Karst Management and the Resource Management Act: putting karst on the resource map

Ian Millar, Senior Conservation Officer, Invertebrate Conservation, Department of Conservation, Nelson, New Zealand


Opportunities for the sustainable management of karst in New Zealand, through the provisions of the Resource Management Act (RMA), are considered. The effectiveness of the Act in karst protection is likely to depend on: the extent to which Councils understand the special nature of karst; which specific values it is desired to protect; the extent to which those values, and how they may be affected by human activities, are understood; and the degree to which those values can be accessed and demonstrated. Potential weaknesses in the Act with respect to karst protection are considered. An example is given of the process of working towards informed karst management through the RMA in Tasman District.


The Resource Management Act (RMA) was enacted in 1991. The purpose of the Act is stated, in Section 5, as the promotion of "sustainable management of natural and physical resources".

Sustainable management is then defined as managing:

"the use, development, and protection of natural and physical resources in a way, or at a rate, which enables people and communities to provide for their social, economic and cultural well-being and for their health and safety while:
a) sustaining the potential of natural and physical resources (excluding minerals) to meet the reasonably foreseeable needs of future generations; and
(b) safeguarding the life-supporting capacity of air, water, soil and ecosystems; and
(c) avoiding, remedying, or mitigating any adverse effects of activities on the environment."

Guiding principles for the exercising of powers and functions under the Act are then stated in the following three sections. Amongst these are a number of provisions which can be applied to karst landscapes and features. They include:

Powers and functions under the Act are exercised at national, regional and local levels, with each level having its own functions.

Functions under the Act which have, or may have, relevance to karst management are:

  1. At the national level
    • Water Conservation Orders: These recognise and sustain outstanding amenity or intrinsic values of water bodies. 'Water body' includes rivers, lakes, streams and aquifers.

  2. At the regional level
    • Regional Policy Statements: These are umbrella documents which provide an overview of the resource management issues of the region, along with policies and methods to achieve integrated resource management.
    • Regional Plans: These cover a number of issues which may affect karst management, predominantly in relation to water:
      • contaminant discharges to water;
      • land disturbance activities (for the purposes of soil conservation or maintaining or enhancing water quality);
      • disturbance to water bodies and their beds (including the taking, using, diverting and damming of waters).

      Under Regional Plans, activities with the potential to have adverse effects on water resources, including the discharge of contaminants, require consent, unless they are specifically allowed for in the plan.

  3. At the local level
    • District Plans: These cover a number of issues which may affect karst management, predominantly in relation to land:
      • land uses (including excavation, tunnelling etc., and any destruction of, damage to, or disturbance of the habitats of plants or animals in, on or under the land);
      • subdivisions.

      Under District Plans these activities need consent only if they contravene a rule within the plan. District Plans can also identify significant natural or cultural areas or features for protection.

In addition, the Act establishes Designations and Heritage Protection Orders for special cases.

Application of the Resource Management Act to Karst Management

A number of factors will determine whether karst areas and individual karst values receive appropriate management under the RMA. These include:

The application of the provisions of the RMA to karst management is here assessed with reference to the various "zones" in karst systems. For each zone, the features or values to be managed, sources of impacts on these and possible mechanisms for management under the RMA are examined.

1. Overall Karst Processes and Water Quality

Water has an obvious integrative role in karst, mediating both the development of karst and the accumulation and development of many significant cave values (speleothems, sediments, fossils, terrestrial and aquatic cave fauna etc.). For this reason surface land and water management and their effects on water quality are likely to have significant downstream effects at every level in the karst system.

Particular problems are sediment and contaminant discharges to karst waters. Because karst systems have little filtering capacity, contaminants can move through the system affecting biological and other values, and persisting into outflow waters leaving the karst. Land disturbance activities (e.g. deforestation) which introduce sediments into cave streams can also cause increased run-off by reducing the buffering capacity of surface soils. This can lead to increased silting of cave streamways, choking aquatic fauna habitats, and causing flooding in areas of the cave which have not been subjected to such disturbance for centuries or millennia. This in turn may lead to the destruction of a variety of in-cave features (e.g. sediments, speleothems, fossils etc.).

Controls on contaminant discharges to karst, and on land disturbance activities causing unacceptable sedimentation of cave streams are available through Regional Plans, as are controls on water abstractions from allogenic streams.

Surface land use changes can have a further impact on karst by altering flow-through rates and chemistry of percolation waters. This may show up as changes to the deposition of speleothems, and even re-dissolving of speleothems. I am uncertain as to how well these processes are understood in detail and relating causes to effects for RMA purposes is likely to be difficult. It is likely that the only controls which would be available under the RMA are those relating to the initial clearance of indigenous vegetation.

Subdivisions and the construction of dwellings can impact on karst water quality through stormwater and wastewater (eg. septic tank overflows) disposal, but also through impacts on diffuse water inputs to karst which may affect in-cave values. For example, buildings and sealed areas (paths, driveways, roads, etc.) remove former diffuse inputs from rainwater into artificial stormwater drains. If these are then deposited to karst, they enter as point source, rather than diffuse, inputs. Controls on stormwater and wastewater disposal are available through District Plans, but impacts on diffuse water inputs are unlikely to be addressed under the RMA unless the karst and cave values likely to be affected are considered to be so significant and vulnerable that subdivision is disallowed.

In specific cases of nationally outstanding karst waters, protective controls through a Water Conservation Order might be considered.

2. Surface Zone

Significant karst surface features, such as landforms, plant associations or rare species may be subject to protective controls through identification in the District Plan. Otherwise such features may be protected by rules in Regional and District Plans governing land uses, vegetation clearance, soil disturbance and earthworks, subdivisions etc.

3. Epikarst Zone

Hydrological processes in the epikarst are reasonably well understood, but specific values of this zone are unknown. Given recent advances in our understanding of cave biology, it is possible that this zone represents a major habitat for some "cave" species.

Epikarst voids are prone to sudden infilling by surface soil collapse as a result of activities such as deforestation. As this does not appear to lead to significant silting of cave streams, there are no controls available through Regional Plans. These plans do, however, provide potential controls on discharges of contaminants etc, into this zone.

4. Vadose Zone (including accessible caves)

This zone contains most of the features and values usually associated with karst below the surface in the "within-cave" values (e.g. sediments, speleothems, fossils, fauna habitat etc.). These are the features most prone to damage by unsympathetic or uninformed cave use.

Opportunities for controls on the on-going small-scale degradation of cave values by cave users are not apparent within the RMA. Individual locally, regionally or nationally significant caves could be identified in the District Plan, with specific associated activities being subject to consent, but this alone seems unlikely to guarantee their protection from this sort of degradation. In some situations identification of such caves could even have the effect of making them more vulnerable. However, plans could be a useful way of increasing awareness and understanding within the community of cave values and the potential adverse effects of cave use.

The RMA potentially provides opportunities to control activities causing physical modification of caves such as excavating, tunnelling, damming cave streams etc. These activities can affect cave stream quality and influence air flow patterns and humidity within caves. In turn, these effects can disrupt cave fauna populations, and affect processes such as speleothem deposition. They may also reduce the aesthetic values of caves. These activities could be covered by provisions in District and Regional Plans. It is interesting to note that structures built to prevent unacceptable damage to cave floors or walls may warrant building consents under the Building Act, whereas simply walking on those areas and disturbing or destroying their features is unlikely to require a consent under the RMA. Identification of significant caves within District Plans could provide the means to place controls on modifying activities.

5. Phreatic Zone

Apart from the karst processes and cave structure which are demonstrated in this zone, the main intrinsic values are likely to be biological (i.e. aquatic cave fauna). This is another zone where the comparative lack of access means that existing values may be undetected and/or undemonstrable and, therefore, not receive adequate protection through controls on development.

The main human impacts on this zone are likely to be through effects on water quality, chiefly on the quality of water coming in from the surface, but possibly also from activities in the vadose zone. Water abstraction could also have a significant effect on the phreatic zone. Water abstraction can be managed through the Regional Plans, provided that there is sufficient knowledge of that particular aquifer that the effects of abstraction can be predicted.

6. Outflow Zone

The main features and values of karst outflows relate to water quality. Controls for managing this are discussed above.

Using the RMA in Karst Management

Karst in Tasman District

The Nelson/Marlborough area does not have the more usual Regional Council - Local Authorities structure. The Nelson-Marlborough Regional Council was disbanded in 1992 and the local bodies declared to be Unitary Authorities, undertaking the roles of both regional and local authorities for their areas.

The three unitary authorities in the area are Tasman District Council (TDC), Marlborough District Council (MDC), and Nelson City Council (NCC). Of these, TDC and NCC have karst within their areas. The karst within Nelson City's boundaries lies entirely within water reserve catchment or conservation land, administered by NCC and the Department of Conservation (DOC) respectively. The karst within Tasman District includes a substantial amount within private ownership.

Tasman District contains the most diverse karst resource of any local body in New Zealand. It includes large areas of karst on Ordovician marble and limestone and on Tertiary limestone, as well as lesser areas on more ancient limestones. Karst occurs over a full range of altitudes from the alpine zone to sea level.

Many key karst areas, particularly those of higher altitudes, are in publicly-owned conservation land, but a significant part of the mid-altitude karst and most of the lowland karst is privately-owned.

The conservation values associated with individual karst areas tends to vary with altitude and between areas. Although there is a good representation of higher altitude karst in conservation land in the district, these areas have different values from the lower-lying, less well represented areas: different geomorphological features, different cave faunas, different fossil assemblages, etc. It is, therefore, desirable that sufficient management controls be extended to karst under private ownership to maintain existing values.

Much of the low to medium altitude karst in Tasman District has undergone a similar sequence of developmental impacts to that of the Waitomo area: initial land clearance, with massive silt invasion of caves and cave streams, followed by phases of often intensive recreational use, with direct in-cave impacts (caving seems to have been undertaken quite widely in the district prior to the Murchison earthquake of 1929). The early recreational phases, in particular, were associated with considerable cave degradation, including graffiti, removal of speleothems and fossils, and the trampling and destruction of sediments and other cave floor deposits.

Tasman District karst has not, as yet, entered the most recent phase being experienced in Waitomo: impacts from intensifying commercial use of caves. However, an increasing trend in the district is the subdivision of formerly rural karst areas into suburban zones or small "lifestyle" rural blocks: local developers have begun to appreciate the added appeal to would-be "lifestylers" of being able to own a piece of limestone outcrop.

Issues involving karst which have arisen within the district in recent time include subdivisions, stormwater disposal into dolines and cave entrances, roading, proposed water abstraction for a hydroelectric scheme, water conservation orders etc.

In 1994 an opportunity to heighten awareness of karst management issues in the district came with the TDC's notification of its Land Disturbance Plan (more formally known as the Regional Plan (Land)). This plan responds to TDC's regional functions under the RMA, and controls land-based activities which can lead to sedimentation in water bodies. It includes provisions controlling land disturbance, roading and tracking and vegetation clearance. In Tasman District the intention has been that the Land Disturbance Plan would ultimately be integrated into the Resource Management Plan (an integrated Land Disturbance Plan, Coastal Plan and District Plan, combining the Council's regional and district functions).

TDC notified its proposed Land Disturbance Plan in 1994. This divided the district into two management zones: Zone 2 comprising land on a group of rock types known as Separation Point Granites, which have a well-documented erosion tendency, and Zone 1 comprising all other lands in the District.

Zone 2 land was subject to higher levels of control over allowable management. Karst was included in Zone 1 and was not intended to be treated differently from any other land category.

DOC made submissions on the notified plan, suggesting, amongst other things, that the karst areas required their own zone within the plan on the basis that many land disturbances on karst lead to soil loss to the subsurface, and ultimately to the silting of caves and cave streams, with degradation of values.

The process following on from this submission has not fully resolved the issues at the time of this conference, but considerable progress has been made and consultation is continuing. As part of this process Dr Paul Williams, a karst geomorphologist from Auckland University, was invited to conduct a seminar on karst and karst management issues, which was attended by staff from both organisations. This meeting was invaluable for all attendees, and helped to sort out more precisely where the issues lay with respect to siltation of caves and cave streams from land disturbance activities.

A positive outcome of the process to date has been the increased awareness of the issues involved in karst management amongst Council staff.

Discussion and Conclusion

It is possible, under the provisions of the RMA, to achieve a degree of informed karst management to avoid or mitigate the permanent effects of development on karst values. However, karst management seems destined to lag behind other areas of land and water management, primarily for three reasons:

  1. A wide lack of understanding or appreciation of karst systems and processes amongst both the public at large, land managers, and those responsible for placing controls on land management.
  2. The comparative, or real, invisibility of karst values and the impacts on them of development. An example would be the difficulty of providing hard evidence for planning decision-making in a case where a cave system, and some of its values, can be inferred, but where there is no physical access to the cave. Karst/cave values need not be accessible to be important, e.g. as habitat for a population of a rare species of limited distribution.
  3. Our lack of knowledge of karst, compared with other land types. For example, in New Zealand while we have some knowledge of the processes which occur in the epikarst zone, we have little knowledge of what other values may reside there, e.g. fauna habitat. There is a clear need for more research into karst values and processes, and the effects on these of the modification (e.g. deforestation) of karst surfaces and cave stream catchments.

In the longer-term it seems that the appropriate management of our karst resources will require a more active approach to informing the managers and users (including landowners) of these resources of their nature, vulnerabilities and limitations, along with appropriate management controls and incentives through the RMA. Regional and Local Councils need to be prepared to make the effort to understand karst management issues, however imperfect our present knowledge base.


I thank Sarah McCrae and Jo Gould for helpful discussions and suggestions in preparing this paper.