THE AHURIRI ESTUARY The story of an urban wetland

Forest and Bird, Volume 21, Issue 3, 1 August 1990, Unnumbered Page

THE AHURIRI ESTUARY The story of an urban wetland

By

David Appleton

URING THE 19TH CENTURY 3,800 ha of swamp and tidal lagoon sprawled between the embryonic Napier township and distant inland hills. Dominant in this sheet of wetlands was an expanse of tidal flood, shellbanks and islets, known to the Maori as Te Whanganui-o-Rotu, a lagoon rich in shellfish, finfish and birdlife and an important source of kai moana for the occupants of numerous surrounding villages. However, these natural wetlands were decisively altered by the 1931 earthquake and its two-metre land upheaval, followed by the construction of a network of stopbanks and sluices that, over a period of years, helped to transform the great lagoon and its surrounding swamps into today’s city suburbs, airport and pastoral flatlands. The remains of Te Whanganui-o-Rotu lagoon exist today only as scattered pockets of saline marshland, spread around the 450ha stopbank-con-stricted tidal estuary. This winds its way inland below the wave-cut hill faces that in earlier times stood as a barrier between the ocean's overflow and the palisaded villages of the local Kahungunu people. Unique Resource Thus, irreversible change shaped Napier and its surroundings, despite which the Ahuriri Estuary and wetlands remain a unique and valuable natural resource in Hawke's Bay. Fisheries researchers have revealed that the tidal waterway provides both breeding and feeding areas for fish species that are not present in other estuaries in Hawke's Bay. Indeed, the estuary functions as an irreplaceable food-source for shoals of immature coastal fish species such as kahawai, mullet and trevally. During summer, runnels and submerged mudflats provide a rich feeding area for myriads of tiny flat-fish, while mature flounders scour the channels for food, in company with parore and grey mullet. Similarly, a wide variety of birds depend upon the tidal flats and saline wetlands, both as a food-source and for sheltered roosting. Flocks of summer-visiting godwits pick over the mudflats and, as the tide floods in across their feeding rounds, they rise, wheeling up and across to the nearby Southern Marsh, to alight and sleep away the high-tide hours. Rarer Arctic breeding birds occasionally drop in to join the godwits: pectoral and sharptailed sandpipers, stints, curlew and marsh sandpipers, and once a shy, solitary yellowlegs (Tringa flavipes) that had wandered over from the Americas. A pair of gull-billed terns stayed for several years while this summer two dusky-winged marsh terns (Chlidonias leucopterus) hawk insects, swallow-like, above the lagoons. There are few places in New Zealand where such a variety of migratory birds can be seen. So, despite its restricted area and city-edge location, the estuary has become

rather special for both local and visiting birders. During 1987 the transformation of government departments into state-owned enterprises resulted in a widespread land reallocation exercise and this eventually saw most of the estuarine waterway and some wetlands passed over to the Department of Conservation. Government activities during the past two years have accelerated plans for changes in coastal land management with

local authorities clamouring for control of both estuaries and foreshores. The current picture of legislative change remains blurred as parliamentary Bills, now under consideration, would place tidal waterways under Crown title but regional authority management, with mandatory management plans to be finally approved by the Minister for Conservation; this is, however, yet to be finalised. Ex-Harbour Board-owned wetlands around the estuary remain subject to outstanding title

claims, lodged by the Department of Conservation. Collectively, this spate of change should eventually add up to considerable improvement on the previous multi-authority control and ownership situation. Enhancement Begins 1989 saw the launching of the Conservation Corps and, in Napier, their work has taken the form of long-needed tree planting and landscape improvements between the lower estuary and nearby factories. At last, thanks to the Napier YMCA who organised the project, we have begun doing something to enhance the tidal waterway, instead of degrading it. After years of planning submissions, public meetings and protests, it might seem that the days of major threats to the estuary could be drawing to a close, but this is unfortunately not so. Recently, plans for a motorway extension across the estuary have regained prominence with the route of the highway planned to cut across the Southern Marsh, so important for migratory birds, also to intrude upon the wetlands of the Wildlife Refuge. There is no indication that preservation of the estuarine environment received consideration during motorway plan drafting. Recently, with survey route marking, an environmental instigation has become essential. Pollution is ever a threat to waterways and industries nearby the estuary have caused intermittent deterioration in estuary water quality, resulting in the death of bottomdwelling plants and fish. It is imperative that tight pollution controls influence future planning of industries, for waste management control has been inadequate during the past. Wetland Abuse It would, of course, be quite reasonable to expect that an area of such outstanding natu-

ral value would enjoy protection and careful management but this has generally not been the case. Over the years a plethora of local authorities, operating under a wide variety of legislation, have interfered with the estuary and wetlands in a mostly self-serving manner. The Hawke's Bay Harbour Board, controlling much of the estuary and adjoining farmland, despite 1958 Wildlife Refuge status, filled wetlands and dredged aggregate from the tidal waterway and, in conjunction with Napier City Council, allocated wetland areas for industrial development. For many years, Napier City Council dumped domestic waste on both tidal and marshland areas. This familiar pattern of wetland abuse continued until recent years, only slowly abating with the involvement of Ecology Action, a then-newly formed organisation that in the early 1970s battled against plans for a residential marina on part of the tidal estuary. Joined by the Napier branch of Forest and Bird, this spearhead of action against estuary degradation eventually culminated in the formation of the Ahuriri Estuary Protection Society Inc. Due to the combined efforts of these groups, local body politicians slowly came to appreciate the ecological and recreational importance of the estuary and its surroundings. In 1979, Canterbury University studies provided data upon which future protective management could be based but the Harbour Board adhered to plans for further estuarine dredging and a museum of technology site was proposed beside a bird-rich lagoon area. Both plans generated public opposition and neither eventuated. During the 1980s there were, however, environmentally sound projects getting underway. New city councillors proved themselves increasingly well informed on environmental matters and the 50 ha West-

shore Domain became the subject of a new, comprehensive management plan that embraced development of the Domain as a wildlife refuge. New lagoon areas were excavated with the material removed being used to replenish the badly eroding Westshore beachfront. A nearby 14.5 ha lagoon, known as the North Pond, for some years allocated for "aerodrome purposes", is now to be redesignated as part of the wildlife refuge. Some years ago the Napier City Council commenced a management plan for part of the estuary but this was discontinued due to lack of finance. Fortunately, the local Department of Conservation office has picked this up and is expanding the plan to cover the whole estuary and adjoining wetlands. The plan needs a long-term view, keyed to sustainable resource use, enabling restoration of degraded wetlands and protection of estuarine fish nursery and feeding habitat. Typically, facilities exist for the restoration of degraded raupo and sedge beds, both important for uncommon local bird species such as bitterns and crakes, while wetland areas need water level control regimes suited to the seasonal needs of wading birds and ducks. With available Department of Conservation expertise, such fundamentally important factors can at last be given the attention they deserve. Adjacent to the city, the estuary caters for a wide variety of public activities such as fishing, swimming, wind-surfing, canoeing and sailing of radio-controlled model boats. With care and public co-operatien the Ahuriri Estuary could become a successful example of controlled and compatible public uses, integrated into a management plan that is centred on the preservation and enhancement of a valuable wetlands ecosystem. #&