My comments refer to numbered locations marked on Appendix 4 (attached - see rhs column), continuing at Section 3 before returning to the Summary & Recommendations (Section 1) at the end.
5.0 Under-estimating the impacts of logging.
9. This caveat is only very peripherally relevant to the proposed TWC sustainable forestry plans because logging will be so fundamentally different. As the DoC Critique emphasises, the past history of logging impacts provides a general precautionary tale (the TWC plan makes the same point), but direct comparison to the new method is strained and repeated over and again in the DoC Critique. Conservation NGO's have made public statements with the same misleading implication by referring to evidence of past impacts of very different logging styles. If a fair and balanced risk assessment is to be made by the New Zealand public in their appraisal of TWC's proposals, loose generalisations based on inappropriate comparisons should not be promulgated by DoC or other conservationists, even if they are proffered for the best possible intentions of protecting the environment.
10. These two studies are of coupes or heavily selected logging regimes, that are therefore not relevant to TWC proposals for grouped-tree removals on comparatively small spatial scales. Grouped-tree removals may still reduce nest hole and food availability to some (probably very minor) extent, so that the level of recovery of populations following predator controls may be capped to some reduced carrying capacity by the logging now proposed.
11. O'Donnell (1991) essentially contains the same approach, data and conclusions as O'Donnell & Dilks (1987). This study is the most relevant of the publised record to predicting impacts of the type proposed by TWC, but even so it is problematical to use it in this way.
Firstly, TWC do not propose to remove the largest live trees or standing dead spars.
Secondly, it is based on data from a different forest type (the DoC Critique challenges TWC for relying on data from overseas or outside their red beech forests within New Zealand, yet now does the same; in reality the comparison by each protagonist is forced by the lack of the relevant data and the only way to remedy this is to initiate relevant research in the proposed TWC sustainable management area).
Thirdly, it tests the model by using data from forests heavily modified by historical methods not proposed for the future.
Fourthly, Spurr's data used for the test of the model compared forests logged recently c.f. long ago (so a spatial comparison was used to infer temporal change; this assumes bird abundance was the same everywhere before logging and that logging was the only important ecological change between areas);
Fifthly, the predictions of the model worked for parakeets and yellowhead, but not for kaka (we should have little confidence in any model until its predictions are upheld for a replicated series of species or place, or until a plausible post-hoc hypothesis is tested for why the model should apply to one species and not another);
Sixthly and finally, the model assumes that the preferences initiated by the bird studies demonstrates need, and so retrieves the over-riding assumption that habitat variables limit the populations. All animals will show preference of some sort or other for particular foods or places, but this does not mean that such preferences have any tangible impact on their numbers. This over-aching(sic) (over-arching ?) assumption is acknowledged by O'Donnell & Dilks (1994) but not by the DoC Critique of TWC plans reviewed here. I agree that the type of investigation proposed by the DoC Critique would be a valuable first step, and therefore urge TWC to consider doing such a study, but I caution that the study will not by itself be sufficient to clinch the key question: i.e. a conclusion about whether the proposed logging will reduce future bird or bat numbers to any significant degree.
12. The model did not predict trajectories for changes in kaka numbers.
13. These two sentences are a scant balance to the several above and following that imply logging impacts are likely from past evidence. The very next sentence re-iterates the same misleading implication. Equally, there is a need for detailed research of the new logging style (group-tree removals) on birds and bats. Common sense and our knowledge of forest processes suggest that these impacts are likely to be much smaller than previous methods, but vigorous research and monitoring of the new method is still needed and necessary as part of the environmentally precautionary principle embraced by TWC in its planning. Fortunately the low intensity approach proposed by TWC gives ample opportunity to do such research before major alteration is imposed on the system.
14. Appealing to "the wide variety " of historical logging techniques as evidence for their potential to predict outcomes of TWC proposals is misleading because it omits mention that the new style of logging proposed is so fundamentally different. New Zealand has gone from large-scale clearfelling to smaller and smaller clearfells, and from logging that seriously alters species and size structure of the forest community to the current proposal to mimic natural forest structure profiles. The latter is precisely the approach taken by foresters in Europe for centuries, and just the approach that is needed to minimise potential risks to biodiversity in New Zealand (Beneke 1996, Kohm and Franklin 1997, Lindenmayer & Franklin 1997).
15. This is precisely the approach signalled by TWC (but this was apparently not included in the draft plan critiqued by Colin O'Donnell).
16. Proposals to predict outcomes and measure risks from uncertainties (using mathematical simulation models and a "sensitivity analysis" are planned).
17. The assertion that logging impacts will necessarily be underestimated is assumption. It may be that the biodiversity impacts overseas may be just as extreme or worse than those expected in New Zealand; and (as partly acknowledged two paragraphs earlier) the types of logging proposed by TWC are so different from those researched in the earlier New Zealand case studies quoted by the DoC Critique that their relevance is highly questionable.
18. All this is fair, but not relevant to the style of logging proposed by TWC. The DoC Critique's criticism here was spurred by the absence of warnings about potential impacts of logging in the Maruia Plan (these were however covered in the overview plan) and a lack of mitigation measures in the Maruia plan itself (Colin O'Donnell in litt., 5 October 1998).
6.0 Mitigation of impacts of harvesting on threatened bat species.
19. It is agreed that the threats to birds are potentially different from those for bats. Very important in this regard is the lack of detailed information one way or the other about the importance of predation on bat numbers. If they are not vulnerable to predation their populations may be much closer to the carrying capacity set by food availability or roost hole availability than expected for the bird species, DoC's bat recovery programme (Molloy 1995) lists predation by rats, stoats and feral cats as a threat to bats. Competition for insect prey with super abundant social wasps is potentially very important in honeydew beech forest areas (Moller & Tilley 1989; Thomas et. al. 1990; Harris 1991).
20. Colin O'Donnell points out that bats are not like birds in that they go into torpor for some months of the year and so can not fly away. A high proportion might then be killed if a key nursery tree is felled. The proposed tree-cavity model can more rigorously calculate this risk after incorporating the bats selectivity, the tree size selections used, and the months of the year in which felling is proposed. Colin O'Donnell and Jane Sedgeley and team have detected in one population in the Eglinton Valley that at least 3 separate social groups exist that restrict their roosting to a much smaller area within a very large range. Other social groups may have been present (Colin O'Donnell, in litt. 5 October 1998). Large areas of that range may have had no roosting by other social groups, or all might have been used. Replicate studies are needed to determine if this is a general pattern for short-tailed bat populations. There is no demonstration that the bats could not move or extend their areas to include new holes being formed in the sustainable forestry area, or nearby. Most importantly, the TWC protocols are striving to maintain a large number of holes by various devices. Had coupe clearfelling been proposed then a risk of hitting and seriously disrupting the roosting area would exist, but this is not proposed. TWC might still consider it prudent to mount a study to identify roosting areas in their forests, but this is a large task ( a minimum of two years work from a dedicated and experienced team) and in the end it will not prove one way or the other what the putative logging impacts might be. It represents a significant start towards assessing and potentially mitigating any putative impacts though. A formalised model of tree hole availability and the impacts of logging on it will objectively measure these risks long before any putative changes are imposed on the system. The model can also test various mitigation measures, including revising tree selection criteria, seeding of new holes by drilling starting holes and inoculating them with fungi etc.
21. Rapid and thorough work principally by Colin O'Donnell and his team has highlighted this change of emphasis to concern for South Island long-tailed bats as well founded and in urgent need of attention.
22. The relative importance of long-tailed bat populations on TWC land compared to surrounding DoC land, or populations elsewhere in South Island, has not been demonstrated nor measured (at least no published account of such a demonstration exists). I urge TWC to consider contracting Colin O'Donnell's team to allow a better regional perspective to be gained. Some of the data from Rhys Buckingham's surveys could help plug the gap ( they also use similar standardised techniques), but new intensified survey effort may also be called for.
23. It is logical to expect that short-tailed bats roost hole requirements will be different, and a paper is in press with New Zealand Journal of Ecology demonstrates that they use larger diameter stems than do long-tailed bats (Colin O'Donnell, in litt., 5 October 1998). However, this evidence is very distinct from any expectation that such holes will be in limited supply, either before or after logging, or in the presence of both bats. There has not yet been an analysis of DoC's wider survey data for both bat species to test whether there are fewer or more bats in heavily cut over or coupe logged sites.