by the Marlborough Conservation Board. Many other claims for use of the area will certainly be promoted by Maori and recreational and tourism interests. Conservation News will keep members informed about when and where to send submissions.