The analysis shows that coal companies have bought up vast areas of freehold land, “including much of the highest quality agricultural land”, in the Hunter Valley and Gunnedah Basin.

In total, coal companies now own more than 284,000ha of freehold land, an area larger than the entire Australian Capital Territory, LTG said.

LTG looked at coal mining leases and land ownership in eight local government areas affected by mining: Gloucester, Gunnedah, Liverpool Plains, Mid-western, Muswellbrook, Narrabri, Singleton and Upper Hunter.

It also conducted land title searches and analysed the information in a digital mapping system. A map was generated by matching NSW cadastre data to land and property ownership information it obtained.

In the Muswellbrook local government area, coal companies now own 24% of all freehold land and 23% of all mapped biophysical strategic agricultural land (BSAL), while in the Singleton local government area, they own 15% of all freehold land and 27% of all mapped BSAL.

According to the NSW government’s Planning & Environment division, BSAL is land with high quality soil and water resources capable of sustaining high levels of productivity, and plays a “critical” role in the state’s $12 billion agricultural industry.

A total of 2.8 million hectares of BSAL across NSW has been identified and mapped, the department said.

“Recent coal mine approvals have mandated mass purchases of rural land by coal companies,” LTG said.

“For example, the number of properties that have been identified for purchase by mining companies because the noise and dust impacts are so severe, including 12 properties near the Maules Creekk mine, 16 properties near the Moolarben mine, 36 properties near the Mangoola mine, 18 properties near Mt Owen.

“The Mount Pleasant proposal, which has not yet gone ahead, identified 47 properties for purchase and the last Bengalla approval had 21 properties within the acquisition area.”

LTG also said there were numerous other mines seeking approvals or expansions “that will see even more of our best farmlands flogged off to multi-nationals”, such as Shenhua's Watermark project on the Liverpool Plains, the expansion of the Mount Thorley and Warkworth mines towards Bulga village and the Rocky Hill coal mine next to Gloucester.

LTG quoted local Hunter Valley historian and resident of Bulga village Stewart Mitchell – “much of which is slated to be bought by international mining giant Rio Tinto for the expansion of their Mount Thorley Warkworth mine complex – as saying the scale of land ownership by coal mining companies in the Hunter Valley has long been a cause of anxiety and speculation.

“Coal mining companies own not just the area being affected by mining, but huge numbers of properties that have been rendered unliveable by the noise and dust impacts of nearby mines,” he said.

“The destruction of flourishing rural villages by multi-national coal mining companies is unique to this part of New South Wales. We don’t want Bulga to go the way of so much of the Valley, bought up by huge mining companies to leave to rot and ruin.”

Lock the Gate NSW Coordinator Georgina Woods said that with so much floodplain land and productive farmland in the hands of mining companies, “we are neglecting the great food growing potential of the Hunter Valley, and we’re at real risk of repeating this mistake in the Liverpool Plains and beyond”

“This map clearly shows that the balance has gone too far towards multinational mining giants. Scores more properties are slated to be bought by coal giants if the next round of mine expansions go ahead, in some of our best floodplain land,” she said.

“We’ve simply got to stop mindlessly flogging off the farm, and tell the coal industry that they’ve taken more than enough of the Hunter Valley already.”

A spokesman for Rio told the Sydney Morning Herald that the company had no interest in commercial properties and that an earlier Planning Assessment Commission decision had provided for voluntary acquisition of the 24 sites.

"A number of local residents, based on their individual circumstances, have expressed a desire for voluntary acquisition of their properties," the spokesman said.

"[Rio] has committed to honouring the voluntary acquisition rights granted to some residents under the Warkworth Extension 2012 planning approval determined by the Planning Assessment Commission.

"Our intention would be to lease out any properties purchased, assuming they are in suitable condition."