KAITORETE SPIT

Forest and Bird, Volume 15, Issue 3, 1 August 1984, Page 6

KAITORETE SPIT

By

Executive Councillor

Margaret Peace

A unique sand dune area in need of protection

Kaitorete Spit is south-west of Banks Peninsula in Canterbury. It is the largest remaining dune area in New Zealand where the vegetation is still dominated by pingao (Desmoschoenus spiralis) and where native plants are stilla conspicuous component of vegetation.

During 1972-1973, | spent hundreds of hours on Kaitorete Spit studying plant species, climate and soils as part of my masters degree. This involved experiencing the Spit in all its moods, from blistering summer heat to winter temperatures well below freezing, dehydrating nor-westers and gale force southerly winds laden with salt. The time spent in that wild and desolate landscape provided me not only with an intellectual . exercise but also a chance to appreciate a vast expanse of sea, sand and fascinating vegetation in complete solitude — a ‘‘wilderness’’ experience within only 50 km of a major city. Formation of the Spit Kaitorete Spit is a barrier beach formed by deposition of Rakaia river gravels along the coast commencing some 6000 years ago, with sand deposition commencing probably about 1000 years ago. Such gravel beaches with associated dune systems are extremely rare world-wide. Forming the seaward boundary of Lake Ellesmere, the spit measures 28 km long, being 3.2 km wide at its eastern end and tapering to 100 m wide at its western extremity (see diagram). The dune system is largely shaped by the onshore south west winds. In the western 8 km the shore line is

being cut back, foredunes measure up to 7.6 min height and their seaward faces are continually wave-trimmed. For the next 13 km eastward the coastline is building out, and dune height decreases gradually to about 1.5m. In the most easterly sector dunes are reduced to a mere scattering of sand over the gravel. Dune profiles are gently contoured, characteristic of sand under pingao. Relicts of much older dunes are scattered over a sandy plain landward of the coastal dune complex. Large deflation hollows up to 200 m across form a prominent feature between the parallel ridges of foredunes and rear dunes. A severe climate and poor soils Climate and soils interact to make the spit an extraordinarily adverse environment for plants. Rainfall measurements on the spit indicate a mean annual figure of 515mm (20 inches) and less than 400 mm in some years. Added to this, the water-holding capacity of the ground is unusually low, since as well as the high proportion of stones in the profile the sand itself is extremely coarse. Very high evaporation rates prevail for much of the year because of the dry norwest winds characteristic of Canterbury,

together with very high summer temperatures — up to 38 °C in the shade at surface level. As a consequence, dryness of the air affect plants for at least twelve hours per day for four or five months of the year. No doubt plants rely to some extent on moisture supplied by internal condensation of water vapour just below the surface, as well as dew, which is frequently heavy. Soil nutrient levels are low, even on the old dunes, indicating unusually slow soil development. Vegetation uniquely adapted to harsh conditions In spite of all these limiting factors, it appears that a remarkably stable vegetation cover was able to evolve on these dunes, partially persisting to the present day, though adversely affected by fires in Maori times and since 1850 by grazing management which also included deliberate burning up until 1948. Existing native species include thirteen shrubs, ten herbs, and seven grasses and sedges. Ngaio, akeake, and kowhai are represented by a few old specimens, presumably relics of a formerly more abundant shrubby vegetation which probably included kanuka. Ake ake (Dodonéa viscosa) and Meuhlenbeckia astonii are found here at the southern-most limit of their distribution. The prostrate broom (Carmichaelia appressa) is a species found only on Kaitorete Spit. It is probably a key component of the ecosystem because of its role as a Soil building nitrogen-fixer. It is also very important in providing a favourable micro-environment for less hardy species. However, the prostrate broom is under constant browsing pressure from hares, rabbits, sheep and cattle, the

last causing major damage by tearing off large branches. It appears that most of these plants are old and there is no sign of regeneration in spite of abundant seed production. All the native species are perennials, able to survive and even grow throughout the driest part of the year — in contrast to the introduced plants which are mostly winter annuals exploiting the period of least water shortage between May and October. Catsear, sorrel and Australian sheep’s burr Survive as perennials, but their leaves wither in the summer drought. Awhole range of adaptations to dry conditions can be observed among the native plants. Some, like Clematis afoliata and prostrate broom are leafless. Leaves when present are generally very small, narrow, covered in a thick cuticle, (i.e. pingao), or covered with woolly hairs as in scabweed (Raoulia australis) and woollyhead (Craspedia /anata). All the native species have extensive root systems, to enable them to absorb and store all available water. Low mounds of scabweeds only a few centimetres high may have roots seventy centimetres long; Prostrate brooms only twenty centimetres high may have roots over three metres long. The vegetation of the Spit is unique and enough of the native vegetation remains today to provide some idea of its primitive state. Threats from weeds, grazing and mining Unfortunately the introduced marram grass (Ammophila arenaria) was planted about twenty years ago on eroding dunes about half way along the Spit, and more has

been planted at the site of a sand quarry near the eastern end. However it is virtually confined to these areas from which it could readily be removed. Several hundred pines, planted 15 years ago on the fore-dunes for about 2 kilometres, are now dropping their first cones. They are serving no useful purpose, are an incongruous element in the landscape, and should be eradicated before spreading further. No other introduced species appear to represent a threat to the native vegetation through competition. Reserves at risk In 1979, two areas of the Spit were gazetted as Scientific Reserves. The larger of these, comprising 169 hectares, was intended to constitute a core area representing some of the most interesting biological features. However, since then little effort has been made to protect the Reserve which is still being used for grazing sheep and cattle by the lessee of the adjoining Crown land block. Rabbits and hares, together with the stock, representa most damaging factor in such a fragile ecosystem where the natural physical factors already impose severe limitations on the plants. It is also important to exclude four-wheel drive vehicles and trail bikes from the dunes. A draft management plan is due out shortly for public comment. Mining Since 1952, sand extraction from the

eastern dunes has been undertaken by a contracting company, originally without any agreement or payment, but since 1964 under a renewable licence from the Lands and Survey Department. Currently a total of 11 hectares of pingao covered dunes have been removed along a 1050 metre stretch, a total of about 274,384 cubic metres of sand. Removal of sand from this dune system is quite unjustifiable. The natural process of dune rebuilding at this end of the Spit is minimal, the ecological damage is immense and alternative sources of sand do exist for the company’s operations. On 8 March 1984 the mining company, Habgoods Ltd, were given three months to apply for a licence under the Mining Act, which would give the public opportunity to object. On 26 June 1984 Habgoods posted an application for a mining licence over a further 23.4 hectares of the Kaitorete pingao-covered dunes. Our Society is objecting to this application and we hope that the Department of Lands and Survey will also object. Aspecial study written by a Lands and Survey planning officer, J.D. Palmer in 1980 and made public by the Department concludes that ‘‘in view of the Kaitorete dunes natural, cultural, archeological and recreational values ... the present extent of reserve land is inadequate. The whole Crown land dune complex is worthy of reserve status"’. ye