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Inventory, forekarsting and karstcare

Kevin Kiernan, Senior Geomorphologist, Forest Practices Board, Tasmania

ABSTRACT

Land management in karst areas is often impeded by an ignorance of what karst is and what it implies; often by a failure to realise that karst is or may be present in an area; and in almost all cases by a lack of information concerning the geography and system relationships of individual karsts. In the Tasmanian case, geological mapping is far from complete and often even where carbonate rocks are known to occur they have not been prospected for possible karst. The Tasmanian Karst Atlas Project has involved the development of an inventory of known and reported carbonate localities, starting from the assumptions that any area of carbonate rock are likely to be karstic to at least some degree, and that it is better to err on the side of caution. The aims have been to gain a first approximation of the potential extent of karst in Tasmania and the degree to which particular sites are karstified. The process has involved seeking to develop a capacity to forecast the potential intensity of karstification in less well known areas based on comparison with other known sites at which there is a similar mix of the natural systems that control karst evolution, in a bid to improve the capacity to plan at a strategic level. Detailed inventory of individual areas where deveopment is proposed can provide a basis for sensitivity mapping as an aid to planning at both the strategic and operational levels. Tasmania's karst is split between a variety of land tenures with the boundaries generally being arbitrarily defined. Sustainable use of karst landscapes, for whatever purpose, demands the adoption of a systems approach. Scope remains for employing reservation strategies to protect particularly important karst phenomena, but more generally the fostering of an ethic of karstcare, akin to Landcare but with a greater focus on the vertical dimension, probably offers the greatest scope for improved karst managment statewide. As with conventional Landcare, education and fostering a sense of community ownership, both of the problems and of the solutions, is essential.

INTRODUCTION

Tasmania's karst estate contains a wide variety of resources. Various components of Tasmania's karst are of nature conservation significance at scales ranging from local to international. Some of Tasmania's karst environments are also places where people work and live. A variety of natural geomorphic hazards potentially confront these residents of karst areas, including the vulnerability of soils and aquifers to degradation, ground surface instability and foundation difficulties (Kiernan 1988a, 1990b). Some Tasmanian karstlands have been formally reserved for conservation or have the potential to be formally reserved, reducing some potential human impacts. Where reserve status does not exist, the potential for geoheritage degradation and for karst geomorphic hazards to impact adversely on communities must be taken into greater account, and alternative strategies are necessary if karst geodiversity is to be safeguarded.

Current data suggests that potentially karstic carbonate rocks underlie in excess of 300,000 ha, or a little under 5% of Tasmania, but geological mapping is far from complete. The most highly evolved karst occurs in Precambrian and Ordovician carbonates, each of which comprises ~45% of this total. A little over 30% of the carbonate lies beneath private land and ~30% lies beneath State forest. Unallocated Crown Land contains ~20% of the total and the remainder is contained within parks and reserves. Some 6% of Tasmania's State forests and a slightly lesser proportion (~5%) of the existing parks and reserves are underlain by them. About 25% of the Ordovician limestone is in parks and reserves but only ~15% of the areas likely to contain accessible caves is reserved. Most of the magnesite karst lies on Crown Land. No magnesite karst is at present formally protected. Hence, a variety of managers and agencies have areas of karst under their control and have the need to develop expertise in karst management.

It is essential that the values, processes and limiting factors of karst are understood if the use of karst is to be optimised and negative impacts upon one another of the numerous potential users are to be avoided or at least minimised. To this general knowledge must be coupled an adequate knowledge of the geography of the karsts, both above and below ground. The highly systemic and interactive nature of karst demands that a systems approach be taken to its management, irrespective of whether the objective is the sustainable development of a particular karst environment or the preservation of karst phenomena that are of geoheritage significance. While knowledge of the geography and values of Tasmania's karst estate is likely to remain incomplete for some time to come, sustainable karstland management is often attainable now, given appropriate goodwill, public and professional education, restraint, and the application of first principles.

FOREKARSTING

Given that knowledge of the distribution of karst in Tasmania remains incomplete, and that knowledge of the drainage and feature distribution in even the best known and most accessible karsts is also incomplete, obvious problems exist in guiding the detail of development and management. In these circumstances it would seem useful if some form of predictive modelling could be developed, perhaps akin to the Archaeological Sensitivity Zoning process undertaken for Tasmanian forest areas by McConnell (1994). "Forekarsting" of this kind would facilitate the more ready recognition of areas that are most susceptible to karstification. On this basis human activities in already-developed karsts that possess fragile heritage values or that pose potential karst natural hazards could be better planned, and new, non-essential development of such areas could be avoided pending further study of them.

At the most basic level, geological maps that depict occurrences of limestone and dolomite are available for some parts of Tasmania, and the accuracy of the geological boundaries depicted has been improved on those maps published by the Tasmanian Department of Mines in recent years. However, in the absence of further geological survey of Tasmania there is unlikely to be any improvement in the geological data available to land managers in the foreseeable future. At present, no detailed geological maps are available for large parts of the island and many of the maps that have been published depict assemblages rather than the specific rock units present at particular sites. Moreover, the appropriate management unit in karst is the catchment, not simply the area of limestone outcrop. There are likely to be many areas of limestone hitherto unrecorded, and hence unrecognised karst catchments. Of course even were this problem resolved, the presence of carbonate rocks alone does not guarantee that karst is present. Rather, karst evolves due to complex interactions between all those system controls discussed in the first two chapters of this study. Hence, highly evolved subsurface drainage systems are not necessarily present in all carbonate areas, even if other karst attributes are known to occur. The fundamental principle in forekarsting is the notion that once a few karsts of various kinds have been studied in detail it may be possible to extrapolate from those to other less well known areas that exhibit a similar mix of system controls.

At the present time, forekarsting can only realistically be undertaken in those areas where potentially karstic rocks are already known to occur. While additional karsts are likely to be found, it is probable that those carbonate areas already recognised include the most highly karstified locations that exist in Tasmania - it is highly unlikely that further karsts as large and highly evolved as Mole Creek, Junee-Florentine and Ida Bay still await discovery. In order to provide some measure of forekarsting, the carbonate areas recognised in this study have been placed into one of four categories. Inclusion of an area in a particular category has required professional judgement regarding the likely intensity of karstification, based upon the writer's personal experience and impressions. The categories are intended to reflect the degree to which karst landforms have evolved or are likely to have evolved in a particular system mix. It must be stressed that the focus here is not upon the prediction of geoheritage values as such any more than it is specifically upon the prediction of karst hazards. Rather, the focus is more general, upon predicting karstification intensity, which may of course give rise to either heritage or hazard or both.

Category A: Intensely karstified or probably intensively karstified: carbonate rock formations known to be highly susceptible to karstification; on the basis of existing knowledge well developed karst is to be anticipated.

Category B: Substantially karstified or probably substantially karstified: carbonate rock formations known to be susceptible to karstification; on the basis of present knowledge karst is more likely to occur than not.

Category C: Partially karstified or potentially partly karstified: carbonate rock formations that may be susceptible to some forms of karstification or within which some karst may be present within specific horizons, topographic situations or in response to other environmental factors.

Category D: Possibly partially karstified: rock formations that are not predominantly carbonate but which contain subordinate carbonates within which karst may have evolved; in cases where there is a high likelihod that carbonates occur within more extensive formations that have not been sufficiently differentiated in geological mapping to allow the specific localities to be indicated, the whole area of undifferentiated rocks has been recorded as Category D pending clarification.

Any category has the theoretical potential to reveal phenomena of significance at any of the four standard levels (system context; landform species and assemblages; landform contents; human use and aesthetics). The categorisation does not imply a hierarchy of geoconservation significance, indeed some phenomena that might be found in categories C and D may be especially significant precisely because of the system context within which they occur. For example, relatively small caves may be important in a particular area because of the general scarcity of caves which exhibit a certain morphology in the rock types involved.

INVENTORY AND MANAGEMENT OF INDIVIDUAL KARST AREAS

The purpose of the Tasmanian Karst Atlas project (Kiernan in press) has been to develop a broad overview of the distribution, significance and management implications of Tasmania's karst estate. It is obviously not feasible for this project to develop detailed inventories of the karst phenomena in each of the many carbonate areas identified. Although detailed inventories of parts of the Mole Creek and Junee-Florentine karsts have previously been undertaken (Kiernan 1984a, 1989c, Eberhard 1994) and case studies of some examples of particular types of karst have been prepared as part of the present project for presentation elsewhere, for the most part specific area inventories do not yet exist. This is the logical next level of analysis, and given the resource implications, the sequence of priority needs to be given careful thought.

There are two fundamental pre-requisites for karst management. The first is flow trajectory and catchment area determination. Figure 1 presents the results of extensive water tracing experiments conducted in the Mole Creek karst. The second fundamental pre-requisite is sensitivity or vulnerability mapping. However, as Aley et al (1993) emphasise, vulnerability mapping in karst is sometimes based solely on hydrological considerations and does not take other environmental risks into account - slope stability, soil vulnerability, geoconservation and geodiversity issues and related matters also warrant attention if the aim is sustainable management.

Karst inventory processes involve the location of the karst features present in an area — the individual sinkholes or polygonal karst zones, streamsinks, springs, dry valleys, caves, residuals, karren etc — and integrating that information with water-tracing results (Kiernan 1984a, Eberhard 1994). Delineation of actual karstic drainage patterns often reveals major differences from the picture that may be suggesed by surface topography. Indeed, attempting to plan any management initiative or development on karst without first determining the patterns of subsurface drainage is akin to not having a topographic map on hand in non-karst landscapes. The situation is further complicated by the fact that it is common for karst streams to discharge to more than one single point, in contrast to most surface streams that concentrate water flows to a single downvalley point of discharge. The catchment area of the karst aquifer recharge system needs to be managed as part of a karst system, even though part of the catchment may not be underlain by carbonate rocks. Furthermore, because few karsts evolve in isolation from other facets of the broader environment, the inventory process must include identification and delineation of other geomorphic or geologic features, such as fluvial, colluvial, glacial, periglacial, aeolian or marine landforms or sediments that occur in the karst catchments (Kiernan 1984a). Appropriate categorisation systems may differ from area to area, hence time needs to be allowed for system development rather than assuming that a system that works in one area can simply be transferred elsewhere and acceptable results achieved.

The mapping of sensitive areas is a land management tool based on the premise that not all karst development and resources have evolved equally, and that some parts of a karst landscape are subject to appreciably greater resource damage potential and groundwater contamination risk than other lands (USDA-FS Tongass 1994). Aley et al (1993) have identified eleven criteria that should be included in vulnerability assessments in karst areas (Table 1). At this point some clarification of terminology may be appropriate however, since workers have tended to use the terms "vulnerability" and "sensitivity" for much the same thing. Future exercises might perhaps best more clearly differentiate between two facets of the the zoning purpose, for "sensitivity" comprises two elements, namely the "vulnerability" to damage of heritage values, and the "hazard" that particular areas of karst may pose in terms of soil erosion, sudden subsidence or groundwater degradation. These two categories are not always coincident. For instance, while karst collapse tends to be most pronounced in low relief, regolith-mantled carbonate areas due to the piping of regolith components into the epikarst, leaving voids in the regolith, features of nature conservation significance such as enterable caves may not be present due to limited groundwater circulation and the blocking of cavities in the bedrock by detritus. Conversely, cave-bearing areas on hillslopes where the regolith is not as thick may not be particularly susceptible to surface collapse.

Figure 1

vulnerability criteria

Table 1: Vulnerability criteria for karst lands (summarised from Aley et al 1993)

  1. Lands within sinkholes or within a minimum distance of 100 ft from any sinkhole or sinkhole complex indicated by field evidence or water tracing to discharge discharge directly during any period of the year to a Class I or Class II stream as defined in the U.S. Forest Service Region 10 Aquatic Habitat Management Handbook - FSH 2609.24 - June 1986) or to a spring or stream used as a domestic water supply. This recognises that subsurface karst conduits are rapid underground plumbing systems that offer negligible natural cleansing of groundwater, and adopts the same protective strategy as is applied to surface streams.
  2. Lands within any sinkhole or within a minimum 100 ft distance of the lip of any sinkhole if no studies have been conducted regarding its relationship to Class I or II streams or domestic water.
  3. Lands within a minimum 100 ft distance of an identified losing stream if evidence indicates it discharges to a Class I or II stream or to a spring or stream used for domestic water supply.
  4. Lands within a minimum 100 ft distance of an identified losing stream if no studies have yet been conducted to establish the relationship between it and Class I or II streams or domestic water.
  5. Lands within sinkholes or within a minimum 100 ft distance of sinkholes demonstrated to drain to a significant cave as defined by the USA Federal Cave Resources Protection Act. "Significant cave" is defined under this legislation as being any cave located on Federal lands that has been evaluated by the authorised officer and determined to have biotic, cultural, mineralogical, palaeontologic, geologic, hydrologic, or other resources that have important values for scientific, educational or recreational purposes. That legislation requires that surface management activities assure that caves under consideration for the National Significant Caves List are protected during the period of consideration.
  6. Lands within sinkholes or within a minimum 100 ft distance of sinkholes where no study has been undertaken to determine their relationship to a significant cave.
  7. Land within a minimum 100 ft distance of a losing stream known to contribute to a significant cave
  8. Land within a minimum 100 ft distance of a losing stream where no study has been undertaken to establish its relationship to a significant cave.
  9. Lands that overlie a significant cave or are otherwise likely to contribute waters to a known significant cave.
  10. Lands that are close enought to the entrance of a significant cave to be capable of altering cave features or the microclimate of the cave entrance, taking into account possible secondary implications of adjacent development activities, such as windthrow after logging.
  11. Slopes in excess of 70%

On the basis of these criteria, Aley et al (1993) developed a four tier vulnerability classification system for United States Forest Service use in the Ketchikan Area karsts, Tongass National Forest, Alaska (Table 2). This is a major karst province that is subject to logging and which, in common with many karsts, contains a wide range of resources other than timber. The system developed by Aley et al is designed to characterise those resource-damage threats created by timber harvest and associated roads and quarries, specifically focussing on threats posed to springs, spring-fed streams, significant caves and cave features. At Ketchikan, the only low vulnerability areas identified were located close to sea level, contributing recharge waters either to a salt water lens or to trivial springs that flow directly into the sea.

Table 2: Vulnerability classification system developed by the United States Forest Service for the karst forests of the Tongass area.

Low Vulnerability

Moderate Vulnerability

High Vulnerability

Extremely High Vulnerability

Aley et al (1993) do not spell out the managment implications of their vulnerability classes. In Tasmania the focus has tended to be more towards management response. The initial Tasmanian attempt to zone a karst area for management purposes was the differentiation of the Mole Creek karst into K1 (highly karstified) and K2 (less highly karstified) zones by Sather and Kiernan for the Forestry Commission Geographical Information System in the late 1980s. K1 zones were envisaged as demanding effective protection status, K2 zones were envisaged as having the potential for timber harvest given the adoption of specific strategies to protect karst values and ameliorate potential karst geomorphic hazards. This has now been superseded to a degree by the development within the former Tasmanian Forestry Commission of a Management Decision Classification (MDC) system that makes provision for protection and special management zones, the latter including categories for both geomorphological and other values, and for hazards (Forestry Commission 1991). However, it is still important to spell out the rationale in zone delineation, and to recognise that the issues involved in karst area management do not stop at the margins of land managed by the Forestry Commission, hence broader trans-tenure zoning is desirable in karst areas. More recently, Eberhard (1994) has developed a three-fold hierarchy of karst sensitivity zones for the Junee-Florentine karst (Table 3, Figure 2). These focus on geoconservation and geodiversity retention. The system is not designed to accommodate natural geomorphic hazards in karst areas, such as accelerated sinkhole collapse or aquifer degradation, other than in cases where geoconservation values are imperilled by these hazards. However, in many cases in the Junee-Florentine karst areas of concern from geoconservation and geomorphic hazard perspectives are coincident. The system adopted by Eberhard (1994) provides clear guidance with respect to appropriate management practices.

Table 3: Sensitivity zoning scheme developed for the Junee-Florentine karst, Tasmania (summarised from Eberhard 1994).

Low sensitivity zone

Medium sensitivity zone

High sensitivity zone

Figure 2 Sensitivity zoning of the Junee-Florentine karst (from Eberhard 1994)

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The need to exercise care and restraint in the management of karst areas potentially gives rise to questions regarding the extent to which exploitative uses may need to be limited. In the late 1980s planners within the Tasmanian Forestry Commission who sought to assess the timber resource in the state's Southern Forests applied a discount to the total wood resource in line with informed estimates of the likely extent of sensitive karst. Similarly, the apparent wood resource was discounted in planning for the former Australian Newsprint Mills Ltd concession in the Junee-Florentine karst. The zoning schemes now completed provide a means of refining the discount that needs to be applied in highly evolved karsts.

The Mole Creek, Junee-Florentine and both Tongass exercises have each involved highly evolved karsts broadly equivalent to Category A karsts as defined by the present study. These four exercises suggest that 40-50% of Category A karsts are likely to be of such sensitivity as to demand full protection status.

For the purposes of sensitivity mapping it is important to recognise that the term "cave" as employed by geomorphologists and hydrogeologists is what is relevant, since it is not necessarily synonomous with what the lay public perceives as a cave, based perhaps on their recollections after visiting a large, highly developed commercial tourist cave. In functional geomorphological and hydrogeological terms even very small conduits are caves. Ford and Williams (1989) define a karst cave as a solutional opening that is greater than 5-15 mm in diameter or width, this being the effective minimum aperture for turbulent flow to occur. The need to protectively manage even those parts of cave systems not yet explored or that lack natural entrances is highlighted in the definitions contained in the United States Cave Resources Protection Act:

"Cave means any naturally occurring void, cavity, recess, or system of interconnected passages which occurs beneath the surface of the earth or within a cliff or ledge (including any cave resource therein, but not including any vug, mine tunnel, aqueduct, or other manmade excavation) and which is large enough to permit an individual to enter, whether or not the entrance is naturally formed or manmade. Such term shall include any natural pit, sinkhole, or other feature which is an extension of a cave entrance."

It should be noted that this legal definition therefore includes sinkholes and other karst features that have direct atmospheric or hydrologic conection to underground caves. However, this definition does not include the small solution conduits regarded as caves by karst geomorphologists and karst hydrogeologists.

There are two main reasons why it is not sufficient that management attention be given only to those caves presently accessible through known entrances. First, in many cases geomorphological and other criteria may make it relatively self evident that caves underlie the surface, even though no natural entrance may yet have been located. The discovery and exploration of caves is a time consuming process and new caves are commonly found from time to time even in well known karsts. Sometimes, humanly accessible entrances are not found until small amounts of soil or sediment are removed from epikarstic systems in sinkholes or karren fields. The second reason why recognition must be given to predictable cave passages that may hitherto remain unexplored is that irrespective of whether they have yet been physically entered by humans or not, such passages nevertheless form the fluid (water and air) drainage system.

TOWARDS KARSTCARE

In recent years the notion of Landcare has become well enshrined in the psyche of most of Australian society. The Landcare ethic, with its focus on land, water and sustainabliity, encapsulates in a primarily two dimensional environment much of what is needed in karst management, except that in karst the vertical (depth) dimension is of very much greater magnitude. The potential for transport of sediment vertically into karst is greatest where there is well-developed and deep epikarst, the highly corroded area between the regolith and the less weathered bedrock at greater depth, due to the the closer spacing and wider development of solution channels in that zone. There is considerable evidence for much of the soil erosion that occurs in karsts involving the loss of soil into the epikarst, with erosion of this kind able to occur on relatively gentle slopes where a soil erosion problem would not normally be anticipated were a non-karst environment involved (Kiernan 1987g, 1990a, Kiernan et al 1993, Harding and Ford 1993). Issues of this kind affect not only primary producers but everyone consuming their products and society bears the economic and environmental costs of inadequate management, either through the price paid in the market or the taxes that contribute to land and water management. The Landcare ethic provides a useful foundation upon which it should be possible to construct a more specific Karstcare ethic - always remembering that in this case we are faced with a very three dimensional environment.

The essential principle of Landcare is community and landowner involvement. Some earlier land conservation initiatives failed because structures erected on properties were interpreted by landowners as government projects that government should maintain (Barr 1994). Community involvement through Landcare involves meetings to discuss issues and priorities, the conduct of field days and farm walks, tree planting, co-ordination of weed and pest control, the fencing of remnant vegetation and stream lines, the conduct of joint experiments to test agricultural practices, and the planning of wildlife corridors (Curtis et al 1994). A similar range of activities would be appropriate in a karstcare program, which would need to pay particular attention to underground catchment delineation and total catchment management, the fencing of some sinkholes and karst channels, areas of land-surface instability and the safeguarding of geoheritage phenomena such as caves.

In some cases, formal reservation of important places is appropriate in order to provide a framework within which these values can be safeguarded effectively. But reservation in itself will not guarantee that these values will survive. Various "reserves" that include some karst features have been established, but some of these have been informal. Even some formally gazetted reserves have been wholly or partly extinguished, while deficient management has also led to degradation of the very values that underlay the creation of some of them (Kiernan 1974a, 1974b, 1995a, Mercer and Peterson 1986, Tasmanian Public Landuse Commission 1995). Moreover, experience with the Limestone Pavement Orders enacted under Britain's Wildlife and Countryside Act 1981 highlights the manner in which some reservation approaches can simply shift the pressure from one site to another - in that case the ornamental stone industry seems simply to have moved its operations from northwest England to Eire where no similar legal protection for limestone pavements exists (Goldie 1993). Reservation is not always the best method of safeguarding these values. For many places a more broadly-based Karstcare ethic could go a long way towards ensuring important heritage values survive, while at the same time vastly advancing the sustainability of economic development in Tasmania's karstlands more generally. Indeed without Karstcare there can be no sustainable utilisation of karstlands.

In England, Cave Conservation Plans are being promoted by English Nature, the British Government's statutory advisor on nature conservation, together with the National Caving Asociation. These involve landowners, cavers, and scientists, who document the scientific resources, likely external and internal threats, and seek to produce realistic conservation measures (Glasser 1994). In addition, the condition of the soil above a cave is a critical factor. For example, if biological activity in the soil is substantially increased as a result of increased soil surface temperatures due to vegetation clearing, it may give rise to an increase in soil carbon dioxide concentrations and, hence, in dripwater emerging into caves. This could result in speleothems being redissolved. The impact of visitors to caves is also likely to be profound and must be taken into account in planning (Spate and Hamilton-Smith 1991).

Maintaining the hydrological system in as near to natural a condition as possible is the foundation stone of karst management. In the absence of detailed inventory data and process information the best recourse is to operate from first principles. Ad hoc development should be replaced by a moratorium on the non-essential development of Australia's karst (Kiernan 1988a). The onus must be placed on developers to demonstrate either that karst will not be adversely affected by their activities, or that the impacts they cause are justifiable and acceptable. There are important heritage values already known in Tsmania's karst estate that warrant vigorous defence, and more will certainly be found. Broad area management rather than a focus solely on a single feature (such as a particular cave entrance) is fundamental, but nothwithstandiing this some individual features will still require specific management.

The development and implementation of the Tasmanian Forest Practices Code over the past eight years (Forestry Commission 1993) and improvements in the location and planning of forestry operations have reduced the negative impacts of logging on Tasmania's karst. A number of the recommendations of the 1984 Karst Forestry Study have now been implemented (Kiernan 1984a, 1988f, 1989i,l, 1995b, Kiernan et al 1991). While the Code has certainly not solved all problems, it has clearly been of value. However, no similar guidance exists with respect to other forms of land use that have significant implications for karst. Farmers are more likely to be more amenable to persuasion than to compulsion, but they also need information: relevant agricultural officers should be familiar with karst. More attention needs to be given to the management of agricultural wastes and the problems of stock having direct access into karst waters, the siting of dairy sheds, and the installation of ponds and filter strips. Land clearing in karst catchments and the diversion of karst waters for use elsewhere are two further matters that demand attention.

Visitors to caves can also generate significant impacts underground. Whereas a carrying capacity can be determined for many environments, based on the rate at which natural restorative processes operate, many such processes in caves occur over a geological rather than a human time frame (Aley 1975). Hence, the carrying capacity of many caves is effectively nil, damage is cumulative and footprints may last for millenia. Cave management can be a very difficult field.

Most Tasmanian caves lack any form of active management or access control, and public ignorance of their existence or location offers their only protection. Roads built by development interests or tracks built by park managers, for whatever purpose, can erode this ignorance and make caves accessible that were previously too distant to attract significant visitor pressures. Hence, those who establish easier access must assume some responsibility for responding to the cave management implications. Not all damage caused by some cave visitors is accidental. Deliberate vandalism and theft of speleothems is not unknown, including sites as celebrated as Croesus Cave and Lynds Cave at Mole Creek. The theft of speleothems from various Tasmanian caves is prohibited under at least three pieces of legislation but policing is difficult. In one recent case a prosecution was attempted following theft, apparently on a commercial scale, from one of Tasmania's most unusual karsts. Although this prosecution was successful the fine imposed by the court was nominal and offered no real deterrent. The new Mines Bill being considered in Tasmania includes a provision at Section 176 that prohibits unauthorised disturbance, collection or removal of speleothems from any cave. This represents a significant advance over protecton being limited solely to State Reserves and State forests. However, it will not resolve the problem that an offender can always claim to have obtained speleothems from some limestone quarry. Legislation with a wider embrace, similar to the Aboriginal Relicts Act (1975) with its prohibition on unauthorised disturbance, possession or sale of artefacts seems a desirable goal.

Management-oriented research into Tasmanian karst is of considerable importance. The exploratory activity of recreational cavers and their diligent documentation represents grass-roots research of considerable worth to land managers (Kiernan 1993c). However, scientists are likely to have the same sorts of impacts on cave environments as any other person who visits a cave. While caves offer important scientific resources and science sometimes offers managers crucial information, scientists are also only one of the groups who compete for a limited resource. Taking account of all the values that caves offer, and making balanced decisions on appropriate use and management, poses a significant challenge for management agencies.

CONCLUSIONS

Appropriate and sustainable management of Tasmanian karst requires a clear picture of the various resources each karst area contains or may contain; knowledge of the geography of the karsts both above and below ground; and a clear understanding of the natural processes that operate in karst areas, the ways in which human activities can interfere with those processes, and the implications of any such interference. It also requires commitment and goodwill.

Some of the most degraded landscapes on earth are karsts. There is nothing fundamentally different between the now highly degraded karsts of the Meditarranean region or China and those of Tasmania in terms of their vulnerability: only the lower population pressures and shorter agricultural history of Tasmania stands between the present condition of Tasmania's karsts and the devastation that has been wrought elsewhere. The question that now faces Tasmanian karst managers is whether the generally much better condition of Tasmania's karsts represents merely grounds for complacency or an opportunity to be seized, a chance to ensure that options fore-closed and mistakes previously made elsewhere will not be repeated here.

A systems approach is essential to sustainable karstland management, with a focus on protection of hydrogeochemical systems, which of necessity implies careful management of soil and vegetation. Fostering of an ethic of karstcare would facilitate many necessary improvements. Given the advanced state of land alienation, developing community and landowner involvement, and a sense of ownership both of the problems and of the solutions, is fundamental to progress. Where land alienation or development is less advanced, and where resource inventories and geographical information are inadequate, "forekasting" provides a potential mechanism for identifying the likely sensitivity of the karsts in broad terms and undertaking resource assessments at a strategic level. Detailed inventory of the range of resources that exists in any karst area, together with the geography and hydrogeology of the area, are necessary in order to provide a basis for sensitivity mapping and zoning that can guide both development decisions and day-to day management. The functionally narrow focus of government agencies may predispose the situation towards the compilation of single-minded resource inventories. Hence, such inventory exercises as have been undertaken to date in Tasmania have focussed either on mineral resources or particular aspects of nature conservation. Such an approach is longer appropriate in karst area management, given what is now known regarding the nature of karst and the many values that have the potential to exist in a karst area. The new Tasmanian Public Land Use Comission may have the potential to play a useful role in stimulating more broadly based inventory work.

Tasmania is in the fortunate position of having the opportunity to safeguard important areas of karst that remain in an essentially natural condition. Some possible forms of land or resource use in some of these areas may be sustainable but may not be appropriate. The concept of sustainable management as a desirable goal too often pre-supposes that what is being undertaken represents the best use of the resource or resouces in the first place. Some forms of development in karst areas may well be sustainable, but may represent a waste of a resource that would better be devoted to another purpose. Geoconservation, including the protection of outstanding and representative examples of system control mixes in operation and their karst geomorphic products, landform assemblages and individual landform species, must inevitably be integrated with the wider issues entailed in living with limestone. But the fact remains that elements of Tasmania's karst stand tall among the karst heritage of the Earth. Past actions, poverty and a desperate quest for human survival mean that some elements of global karst geodiversity will never be safeguarded with anywhere near the level of integrity that is achievable in Tasmania. Notwithstanding Tasmania's relatively privileged position both environmentally and economically, the present conservation status of the state's karst geoheritage is generally poor: while various areas of karst have been included in parks and reserves these encompass a rather restricted range of the mixes of the system controls that have given rise to karst geodiversity in the state. Some proposals to improve this situation through formal reservation have been advanced in the past, others await development (Kiernan 1984a, 1989, Podger et al 1990, Dixon 1990, R. Eberhard 1994, Kiernan et al 1994).

On the other hand, many of Tasmania's karsts have already been subject to various forms of development, and are no longer in a natural condition. This development has included activities such as farming, forestry, mining, tourism, and the construction of dwellings and towns, with the attendant issues of servicing, including the problem of waste disposal in a situation of high aquifer vulnerability. Obviously not all karst geoheritage values are necessarily extinguished by partial development of the land surface in a karst catchment. Many important values remain in Tasmania's developed karsts such as the caves in the Mole-Lobster divide and in the Croesus area at Mole Creek, the Dogs Head Hill hum, and the Mayberry polje and polygonal karst in the same area. Similarly, important phenomena remain in good condition in the Junee-Florentine karst, Gunns Plains karst and elsewhere. Decisons need to be taken as to the most appropriate use of these sites, not only whether a proposed use for one purpose or another might be sustainable. However, sustainable management of Tasmania's karst environments, for whatever purpose, is not attainable unless the karst context is taken into account and catered for fully.

REFERENCES

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