Those points were made by a series of submitters, including for the Department of Conservation, at a Dunedin resource consent hearing yesterday.
Making legal submissions on behalf of director-general of conservation Lou Sanson, Pene Williams acknowledged the economic importance of the mining in North Otago and the wider Otago region.
And the director-general also accepted that the physical constraints of mining at Macraes meant it was not appropriate for OceanaGold to avoid all adverse effects of its activity.
But, if consents were granted, adverse effects, especially over biodiversity, should be ''appropriately avoided, remedied or mitigated'', Ms Williams said.
Discussions with Oceana had proved fruitful and some of the director-general's concerns were being addressed through changes to proposed consent conditions.
Part of the submission focused on adverse effects on native fish habitat, including for non-migratory Taieri flathead galaxiid fish and koura, a native freshwater crayfish.
Any proposed conditions over the mining extension project should ensure ''robust ongoing monitoring'', and the consent authorities' duties should not be delegated to ''some other person or entity'', she said.
Department of Conservation technical adviser Lynn Adams said in another submission it was ''highly probable thousands of lizards will be lost''.
Avoiding ''important habitat'', with higher lizard abundance, was the best way to reduce impacts, and the footprint of the mine and waste rock stack should be reduced and some areas of high-value vegetation avoided, she suggested.
Oceana wants to open a 63ha pit called Coronation North, which could result in a two- to three-year mine-life extension at Macraes, in East Otago.
Oceana has applied to construct Coronation North, extend the existing Coronation pit to 85ha and build a waste rock stack of up to 202 million tonnes, covering 197ha. The company also wants a dam at Coal Creek.
Boundary overlaps mean the company needs resource consent from the Otago Regional Council, Waitaki District Council and Dunedin City Council, and the ORC is overseeing the process.
The hearing opened in the Dunedin Municipal Chambers on Monday before chairman Dr Brent Cowie and commissioners Colin Weatherall and Waitaki councillor Peter Garvan.
Company general manager Dale Oram has said the mining extension would contribute'' significantly'' to the economy, and the company would provide mitigation and compensation for ''unavoidable effects'' on the environment.
Among other submitters yesterday, Brian Rance, a technical adviser at Doc in Invercargill, gave evidence on behalf of the director-general.
Several wetland types were present in the proposed project impact area, and such wetlands were features of national importance, including ''ephemeral wetlands'', which were ''critically endangered''.
Oceana had proposed an ecological mitigation package, and Mr Rance supported providing protective covenants for indigenous vegetation areas known to be ecologically important.
But, overall, the proposed package had ''some deficiencies'' and should be improved, Mr Rance said.
The hearing is scheduled to end today.
