With negotiations over coming months to restart logging in the critical Bermagui to Tathra area, ecologists are warning of the need to protect the habitat of the vulnerable coastal colony.

Chris Allen, one of the leading researchers of the southern koala, said there were signs numbers on the far south coast had increased since the previous study, finished in 2009, estimated fewer than 50 were left.

''We have gone back through that country in 2012-13 and there are some indications koala numbers have increased,'' he said.

''In some areas, there's possibly an expansion … up to 30 per cent, and in other parts there is a contraction.''

Mr Allen, a senior threatened species officer with the NSW government's Office of Environment and Heritage, said while no specific figure could be given with certainty, the population estimate of 60 by conservationists was ''probably in the right ballpark''.

The perceived increase is based on extensive field work - recording koala droppings over 35,000 hectares - and not on reported sightings.

Mr Allen said a rise in numbers was likely because of better rainfall, which led to higher quality eucalyptus leaves, and freedom from natural and human-controlled impacts such as bushfires and logging.

''In those areas where [there] appears to be recovery, there appears to be significantly less impact … there has been a significant absence of impacts in the past 30 years,'' he said.

The koala ecologist said destruction of habitat was the major reason for the longer-term decline in numbers, with rural subdivision ''almost certainly a factor'' in the loss of koalas north of the Bermagui River.

The forestry industry had not logged in the populated areas but Mr Allen said there were important impending decisions to be made by government about future use of state forests.

''State forest areas being used by koalas have been committed as timber supply areas,'' he said.

Forestry Corporation of NSW's Daniel Tuan said selective logging was likely to be renewed in state forests between Bermagui and Tathra, but negotiated amendments to a threatened species licence - hoping to be made by the end of June - would include extended protection zones.

''It will be in the realms of several thousand hectares of exclusion zone,'' Mr Tuan said.

Peter Rutherford, forestry manager at South East Fibre Exports, which runs the Eden chip mill, said the company did not take the primary tree species koalas sourced for food.

''Forest red gums, woollybutt, ironbark … we don't take them,'' he said. ''We take stringybarks, silver top ash. Koalas will eat them, but they're not preferred.''