Mining giant Rio Tinto has formally handed over more than 2000 hectares of former Coal & Allied land at Stockrington and Black Hill to the state government.

The land, which includes the prized Tank Paddock area at Minmi, and extending down the M1 through the local government areas of Newcastle, Lake Macquarie and Cessnock, will become national parkland.

It ends a nearly a two-decade skirmish between conservationists, mining companies and the state government to complete the “green corridor” – a natural buffer zone between housing and wildlife and endangered ecosystems.

​The transfer is particularly meaningful for the Green Corridor Coalition, which has heavily campaigned for a protected continuous stretch of native vegetation between the Watagan Ranges and Port Stephens since 2003.

The land now in the fold was first set aside as per development approvals for housing estates in Minmi and Black Hill in 2006, but its hand over was delayed by the slow wheel of bureaucracy.

“This was the missing link,” coalition co-ordinator Brian Purdue said. “We’ve been waiting 10 years for this day to come. We couldn’t be prouder.”

The completed corridor is environmentally rich, containing at least five endangered ecological communities including freshwater wetland, lowland redgum, spotted gum ironbark, swamp mahogany paperbark and swamp oak bushland.

It is also home to the threatened koala and masked owl species.

Rio Tinto Coal Australia managing director Sinead Kaufman said the past would be preserved forever.

The eastern end of the land is littered with the Hunter’s mining history, and includes a steam railway corridor, timber trestle bridges and brick-lined tunnels.

“This land will provide an enduring legacy for the community and future generations,” Ms Kaufman said.

Other land already in the corridor belonged to BHP.