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Karst Gems Before Swine - Who Cares?

Les Kermode, Auckland, New Zealand

ABSTRACT

The preservation of noteworthy caves and distinctive karst landforms is jeopardised not only by diverse legitimate land uses, such as quarrying, farming, forestry, groundwater extraction, and urbanisation, but also by unacceptable abuses, such as inappropriate commercial tourism, disposal of polluted wastewater, vandalism, and imprudent sport and adventure activities. An educational strategy must evolve to encourage the wider population to become aware of the need to conserve undamaged, rare and representative karst landforms, together with the much less visible caves and aquifers, that are often the habitats of distinctive flora and fauna. Legal protection for geological heritage features becomes most effective where such features and their associated values are clearly described and better understood by the entire community. Both cave tourism and speleological research should assist in formulating an objective scheme of cave and karst assessment that is capable of being used as a tool to promote sustainable resource management. The examples presented are mainly of Auckland lava caves.

INTRODUCTION

Conservation is an expression of a community's perception of its heritage.

The first aim of ACKMA is "to develop improved standards in the management of the cave and karst heritage of the Australasian region". Nevertheless, it is possible that the ultimate control of some cave and karst tourism operations might be managed by persons who do not accept the above aim. Recently ACKMA members have had the opportunity to study the "Guidelines for Cave and Karst Protection" published by the World Conservation Union (IUCN) (Watson et al., 1997). Currently the International Union of Speleology (IUS) is preparing "Guidelines for Selection, Development, and Management of Show Caves" (Holland, 1998).

LEGISLATION

In New Zealand major changes to town and country planning legislation have accelerated the devolution of decision making away from central government. The Resource Management Act 1991 (and its amendments) seeks "to promote the sustainable management of natural and physical resources" while "avoiding, remedying, and mitigating adverse effects on the environment". It also promotes, as a matter of national importance, "the protection of outstanding natural features and landscapes from inappropriate use and development". This Section 6 of the Act harmonises well with the concept of sustainable cave and karst management, and is especially relevant where an important feature is located on, or under, an ill-defined traditional administrative boundary, such as riparian land. However, many of the territorial local authorities, to which the new administrative tasks were allocated, were woefully unprepared to take responsibility for the identification, evaluation, and protection of natural heritage features - a moot point when one considers that academic geomorphologists have debated the origins and values of conspicuous landforms for decades. During 1997, storms of protest were vented in the media and swept throughout New Zealand, after some district councils had clumsily designated private land as areas to be protected by restrictive land uses. Watchdog environmental groups were virtually legislated out of existence by the threat of liability for excessive financial penalties in the form of court costs. The Regional Councils, which were first set up for planning purposes, were stripped of many of their duties and powers.

HISTORICAL DOCUMENTATION

From the time of its first European settlement in 1840, Auckland has been known for its distinctive landscape dominated by two extensive harbours and numerous, small volcanic cones and craters (Dieffenbach, 1843; Hochstetter, 1864). The current Auckland Regional Policy Statement (Auckland Regional Council, 1995) noted that "a diverse and representative range of geological features had not been protected"

"Out of sight, out of mind" is often used to avoid cave conservation issues, because the location, character, rarity, and distinctiveness of caves are unseen parts of a community's concept of its heritage. The public respond readily to pleadings to protect spectacular plants, and endangered animals, but they generally ignore the plight of extensive landforms or unseen caves threatened with damage or destruction.

In response to growing environmental concerns, and encouraged by the Department of Conservation, the Geological Society of New Zealand assisted by the New Zealand Speleological Society compiled a geopreservation inventory for caves and karst (Worthy, 1990). It included a total of 103 features of significance, namely, 59 solution caves, 5 lava caves, 9 sea caves, 19 karst features, and 11 karst systems. Of these, 61 were within protected sites, 5 partially protected, and 37 were within unprotected sites.

Unfortunately, greater public awareness of caves brings the added threat of vandalism and of damage by careless sport cavers. Many cave explorers fiercely defend their right to continue sport-caving activities without being prepared to acknowledge the degradation and potential destruction caused by their sport. Moreover, collectors throughout the ages have plundered the caves of the world for speleothems, fossils, and artefacts.

PROGRESS

At the 1997 ACKMA Conference at Waitomo, my paper "Geopreservation of lava cave in Auckland" was subtitled "a lack-of-progress report" (Kermode, 1998b). Happily, that subtitle is no longer applicable, although some of the progress since 1971 has not been as exciting as was hoped.

What has happened to Auckland's "lava tunnels and pseudokarst" since 1997?

Wiri Cave, in Manukau City is New Zealand's longest and most important educational lava cave. It is an unbranched lava tube about 290m long, up to 6m wide, up to 4m high, and with a variety of passage shapes. There are many diverse flow features on the walls, ceiling, and especially on the floor (Kermode, 1970, 1987, 1994, 1996b). After almost 30 years of procrastination by innumerable politicians (Hughes, 1990) the cave was gazetted as a Scientific Reserve in 1998 - a credit to the NZ Speleological Society and the Geological Society of NZ. Quarrying operations continue nearby, and this naturally-fractured lava tube is still threatened with destruction by excavation-induced ground settlement into the adjacent deep excavations. A precise levelling survey has been completed (St George, 1997). At present there are no plans to allow general public access to this cave.

Southern Cave, on Rangitoto Island, in Hauraki Gulf Maritime Park, within Auckland City is the most frequently visited lava cave in New Zealand. It is a straight downslope segment of a closed lava trench, which is formed within compound lava levees, and merges into a lava tube cave. This two-part cave is about 60m long, up to 4m high, and up to 3m wide, with a natural, central entrance (Crossley, 1970; Kermode, 1994, 1996a, 1997). Only one small lava-roll occurs. There are no modifications, such as boardwalks or artificial lighting. The explanatory display panels prepared in 1996 have not yet been erected.

Stewart's Cave, in the Three Kings residential suburb of Auckland City, has once again become an important educational lava cave. It is about 180m long, up to 14m wide, and up to 8m high, and has many interesting geological features: three interconnected lava tubes, several passage levels, some large passage cross-sections, flow-surge marks, a cave-in-cave, a large ceiling sag, a spacious terminal lobe, and a variety of flow features (Kermode, 1994, 1998c). Even although this lava cave is designated for protection, its future existence of could be threatened by residential redevelopment, because the detailed published cave plan (Stewart, 1870) has not yet been precisely oriented (Crossley, 1988), and is therefore unsuitable for use by the suburban landowners who are affected by the presence of the cave beneath their land.

PHILOSOPHY OF GEOHERITAGE

Heritage is a very broad concept that grades imperceptibly from physical-material to cultural-intellectual. Geological heritage includes landscapes, landforms, exposures, outcrops, and caves - all formed of naturally occurring earth materials. The guardianship of heritage passes passively from generation to generation.

Geoheritage planning objectives should aim to identify and protect both rare and distinctive, as well as diverse and representative, geological features of scientific and educational significance, and also to enhance public perception of, and identity with, the features. Local government policies and strategies should establish principles for the management, maintenance, and enhancement of those features. The expected outcomes of geological heritage planning should be that statutory protection of significant features will result in their continued, unaltered retention; a better appreciation of them by present and future citizens; and an exemplary administration of publicly-owned features that encourages private owners to do likewise.

SELECTION AND ASSESSMENT

The IUS Show Cave Commission guidelines for the selection of a show cave should recommend the consideration of three potentially objective criteria:

There are also other important subjective values to be considered. A complete assessment of a cave, or a landscape, should include intrinsic values such as:

and also additional values such as: The assessment of the rarity or the representativeness of a cave or karst feature should consider descriptive elements such as:

Territorial local authorities identify, assess, and protect important natural features and landscapes by marking their locations on a map and listing them in a schedule of sites. However, an enlightened authority will, in addition, attempt to encourage its citizens to be aware that natural features and landscapes are sensitive and finite and could benefit by having controls put on access to them. It is essential to define the location and extent of the landscapes and features to be managed, and that the owner's legal rights are respected. Whether natural features are to be protected permanently, or allowed to be degraded by careful usage, their managers should always remain sensitive to the feature and to people.

Rules for the management of lava caves and volcanic landscapes should help to:

and in addition

There is a belief amongst some managers that all things to be administered can be awarded complex numerical values that will allow for comparative rankings to be made for the purpose of allocating funds, for example, the site score system and its fudge factors (Brown, 1999). Such systems can be excellent checklists, but several questions must be asked:

Each of the assessment factors mentioned previously can be ranked in order of significance, but it is illogical to have carefully derived numerical scores for the various components totalled into a complex ranking that is later biased by a subjective fudge factor. It would be hard to justify such a system to an environmental tribunal of astute lawyers. It is hoped that the IUS will deliberate on these issues during the preparation of the guidelines for the selection of show caves.

More than 20 years ago the ASF (Australian Speleological Federation) produced a cave summary form which was an excellent checklist for use when describing a cave or a karst area. However, that cave summary form, with its mixture of hundreds of subjective and objective inputs, was quite unsuitable as a basis for producing a meaningful ranking of aggregated values.

Nevertheless, if research and development funding requires an assessment of value to be made, then it is preferable that the data collected should have been screened through a thorough checklist. If any simplification of the process is undertaken, the boundaries between classes become less clear and subjectivity creeps in. The relative values of component characteristics can be selected to construct a model feature, and can then be apportioned percentages of the total. Although personal expertise and professional experience should counteract any tendency towards bias, attempts to balance the relative values of diverse characteristics in an evaluation exercise makes one realise how subjective objectivity can be.

EXAMPLES

The Grotto (Onehunga) is a rare, doline-like, circular depression with steep walls. It is about 12m deep, and about 60m across the rim. The rocky floor is covered with vegetation, and the neighbouring lava field is mantled with thick beds of tephra. The processes that formed this volcanic landform are not clearly understood. It is neither a volcanic vent nor a crater, and it is most unlikely to have been formed by the collapse of the roof of a lava cave (Kermode, 1998). Geological investigations continue. This landform was first scheduled for protection in the mid 1980s and is entirely within three private residential properties. Successive owners have planted gardens and dumped rubbish in it. Any new construction, or the infilling of the depression would destroy its shape and character, and geotechnical investigations would be needed to determine the strength of the unknown deeper strata. One owner is currently seeking to have the protection designation removed.

The Pond (Onehunga), about 200m from the Grotto, is a larger oval depression that is about 100m by 80m across its sloping lava rim, and about 14m deep. The muddy floor is underlain by about 25m of siliceous silt. The groundwater level has been lowered to about 4.5m above sea level by artificial drainage. The processes that formed this volcanic landform are, like the Grotto, not clearly understood. It is neither a volcanic vent nor a crater, and it cannot be interpreted as a collapse of the roof of a lava cave, because no heap of debris lies at the base of the soft sediments. Geophysical investigations continue (Cassidy, 1998). This unencumbered urban landform is designated as a protected site of scientific interest, but the owner hopes to develop it for future sale.

Ascot Cable Cave (Ellerslie) is, or was, a low multibranched lobe (about 1m high, and less than 2m wide) totalling about 45m length. It was one of several, small lava caves about 2m to 3m beneath the distal end of a lava flow mantled with tephra. It was discovered during the installation of electric cables late in 1997. Thick deposits of water-borne ash have been washed in, and small, mud-covered, well-developed lava-rolls lined about 20 m of the walls (Phillips, 1997). This cave was totally unknown before site development began. The temporary entrance was buried and major earthworks have obscured the site. It is possible the cave still exists, saved only by a protected oak tree, the roots of which penetrate into the lava cave. Unfortunately, the usual civil engineering response to a lava cave discovery is to have the feature totally obliterated by smashing it in, or by filling it with rubble and concrete. A 30-metre long, nondescript, muddy lava cave discovered in the Sylvia Park industrial area (distal McLennan Hills lava flow) in 1993 suffered a similar obliteration (D. Dunn, pers. comm.).

Incompetence Cave (Ellerslie) was another unknown and undetected lava cave close to Ascot Cable Cave. It was a simple oval gas blister about 19m by 9m and about 2.5m high. The roof was less than a metre thick. The cave was broken into during site development early in 1999. This cave was almost devoid of ash infiltration, so pristine aa lava flow features, lightly encrusted with minerals, formed most of the floor that was patterned into flow swirls. Well-developed lava-rolls lined the walls. (Kermode, 1999). The cave was totally destroyed and buried within three working days. Heritage planners from Auckland City are attempting to stop further destruction of lava caves, because modern geophysical techniques (ground penetrating radar, electromagnetic induction) can readily detect lava caves at shallow depths, and structural designs can be amended to avoid interference with the caves.

Stony Batter Boulder Field on Waiheke Island is a conspicuous hilltop area of innumerable, large, closely-spaced, rounded boulders, many of which have vertical solution rills, or karren. During tens of millennia the boulders were formed by in situ weathering of the basaltic andesite lava flows (Halcrow, 1953). The development of the rills is similar to that in limestone karst, that is, it has resulted from the action of corrosive water that drained from forest trees and epiphytes. Lichens continue the process, usually on the sunniest sides. This distinctive boulder field has been noted in the Geopreservation Inventory (Kenny & Hayward 1996), but is not designated for protection. Only a minor part is within public reserve land, and the remainder is within privately-owned farm land. The visual character of this boulder field depends on the land being kept grazed, because afforestation would obscure this unusual landscape (Kermode, 1999b).

Scotlands Cave (Onehunga) is a 160-metre long, slightly-sinuous segment of a typical lava tube. Most of the cave lies a few metres beneath several commercial properties. The widest part of the cave is less than 7m, and much of the passage is less than 1.5m high. There is a short upper level near the mid-cave entrance. There are two stormwater-drainage inspection manholes for access (Crossley, 1970; Kermode, 1994). The significance of this lava cave is not only its geological features, but also its remarkable survival after abuse. The floor and ceiling have been modified in places. An inspection manhole has been fitted to the mid-cave entrance that was once blocked with domestic rubbish. Buildings have been constructed over the cave, street works have broken into the upper end, and a stormwater drain is directed into it. Sediment and other street flotsam accumulate in the cave at an observable rate, and could conceivably block the passage. The old, inaccurate, tape-and-compass map, which was added to the cadastral map caused difficulties for planners and developers, but is now superseded by a theodolite survey. (Hampson, 1999).

Maungarei Lava Shaft (Mt Wellington) is a 16-metre deep, conical chamber (Crossley, 1976). At floor level the shaft is about 16m diameter and the rock walls expose striations and ledges left by the surging, solidifying lava. Small (dm) naturally-broken blisters of thin (mm), smooth lava are still extant. This shaft and its features are unique in New Zealand (Kermode, 1994). For safety reasons, the small, restricted entrance has been sealed with a concrete slab. It was last inspected in 1988, and there are no immediate threats to its survival.

The Cave of the Thousand Press-ups (One Tree Hill) is a network of small, lava tubes, less than 2m beneath a busy suburban road. The passages total about 270m in length, and are low (less than 1m high) and narrow (generally less than 3m wide). The ceilings are arched, and the floor is mainly rugged aa. The only access is through a drainage inspection manhole in a public street. The grid pattern of passages in this lava cave is unique in New Zealand (Crossley, 1979; Kermode, 1994). This cave is potentially threatened by future upgrading of the busy road above, by increasing numbers of heavy vehicles using that road, and by slow accumulation of street sediments washed in from drains. Future intensive residential development (and any associated excavations) could either damage or extend the cave, which is seldom visited.

Helena Rubinstein Cave (Onehunga) consists of several divergent lava lobes that total about 320m in length, and are only a few metres beneath several commercial properties. The cave has been inaccessible since 1966. The flat arched ceilings (0.5m to 2.5m high) are generally less than 5m wide, and the floor is mainly level and covered with mud. Some parts of the cave are subject to occasional flooding. There are many well-formed lava wall-rolls (lava peels), several centimetres thick, and up to a metre in diameter. Wall-rolls are rare in New Zealand lava caves. The pattern of passages in this lava cave is unusual in New Zealand (Kermode, 1970, 1994). This cave will be threatened by future redevelopment of the light industrial sites above, by excessive industrial vibration, and by an increase of sediments washed into it. Future road works could either damage or reopen the cave.

Landscape Road Cave (Three Kings) is a 90-metre long segment of a typical lava tube only a few metres beneath a public street. The passage is less than 7m at its widest, and the ceilings have a variety of arched shapes that vary in height between 0.6m and 3.0m (Crossley, 1970). The only natural collapse-entrance is privately owned. This cave was adapted as a World War II air raid shelter, and has not collapsed under the heavy loadings of the traffic that now uses the street. It is rarely visited. Future road works could either damage the cave or form a new entrance. The Geopreservation Inventory (Worthy, 1990; Kenny & Hayward, 1996) merely noted, "An excellent example of a lava cave; 100m length, 10m diameter tunnel."

Motor Holdings Cave (Mt Wellington) is a segment of a lava tube a few metres beneath a public reserve. The single passage is narrow and arched (about 1.5m high generally about 2m wide and about 114m long), with many interesting flow features: lava wall-rolls, a roof sag, a floor bulge, a ponded flow, and an aa lava floor. This cave has been inaccessible since 1975, its exact location has been forgotten, and no photos were taken during its brief accessibility (Crossley, 1988; Kermode, 1994). Although this cave is currently protected by park status, the construction of the proposed eastern motorway would be a serious threat to it.

In 1995, during possum and wallaby eradication operations, a "New" lava cave (Rangitoto) was discovered. It has a pit entrance (about 6m deep and about 6m diameter) from which a fragile passage containing much ash and rubble leads up flow for about 15m.

A much longer passage leads down flow past a small collapse entrance and into a passage with distinctive flow features (M. Edge; pers. comm.). The cave is well-hidden in the forest-covered rugged terrain, and is never visited. A mapping and description project is to be undertaken.

During the same pest control programme "Hornito" lava cave was also discovered. It is a narrow hornito chimney about 5m tall that stands above a 1-metre diameter pit about 6m deep and 3m wide at the bottom (S. Woodward, pers. comm.). This feature is unique in the Auckland Volcanic Field, and in New Zealand. The cave is well-hidden in the forest-covered rugged terrain, and is never visited.

PUBLIC EXHIBITIONS

During 1994 a special natural history exhibit was opened at the Auckland War Memorial Museum. "Volcanoes and Giants" included a walk-through gallery that depicted the sights, sounds, and origins of a typical lava tube cave. Early in 1999 several new natural history galleries were opened, including "Origins - the land". This includes a walk-in gallery that depicts and explains the major features of limestone caves, their origins and their common contents.

CONCLUSIONS

Auckland City planners are keen to see lava caves of heritage significance protected, but the development of a simple and effective management strategy has yet to be completed. Although ACKMA members who are managers, researchers, and guides are resolute in their conservation aims, there is still some ambivalence amongst business developers.

It is important to support educational and interpretive ventures that go beyond the captive audiences that already visit caves and karst, and to take those initiatives to the general public, and especially the to the upper hierarchies of control - national and local politicians, chief executives, planners, financiers, and would-be sponsors.

Everyone involved in the discovery, recording, protection, and development of caves and karst should work closely together to cultivate a wide-spread appreciation of the diverse heritage of intrinsic cave and karst treasures that can be experienced and enjoyed in a sensitive and sustainable way.

References

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