About 40 hectares of coastal land in South Australia's lower south-east has been bought by the State Government in a bid to protect the habitat of the critically-endangered orange-bellied parrot.

Environment and Conservation Minister Ian Hunter has announced two properties between Carpenter Rocks and South End have been bought to add to the protection of 50 kilometres of coastal habitat.

Mr Hunter said the land purchases would provide an important corridor of remnant native vegetation which would benefit the parrots, which are known to migrate along the coast.

"Some of them are the thatch and grass sedgeland — it's a wetland community — that's considerably vulnerable due to clearance and drainage, swamp habitats and also the antechinus, the swamp antechinus, the olive whistler bird and of course the very famous orange-bellied parrot," he said.

"It's been long known to be a vulnerable population and linking up areas of habitat give it the best possibility of maintaining its nesting sites.

"It's very important that we can actually consolidate these areas of protected reserves so we actually increase its range and increase its ability to produce young in the wild."

He said one property — about 30 hectares adjacent to Carpenter Rocks Conservation Park — held high biodiversity value and would provide protection for the Carpenter Rocks Gum, a species listed as vulnerable in the state.

The second property is about 10 hectares in size and adjacent to Bucks Lake Game Reserve.

Mr Hunter said conservation and parks organisations assisted in the process with the Foundation for National Parks and Wildlife New South Wales, the Nature Foundation SA and Friends of Naracoorte Caves National Park giving "significant funding assistance" for the land adjacent to Carpenter Rocks Conservation Park.

The Friends of Mount Gambier Area Parks, the Friends of Shorebirds South East, the Friends of Beachport and Canunda Parks, and the Millicent Field Naturalists contributed to buy the property adjacent to Bucks Lake Game Reserve.