17 OGNZ WUG mine: assessment of potential ecological effects Project 2034 by DOC at Whareorino and the successes of private landowners on the Coromandel13 at controlling pest species over smaller areas with demonstrated benefit for Archey’s (and Hochstetter’s) frogs; and 3. The spatial location of the proposed pest control areas is intended to buffer and augment existing areas where Archey’s frogs are known to exist, and target habitat where high densities of frogs are known or predicted to exist (based on habitat-abundance associations modelled through other parts of the Coromandel Peninsula). With effective pest control in place, the Boffa Miskell report anticipates that a level of population enhancement of Archey’s frogs could be expected of at least 2.3 x the current population over a period of 3-4 years (and possibly greater in years after that). This means that in the very unlikely event that all frogs die within the 314 ha area of WUG subject to surface vibration greater than 2 mm /sec (i.e. more than the levels at which they have been recorded along roadside margins in the Coromandel), the potential benefits of undertaking pest control within 318 ha of habitat adjoining the vibration exposure areas of the WUG surface footprint would be more than sufficient to balance losses that may occur under a pessimistic scenario of adverse effects on Archey’s frogs within the >2 mm /sec vibration area of the WUG surface footprint. Pest control within surrounding buffer areas and the Otahu Ecological Area would provide additional benefits to frogs on top of this. Collectively, the proposed enhancements to frog habitat are intended to provide for a net benefit to Archey’s frogs as a result of the WUG project. Providing assurance around net benefit requires an understanding of how the projected benefits from enhancement (in this case pest control) will result in no-net-loss of frogs, so that benefits beyond no-net-loss can be proposed. Calculations of potential loss and potential gain (enhancement) for frogs, together with considerations of risk, uncertainty and time lags, will be presented by OGNZL in the next suite of technical documents regarding the management programmes proposed for Archey’s frogs. 6. Monitoring Monitoring provides validation of both management inputs (results) and conservation benefits (outcomes). Monitoring is especially important for a project such as this where is uncertainty over the level of response by frogs to activities associated with the mine that may cause potential adverse effects, and where the level of benefit that the enhancement solution (pest control) may deliver is informed by only one long-term project (DOC at Whareorino). Result monitoring to assess the performance of pest control programmes is laid out in the Boffa Miskell pest animal management plan (Boffa Miskell, 2022). The monitoring includes targets, thresholds for action and contingency measures in order to ensure that pest control is effective and can reduce and sustain pests to agreed levels. Outcome monitoring involves selecting indicators of frog population health, ideally those that communicate aspects of breeding success, recruitment, conspicuousness, population structure (demographics) and population abundance so that the merits of pest control programmes can be attributed with certainty. A difficulty for the monitoring of Archey’s frogs is that the species is cryptic and that intensive effort is required to obtain even basic information on population health (abundance and distribution), let alone dynamics and trends over time. Indeed, it is probably unreasonable to expect that many of the ideal indicates of frog population health will be able to be meaningfully measured on the ground – or at least without a level of effort that is financially unachievable and which would most probably be of considerable damage to frog habitat (and perhaps to the frogs themselves through repeated handling) in the process. We recognise that effective monitoring of Archey’s frog populations before and after, and ideally without and outside frog management areas is necessary to validate pest management as a means of providing benefits – 13 These are two programmes on private land ion the Coromandel Peninsula that individuals within the OGNZL team are aware of, and for which there is definitive evidence of recovery of Archey’s and/or Hochstetter’s frogs within several years of intensive control of rats and mice.
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