A brief history of lowland degradation
As a piece of the jigsaw puzzle that make up New Zealand's natural ecosystems the lowlands are an important, and for some time, neglected part. Their history of neglect is primarily a result of the impact of development in this area for urban and agricultural use.
Prior to human occupation of New Zealand, variously debated as beginning between 700 and 1000 years ago (McFadgen et al. 1994 in Anon. 1997), 78 to 85% of New Zealand was under some form of forest or tall shrubland cover (King 1984, Anon. 1997). Today only 23% remain (McGlone 1989), the majority of this being in the high country of New Zealand. Nearly 90% of the lowland forest has been cleared, with only Stewart Island, Westland and Fiordland retaining vast tracts of lowland forest (Cobb 1992). What remains in most lowland areas of New Zealand is a mosaic of small, modified, natural ecosystems among urban and agricultural land uses (Figure 1).
Conservation of lowland ecosystems
During the 1970s the lack of representativeness (protection of all types of natural ecosystems) in the existing protected natural estate, and poor knowledge of New Zealand's natural areas were becoming recognised (Park 1983). It was particularly apparent in the lowlands, which for various reasons were not regarded as being as important for protection as the alpine environments, upland forests and offshore islands that were already well protected (O'Conner et al. 1990). Foremost among the reasons for not conserving lowland areas coastal ecosystems, lowland forests and wetlands was that they were valued more for their development potential than for conservation (Figure 2).
The lack of representativeness in, and information about, New Zealand protected natural areas was to be addressed by two projects. One, which was completed in the early 1980s, classified New Zealand into homogeneous biogeophysical units, known as ecological districts (Simpson 1982). These 268 districts form the organisational framework for the second project, the protected natural area (PNA) survey program. This program aims to compile information for each ecological district about existing protected natural areas and the range of natural areas that occur, and analyses and ranks those areas which still need to be protected (Park 1983). While all ecological districts have yet to be surveyed many of the important lowland areas have been completed.
Those districts that have been surveyed have highlighted the small number and total area of protected areas in the lowlands. For example, it is usual to find less than 15% of the remaining natural areas in lowland ecological districts are protected and around 1% of the total area are protected (Mitchell et al. 1984, Ravine 1995 and Townsend 1996). In addition they have confirmed the non-representativeness (lack of, or low numbers and area of, the full range of ecosystems) in our existing protected natural areas.
The challenge of conservation in the lowlands
Giving cognisance to the above it is generally recognised that for a representative protected natural area network in New Zealand to exist, more effort has to be made in lowland areas. It is here that the greatest conservation gains can be made, however, there are considerable challenges.
Generally the natural areas that would be required to complete a representative sample are small, fragmented and often isolated. This is due to the very nature of the natural areas that remain in the lowlands. These factors indicate the worst possible set of circumstances for protected areas. Principles that were developed by MacArthur & Wilson (1967) show a decreasing number of species present in areas of land that are both smaller and have greater isolation. These principles were refined and adapted to the specifics of protected natural areas by Dimond (1975). In his seminal paper on the topic larger, intact, nearby, connected and compact areas were regarded as being more viable for conservation than their inverse.
The reasons for these principles are well known but nonetheless worthy of brief repetition.
Small areas contain fewer species than larger ones. Invariably it is the more uncommon species, those that are distributed more thinly, or only in a specific site that are not present. In smaller areas there is a lower chance that these species will occur or that the required habitats for these species will be present thus biodiversity is lower.
b) Effect of perturbations
The likelihood of a chance disturbance event or environmental perturbation having a large impact on a small remnant is high. A small area can be entirely affected, while a larger area may be only partially impacted on. In addition, after disturbance the recovery of a small remnant is impaired. With fewer species present those that might be adapted to and able to withstand the perturbation, or be able to recover after it, may be absent.
Related factors such as edge effects a greater edge to interior ratio and lack of buffers are more common in small remnants and act to reduce sustainability. These factors are enhanced in small remnants where there is often little healthy 'interior forest' compared to the 'edge forest', which is affected by higher wind and light conditions and often has a different moisture and temperature regime. An absence of buffers, which help to protect a remnant from edge effects and can mitigate environmental perturbations, means often there is an abrupt, or 'hard' edge between it and the surrounding land.
Value for money?
In addition to ecological constraints the protection of lowland natural ecosystems can be expensive if traditional purchase and protection mechanisms are used. Lowland areas have high land values due to their production potential and the desire of people to live there thus the values of land to be conserved must be compared with the cost. Ongoing management can be expensive, due to management issues predilection to weed and pest infestations, high cost of fencing for the area protected and the widespread nature of remnants in the lowland landscape.
Lowland remnants necessary or marginal for conservation?
The accepted ecological principles and economic reasons introduced above might suggest that small lowland natural ecosystems have marginal values for the conservation effort required to protect them. However, remnants that might be regarded as being ecologically unsustainable or economically non-viable do have value. To achieve a representative network of protected natural areas in New Zealand these remnants need protecting, thus we have a conundrum of effort required versus the value to conservation.
Despite the ecological principles that might suggest otherwise there are factors that offset the efforts required to protect small, isolated remnants.
Many areas being assessed for protection, despite their size, isolation and other characters that are negative for conservation may be simply all that remain. Their value thus lies in their uniqueness.
In Northland two valuable and unique remnants protect the habitats of threatened species. In one, a remnant kahikatea and matai forest on an alluvial plain, which is rare in it's own right, three threatened species occur. They are the endangered Northland soft fern (Christella aff. dentata), heart-leaved kohuhu (Pittosporum obcordatum) a species regarded as rare (Cameron et al. 1995) but recovering (de Lange et al. 1999 and Dopson 1999) and dwarf musk (Mazus novaezeelandiae subsp. novaezeelandiae) an endangered species. In the other, Baumea complanata, a declining (de Lange et al. 1999) or vulnerable (Cameron et al. 1995) sedge, the vulnerable king fern (Todea barbara) and an uncommon bladderwort Utricularia delicatula, a carnivorous plant, occur in a wetland (Johnson 1989 and Wilson 1989).
Both protected areas are unique in being the last remaining known habitat for these species associations. But they are small and isolated, clearly if ecological principles alone were the arbiter for protecting these areas then their protection may have been ignored.
Some small remnants, which might not be suitable for protection of species that require a large area, such as kokako (Callaeas cinerea wilsoni), are suitable for the protection of smaller, but equally threatened species, such as invertebrates. In this regard the protection of a two and a half hectare remnant near Levin for a giant land snail (Powelliphanta hochstetteri traversii) population is a sufficient size to hold a viable population of this threatened snail species.
Remnant natural areas, isolated from similar, larger protected areas can act as a valuable protection adjunct. They offer security in the event of disturbance to the other protected area, greater chances for genetic diversity and more options for management; for example supply of material for ex-situ population recovery programs.
Threatened species in lowland remnants
Some of the most compelling evidence for the protection of lowland ecosystems is the presence of threatened species. Recent research (Dopson 1999) indicates a high number of threatened species (similar to the critically endangered, endangered and vulnerable categories of de Lange et al. 1999) occur exclusively in lowland areas (Figure 3). The presence of threatened species in lowland remnants indicates protection of small remnants is required to conserve both these species and indigenous biodiversity.
Three species that are protected in a variety of lowland natural ecosystems throughout New Zealand illustrate the importance of protecting a range of lowland habitats. Very few populations of these species occur in large areas. Thus for effective conservation small, isolated remnants need to be protected. The species, which commonly occur together, are Coprosma pedicellata a vulnerable species (Molloy et al. 1999), dwarf musk and heart-leaved kohuhu. They occur from Kaitaia to Southland (Dopson 1999) primarily on margins and in light gaps in alluvial podocarp forest remnants in the east of New Zealand. These habitats have been severely depleted by humans and thus protection of any habitat with these species is a valuable addition to the conservation estate.
The protection of small remnants is vital if we are to conserve a fully representative sample of ecosystems, and as full a complement of species and habitats that remain as possible. Though the theoretical ecological constraints and expense in conserving small remnants are greater than those on larger ones they are surmountable and should be regarded as necessary challenges for conservation planning. For without protection of these areas we resign ourselves to significant depletion of our biodiversity.
Covenants a cost-effective answer to the lowland protection conundrum
There is a raft of protection mechanisms available to protect lowland natural areas. They range from purchase to voluntary protection agreements arranged with various agencies. One type of protection agreement is a contract between a landowner and a local authority or the Department of Conservation. In these contracts certain management principles that both parties can adhere to are agreed upon. They are by their very nature a short-term protection mechanism for they require only the current landowner to adhere to these management principles. If the land is sold to another party the agreement must be re-negotiated. Purchase by an agency (local authority or Department of Conservation) capable of legally protecting (through legislation such as the Reserves Act 1977) is a more secure method of protection. Private groups or individuals are also involved in land purchase for protection. Land may be legally protected using a number of methods (see below) by these groups. Alternatively the ownership of these groups and their rules or constitutions may adequately safeguard the land.
There are obviously large costs involved in purchasing land and while it does provide good security in many situations a covenant can provide an equally binding, secure and more cost-effective means of protecting land, especially in lowland areas. Covenants are legal agreements between a landowner and an organisation (such as the Queen Elizabeth II National Trust, the Department of Conservation and local authorities) with a mandate to protect land. Each has different legislation that enables such protection (Queen Elizabeth II National Trust Act 1977 and the Reserves Act 1977). The covenant is registered on the certificate of title and usually remains in perpetuity. Subsequent landowners are notified of the existence of a covenant by the memorial on the certificate of title and are bound by provisions determined between the original landowner and the organisation. The protection organisation is the perpetual trustee for the landowner in ensuring the provisions of the covenant are upheld by subsequent landowners.
Covenants were recognised early on in their existence in New Zealand for their ability to be an integral part of conservation protection. Open space covenants (QE II National Trust) can protect a wide range of values on land including landscape, scientific, recreational and ecological values. Conservation covenants (Department of Conservation) have a less wide-ranging mandate. Both have mostly been applied to the protection of natural areas rather than for landscapes and other protection purposes.
There are significant benefits to this protection mechanism in lowland areas. Firstly, there is no initial cost in purchasing land; this is in itself very significant in lowland areas, which often have very high land values. Secondly, the ongoing management of small areas, which due to the above ecological reasons can be time consuming and expensive is generally undertaken by the landowners. For most covenanters the reason for entering into a covenant is benevolence or desire to protect in perpetuity something they care greatly for. However, there may be other benefits in covenanting natural areas. For example assistance with the initial cost of new fencing this can be an incentive to fence off natural areas on farms and may also assist with stock management. Local authorities are able to offer rate relief for areas protected in perpetuity.
While covenanting sounds very appealing in terms of efficiency in conservation spending it has to be realised that it is the benevolence of land managers and landowners that are contributing to this conservation. Landowner goodwill is a major feature of the success of covenanting. Many landowners have put significant and measurable financial resources into covenanting land. For example: some landowners have spent upwards of $30 000 on fencing and managing remnants, others forego the ability to use remnants for developments such as housing, high value dairying or for logging high value trees which may more than double the above figure. Not many New Zealanders can boast having put this much into conservation. In the main the costs of this conservation are being disproportionately borne by a few landowners, for the benefit of society as a whole. Some local authorities agree and offer the landowner significant financial assistance in completing covenants. In the main though the community too often ignores the goodwill of landowners instead of supporting and nurturing it. There are obvious benefits to the community through water and soil conservation, biodiversity protection and landscape and ecological enhancement but financial assistance for voluntary protection is increasingly being required by landowners to effect society's objectives. Many feel that the additional expense they go to in order to achieve conservation should be recognised and financial assistance should be offered a genuine partnership formed.
With the recent release of The New Zealand Biodiversity Strategy (Ministry for the Environment and Department of Conservation 2000), there is considerable hope that suitable funding to sustain and increase voluntary protection on private land will be provided. To date a lack of funding has hampered the protection of natural features in lowland areas which as noted above and in the biodiversity strategy itself has the potential to protect important natural areas in the lowland of New Zealand, and in the process help conserve and enhance biodiversity.
While there are considerable challenges in conserving lowland areas the risks of not accepting these and working toward achieving them mean New Zealand's biodiversity is at risk. Using a range of protection mechanisms, but particularly voluntary protection by covenant, conservation planners can achieve significant gains in biodiversity protection. To do this more funding assistance needs to be allocated by central and local government to organisations achieving results in voluntary protection of lowland areas. In this way the imbalance between conservation costs borne by the landowner and the benefits accrued by the community in the current funding regime can be equalised.
The writer wishes to acknowledge the input of Philip Lissaman, QE II National Trust, to earlier drafts of this paper.
Allan, H.H. 1961. Flora of New Zealand Vol I. P.D. Hasselberg, Government Printer, Wellington.
Anon. 1997. State of New Zealand's environment 1997. G.P. Publications. Wellington.
Cobb, J. (ed.) 1992 The living forests of New Zealand. Native Forest Restoration Trust. Bateman, Auckland.
Cameron, E.K., de Lange, P.J., Given, D.R., Johnson, P.N., Ogle, C.C. 1995. New Zealand Botanical Society threatened and local plant lists (1995 revision). New Zealand Botanical Society Newsletter 39: 15-28.
de Lange, P.J., Heenan, P.B., Given, D.R., Norton, D.A., Ogle, C.C., Johnson, P.N. and Cameron, E.K. 1999. Threatened and uncommon plants of New Zealand. New Zealand Journal of Botany 37: 603-628.
Dimond, J.M. 1975. The Island dilemma. Lessons of modern biogeographic studies for the design of nature reserves. Biological Conservation 7: 129-145.
Dopson, S.R. 1999. The conservation requirements of New Zealand's nationally threatened vascular plants. Department of Conservation, Wellington.
Johnson, P.N. & Brook, P.A. 1989. Wetland plants in New Zealand. DSIR Publishing, Wellington.
King, C.M. 1984. Immigrant killers: Introduced predators and the conservation of birds in New Zealand. Oxford University Press. Auckland.
MacArthur, R.H. & Wilson, E.O. 1967 The theory of island biogeography. Princeton University Press, Princeton, New Jersey.
McGlone, M.S. 1989. The Polynesian settlement of New Zealand in relation to environmental and biotic changes. New Zealand Journal of Ecology 12 (Supplement): 115-130.
Ministry for the Environment and Department of Conservation (2000) The New Zealand biodiversity strategy our chance to turn the tide. Ministry for the Environment, Wellington.
Mitchell, N.D., Campbell, G.H. and Cutting, M.L. 1984. Rodney Ecological District. Survey report for the Protected Natural Areas Program. No. 18. Department of Conservation, Auckland.
Molloy, B.P.J., de Lange, P.J. & Clarkson, B.D. 1999. Coprosma pedicellata (Rubiaceae), a new species from New Zealand. New Zealand Journal of Botany 37: 383-397.
Newsome, P.F.J. 1987. The vegetative cover of New Zealand. Water and Soil Miscellaneous Publication No. 112. National Water and Soil Conservation Authority. Wellington.
O'Conner, K.F., Overmars, F.B. & Ralston, M.M. 1990. Land Evaluation for Nature Conservation. Department of Conservation, Wellington.
Park, G.N. 1983. Defining and mapping priority areas for nature conservation in New Zealand The evolution of the scientific base for a national protected areas program. In: Myers, K., Margules, C.R. & Musto, I. (eds) Survey methods for nature conservation: Proceedings of a workshop held at Adelaide University, 31 August - 2 September 1983.
Ravine, D.A. 1995. Manawatu Plains Ecological District. Survey report for the Protected Natural Areas Program. No. 33. Department of Conservation, Wanganui.
Simpson, P. 1982. Ecological regions and districts: a natural subdivision of New Zealand. Biological Resources Centre Publication 1. Wellington.
Townsend, A.J. 1996. Maungaharuru Ecological District. Survey report for the Protected Natural Areas Program. No. 35. Department of Conservation, Napier.
Wilson, C.M. and Given, D.R. 1989. Threatened plants of New Zealand. DSIR Publishing, Wellington.
Royal New Zealand Institute of Horticulture