The Lower Hunter green corridor's starting point was a hotchpotch of national parks, privately held land and miscellaneous conservation lands that barely covered a total of 4000 hectares.

It now stands as a definable 23,000 hectares - that's about 50,000 football fields - of ecologically diverse asset stretching between the Watagans and Stockton Bight.

"I don't think it has really sunk in for a lot of people what has been accomplished here," Green Corridor Coalition foundation member Brian Purdue said yesterday.

"We have Blackbutt in Newcastle but that pales in comparison to what has been accomplished out here."

The corridor supports hundreds of animal communities ranging from the spotted quoll in deep in the Watagan Mountains the sea eagle on Stockton Bight.

"Hexham Swamp is a vital link between coastal wetland environment on one side and the hinterland on the other," retired fisherman and wetland rehabilitation volunteer Dennis Hirst said. "The merger of these two environments promotes an incredible diversity of wildlife."

The green corridor achievement would not have been possible without skilled and determined negotiations between community representatives, government departments, industry and private landowners.

One of the most significant wins was the transfer of 2500 hectares of former Coal & Allied-owned land at the Tank Paddock near Minmi.

"The co-ordination that's occurred between government departments, local council planners, developers and the catchment management authority to make this happen has been remarkable," director of the University of Newcastle's Tom Farrell Institute for the Environment Professor Tim Roberts said.

"It's a project that's a testament to the skill of everyone involved and its legacy will last for generations to come."

The corridor today is made up of a network of beach and dunes, swamp, wetland and various types of forest.

While much has already been achieved, several major land transfer issues remain unresolved. Arguably, the two most important involved Hunter Water Corporation-owned wetlands at Minmi and Hunter Development Corporation land west of the M1 motorway at West Wallsend, Mr Purdue said.

Wallsend MP Sonia Hornery, who lobbied to establish the corridor, said it was essential that the gains made were not undone by the pressures of urban development.

"I'm very conscious about the need to ensure that future development does not compromise what has been achieved," Ms Hornery said.

"I'd be concerned if the route of the Lower Hunter freight rail bypass ran across the Tank Paddock."