6 - Ecologically Sustainable forestry in New Zealand

Approximately 25 percent of the earth's terrestrial environment is in forest. While the vast majority of this forestry land is native or semi-natural forests (97 percent), with forestry plantations comprising only 3 percent, much of the native or semi-natural forest is managed, thus up to 20 percent of the terrestrial area is in managed forests. As much of the world's biodiversity is contained within the forest ecosystem125 any decline in the global biodiversity126 becomes or is a forestry issue. All forest areas from protected forest areas to semi-natural management forests, and plantation forests have a role in forest biodiversity and conservation. Therefore, all forests should be managed on an ecologically sustainable way at least to maintain present forest biodiversity levels. There is difference between ecological sustainability and other interpretations.

6.1 - Sustainable forest management - an introduction

Sustainable Forest Management is one of the keys necessary to reach sustainable use of forest biological diversity, but when we talk about "sustainability" in the forestry sense we need to be careful with what we mean. Sustainability in managed forests in the past was often based on the sustainability of a "yield" of production or profit. However, sustainable forestry management should be thought of as at least the management of forests for multiple uses, in such a way that future generations will have access to at least the same assets as those available today127.

Ecosystem management of forests goes even further in being primarily concerned with maintaining all ecosystem processes, whether they are of direct benefit to people or not. This wider concern differentiates sustainable yield from sustainable management. Thus sustainability is not only related to production or profit but also the sustainability of the ecosystem(s) and the biodiversity contained within it.

The underpinning processes that influence forest biological diversity are more or less common to all forest biomes. These factors include historical events (e.g., glaciation, earthquakes), niche space, forest productivity (which is related to climate, soils, and available water), extent of forest, forest fragmentation, forest landscape heterogeneity, and species interactions. Within forests, not all available habitat is necessarily occupied. Habitat suitability within the forest landscape differs for any given species depending on the size of the habitat, presence of required structures (e.g. snags, dead spar, roost holes), plant species composition (e.g. availability of fruit and nectar species for birds), age, and isolation from other patches. Many species respond at the landscape structure level, rather than stand or compartment level. While many forests are managed well at the stand/compartment level it is the distribution of forests across the landscape that has implications for maintaining biological diversity.

An essential part of this landscape planning includes mapping the key areas for biota, identifying landscape and cultural values, maintaining and/or including ecological corridors and stepping stones for the biota, and maintaining representative structural characteristics of forests through simulating natural dynamics. Therefore, any successful management of these forest ecosystems and their biodiversity will require a thorough understanding of the complexity of interactions between forest management, the forest ecosystem and landscape functioning.

Forestry Practices

The economic pressure to simplify a forest ecosystem in order to increase yield and reduce operational cost can be at odds with practices designed to facilitate biodiversity128. Forestry can negatively impact on forest biodiversity through management practices such as large scale clear-cutting in areas without natural large scale disturbances, use of inappropriate species, removal of important forest structures such as dead and decaying wood, destruction of key habitats, and drainage of natural wetlands. The replacement of natural and semi-natural forests by monospecific and even-aged plantations also impinges on forest biodiversity. Thus improper management for timber production carries with it a risk of extinction of local endemics and those species particularly vulnerable to physical disruption of their habitats129.

6.2 - Forest landscapes

Fragmentation

Forest fragmentation looms as one of the major threats to forest biodiversity. According to the theory of island biogeography130, when an area loses a proportion of its original habitat, especially if the remnants are in fragmented patches, then it will eventually lose some of its species. Surprisingly, forest fragmentation can also lead to an increase in species-richness of those species that have the biological attributes enabling them to adapt to modified remnant forest fragments, including forest/cleared land ecotones. These generalists include pioneer and secondary tree species, omnivorous bird species and, in the case of New Zealand, small mammalian predators. This appearance of increased species richness is potentially achieved at the expense of forest interior specialists.

While fragmentation increases ecosystem vulnerability to such invasive generalist species additional impacts can also occur from fertiliser and herbicide drift from agricultural land. Micro-climate changes can also occur resulting in localised extinctions of vulnerable species. Forestry practices such as harvesting and logging roads, cause fragmentation. Roading introduces corridors that promote the introduction of invasive plants, insects and animals131, in addition to fragmenting the natural habitat for wildlife and modifying the drainage pattern.

Scale

Forest ecological studies suffer from a major problem. Generally these studies are conducted at limited temporal and spatial scale132. If forest biodiversity must be managed at the appropriate scale, then research and monitoring must also be at that appropriate scale. Practical considerations, rather than environmental or ecological reasoning direct the scale of these studies 133. Research, for example, has been based at the immediate before and after effects of stand/compartment harvesting on single bird species (for example, kiwi)134, stream inputs135, and aquatic wildlife136.

For exotic plantation forestry, in fact for any land use, the effect of management practices on biodiversity may be applicable over a longer temporal scale than the rotation duration. From another perspective, immediate adverse effects may not be long lasting or require intervention137. In addition, the effects may occur over wider spatial scale, such as the whole forest, catchment or landscape and not just within the stand being managed.

The typical study correlates abundance with forestry management practices. These studies usually last up to 2 years, looking at the immediate before and after effects of management practices such as harvesting on avifauna abundance, the effects of woody inputs on macro invertebrates and/or aquatic fish life. These studies also use between 1 and 3 replicates and tend to be at a limited spatial scale i.e. over a stand or compartment and not through the landscape or watershed.

Similarly, in New Zealand many plantation studies focus on the immediate before and after effects of forestry harvesting operations on such things as species, the woody debris within streams, or avifauna. Overseas studies would suggest that the effects of harvesting (at least) can cause changes in wetland that persist for up to 15 years or more138. For example, the regeneration capacity of bird communities within logged compartments was studied for 23 years in the Uganda139. Here it was found that while many of the original interior birds had re-colonised or persisted in the logged forest over 14 percent of the original forest species were missing. Other long-term studies have found varying results to the regeneration capacity of bird communities. Wong (1985) found that bird communities in logged indigenous forest were similar to communities in primary forest after 25 years, while in other studies forest birds communities failed to recover fully140.

It is surmised that different ecological and environmental factors operating on individual species makes their vulnerability to logging vary. Some of the important factors are species-specific habitat requirements, dietary specialisation and manoeuvrability141. This suggests that to safeguard against loss of biodiversity, the retention of a mosaic of primary forest patches is needed. This ties in with the other research and would be a good study for New Zealand to pursue, as we know that some species such as the mohua142 are restricted to primary forest.

Overseas there have been some avifaunal studies relating forest management practices to the species studied143 and conducted at the appropriate scale144, but such studies are sadly lacking in New Zealand. Monitoring at the wrong scale may be as dangerous as monitoring the wrong species.

There is confusion of the literature concerning the process of monitoring biodiversity within the forest ecosystems. Much of so called monitoring in the past has been either an inventory checklist of species present within forest type145, a comparison between species in two different types of forest or monitoring of the effects of a forestry practice on a species or species assemblage146. Real monitoring refers to the collection of data over time, while assessment or inventory is the compiling of data on aspects of the biological diversity chosen to monitor. While inventories are important, especially where the distribution of species within an ecosystem or ecosystems is unknown, they do not take the place of monitoring. While the monitoring of the effects of forestry practices on species is important in many cases such monitoring occurs only during the immediate before and after disturbance. Good monitoring programmes are sparse in overseas studies also147.

An example of choosing an inappropriate ecological scale can be seen in monitoring the effects of forestry practices on freshwater fish species. Exotic forest management practices have the potential to adversely affect indigenous fish populations through the loss of stream bank vegetation, changes in fish passage, contamination of the waterways and increased sedimentation148. Therefore, monitoring the effects of exotic logging practices on native stream fauna is important.

Overseas stream habitat indices or indices of biotic integrity (IBI) have been used to monitor the effects of landuse on fish species and fish communities. IBIs have been used to evaluate stream restoration following catastrophic events149 as well as the effects of different landuse on stream communities150. While IBIs can be based on fish community structure such as species richness, disease incidence and fish biomass, they can also be used at the population level.

Although this approach is practical, the uniqueness of our fish fauna makes this IBI method problematical in New Zealand. Over 70 percent of the fish fauna in New Zealand, including the rare short-jawed kokopu, migrate between the marine and freshwater environments151. The expected relationship between fish abundance and habitat quality will breakdown where there are high proportions of migratory species 152 because downstream difficulties in fish passage excludes some species from available habitat. New Zealand fish abundance may differ amongst upland streams in ways unrelated to the quality of the local habitat. By looking at the stand/compartment scale and not the total landscape or catchment, the effects of tree harvesting on fish abundance would not be determinable because downstream effects have the dominating influence.

Habitat Matrix

The importance of the landscape level approach is also supported in research here and overseas when we look at the complexity of species habitat relationships. Research overseas has shown that for some vertebrate species multiple habitats are required to provide the different resources needed at different parts in their life cycle153. For these species any one habitat is not diverse enough to provide them with all of their needs.

Bats in Australia use a mosaic of habitats such as agricultural land, indigenous remnants and pine plantations during their life cycle154. The ability to move between these habitats is important, especially where fragmentation is increasing. Although the management of single habitats, such as plantation forests or indigenous fragments is important for biodiversity conservation, in certain circumstances it is the conservation of habitat patches and the context in which they appear within the overall landscape that may be more important155.

Such patterns of habitat mosaic use are thought to occur in New Zealand's fauna. It is known that short tailed156 and long tailed bats157 forage and move across different habitats. Kereru 158 and kaka also move around different habitats, including seasonal forays into pine plantations159. But the extent to which mosaics of habitat are used and which habitats are important is unknown at present.

Island biogeography and Edge effects

Research into the effect of edges on forest ecosystems and their biodiversity is important. The penetration of effects from ecosystems bordering forests can determine the flora and fauna species composition within the forest160. Edge effects can also determine the limiting size and shape of a remnant161.

In New Zealand there have been several studies on the effects of edges on forest processes162. Habitat generalists can cope with small patches because they can use the surrounding habitats for resources that are absent or scarce in the fragmented forest163. As discussed above this can lead to an increase in the biodiversity across habitats within the landscape, due to new generalist species entering these new habitats at the expense of forest interior species. The size of forestry blocks is therefore important for biodiversity to ensure both edge and interior habitats.

Another important aspect of island biogeography theory as suggested by MacArthur and Wilson (1967) is the species area/relationship. It is suggested that as island area decreases so does the number of species. Therefore when considering conservation of biodiversity, the bigger the forested area conserved or managed, then the more species that are contained within it. Many forest management protocols suggest that protection of the largest area is best. This can be seen in New Zealand where many environmental forest management protocols suggest that the largest streams within the forest should be protected by the widest riparian buffers. While this in itself does not constitute a problem, it is the extrapolation of this design which suggest that smaller streams therefore need little if any riparian protection as few species will be present within them. However, many of the smaller streams in New Zealand are important habitat for endangered fish species. This illustrates an international debate on the relevance of island biogeographic theory to reserve design. Habitat quality and heterogeneity may be more important for biodiversity than reserve size per se.

Optimal design of wildlife corridors should also consider the specific requirements of particular species. In the past corridor widths have been based on the minimum size being proportional to the home range of a species164. A research programme for the conservation of Leadbetters possum in Australia 165 found that many of the habitats were not being used even though there was ample connectivity between them and the habitat was suitable for the species166. From these studies it was found that such characteristics as social structure, foraging patterns, site context and connectivity all determined the size and shape of appropriate corridors. In the case of the Leadbetters possum, while the corridors were in theory wide enough based on the home range of the species they were in fact too thin to meet the social behavioural characteristics of this species.

There is general support for the use of corridors, but as yet there is little data on their effectiveness and no scientific guidelines to assist in the evaluation and design of such corridors. In New Zealand the research is even further behind. We have not begun to look at the idea of corridor design within forest systems.

Reserves

It is not always possible to maintain all of the characteristics of a natural forest landscape and forest structure, within managed forests. For this reason, the foundation of nature reserves is important167. These areas also provide scientific 'benchmarks' against which to measure progress towards sustainability in forest management. Protected forest areas are of special interest, because their primary aim is the conservation of forest biodiversity. These areas however, should be managed in context168 with the surrounding landscape169 and not as static entities. Research into the context aspects of landscape and forest biodiversity has not been extensively examined in New Zealand.

Biological diversity conservation is sometimes directed solely on individual species conservation170. The problems with taking such a wholly single-species approach has been well documented171. Nevertheless, such a 'hot spot' approach will continue to play a role in conservation of forest biological diversity, especially in New Zealand where high rates of endangerment of endemics is an urgent priority..

Restoration of Degraded Habitats

Restoration of degraded forest can make a substantial contribution to the conservation of forest biodiversity. There is increasing evidence that forest plantations can play a key role in enabling long-term forest ecosystem rehabilitation172. Studies have shown that under certain conditions, forest plantations significantly accelerate natural successional processes by attracting increased seed inputs from nearby native forests and overcoming barriers to natural regeneration. Silvicultural management aimed at allowing woody understorey vegetation encourages the monospecific plantation system to be replaced by mixed forest comprised of the planted species with an increasing number of early and late successional tree species and understorey plants from nearby forest areas173. Eventually the planted species may be harvested or allowed to die-out (short-lived, light demanding pioneers), leaving a floristically-rich secondary forest.

The potential role of plantations in forest restoration in New Zealand has not been fully realised. Often the approach taken in restoration is to remove all introduced elements including those species that are not locally indigenous. Such practices do not look at the ecological functions these species may provide, or the protection obtained from cover species. One example is the question of appropriateness of using an indigenous species in restoration processes - or one that was not locally indigenous, at least in recent times (Olearia paniculata) 174.

Importance of Restoring Underlying Function on which Structure and Composition Depend

Overseas studies have suggested that even if you try to restore agricultural land back into forest through protection from grazing175 and forest management176, natural forest structure may still be lacking. In the Australian study177 the critical issue was the lack of disturbance and loss of biotic interaction from the land that sustain woodlands. While reforesting agricultural lands in USA even after 50 years the stands were monocultures due to the lack of natural dispersal.

In New Zealand 178 it has also been found that restoration must go beyond the reconstruction of structural composition and site appearance179 and include the restoration of biological interactions and processes180. Without the ecosystem functions that underpin forest structure - such as seed pollination and set, seed dispersal and seedling establishment - then an artificial restoration of structure alone is destined to either fail or require continual intensive inputs until the key ecological functions are restored181.

The importance of frugivorous birds for seed dispersal in the New Zealand forest ecosystems is well documented182. Many of our indigenous plants with fleshy fruits depend on these birds. Restoring conditions that attract these birds is therefore a key objective of restoration. Planting fruit bearing plants is one option that could assist plant colonisation and establishment via birds183, however the provision of perches and nesting areas - and the proximity of seed sources from which colonisation can be sourced - may be just as important184.

6.3 - Practices to maintain biodiversity

New Zealand's Uniqueness

As overseas, past forestry practices in New Zealand have threatened bird numbers by removing habitat, fragmenting the landscape and causing an increase in edge habitat compared to cores185. But the factors causing initial declines in biodiversity are not necessarily the main threats now. Ongoing declines for some species are occurring even where habitats remain unchanged testify to the dominating restructuring force of the introduced predators and competitors.

Other important differences between New Zealand and overseas can be seen in some of the effects of plantation forests on stream communities. Overseas, the threat of increased acidification in streams186 is an important adverse effect caused by native vegetation being replaced by coniferous plantations. This threat does not appear to be the case in New Zealand. In a study in South Island streams, pH did not differ for coniferous or native forest streams, both of which are dominated by acid litter plants. It is possible that there is a lack of acid precipitation and therefore a lack of opportunity for exotic forests to exacerbate the problem187. There is also less acidification through soil inputs here as compared to say Denmark and this may be caused by the differences in soil type as well as conifer type. In addition, plantation forestry in New Zealand tends to be less dense than plantation practices overseas 188. Other vegetation beneath the forest canopy, as well as riparian buffer strips, may have some mitigating effects on acid inputs.

New Zealand Forestry History - a Dominance of Plantation Forests for Timber Production

Before human settlement, New Zealand was largely a forested environment with approximately 85 percent of the total land-mass in forest189. Since human colonisation almost two thirds of this forest cover has been removed, with about half of this forest removal occurring in the last 150 years190. Clearing of forests during this one and half centuries tended to be for agricultural purposes and to provide timber for the new settlements. As a result of this deforestation, presently less than a third of New Zealand is forested, of this 78 percent is in indigenous forest while 22 percent is plantation191. Of the indigenous forest about 1.6 million hectares or 20 percent is privately owned and half of this is potentially available for production. In New Zealand 80 percent of the privately owned indigenous forest resource is in beech forest192 while 90 percent of the exotic plantation forestry is dominated by one species, i.e. Pinus radiata193.

Management of Indigenous Forests in New Zealand - The lack of Adaptive Management and Essential Functional Knowledge

Management of indigenous forests is covered by the Forests Act 1949. This act was amended in 1993 (Forest Amendment Act 1993) to include the provisions for sustainable management of indigenous forests on private land. The amendment became Part III of the Forests Act. The aim of the Forests Act is to "promote the sustainable forest management of native forest land" (Section 67B) where sustainable forestry management is defined as "...the management of an area of forest land in a way that maintains the ability of a forest growing on that land to continue to provide a full range of products and amenities in perpetuity while retaining the forest's natural value" (Section 2).

Legislatively the indigenous forests (though this does not include DoC and SILNA lands) are required to be managed sustainably if timber is harvested. Although the Indigenous Forestry Unit of MAF is required to monitor the plans and permits of the private forest owners194, there is neither the resourcing, nor adequate provision in the Act for scientifically robust ecological monitoring to take place within the forests. Nor is there any provision within the Act for any adaptive management framework, as emphasised by the CBD Ecosystem Approach.

This lack of monitoring seriously impinges on the ecological and management knowledge required for ecologically sustainable forestry. In a recent proposal for operational research by the Indigenous Forestry Unit the comment was made that the ecological and management knowledge of indigenous forest was insufficient to provide ecologically sustainable management195.

Within New Zealand sustainable plantation forestry could face the same charge levied against indigenous forestry (insufficient knowledge), as could all land use - including the conservation estate. Knowledge of ecological composition, structure and function across various landscape scales of space and time, as well as adaptive management learning processes, are critical to sustainability. This is a point also emphasised in a recent analysis of the state of knowledge relating to biodiversity in plantation forests196, whose finding relate to our own.

Forest management should protect, maintain and/or restore the structure and function of the natural process of forest ecosystems and its components within the appropriate landscape and time scales. Managers need to monitor and analyse the forest health and use predictive models that enables them to assess risks. Long-term data is vital for the understanding of forest changes, functioning and its potential behaviour under changing environmental conditions. Only in this way can forests be sustainably managed and the forest biodiversity within them maintained197.

In New Zealand forestry there have been few long-term monitoring programmes in place to quantify recent trends in biodiversity in New Zealand forests. The perception that species are sliding further towards the "extinction vortex"198 comes from shrinking distributions and anecdotal reports that wildlife abundance was much higher at the end of nineteenth century.

Indigenous and Exotic Forestry - A False Dichotomy

While overseas natural, semi-natural and plantation forests are seen as a continuum and all potentially used by humans for resources and containing elements of important biodiversity , in New Zealand we tend to view our forests as either indigenous and 'natural' and not managed, or plantation and 'exotic' and managed. This does not mean that in reality such a dichotomy exists and both indigenous and exotic forests have been and are being managed. The perceived dichotomy between indigenous and exotic forests has also lead historically to a mind-set that has thought of plantation forests as being biological deserts. As a result, conservation management has been almost entirely concentrated on indigenous forest within New Zealand.

Contrary to perceived ideas, exotic forests are not deserts in the biological sense, and are potentially valuable habitats for native avifaunal, invertebrate and floral biodiversity199. Insectivorous and omnivore birds inhabit these plantation forests because they harbour abundant insect life, and because competing insectivores that need holes in trees for nesting or have a high proportion of fruit in their diet are absent200. Enclaves of indigenous forest within exotic plantation potentially create ecotones with particularly high biodiversity values.

Therefore we must realise that biodiversity is not confined to any one human-made forest categorisation, and must be considered within a landscape context. Thus, any biodiversity issues globally and within New Zealand must take into account both indigenous forests and exotic plantations.

New Zealand forest ecosystems comprise protected natural indigenous forest, highly managed exotic plantation forest and managed indigenous forest. However, past research has tended to avoid the role of exotic forestry in biodiversity. Of the research into biodiversity within plantation forests that has occurred, most has been directed towards the effects of management practices on biodiversity. This research has also been directed towards relatively simple assessment of particular stands under particular conditions rather than the role forest management can play in sustaining biodiversity across the total landscape, or even the entire forest.

Similarly research into the biodiversity values of managed indigenous forests has generally avoided these broader sustainable management perspectives. The exception to this, until very recently, was the proposed "Sustainable Management of Beech Forests" by Timberlands West Coast201.

With the demise of this beech scheme much of the innovative ecosystem management approaches to indigenous forestry have faltered. In a recent (1999) forum202 on the use of indigenous forestry, the sustainable management of these forests for biodiversity values was not specifically addressed. Where sustainability was mentioned it was in respect to the sustainability of productive yield. Yet there has been some recent movement towards the ecosystem management of indigenous forests for biodiversity. In a symposium on sustainable management of indigenous forest203 several issues including the use of invertebrates as indicator species for sustainability204, the process of disturbance in natural systems205 and the matching of silvicultural practices to mimic natural processes within beech206 were addressed. This is not to say that "monitoring" such effects is not important, but by performing research in this way we have tended to look at immediate answers, or, at best, answers at a small scale. This approach is not always appropriate to the range of issues related to biodiversity.

Forest Management Practices to meet New Zealand Conditions

A number of forestry environmental management practices are already well established in the New Zealand forestry sector. However, these mainly address such concerns as soil and water conservation issues relating to operations such as roads and machinery operations. For instance, use of cut-offs, flumes and water tables when constructing roads can control runoff and reduce sediment inputs direct to water bodies. Operational standards used by forestry companies also ensure that road construction and maintenance are timed to avoid stream disturbance during fish spawning seasons.

Although the use of such environmental management systems is a good start and the forestry sector seems to be some way ahead of its agricultural counterparts at least in the industry environmental management systems, there are some fundamental flaws in the Streamside Management Protocols. One problem arises from the use of fish passages wherever roading interferes with waterways. While overseas research indicates the use of fish passages within streams are essential207 this is not always the case in New Zealand. In New Zealand, introduced species can impact on the distribution of native fish208 , therefore it is very important that the appropriate culverts/fish passages are used to ensure introduced species are kept restricted in their range, while climbing native species (e.g. eels, kokopu) have passage upstream209. Monitoring the effects of fish passage structure in New Zealand forests on indigenous stream life has not been researched.

Another conceptual problem not always addressed in New Zealand, is the importance of small streams. Again overseas the trend has been to concentrate on large streams and rivers for conservation concern210. This has given rise to the idea that small streams are unimportant, or of low priority. In New Zealand the case can be very different with many small streams providing important habitat both for native fish species211 and for invertebrates212. Therefore any monitoring and management programmes in New Zealand needs to take into consideration important representative habitat streams regardless of size.

In New Zealand relatively little research has been done on the effects of plantation logging practices on native stream fauna. What research there has been has tended to show varying trends. Comparisons between fish populations and fish communities in exotic and indigenous forest ecosystems have shown these fish assemblages to be similar213. Even within pristine indigenous ecosystems, fish communities can be similar to fish communities within modified ecosystems throughout New Zealand214.

Riparian Research in New Zealand

One of the most effective ways for protecting these streams and streams of all sizes is the use of 'riparian buffers'. Riparian buffers are defined as the natural vegetated terrestrial areas boarding streams and rivers215.

The positive functions of riparian areas in forestry relate particularly to water quality and soil conservation and ecological effects within streams. However, riparian areas also provide for useful corridors for wildlife, provide food for aquatic and terrestrial biodiversity, and are often associated with a different species composition than might occur elsewhere in the forest. Their most documented role is in the protection of streams from overland flow of pollutants from farmland and for their role in reducing sedimentation and stream damage due to forestry harvesting and roading.

Riparian management strategies in managed forests based on research and field trials are not yet well developed in either New Zealand or overseas216. Where it is available, its emphasis tends to be based on the short-term soil conservation and water quality effects, rather than the relationships with terrestrial and aquatic biodiversity.

The most comprehensive review within New Zealand was the report published by NIWA involving a review of forest harvesting and riparian management217. It addresses many of these issues. The other important source documents are the 1995 reports produced by NIWA and the Department of Conservation218.

While the use of riparian buffers for stream protection is largely acceptable219, deciding which streams need protection and how wide riparian strips ought to be is more contentious. These factors can be dependent upon the species affected220, with one configuration suiting one species, while not another.

Overseas, riparian area widths have been researched in relation to forestry operations221. In many of these studies widths of less than 30 metres did not provide significant protection from logging operations for biodiversity values 222, while strips 30-100 metres wide provided adequate protection223. Generally codes of practice for forestry base their width and management specifications of buffer strips on stream size and catchment size224. On the one hand, the more and larger the riparian buffers used the less likely there will be an effect on stream fauna, while on the other hand this approach would severely limit any potential exotic harvesting operation in areas such as the West Coast of the South Island. Therefore, the use and size of riparian buffers needs to be a compromise between the expectations of stakeholders and take into consideration the representative value of the stream, and likely effects of forestry operations on stream fauna.

Practices to improve biodiversity within forests

In the United Kingdom research was undertaken to enhance forest biodiversity in plantations without affecting productivity225. This research was based on a reference database that examined ways of restoring and maintaining biodiversity levels. From this, several proposals were formulated that would meet the required biodiversity levels without curtailing productivity. These included:

  • the provision of open space habitat,
  • the increase in tree species richness,
  • the retention of dead and dying trees,
  • maintaining stands of old growth forest,
  • establishing riparian zones with indigenous vegetation,
  • the management of understorey vegetation and
  • the implementation of wildlife resources such as nest boxes.

A comprehensive guideline for forestry management for biodiversity is available on-line as one of the resources produced by the Fundy Model Forest which elaborates the concepts above in more detail226.

It is possible that such a management approach could be used in New Zealand both for plantation forests and managed indigenous forests, though, at present some incentives may be lacking227.

Forest Codes of Practices and Guidelines

Codes of logging practice have been developed228 along with guidelines for reduced impact logging in different forest types and conserving biological diversity229. These codes, in the case of indigenous forests try to use management methods that mimic natural disturbances regimes. The use of local and site adapted species, increased complexity in the forest stands through use of species diversity, diverse ages and structures, maintenance of important micro-structures such as dead and decaying wood, protection of key habitats, limited use of pesticides and fertilisers and appropriate drainage management are also used to reduce logging impacts230.

Similarly for plantation forests there are guidelines (codes of practice) that list the possible adverse impacts of production forests on especially erosion, excess run-off and increased sedimentation to watercourses, compaction of soils and chemicals entering the water cycle. The codes of practice also note the potential scientific and ecological values within plantation forests that should be valued.

These codes of practice are used by forestry management to meet their local and regional regulations as well as meeting "good neighbour" obligations, whilst to some extent promoting forest biodiversity and sustainable forestry. Forest companies now potentially have economic incentives based on sustainable management of their forests. One such incentive available to forest managers overseas and gaining momentum in New Zealand forestry is the concept of forest certification.

Forest Certification

Certification schemes can play an important role in sustainable forestry management. The main aim of certification schemes is to provide stakeholders and consumers with a guarantee that the forest products they buy originate from forests that are managed according to sustainable forestry management agreed standards. This allows "green labelling" of forest products.

For such schemes to be financially successful the costs involved in meeting forest certification commitments must be met by the consumer's willingness to pay a premium for certified wood above the cost of wood products from uncertified forests. There is some evidence from overseas suggesting that consumers are willing to pay for certified timber231. However, the real benefit of certification for the forestry industry, especially in New Zealand, is likely to be access to markets that would otherwise be closed to them232.

The Forest Stewardship Council (FSC) is an independent, non-profit, non-governmental organisation founded in 1993 offering an international timber certification scheme for all forest types and plantations. The FSC is committed to environmentally appropriate, socially beneficial and economically viable forest management. Its aims are endorsed by leading environmental organisations, including WWF, Friends of the Earth and Greenpeace.

6.4 - Monitoring versus assessment

In many cases there is an inadequate knowledge of natural and managed ecosystems (their components, structure and functioning). These gaps in knowledge arise from an insufficient research effort in the study and monitoring of forest ecosystems. Such research is necessary to better understand how various components interact and where to execute appropriate changes in ecosystem use.

As described above, the concept of sustainability commonly associated with forestry practices is based mainly on the sustainability of production and profit, and not towards sustainability of the ecosystem(s) and the biodiversity. This profit and production view of sustainability is part of the New Zealand's plantation forestry sector thinking. To meet CBD recommendations, forestry practices must take into account forest biodiversity quantified at different scales. These scales include assessing the genetic diversity within species, the number of species per area (e.g. local, regional, national, continental, global), classifying amounts and types of forest ecosystems, determining communities of species associated with forest ecosystems and determining numbers and arrangement of forest types and ages. Forest management methods need to focus on 'ecosystem management' to cover such a scalar approach. To even begin to apply this approach we need data to show the effects and trends instigated by forest management practices on forest biodiversity. To ensure that biological diversity is maintained in time and over space we need to assess and monitor what is happening. Using this approach forest management programmes should be regularly modified, or adapted, based on results of monitoring programs. Thus monitoring programs are an important component of the sustainable management of forests.

Assessment or inventory is the compiling of data on aspects of the biological diversity chosen to monitor, while monitoring refers to the collection of data over time. Monitoring is an important component in any forest management programme and especially in the conservation of forest biodiversity. To begin monitoring, first you need an understanding of the distribution of the element(s) to be monitored and their initial baseline conditions. This understanding is obtained from assessment or inventory data. Depending on the technical ability and the state of knowledge gained from assessment data, forest types (area), forest ecosystems (area, age classes), landscape structure (patch sizes, associated selected variables), species (indicators, endangered species, key species), and genetic diversity (useful species, endangered species) can be monitored.

Forest biodiversity assessment acquired from stratified biological surveys can be used in combination with other data sources, such as remote sensing information, and maps/GIS of environmental data (climate, soils, geology, topography, land use) to generate a more complete picture of biodiversity. In detailed inventories of some areas, environmental information and precise species distribution data can be combined with forest maps to map the distribution of particular species and/or predict where species, both flora and fauna, are likely to occur. These data can then be combined to identify priority areas for conservation (e.g. Uganda233; Australia234; India235). While inventory and monitoring of biodiversity should be undertaken at various levels (ecosystem, species and gene), so far much of the effort overseas, except for those named above and within New Zealand, has focused on species assessments or checklists.

Indicator Species

Ideally monitoring programmes should take into account all aspects of the biodiversity that are likely to be affected by forestry management practices. But to examine the effects of these forest management practices is not always practically possible. In many cases we have incomplete species knowledge, difficulties in selecting aspects to monitor, lack of classifications of local ecosystems, logistical and cost considerations. Further, even when a species is identified, considerable work remains to determine its range, habitat requirements, and relative priority for conservation. Therefore based solely on pragmatic considerations, management of biological systems may be simplified and made more cost-effective by considering only a small group of indicator species, as surrogates for the complete system236.

The concept of an 'indicator species', is one of a species that is associated highly with a specific habitat type and can be monitored to determine the possible reaction of the species to changes in this habitat type. Moreover, if this species is associated positively with a number of other species, then one may assume that habitat needs of the other species are also being met. In the case of monitoring of species, it is important to carefully and systematically select species that can indicate sustainable use and forest change.

There is some controversy in using this system with the general consensus that no species is likely to be a wholly satisfactory indicator of the viability of other species. However, this does not say that some species do not provide an indication of the status of some portion of the forest system237. This is one reason why some overseas agencies prefer to use the term 'focal species'238.

Tree species diversity can also be a useful surrogate for overall species diversity in most forest ecosystems. It is particularly relevant in some native forest ecosystems, where many animal and fungal species are obligate associates of particular tree species (e.g. mistletoe in New Zealand), given well-developed methodologies for inventorying forest tree species239.

If forest processes are altered, then the structure of animal communities will probably be affected. It often makes sense to examine species assemblages as indicators, rather than trying to monitor all species present. For many taxa of species, animals or plants, all (or most) species in an area may be sampled simultaneously, for example many bird species can be counted during bird counts240. Therefore, many of these data sets lend themselves to community analyses. In production forests structure-based indicators such as stand and landscape level features of forests, structural complexity and plant species composition, connectivity and heterogeneity are potentially useful for monitoring biodiversity241.

Many techniques exist for monitoring species and communities of plants and animals. Regardless of method, methods should be consistent among surveys and observers to enable comparisons among years and locations. Surveys must also be properly designed to allow proper data analysis and valid results. Monitoring should also be conducted to test hypotheses that relate to change in forest capability to support biological diversity.

6.5 - Motivation for forest management change

Forestry environmental management has changed dramatically over the last twenty years. Operations which were common place - such as burning, the physical removal of topsoil pre-establishment, harvesting without regard to the stream system or the soil health of the stand - are now a significantly smaller proportion of the landscape. This is especially the case in larger companies, whose resources allow them to put in place environmental management systems. Smaller forest owners must usually rely on the professional standards of consultants to maintain environment performance.

However, much of this improvement in operational management - though providing benefits to biodiversity - was directed at soil and water values, and was related to operational standards of operations within compartments. Biodiversity in forests is relatively good when compared to more intensive land uses, and the perspective has usually been that what is currently occurring is "good enough".

For forestry companies, the motivation to improve environmental performance to cater for landscape issues specifically related to ecosystem function and biodiversity may come from many sources. The most likely motivators are those where there is a direct interest in the change - either through a change in personal values, or to the value a market or society decides to place on management. Simply appreciating a forest's "health" as dependent on a full range of ecosystem functions - rather than just wood quality - may be enough. This represents a solution through the development of a land ethic, perhaps the strongest motivation of all in the long term because it involves the simple feeling of what is "right" or "good" management.

Perhaps the strongest potential driver for a landscape level approach to forestry management down to a stand level is the certification Principles and Criteria which all certified forests must comply with. This is having an immediate impact, at least in the short term. Criteria six of the Forest Stewardship Council relates to biodiversity at a landscape scale242. The Montreal Process has similar criteria243.

One other motivator for a landscape approach to harvesting pattern could be the rise in public understanding that could result from a more fragmented and obviously worked landscape. At present the change in land use from pasture to forest, and then forest to clearfell site across a broad scale can be too much for their senses to reconcile. As a result, they object. A more fragmented landscape does not represent such a scale of change because it is ongoing. The reality of a constant change at a reduced scale is more acceptable.

The final important point that contributes to spatial heterogeneity within a forest is management that incorporates different species, and different management regimes relative to microsite, because of strategic marketing and management. This is a trend in New Zealand forestry at present, with a range of species being considered. The effect over time is a heterogeneous pattern, as occurs in some of the older forest whose inception was based on a similar philosophy (Flagstaff and Ross Creek in Dunedin, Whakarewarewa in Rotorua, Hanmer in Canterbury, and the Tapanui forests of West Otago). These are rich and ecologically healthy forests from a biodiversity point of view.

6.6 - What is missing from New Zealand forestry research?

The main missing research focus here is determination of appropriate spatial and temporal scales for forestry management and monitoring. Ideally we should be managing our forests on a spatial scale that relates to the total landscape and across a temporal scale that is relevant at least to the forest ecosystem. In contrast, much of our research is based at the stand or species level whereas, ideally, it should be investigating the ecological processes across the landscape. A major component in this exclusion is the lack of knowledge of the basic ecology of our native species. Tied in with this is the dearth of knowledge of where our biodiversity is at present: how much there is; and how we can best monitor it.

Forestry research gaps

Forestry research gaps include research within the following areas:

  1. Development of an inventory methodology to assess the biodiversity within plantation and indigenous forests.

This inventory data can be used in combination with other data sources, such as remote sensing information, and maps/GIS of environmental data (climate, soils, geology, topography, land use) to generate a more complete picture of biodiversity.

  1. Monitoring forest biodiversity at the landscape level and appropriate temporal level using the inventory data collected in point 1
  2. Identification of 'umbrella' assemblages that can be used to indicate forest health244 within indigenous and plantation forests.

To monitor all the species within a forest can be logistically impossible, but the adoption of subsets of appropriate 'indicator assemblages' can save both time and money. Research on suitable forest (indigenous and plantation) health 'indicator species' is occurring245 but more emphasis is required in this area in order to understand the main ecological drivers affecting biodiversity. These tools are essential to enable managers to predict the effects of forestry practices on the ecosystem as a whole.

  1. The role of plantation forests in the conservation of indigenous biodiversity.

Plantation forests have been described in the past as biological deserts, but initial research in New Zealand would suggest that this is not the case. Plantation forestry here and overseas is increasing, therefore, it is important that their role in conserving biodiversity is investigated, particularly in relation to the wider landscape.

  1. The use of plantation forests by native avifauna and their requirements for enhancement.

Research suggests that indigenous understorey vegetation is important for native avifauna to occupy niche space within plantations. Old forest growth, indigenous remnants, retention of dead spars, snags and holed trees are also potentially important for native avifaunal biodiversity. Overseas enhancement through artificial nest, perch and roost habitat have been used to "entice" native bird biodiversity into plantation forest ecosystems. In New Zealand we do not know the significance or importance of these 'enhancements' for native biodiversity within plantation forests.

  1. The role of island biogeographical relationships within forests: such as edge effects, corridor size and shape, indigenous remnants and/or plantation forests as islands and/or stepping stones for native biodiversity, the effect of shape, size and complexity within New Zealand's ecosystems is unknown.

Forests are just part of the overall landscape and potentially act as islands for biodiversity on the one scale. Forests also contain islands within them, for example, riparian areas, remnant indigenous forest and gaps. At both scales these islands may be potentially important but research is lacking both here and overseas.

  1. Developing a monitoring system to monitor the effects of forestry practices on native fish species accounting for the difficulty involved with the high proportion of migratory fish species.

Much of the focus of harvesting practices is directed at the effect on aquatic wildlife, in many cases, native fish. A very high proportion of New Zealand's native fish fauna are migratory and thus downstream effects can be as important or more so than what is happening at the harvested stand end. This migratory characteristic will cause 'noise' in systems set up for monitoring the effects of forestry practices on stream systems and has to allowed for in such programmes.

  1. Identification of proper riparian zone protocol for the protection of important stream habitat and not just base the zone size on the size of the stream.

Many of New Zealand's small streams are important habitats for native fish. If riparian management is directed solely towards large water-bodies, there is potential for protection of the wrong habitats.

  1. Research on public attitudes towards indigenous forest management so that the needs for public information can be realised.

There is potential for indigenous forests to be sustainably managed within New Zealand but, at least for a proportion of the populous, the perception of such practices is negative. It is important to discover why these perceptions occur, and if these fears are allayed by documentation of management effects on biodiversity. It is also important that where possible, public attitudes should be addressed with appropriate management practices to ensure sustainable outcomes for all forest functions and elements. Early indications are that such fears would be allayed246. Indigenous forestry appears to have a "bad" name but if it was managed sustainably with relation to CBD commitments then there would be scope for public attitudes to be more positive.

  1. Research on public attitudes towards the role of plantation forest management in conserving biodiversity so that the needs for public information can be realised.

As expressed above, plantation forests in New Zealand are thought of as biological deserts. The reasons behind this opinion relate to personal perceptions. These forests may be very important in conserving New Zealand's biodiversity. Their potential in this role should be researched, and the practices necessary to optimise this advocated.

Previous PageTable Of ContentsNext Page

Contact for Enquiries

MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND

Fax: +64 4 894 0721
Contact this person

 
Print this page Print this page




WebSite survey