News & Reports » Environmental Research » Biodiversity

Identifying Complementarities for the Dairy and Forestry Industries in the Central North Island

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This study was commissioned by Oji Fibre Solutions (OjiFS) and the Waikato Regional Council to provide sound evidence about the effects of land use in New Zealand using the dairy and forestry industries in the Central North Island (CNI) as a case study. The study was independently reviewed by the New Zealand Institute of Economic Research (NZIER) to confirm its validity. The aim of the study is to provoke and promote constructive discussion on how complementarity opportunities can be generated at a land enterprise (farm or forest) and catchment level to create beneficial scenarios for both industries.

Plantation forests protect our biodiversity

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New Zealand's plantations have been criticised because it is claimed they are breaking our commitment to the 1992
Biodiversity Convention. If we look at the world human population and its interrelationships with agricultural and horticultural systems, it is obvious that all are totally dependent on the control, manipulation or even elimination of unwanted species, (i.e. biodiversity). It is questionable, therefore, if we are sincere when we claim that the protection of all biodiversity is essential to life. Within New Zealand, plantation forests now provide almost all our wood needs. This will allow almost all the
remaining indigenous forest of New Zealand to be protected from wood harvest. Plantation forestry is saving and
enhancing our indigenous biodiversity, not reducing it.
A key factor that is often ignored in plantation forestry is the importance of attracting" investment. That investment
will only be forthcoming if plantation forestry has a proven record in growth, utilisation and marketing. Unproven or
expensive plantation forestry will not be funded. The best means of protecting indigenous forest biodiversity will be to have profitable, proven plantation forestry such as our radiata pine.

Plantation forests and biodiversity: oxymoron or opportunity?

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Losses of natural and semi-natural forests, mostly to agriculture, are a significant concern for biodiversity. Against this trend, the area of intensively managed plantation forests increases, and there is much debate about the implications for biodiversity. We provide a comprehensive review of the function of plantation forests as habitat compared with other land cover, examine the effects on biodiversity at the landscape scale, and synthesise context-specific effects of plantation forestry on biodiversity. Natural forests are usually more suitable as habitat for a wider range of native forest species than plantation forests but there is abundant evidence that plantation forests can provide valuable habitat, even for some threatened and endangered species, and may contribute to the conservation of biodiversity by various mechanisms. In landscapes where forest is the natural land cover, plantation forests may represent a low-contrast matrix, and afforestation of agricultural land can assist conservation by providing complementary forest habitat, buffering edge effects, and increasing connectivity. In contrast, conversion of natural forests and afforestation of natural non-forest land is detrimental. However, regional deforestation pressure for agricultural development may render plantation forestry a ‘lesser evil’ if forest managers protect indigenous vegetation remnants. We provide numerous context-specific examples and case studies to assist impact assessments of plantation forestry, and we offer a range of management recommendations. This paper also serves as an introduction and background paper to this special issue on the effects of plantation forests on biodiversity.

Biodiversity in New Zealand plantation forests: Policy trends, incentives, and the state of our knowledge

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Biodiversity is an issue of increasing relevance to plantation forests in New Zealand. The New Zealand
Biodiversity Strategy and other recent policy documents
advocate 'sympathetic management' to conserve biodiversity on private land. As a component of sustainable forest management, biodiversity is also included in international agreements (e.g., Montreal Process) and in the certification of forest operations. However, a review of these and other policy and legal instruments revealed shortcomings in the definition of biodiversity as well as a lack of clear guidelines on how biodiversity should be considered in plantation forest management. In the few cases where explicit references have been made, 'biodiversity' is mostly used in the sense of 'threatened species.' Although our knowledge of vascular plants and birds occurring in plantations is relatively good for some regions, little knowledge is available about other taxa and the presence of threatened species. Moreover, it is not clear what exactly is meant by 'sympathetic management' and hardly any research has been undertaken in this area. More active management for preservation or enhancement of
biodiversity in plantations could lead to improved public
perceptions and international market access, and might
enhance 'ecosystem function.' In this paper, we also
discuss biodiversity indicators and provide a summary
of recent research on biodiversity sustainability issues
in plantations. To adequately address biodiversity in
plantations, more research is needed, for example, on
threatened species and other indigenous flora and fauna,
sympathetic management (including cost-benefit analyses), and long-term monitoring. Interactions between policy makers, scientists and forest managers should be improved.

Environment Court evidence: Kiwi conservation in Whangapoua forest, Coromandel

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My evidence addresses:
1) The taxonomic and conservation status of the North Island Brown Kiwi;
2) The causes of kiwi decline on the Coromandel Peninsula;
3) Whangapoua forest as a habitat for kiwi;
4) The effects of forestry harvesting on kiwi populations;
5) Kiwi utilisation of riparian strips;
6) Voluntary steps by Earnslaw One Ltd to protect and conserve kiwi in Whangapoua Forest.

Role of exotic pine forests in the conservation of the critically endangered New Zealand ground beetle Holcaspis brevicula

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The Canterbury Plains in the eastern South Island is one of the most modified regions of New Zealand with less than 2% of indigenous vegetation cover remaining. The critically endangered ground beetle Holcaspis brevicula Butcher, a local endemic known only from a small area in that region, is thought to be threatened by the loss and fragmentation of the formerly widespread forest and shrubland habitat. Previously, only the two type specimens, both male, were known to science. From 2000–2005, we conducted a survey for H. brevicula, using pitfall traps and active searching, in four of the largest remnants of the once extensive low forest and shrubland of känuka, Kunzea ericoides, each covering less than 20 ha. In addition we conducted extensive trapping in an adjacent 7000 ha plantation forest of exotic Pinus radiata, in grassland and pasture areas, exotic shrubland, and in the nearest mountain beech (Nothofagus solandri var. cliffortioides) forest in the foothills of the Southern Alps. A total of 8658 carabids representing 47 species were collected over 57 494 trap-days, including five specimens of H. brevicula, all found in the pine plantation. A search of all major New Zealand collections for this species revealed three additional specimens, bringing the overall total of known specimens to ten, all of which were collected in this plantation forest. We propose that the exotic plantation forest inadvertently provides an important substitute habitat for this forest carabid, whereas the few small and fragmented native känuka remnants appear to be insufficient to maintain populations of this species.

Environment Court evidence: biodiversity in Whangapoua forest, Coromandel

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My evidence will:
1) Outline the terrestrial indigenous biodiversity present within indigenous enclaves of the Whangapoua Forest, the significance of any vegetation, and the conservation status of species where this is noteworthy.
2) Describe the terrestrial indigenous biodiversity present within plantation forests of the Whangapoua Forest.
3) Describe the effects of the planned harvesting operations on terrestrial indigenous biodiversity within the Whangapoua Forest.
4)Discuss the need for a planting setback of a further 5 m on riparian strip widths.
5) Consider the need for a riparian strip of 40 m versus 10 m, vegetation succession that might occur within riparian strips, and the value of riparian strips as corridors.
6) Discuss the value of indigenous enclaves within the forest to be protected above 1 hectare in area, and the effects of dragging or hauling through these areas in accordance with the amendments sought by Ernslaw in its appeal.

Responses of stream macroinvertebrate communities to progressive forest harvesting: Influences of harvest intensity, stream size and riparian buffers

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Harvesting of forests causes a range of disturbances, including changes to hydrology, nutrient inputs, water quality, food sources, habitat structure and channel morphology, which can impact streams over several years and are reflected in changes in community structure. We aimed to determine the relative magnitudes of impact and rates of recovery of benthic macroinvertebrate communities, and associated changes in biotic indices (Quantitative Macroinvertebrate Community Index and an Index of Biotic Integrity), in reaches of different sized streams within progressively logged catchments. We conducted annual summer surveys over seventeen years in fifteen New Zealand streams that differed in size (upstream catchment area between 40 and 2360 ha, mean channel widths between 2.5 and 16m) and harvest intensity in the surrounding catchment. The largest post-harvest changes in biotic indices and community structures occurred in streams draining relatively small to medium catchments (<500 ha) where >40% of the upstream catchment had been harvested, and particularly after harvesting of overstorey riparian vegetation adjacent to study reaches. The impacts of harvest on invertebrate communities were less evident in wider streams draining catchments over 500 ha, but the largest changes from pre-harvest biotic indices and community structure still generally occurred after harvesting of riparian vegetation along these streams. The changes in community structure after harvesting of riparian vegetation typically included increases in the densities of Diptera, Mollusca and Oligochaetes, and decreases in the densities of Ephemeroptera. These results demonstrate that impacts on benthic macroinvertebrate communities increased as the proportion of upstream catchment harvested increased and/or after riparian vegetation was harvested. Some of the communities in headwater streams had largely recovered towards pre-harvest structures, whereas post-harvest recovery was less evident in relatively large streams, over the duration of the study.

New Zealand’s exotic plantation forests as habitats for threatened indigenous species

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The contribution of exotic plantation forests to the conservation of New Zealand’s flora and fauna is a somewhat controversial issue, partly because the establishment of some plantations involved the conversion of indigenous vegetation. Such conversion no longer occurs within the professional forest industry and there is a growing appreciation of the contribution of ‘production’ land, including plantation forests, to the protection of New Zealand’s unique indigenous biodiversity. This paper provides a comprehensive synthesis of information currently available on threatened species known to occur in New Zealand’s plantation forests. Based on an evaluation of the published literature, unpublished reports, national threatened species databases, and personal observations we have compiled records of 118 species classified by the Department of Conservation as threatened that occur in plantations. Of these species, 16 are classified as ‘Nationally Critical’, 17 ‘Nationally Endangered’ and 17 ‘Nationally Vulnerable’, while the majority are classified as either in ‘Gradual Decline’, ‘Sparse’ or ‘Range Restricted’. We highlight the direct and indirect benefits of plantations to various threatened taxa and draw attention to the missed conservation opportunities that are generated by a lack of understanding and the somewhat ‘puritanical’ views of New Zealand’s mainstream conservation paradigm. We also discuss some of the potential negative consequences of plantations such as their potential function as ‘population sinks’ and ‘ecological traps’. We conclude with a discussion of future research opportunities that aim to improve the conservation value of plantation forests.

Impacts of forest harvesting on giant kokupu, Ngakaroa Stream, Omataroa Forest, Bay of Plenty

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The aim of this study was to determine the effects of logging a pine forest catchment upon a population of giant kokopu (Galaxias argenteus) in a small third-order stream. Spotlighting was used to estimate fish abundance in the Ngakaroa Stream, Omataroa Forest, Bay of Plenty, New Zealand, on 15 occasions from February 1995 to July 2000. Between July 1997 and March 1998, the forest compartment enclosing the study area was clearfelled, using a combination of skyline hauling and skidding, and the compartments were replanted over winter 1998 and 1999. Abundance of giant kokopu varied greatly over the study period, ranging from two to 22 fish over the 600 m study reach. Although there was no statistically significant difference in the abundance of giant kokopu in the Ngakaroa Stream before or after logging, the study suggested that deliberate planting of riparian zones with pine trees can encourage regeneration of shade-tolerant, native scrub-hardwood species, thereby providing acceptable conditions for a range of native fish, including giant kokopu. This contrasts with reserving unplanted riparian ‘buffer strips’ which led to invasion by light-demanding exotic weed species. This pragmatic approach could lead to cost-effective and comparatively rapid restoration of habitat for native forest-dwelling fish such as giant kokopu. Appropriate planting and harvesting regimes are described.

Effects of Pinus radiata plantations on environmental weed invasion into adjacent native forest reserves

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Much marginal pastoral land, including land adjacent to native forest reserves, has been converted to pine (Pinus radiata) plantations in recent decades. In this study, we tested a recently advanced hypothesis that weed invasions of native forest reserves are reduced when pines are planted on reserve boundaries. We selected 45 native forest patches with adjacent landscapes of either young pines (including recent cut-over), mature pines or pasture, in three regions of New Zealand: Auckland, Bay of Plenty and Wellington. We recorded the frequency and percentage cover of all plant species listed as weeds in the Department of Conservation (DOC) National Weeds Database. We also sampled the adjacent landscape, the native forest edge, the native forest core, and tree-fall canopy gaps within the native forest core. We found few statistically significant effects of pines on weed composition or abundance in native forests. Native forest edges adjacent to young pines tended to have more weeds species than those adjacent to mature pines or pasture. Only 29 weed species were found in native forests; half of these were recorded in tree-fall gaps, while only six were recorded in the understorey of the native forest core. There were more weed species at our Wellington sites, which were on average closer to towns than the sites sampled in other regions. This suggests that propagule pressure from human settlements is an important determinant of weed invasions in native forest reserves. The presence of pines
does not appear to reduce weed invasions. Rather, weeds may be encouraged during pine establishment and harvesting. Consequently, care should be taken to control weeds during these phases, especially on associated roads and log-hauler

Ecological monitoring for potential effects of forestry activity on the intertidal habitats of Whangapoua Harbour

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In 1992, NIWA was commissioned by Ernslaw One Ltd to assess the need for a monitoring programme to detect effects of forestry activity on intertidal areas of Whangapoua Harbour. A monitoring programme was subsequently developed for Whangapoua Harbour, focussing on the intertidal sediments of the harbour and their biological communities, and NIWA was commissioned to implement it. Due to the diffuse and widespread nature (in both space and time) of the forestry operations, it was not considered practical to implement a monitoring programme capable of establishing a cause and effect link between forestry activity and any potential changes occurring in the harbour. Rather, the programme was established by Ernslaw One to provide a sound scientific basis against which to assess whether changes occurred in the harbour. Then, if changes did occur, methods of determining the role of harvesting could be investigated. This report summarises the findings from harbour monitoring conducted between 1993 and the present and provides a review of the programme that meets requirements set out by the Environment Court.

Role of wood in pumice-bed streams: I: Impacts of post-harvest management on water quality, habitat and benthic invertebrates

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Harvesting slash was experimentally manipulated in three headwater, spring-fed, pumice-bed streams draining Pinus radiata catchments in the central North Island, New Zealand. Changes in water quality, benthic sediments, organic matter and invertebrate communities were studied up to 5 years after (i) removal of most wood from the channel (low-wood site), (ii) removal of large wood only (medium-wood site), and (iii) retention of all wood (high-wood site). We detected minor effects of wood treatment on water temperature, short-term effects on dissolved organic carbon, nitrite-nitrogen and dissolved reactive phosphorus concentrations (<6 months post-treatment), and longer term effects on dissolved oxygen concentrations (>1 year). Post-harvest dry mass of stored benthic organic matter declined at all sites over 1–3 years to levels recorded at an unharvested reference site. In contrast, changes in the percentage of surficial sand and gravels were still evident 5 years after treatment. Significant temporal differences in the taxonomic richness and density of benthic invertebrate faunas were detected at all treatment sites, and initially appeared to reflect degree of channel disturbance during harvesting and wood management. Following these initial impacts, richness and densities of some major invertebrate groups increased as successional taxa colonised streams, apparently in response to trophic subsidies from organic matter inputs or increased primary production, and recovery of sites from disturbance. Pre-harvest and reference site invertebrate community composition was considerably different from that at the low-wood site until 1 year after treatment, and at the high-wood site until 3 years post-treatment when communities at all sites were broadly similar. By carrying out a medium-term study and manipulating stream channel wood along the length of perennial flow in headwater basins, we have provided a basis for understanding the magnitude and duration of ecological impacts, and the timescales of recovery associated with different post-harvest wood management approaches in pumice-bed stream ecosystems.

Riparian buffers mitigate effects of pine plantation logging on New Zealand streams 2. Invertebrate communities

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The influences on forest stream invertebrate communities of riparian forest type (native/exotic Pinus radiata) and logging, with or without native forest riparian buffers, were investigated at 28 stream sites on Coromandel Peninsula, New Zealand. Stream reaches were surveyed under summer, baseflow conditions in six riparian/forest vegetation types: native forest, mature pine plantations with pines planted to the stream edge, mature pine plantations with native forest in the riparian area, clearcut pine plantations, and logged pine plantations with patch buffers of native forest vegetation (upstream areas clearcut) or continuous buffers along the perennially flowing stream length. Multivariate analyses showed that clearcut reaches differed in invertebrate community structure from pine and native forested reaches, and from logged reaches with continuous riparian buffers. Communities at patch buffer sites were intermediate between these groups. Amongst the common taxa, mayflies were the most sensitive to clearcut logging, with three species less abundant at clear-cut and/or patch buffer sites; only the algalpiercing caddis Oxyethira albiceps (Hydroptilidae) responded positively to logging. Clearcut reaches had lowest diversity, taxon richness, relative abundance and numbers of the sensitive mayfly, stonefly and caddisfly taxa, and index of biotic integrity. In contrast, sites that had been logged leaving continuous buffers did not differ in these biometrics from those in intact native or mature plantation forest, indicating that buffers greatly reduced disturbance associated with logging. Logged sites with patch buffers had biometric values intermediate between clearcut and forested/continuous buffered reaches, indicating less protection from logging impact. Correlation and multiple regression analyses showed that logging impacts are strongly related to increases in periphyton biomass and water temperature, associated with changes in stream lighting, and increased channel instability/fine sediment. The findings indicate that late-rotation exotic pine plantations can support very similar stream invertebrate communities to native forests, and highlight the benefit of retaining forested buffers along stream riparian areas to avoid harvesting impacts on stream habitat and invertebrate communities.

Effects of progressive catchment harvesting on stream invertebrates in two contrasting regions of New Zealand's North Island

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We examined changes in stream habitat and benthic invertebrate communities in two contrasting regions of New Zealand’s North Island over a 9–10-year period as pine forest harvesting progressed through the catchments. Increases in streambed cover by sand/silt, wood and macrophytes were recorded as harvesting progressed, but little change was observed in qualitative periphyton abundance. Despite similar high-level taxonomic structure of invertebrate communities between the two regions, differences in percentage and log-transformed abundance indicated an effect of landscape context that reflected different hydrologies and bed-substratum stabilities. Within regions, ordination plots indicated broadly distinct site clusters that persisted through time and reflected variations in stream size, substratum composition, periphyton abundance and degree of catchment harvesting. Generally, few of the invertebrate community metrics examined showed clear responses to progressive catchment or onsite harvesting relative to previous intra- and inter-annual variation. The most noticeable exceptions were percentage Ephemeroptera, Plecoptera and Trichoptera (excluding Hydroptilidae) abundance and percentage Elmidae abundance, which were negatively and positively correlated, respectively, with percentage catchment harvested. We identify three broad response categories to catchment harvesting that reflect subsidy–stress effects as logging progressed and discuss the relevance of these findings to potential pine forest harvesting effects in southern Australia.

Effects of logging with and without riparian strips on fish species abundance, mean size, and the structure of native fish assemblages in Coromandel, New Zealand, streams

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We determined the effects of logging, both with and without a riparian buffer strip, on the native fish fauna at 27 stream sites in an exotic pine (mainly Pinus radiata) forest on the Coromandel Peninsula, New Zealand. Fish abundance at the logged sites was compared with reference sites in both unlogged pine and native forest. The abundance of Anguilla dieffenbachii (Gray) and Anguilla australis (Richardson) was not significantly affected by logging. However, the abundance of Galaxias fasciatus (Gray) and Gobiomorphus huttoni (Ogilby) was. There were fewer Ga. fasciatus at the logged sites without buffers than at the reference sites, but more at the logged sites with buffers. The abundance of Go. Huttoni was higher at the logged sites than at the reference sites, and was highest at the logged sites with riparian buffers. Overall, the different, species specific responses to logging maximised total fish numbers at the logged sites. As total fish numbers, the abundance of Ga. fasciatus, and species equitability, a measure of fish assemblage structure, were all highest at the logged sites with riparian buffer strips, we concluded that riparian strips enhanced the native fish community of streams within these logged catchments.

Effect of Pinus radiata logging on stream invertebrate communities in Hawke's Bay, New Zealand

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Invertebrate communities and associated environmental characteristics were monitored at three Pinus radiata and three pasture stream sites in the Pakuratahi and Tamingimingi Stream catchments, New Zealand, respectively, at nine irregular intervals between December 1996 and April 2001. The Pakuratahi sites were logged between May 1998 and September 1999. Following logging the Pakuratahi Stream invertebrate communities changed from being dominated by a diversity of mayfly species to communities dominated by a high abundance of Chironomidae, Aoteapsyche sp., Elmidae, Ostracoda, and Potamopygrus antipodarum. Invertebrate communities that developed following the pine forest harvesting closely resembled those at pasture stream sites in the adjoining Tamingimingi catchment. Invertebrate communities at the pasture stream sites were dominated throughout the study by the same taxa as in the post-harvest pine sites, except immediately following a storm in July 1997 when mayflies became proportionally more abundant. Biotic indices of water quality, such as the Macroinvertebrate Community Index and Quantitative Macroinvertebrate Community Index, reflected the change in invertebrate communities at the Pakuratahi sites after harvesting, shifting from impact "sensitive" taxa to more "tolerant" taxa. In April 2001 (1.5-2.5 years after harvesting) invertebrate communities had not recovered to their pre-harvest structure. Recovery of invertebrate communities from a natural disturbance, a major storm in July 1997, was much more rapid (5 months) than the recovery observed from forest harvesting, however. An increase in streambed fine sediment may have been primarily responsible for the changes to invertebrate communities following
forest harvesting.

Biodiversity in New Zealands plantations

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A common view that New Zealand’s plantations are mono-cultures reflects negatively on forestry as a land use. This paper evaluates components of biodiversity in plantations by addressing two questions: 1) are plantations biological deserts?; and 2) how does plantation management influence species composition? An ecological perspective is presented showing the relevance of human-induces ecosystems to the maintenance of biological diversity, and illustrating the value of compositional information to other facets of plantation management.

The sustainability paradox - an examination of The Plantation Effect - a review of the environmental effects of plantation forestry in New Zealand

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This article provides a brief summary of various environmental effects of plantation forests, including soils, water quality, biodiversity, landscape values, risks, and the economy.

Effects of Plantation Forestry on Birds in New Zealand

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(1) The relative densities of birds were compared, vegetation profiles measured and bird food resources assessed in seven exotic conifer plantations and five areas of native Nothofagus forest in New Zealand. (2) Of sixteen native bird species, seven were most abundant in native forest and two in conifer plantations. In contrast, none of the ten introduced birds preferred native forest, but at least seven were commonest in plantations. (3) There was no significant relationship between overall bird species richness (BSR) and foliage height diversity (FHD). However, when introduced and native birds were considered separately, the BSR of introduced species was negatively correlated with FHD whereas BSR of native birds was positively correlated with FHD. Several introduced passerines preferred structurally simple plantations, but there were always more native bird species in native forest than in plantations. (4) The distribution of birds between areas was largely explained by the differing availability of food such as fruit and honeydew, but for some species vegetation structure or the presence of tree-holes for nesting may be important factors. (5) The native birds which suffer most from replacement of native forest with conifer plantations are frugivores, nectar-feeders and hole-nesters. Conservation of these species in large exotic forests is best achieved by retaining areas of native forest within conifer plantations.

Effects of rural land use (especially forestry) and riparian management on stream habitat

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Mature plantation forests provide broadly similar stream habitat conditions to native forest ans streams in these land uses typically have quite similar invertebrate and fish faunas. However, logging and replanting create regular disturbances to streams in plantations that can impact adversely on aquatic habitat and biota. Streamside riparian areas occupy the interface between the land and water and recent New Zealand studies have shown that maintaining forest vegetation in the riparian area during logging, together with sound land management practices elsewhere in the catchment, can protect streams from much of the disturbance that otherwise occurs during and after logging.

Waiapu River Catchment Study

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This report presents the work undertaken on the Waiapu River Catchment Study, the purpose of which was to investigate the geophysical, social, cultural, and economic dimensions of the erosion problem in the Waiapu River catchment in order to inform future policy decisions with respect to the catchment in the context of the Deed of Settlement between Ngāti Porou and the Crown. The report includes:
1) An outline of existing knowledge related to the (i) geophysical and land use aspects and (ii) social, cultural, and economic aspects of erosion and land use change within the Waiapu River catchment and the wider East Coast region.
2) Identification of gaps in the existing knowledge apparent to the research team, and recommendations for addressing any gaps identified.
3) A description of a baseline from which future progress in the Waiapu catchment may be measured (benchmarking) for the (i) geophysical and land use aspects and (ii) social, cultural, and economic aspects of erosion against the values of Ngāti Porou for the catchment and well-being of the people.
4) An outline of the project team‘s interpretation of a desired state for Ngāti Porou and consideration of possible options for addressing the erosion problem.
5) Assessments of the scope (size and scale) of the erosion problem in the catchment and critical evaluations of the effectiveness of erosion mitigation measures for the (i) geophysical aspects and (ii) social, cultural, and economic aspects of erosion.

Sustainable land management and the East Coast Forestry Project

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Chapter 5 is a brief description of the potential physical, economic and social impacts of the project. This includes effects on erosion, soil quality, water quality and quantity, biodiversity, climate change and greenhouse gases, and factors involved in agriculture-forestry changes.

Recent Findings on the Environmental Impacts of Planted Forests in New Zealand

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This is a summary of recent literature on the positive and negative environmental impacts of planted forests in New Zealand. Key results are as follows: Biodiversity - plantations provide a habitat suitable for a wide range of indigenous forest species, both aquatic and terrestrial. Water yield - afforestation can reduce peak catchment flood flows by up to 50%. Water quality and leaching - planted forests have the lowest potential for nitrate and phosphorous leaching with levels similar to indigenous forests. Sediment yield - afforestation of whole catchments can reduce sediment load to waterways by 50-90%. Soil erosion - recent research provides further support that plantations mitigate soil erosion. Impacts on soil nutrients the high level of soil organic N present in established pastures decreases markedly when the pasture is planted in pine forest. This information is relevant to forest managers needing to manage the environmental effects of their trees, and provides the baseline for further research. For the Forest and Environment FRST programme the information will contribute to planning research on indicators of sustainability.

The Pakuratahi Land Use Study

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Researchers compared pastoral farming with forestry over 12 years and found that a forest produces less sediment, uses slightly more water, reduces soil erosion, has a more positive effect on stream environments, and makes no real difference to water quality. Begun in 1993, the land use study was a response to public concern about the environmental effects of forestry on Hawke's Bay hill country. It was completed in 2005.
A paired catchment study approach was used, with one catchment in forest (Pakuratahi) and the other in pasture, farmed with sheep and beef, as a control (Tamingimingi). The catchments represented North Island hill country. Researchers compared the environmental effects of commercial forestry and pastoral farming through various stages of the forest rotation. The sequence of pre-harvest, harvest, replanting, and canopy closure covered time of major environmental change.