KAHIKATEA

Forest and Bird, Volume 18, Issue 2, 1 May 1987, Page 4

KAHIKATEA

by

Kevin Smith

The Feathers of Tawhmtan

Society — West Coast Convervation Officer

~ ahikatea! What a suitably grand name for this noble tree, a true rangatira of Tane’s forest world. It reaches heights of over 60 metres, it is New Zealand’s tallest tree and lives for five or more centuries. The sheer magnificence of kahikatea forest holds one in awe. Lofty, grey columnar trunks often heavily buttressed at the base, support sparse feathery foliage which typically forms an open canopy high above a thick low undergrowth. This sight has inspired many graphic descriptions particularly from the early explorers who knew these now sadly depleted forests much better than we do. Pioneer botanist, Leonard Cockayne (1910) vividly portrayed kahikatea swamp forests as being composed of ‘‘multitudes of long straight trunks like the masts of ships rising from the swampy grounds." Though perhaps the best description came from Thomas Kirk in his famous treatise ‘The Forest Flora of New Zealand’ (1889):

‘By quiet lagoons the swamp forest floats as on a raft and birds come to rest in safety.’ (Our Forests Ourselves, Peter Hooper).

‘A virgin kahikatea forest affords one of the most striking sights in New Zealand forest scenery. Straight unbranched trunks rise one after the other in endless series . . .; The naked symmetrical shafts tapering almost imperceptibly, appear to form dense walls which completely shut out every glimpse of the outer world.’

Only 2% of the original forest remains

Few New Zealanders alive today would recognise this scene for it is kahikatea forest itself which has been shut out from most of the country. Only on the narrow coastal plains of South Westland do mature kahikatea forests still survive. Most of these remnant forests, which amount to no more than 2 percent of the original extent of kahikatea forest, are unprotected. South Westland's remote setting and surrounding physical barriers have so far largely protected these forests from exploitation. Timber millers, who know the tree somewhat derisively as white pine, are now seeking to log these forests as they rapidly exhaust available supplies of indigenous timber to the north. Fortunately, kahikatea forest has a determined ally in the forest conservation movement. Conservationists are seeking permanent legal protection for all the kahikatea forests of South Westland. They want them included along with the other pub-licly-owned natural lands of South Westland in the South-West New Zealand World Heritage area. This is the major forest campaign of 1987 when the Government will decide the future of these forests.

Food basket of the forest.

Kahikatea forest is at its best in the autumn. Female trees may bear an extraordinary abundance of lush purple and orange coloured fruit. In a good season, a fruiting kahikatea — called ‘‘mapua"’ by the Maori can produce up to 800kg of fruit containing about 4,500,000 seeds. Fruit-eating birds such as pigeon, tui, bellbird and parakeet flock into the forests whose seeds are widely dispersed in their droppings. The highly delicious fruits were also keenly sought by the early Maori. In daring feats of strength and skill they climbed the tall trees to collect fruit in baskets which were lowered to the ground by a cord. The Maori people made use of the kahikatea in other ways too; soot obtained by burning the hard resinous heartwood was used as a fine pigment for tattooing and spears were also fashioned from the strong heartwood known as mapara.

New Zealand's most primitive podocarp

Scientists have an equally fascinating account of the origins of kahikatea which they know as Dacrycarpus dacrydioides. Like rimu and most of our other big timber trees, kahikatea belongs to the Podocarp family (seed suspended on a fleshy foot or carpel). This is an ancient Southern Hemisphere gymnosperm family of mostly forest trees whose evolutionary lineage can be traced back to the Gondwanaland forests of the Mesozoic.

Kahikatea is the most primitive of New Zealand's podocarps. Fossil pollen grains from Dacrycarpus, of which kahikatea is the only modern day representative in New Zealand, occur in 110 million-year-old deposits found in Fiordland and the south Nelson district. Today's kahikatea swamp forests probably closely resemble the forests of ancient times before mountain building commenced. These are truly dinosaur forests — nothing as ancient occurs anywhere else in the world. Before settlement, kahikatea forests spread across most fertile lowlands

from North Cape to Bluff. In some regions, such as Taranaki where the soil was rich and the rainfall plentiful, it occurred as a component of forest on the easier hill country. However, the best developed stands were found on the flood plains and in the swampy lowlands. Great walls of kahikatea lined lowland riverbanks. Dense kahikatea swamp forests and open flax or raupo swamp spread across the poorly drained plains away from the rivers. A great kahikatea forest between the Thames and Piako rivers was reputed to be the largest in the country.

Captain Cook heralds an era of destruction

Captain Cook discovered this forest for Europeans in 1769. He recorded in his journal that’. . . The banks of the river (Thames) were completely clothed with the finest timber my eyes ever beheld . . . every tree as straight as a pine and of immense size. . ." But Cook was in search of resources not beauty and he soon had his measuring tape out. He noted the trees’ dimensions in his journal then added: "It was as straight as an arrow, and tapered but little in proportion to its height, so I judged there were 356 cubic feet of solid timber in it. As we advanced we saw many others that were still larger."’ When the Europeans arrived en masse the slaughter of the kahikatea forests began in earnest. They were the very first forests cleared and none were spared. The trees yielded a serviceable, easily worked timber and the cleared ground grew lush pastures. The non-tainting properties of the wood ideally suited it for use as butter boxes for the rapidly expanding dairy industry. The onslaught led to the very early demise of kahikatea. As early as 1908, it was noted that ‘‘the forests of pure white pine that used to exist in the Auckland district have almost gone...’ (Annual Report, Department of Lands, 1908). Concerns about the future of kahikatea were expressed by the Royal Commission of Forestry in 1913: ‘How long the white pine will last at the present rate of consumption we cannot say.’"’ Conservation concerns were raised in 1918: "considerable public interest has been manifest in discussing the importance of conserving New Zealand timbers, more especially as regards kKahikatea which is fast becoming scarce’’. (Annual Report, Department of Lands 1918). Yet the clearance continued. By 1919 it was impossible to obtain adequate supplies and by 1924 even the inland forests were largely

cut out with ‘‘the exhaustion of the white pine resources (of the King Country) driving millers far afield.’ (Annual Report State Forest Service 1924.) Attitudes were succinctly summarized by the State Forest Service in their Annual Report for 1947: "The problem is a simple one. It is merely dairy farming versus white pine forestry: and there can be little doubt about the decision. Dairy farming demands such land (and timber) in the national interest and kahikatea forests are therefore impossible."’ The production-oriented Forest Service adopted a pair of kahikatea trees as their emblem. The irony in this may have been lost on the foresters, but not on conservationists who marketed T-shirts in the 1970s showing the trees cut off at the stumps.

Now as rare as mature kauri

Today, mature kahikatea forest is a nationally rare and endangered ecosystem. Because only a handful of pocket handkerchief stands survive, it is no longer included in the list of North Island forest types, (Nicholls, 1976). With the exception of South Westland, the story is the same in the South Island. Throughout the country a few tiny relicts survive near cities and towns. Claudeland’s bush in Hamilton, Riccarton bush in Christchurch, Waihopai bush in Invercargill give us an inkling of what these flood plains

were once like. They leave us feeling vaguely uncomfortable about our culture, being little more than museum pieces often severely damaged by changes in the surrounding water table, the influx of weeds and the impact of heavy human use. Logging of privately-owned kahikatea in South Westland continues unabated, the greatest tragedy being the clearfelling of a magnificent forest at the Waiho rivermouth below the Franz Josef glacier. Conservationists campaigned for the protection of this State forest in the mid-70s as part of the Okarito-Waikukupa Westland National Park addition. However, Waiho Sawmills Ltd secured it in a land exchange approved by then-Minister Venn Young and have been clearfelling it ever since. The publicly-owned forests of southern South Westland from Fox Glacier to Haast are presently under a logging moratorium. Before the moratorium was imposed in 1982, over 80 percent of the kahikatea forests were zoned by the Forest Service for immediate logging. The kahikatea forests of South Westland lack the floristic diversity of the largely extinct Kahikatea forests of the North Island. Characteristic North Island forest companions of kahikatea such as the buttressed pukatea, swamp maire, perching pittosporum and nikau only grow south to Karamea. However, South Westland kahikatea’s scenic setting is without parallel. Crammed onto the tiny shelf of low-lying land between the Tasman Sea and the snow-clad peaks of the Southern Alps are a series of great kahikatea forests. Kahikatea line the banks of big brawling rivers and sluggish meandering streams and stretch around the margins of flax swamps and lakes. The total extent of the remaining dense stands in South Westland is 4500 hectares. There are 5350 hectares of medium and low density stands where kahikatea may occur in association with rimu, kamahi, silver beech (south of Paringa) and other hardwoods. The combined total of 9850 ha is just a little more than the area of another heavily exploited forest type — mature kauri forest — of which only 7400 hectares remain mostly protected in forest sanctuaries such as Waipoua.

Forests of river flood plains

Virgin kahikatea forest in South Westland is broadly of two types — alluvial forest and swamp forest — both of which are confined to the post-glacial rivers. Their flood plains provide an ever-changing landscape as rivers flood and periodically change course. The combination of high rainfall (34000 mm on the coast rising to 13000 mm inland) and a rising, eroding mountain range, means that few places anywhere in the world experience such regular flooding and erosion. Westland National Park’s only two small stands of kahikatea were both virtually destroyed by overnight changes in the course of the Cook and Waitangitaona rivers in the early 1970s. Because of its abundant seed production and light-de-manding seedlings, kahikatea is well adapted for survival on these dynamic flood plains. Successions from flood plain to forest develop on areas recently abandoned by the river. Herbs and grasses slowly give way

to shrubs, such as Coprosma propinqua which provide shelter for the seedlings of kahikatea. Very dense stands with more than 200 trees to the hectare may develop on the silt terraces. Good examples occur in Ohinetamatea forest, along the bank of the Karangarua river in Hunts Beach forest, and to the south in the Ohinemaka forest. Further flooding and silt deposition can rejuvenate these stands. A new wave Of kahikatea regeneration can establish amidst the flooddamaged forests. On better drained sites, where young kahikatea have difficulty competing against an understory of hardwoods, low volume stands develop which feature scattered large kahikatea. Forest of this sort lies between the meanders of the Ohinetamatea River.

Unfortunately, the expansion of farming on the river flats means that few new stands of kahikatea can now develop. Grazing maintains the grass sward, preventing regeneration. This is leading to a gradual diminution of the kahikatea forest estate. If undisturbed by floods, rimu slowly enters the alluvial kahikatea forests leading ultimately to a rimu-dominant forest. But this only happens on sites where the water table is low enough to permit root mats to cover the forest floor. Unlike rimu seedlings, the fertility-demanding kahikatea seedlings are unable to establish in the root mat and are pushed out as the areas of bare silt or mud diminishes and as soil nutrient levels decline over time. Ohinemaka forest contains excellent examples of these successional sequences.

The floating forests

If the water table is high and nutrients are brought in by inflowing water, the alluvial stands may develop into dense kahikatea swamp forests. Such forests can also develop from the gradual colonisation of fertile flax swamps. The premier swamp forests are those of Hunts Beach and Mataketake forest. Open water covers much of the swamp forest floor especially after heavy rain. These forests grow on layers of deep peaty ooze. Interlocking root systems form a platform over the ooze or even over flowing water, resulting in a truly floating forest. Few other forest trees can cope with these wet conditions. While kamahi may be common in the swamp forests, the trees are rather spindly. The understory vegetation may be abundant. Sprawling masses of KieKie are a feature of coastal kahikatea forest and, in places, huge colonies of the flax-lik« Astelia grandis can give the swamp forest a very distinctive appearance. These swamp forests regenerate freely. Kahikatea’s spongy rootlets seem to enable it to move oxygen downwards so that its roots can function in waterlogged conditions. This ability enables kahikatea to exploit a regeneration niche unavailable to other trees: the often inundated areas of bare mud on the forest floor. Its seedlings establish around the margins of the mud pools or on debris, such as tree branches or punga trunks, that fall into the pools. Seedlings germinating on the debris may survive if they reach a sufficient size before the debris rots away. This is a brilliant regeneration strategy as the seedlings avoid root competition from other plants and the young kahikatea can grow up to the canopy in the light wells that usually exist above the pools. All stages of the regeneration cycle can be seen in the mature swamp forests — dispelling once and for all the forester’s myth that these are single crop forests. The kahikatea forests have recently been investigated by scientists and foresters in a $6 million research effort initiated by the Forest Service with the aim of allowing "balanced decisions"’ over the southern South Westland forests, wetlands and mountainlands. One of the outcomes of this massive research effort has been a recommendation from Forest Service and Lands and Survey scientists for reservation of all remaining kahikatea forest areas (Stengs and Comrie 1987).

Haven for fish and birds

South Westland’s kahikatea forests are a rich wildlife habitat, all year round. In good seed years there is also a massive influx of fruit-eating birds into the forest. Mature kahikatea trees are commonly also laden with heavily fruiting epiphyte species and are emergent from an understory of nectar and berry-producing hardwoods, so the whole forest is of immense value for native birds. Standing dead kahikatea are also immensely attractive for both insectivorous birds and as nest sites. For several birds South Westland’s lowland forests are an important winter refuge. Numbers of silvereyes, bellbirds, fantails, tuis and pigeons increase three to four fold in winter com-

pared to summer (O'Donnell and Dilks, 1986). Fernbirds, crake and bittern abound in the open swamps associated with the swamp forests. Just on half the bat records from South Westland are from kahikatea forests, suggesting they provide vital habitats. Soft kahikatea wood is full of holes, ideal as bat roosting sites. It is therefore no surprise that loss of kahikatea forest elsewhere in New Zealand is paralleled by the disappearance of native bats. Kahikatea forests also provide crucial swamp and forest stream habitats for a number of declining native fish, including several of the galaxiid species that make up South Westland’s famous whitebait fishery. Most notable of these is the giant kokopu which is scarce outside the region, but survives in good numbers in South Westland’s swamps and meandering lowland rivers. To protect these species and 15 other native fish in the region, the Ministry of Agriculture and Fisheries is seeking the protection of the wetland and swamp forest complexes of Ohinetamatea and Mataketake forests. For all these reasons the Wildlife Service has recommended the protection of all the kahikatea forests of South Westland.

Preservation or production?

Given the irreplaceable natural heritage values of South Westland’s kahikatea forests, it is not surprising that government scientists, conservation groups and other environmental agencies are seeking their complete protection. The case for further logging or clearance for farmland is particularly weak and cannot be supported on economic or social grounds. Kahikatea has a pale and featureless timber which has no importance as a decorative material and no essential specialist

uses. Large quantities of kahikatea from private and leasehold land in South Westland have been used as boxing around concrete poured on the Waitaki power project. Otherwise, the major use of kahikatea is in weatherboards, fasciaboard and scaffold planks. There is a Japanese interest in kahikatea panelling because of its bland featureless appearance. The Forestry Corporation, West Coast Sawmillers and Westland Country Council are expected to lobby strongly to open these forests up for logging, possibly at a low level of cut. Yet despite years of costly and destructive logging trials foresters have been unable to find a workable sustained yield logging technique for the South Westland podocarp forests. They have also completely failed to examine the economics of sustained yield timber production from these remote forests. Joint Forestry Campaign researcher, Dr Peter Grant, contends that the bulk of the timber could only be logged at a loss. Moreover, no sawmills operate in these southern state forests at present. Mills interested in logging the kahikatea forests are located far to the north in the Whataroa and Hokitika districts. Agricultural economists have shown that forest clearance for land development in the region would be uneconomic and contrary to the national interest.

Tourism far exceeds forestry

Kahikatea forest can make a major contribution to the regional economy through tourism. Kahikatea, if given the protection and promotion it deserves, could attract tourists just as Kauri does to Northland and the Coromandel. Yet ironically, at present, there is not a single track through South Westland kahikatea forest. Tourism is al-

ready big business in the West Coast. For the year ending 31 March 1986, 465,000 tourists visited the West Coast with a direct income to the regional economy of $91 million. The value of tourism to the region far exceeds the $61 million contribution from the timber industry — a fact that is helping to win West Coast support for conservation. The Government has set up a committee chaired by the Secretary of the Environment, Dr Roger Blakeley, to make recommendations on the future of these kahikatea forests and other natural lands of South Westland. This committee has invited public submissions on the future of these forests. The outcome of this exercise will be entirely dependent on the amount of public support there is to give full legal protection for the kahikatea forests in a South-West New Zealand World Heritage Area. This is perhaps the greatest conservation opportunity this country has ever seen, and it is an opportunity that will never come again. Kahikatea! May the feathers of Tawhaitari bear fruit forever in the midst of the waters of South Westland. #

References

_ 4. 5. . Cockayne, L. (1910) New Zealand Plants and their Story . Laing, R.M. and Blackwell, E.W. (1906) Plants of New Zealand . Nicholls, J.L. (1976) A revised classification of the North Island Indigenous Forests. NZ Journal of Forestry 21:105-32 O'Donnell, C. and Dilks, P. (1986) Forest Birds in South Westland NZ Wildlife Service Stengs, H. and Comrie, J. (1987) Ecological reserve proposals for Southern South Westland. Management Evaluation Programme. NZ Forest Service and Dept. of Lands and Survey. . Wardle, P. (1974) ‘The kahikatea forest of South Westland’ Proc. NZ Ecol. Soc. 21:62-71