14 OGNZ WUG mine: assessment of potential ecological effects Project 2034 Under the EIANZ effects management framework, residual adverse effects that are predicted to be Low or Very Low require that normal design, construction and operational care should be exercised to minimise adverse effects. Very low level effects can generally be considered to be classed as ‘not more than minor’ effects under the RMA 1991. The underlying context for frog populations at this site is assumed to be the same for Archey’s and Hochstetter’s frogs elsewhere – that populations are moderate to large with low ongoing or predicted decline. Predicted long-term (i.e., over three generations or ~30-45 years) declines of 10-30 %, primarily the result of mammal predation (rodent and larger predators), are anticipated. Furthermore, loss of recruitment through loss of adults, or loss of young frogs possibly caused by smaller predators (such as mice), may eventually lead to the loss of Archey’s and Hochstetter’s frog populations across this site and others. Where possible loss or decline is predicted to occur, this suggests that there must be research and management avenues to investigate practical means of stabilising or reversing decline trends. The WUG project places risks on frogs that are in addition to the probable risks already faced by the populations at this site by introduced predators. At the smallest end of the risk scale – i.e. the loss of small areas of habitat from vegetation clearance and human activities around the surface of WUG – the loss of, or increased vulnerability of, frogs may result. The intention by OGNZL is to manage these above-ground effects through a suite of on-site management interventions (as outlined inTable 2); however, there is scope to include positive initiatives within the adaptive management programme described below, which is proposed to address the key potential effects described inTable 3. Because there is no available information on the sensitivity of Archey’s and Hochstetter’s frogs to blast vibration (beyond the levels measured elsewhere) and air discharges (albeit less than roadside locations where Archey’s and Hochstetter’s frogs persist), there is a case to be made for either: 1. Avoiding works that create vibration and air discharges in the Wharekirauponga area, or 2. Applying the most stringent engineering designs practicable to minimise likelihood of adverse effects; or 3. Proposing a range of initiatives that could provide benefits to Archey’s and Hochstetter’s frogs at this site or elsewhere to balance risk of loss at WUG. There is no feasible means of mining the resource at WUG without creating some vibration and air discharges; therefore, avoidance of all vibration and air discharges is incompatible with the development of the WUG mine. OGNZL has applied a standard of engineering design that exceeds standard designs elsewhere and is specifically designed to reduce potential adverse effects. The use of further reduced explosive packages and vent air scrubbers is technically feasible to apply; however, may jeopardise the commercial viability of the project. These initiatives will be held by OGNZL for application if they become absolutely necessary. Therefore, a pro-active approach that recognises the low (but uncertain) level of residual risk posed by the project to Archey’s and Hochstetter’s frogs and frog habitat has been adopted by OGNZL. There are a range of initiatives that could be undertaken by OGNZL on-site and off-site that could result in tangible, additional benefits for Archey’s and Hochstetter’s frog populations at Wharekirauponga and elsewhere. These constitute actions that are defined as further mitigation, or biodiversity offsetting, or ecological compensation and, for this project, would seek to provide measurable benefits for Archey’s and Hochstetter’s frogs. The intended outcome of either of these approaches (on-site or off-site programmes) is supported by OGNZL and aligns well with its company ethic of providing for ‘net-gain’ or a clear benefit for areas of environmental risk in the locations that it operates. The Department of Conservation has also recently started to pursue ‘net benefit’
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