The site, known as Mount Malumla, is next to Barrington Tops National Park.

Biodiversity Land, a Hardie Pacific subsidiary, owns the site.

Hardie Pacific founder Duncan Hardie is known in the Hunter for gaining development approval for the massive Huntlee project, near Branxton.

The entrepreneur bought the Barrington site in 2007, foreseeing its potential as a biodiversity investment.

His dedicated biodiversity land company was established in response to rising public awareness about the need to protect the environment for future generations.

The company owns about 20,000 hectares of biodiversity land, mainly next to national parks and in environmental corridors.

Jamie Boswell, Biodiversity Land's property manager, said the Barrington site was a degraded rural property with cattle when the company bought it.

The land has since had its boundary fencing upgraded and access blocked to protect the ecology. Feral pig eradication and weed removal were done to help the native plants and animals to thrive.

Work was done over the past 15 years to help the koala habitat regenerate.

"We're finally seeing vast improvements up there," Mr Boswell said.

"We've always known koalas were there. We've seen them there multiple times."

The site contains a large amount of Sydney blue gum trees, which is core koala feeding stock.

Mr Boswell said photos taken on the land could be used as "a tourist brochure". The land is zoned rural and could have been logged, for example, but the company has chosen to protect and improve its biodiversity.

"A lot of people take the negative side of developers not doing anything for the environment, but we've been doing this for a lengthy period," he said.

"This is a different side that people don't see. It's not always the greedy developer."

Mr Boswell said the company had received various approaches for the land over the years.

"At this stage we've just been improving the property," he said.

The site could be sold to the NSW government under its $193 million koala strategy, which aims to protect 22,000 hectares of koala habitat.

It could also be part of an expanded national park, or be used as a biodiversity offset for a range of developments such as wind farms, land developments and infrastructure projects.

Mr Boswell said the company had invested a substantial amount to improve the property, but the exact figure is confidential.

He said the property could generate about $20 million in offset credits.

"At a point in time there will be a clear direction on which way to go, whether it's setting up offset credits or potentially selling the site as a whole. It's been rewarding not to rush with the property. The photos speak for themselves," Mr Boswell said.

He said an ecological survey had recently recorded about 10 koalas on the site.

The ecologists couldn't get pictures of them, but made sound recordings.

"Most of the recording work is done nocturnally. They set up song meters that record them over two weeks. It's challenging during the day to spot a koala with this rain we're having because they generally bunker down and don't move too much.

"Historically there have been multiple koala sightings and recordings in the adjacent national park. It was exciting to have recorded multiple koala activities on this property."

The Barrington Tops National Park is part of the Gondwana rainforest area, which is known as an ancient landscape.

Now the Mount Malumla site has been restored, it has a similar feel.

"The ecologists that went up there say it's almost like going into a different world," Mr Boswell said.

Fieldwork on the land has also identified glossy black cockatoos, southern myotis (fishing bat) and yellow-bellied glider, all of which are threatened in NSW.

Other threatened species recorded on the property include spotted-tail quoll, greater glider, powerful owl, masked owl, sooty owl and squirrel gliders. Hundreds more species are thought to be on the site. "The more ecology work we do, the more we discover," he said.

Biodiversity Land's portfolio has so far provided environmental offsets for projects including Bengalla mine, Integra Coal, PWC T4 terminal, Huntlee and various other residential land developments in the Hunter.

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