(See comment 9) Logging, as done in the past has clearly caused considerable impact on wildlife, particularly threatened species (See reference list in O'Donnell, 1991 and Unpublished NZ Forest Service studies from central Westland). A review of the historical effects of logging on forest birds (O'Donnell 1991) indicated that obligate forest-dwellers disappear from logged forest. The occurrence of six key bird species in 17 comparisons between logged and unlogged forest was summarised by O'Donnell. Kaka and rifleman were absent from 10 of the 13 sites where they formerly occurred. Kaka occurred in lower numbers at the remaining three sites and rifleman at one. Parakeets were absent from five logged areas and present in lower numbers at the other seven. Although brown creeper, tomtit, and NZ robin were usually still present in logged forests, their numbers were frequently lower.
Predictive studies have indicated that coupe logging and individual tree selection techniques could cause significant impacts on native wildlife (O'Donnell & Dilks 1987,
(See comment 10) Spurr et al. 1992, Warburton et al. 1992).
(See comment 11) A model for predicting the impacts of logging on forest birds was developed by O'Donnell & Dilks (1987 & unpubl.).
The model analysed the degree of overlap between the trees preferred for foraging and those targetted for logging, and predicted the proportions of preferred habitat lost at different (tree - Ed.) extraction (felling - Ed) rates. A comparison between predicted loss of habitat and actual declines in bird numbers from logging silver beech using Spurr's 1987, 1988 data for Rowallan forest indicated that beech management would be highly detrimental to key forest birds
(See comment 11) (O'Donnell 1991).
(See comment 12) Selection logging of rimu, even in very small amounts would also have severe impacts on kaka and parakeet (O'Donnell & Dilks 1987).
5.2 Predicting impacts of new harvesting regimes
"Avifauna remains one of the greatest unknowns in terms of the effects of any management" (BSM, p. 169).
(See comment 13) TWCL are using a new harvesting technique for North Westland forests so obviously there are no data on its impact on wildlife. Therefore, at this stage we can only use predictive approaches to assessing potential impacts.
However, the fact that a
(See comment 14) wide variety of historical harvesting techniques
have all led to significant declines in numbers of threatened species serves as a warning. Recent surveys by TWCL confirm that lower numbers of great spotted kiwi, kaka, parakeet, rifleman, and robins occur in the most recently heavily logged forests (BSM, p.70).
The BSM largely deals with effects of logging on foraging habitat for birds - but not roosting or nesting habitat, and not bat habitat. We need to go some way towards predicting impacts at this stage (see below) but if the logging is to go ahead then a
(See comment 15) rigorous research-by-management approach needs to be adopted and specific logging prescriptions need to be changed as necessary if adverse impacts are detected. Studies of wildlife foraging, breeding and roosting preferences
(See comment 16) in red beech forest will be required to make accurate predictions.
In contrast, however, the MSMP (p.29), the document which should be specifically outlining mitigation procedures to reduce these effects, chooses not to acknowledge the New Zealand research. Rather, it chooses to quote overseas papers in tropical forest types where bird communities and forest types are completely different.
(See comment 17) Thus the MSMP under-rates the potential impacts of logging.
Quoting tropical studies which show only localised loss of wildlife after logging while ignoring New Zealand studies (see above) which show significant impacts seems inappropriate.
(See comment 18) It is well known that logging can increase diversity of forest birds per se (including in New Zealand e.g. McLay 1974). However, increased diversity results from more edge species, introduced species, and honeyeaters temporarily if there is an increase in the numbers of successional plant species (especially along roads). These "increases" in diversity are at the cost of endemic, specialised and threatened species (e.g. O'Donnell 1991).
The MSMP should specifically address the conflicts raised in the BSM, rather than ignoring them.
(See comment 19) It is not appropriate to assume that measures proposed for forest birds will also assist bat populations (BSM, Section 184.108.40.206) because they have different requirements (see below).
While ranging over 50 km2, including forest edges, riversides and grasslands, long-tailed bats always return to traditional patches of forest as small as 2 km2.
(See comment 20) The implication of this is that unless these roosting patches are identified and protected then there is a high risk of localised habitat modification wiping out a whole population.
Sampling of trees available to long-tailed bats in the Eglinton Valley, Fiordland, indicated that suitable trees were rare in the forest. Roosting trees were concentrated in lowland forests on river terraces and outwash fans on the valley floor (Sedgeley & O'Donnell in press). Few bats were present in higher altitude forests. Long-tailed bats selected trees which were > 80 cm DBH.
There is an active recovery programme being run by the Department of Conservation (Molloy 1995). The Recovery Group is becoming more concerned about the conservation status of long-tailed bats. Preliminary survey work on long-tailed bats has indicated that numbers may be much lower, at least in some regions, than was previously thought,
(See comment 21) and populations could be declining. Recent work investigating the genetics of long-tailed bat populations indicate that North and South Island populations are distinct, and there is greatest concern for the viability of South Island long-tailed bats. Intensive work has indicated that long-tailed bats are very rarely encountered in many areas, even when considerable survey effort has been made. They are very rare or absent at several South Island sites where they were widespread in the 1960's.
(See comment 22) This means that conservation of bats in the TWCL areas is of very high priority.
A second threatened bat species, the short-tailed bat may be present in North Westland forests. This species has recently been re-discovered in the Karamea (conformed) (sic) and Punakaiki (unconfirmed) areas, as well as the Eglinton Valley in Fiordland (O'Donnell et al. in press).
(See comment 23) If short-tailed bats were to be found it is likely that they would have different tree roosting requirements than long-tailed bats and different models of the potential impacts of harvesting on this species would need to be developed. For example, preliminary data on roost cavity characteristics of the Eglinton Valley show that although there may be some overlap in roost cavity size between the two species, most short-tailed bat roosts have larger entrances and internal dimensions and are located closer to the ground (O'Donnell et al in press). The agility of short-tailed bats on the ground and its maneuverability (Webb, Sedgeley & O'Donnell, in press) enable it to roost in lower cavities and basal hollows which long-tailed bats do not use.