Rehabilitation of mine sites in Western Australia may be improved after Perth researchers identified several species of native plants well suited to tolerating conditions at the old sites.
Rehabilitation of mine sites in Western Australia may be improved after Perth researchers identified several species of native plants well suited to tolerating conditions at the old sites.
The research team from Curtin University looked at how about 50 native plants grew on mine tailings at the Karara iron ore mine in the Mid West to determine how they fared compared with plants grown in natural topsoils.
The research, supported by BHP Group, Hanson, Karara Mining, Mineral Resources and Sinosteel, found initially only a few species could prosper on the sites.
Curtin University ARC Centre for Mine Site Restoration research fellow, Adam Cross, said mine sites caused soils to be altered sharply from their natural physical and chemical characteristics.
Dr Cross’s team had been trying to identify whether or not it was possible to return native plants to these environments.
“The numbers of species that were very tolerant to this material were quite low, only 4 per cent of species that we tested performed as well on this tailings material or better than on the native soils,” Dr Cross said.
“But interestingly, those species were from groups that are able to fix their own nitrogen from atmospheric nitrogen.”
He said most plants struggled to grow because the natural soils in the area had a pH of around four or five, which is quite acidic, and mining activity had changed the pH level to nine or 10, which was very alkaline.
“A number of species are simply excluded from growing because they don’t have the physiological tolerance to be able to take in nutrients at that sort of pH level,” Dr Cross said.
Although the researchers only tested a handful of species, he said it seemed likely there would be others that were as tolerant or capable of growing.
He said the study was useful as a similar approach could be applied to other areas of WA.
A Senate inquiry into mine rehabilitation completed in March 2019 reported there were about 50,000 abandoned mine sites throughout the country and nearly 10,000 in WA, but these figures were incomplete due to a lack of data compiled by the states.
Abandoned mines occur when mining leases or titles no longer exist so the responsibility of rehabilitation cannot be allocated to the operator and remedial work falls to the government.
In WA, miners contribute levies to the Mining Rehabilitation Fund to ensure there is funding the governments to respond to the issues of abandoned mines. Five rehabilitation projects are currently funded by the program.
“It is not an exaggeration to say that, in the last decades, industry has certainly not achieved what has been expected of them in their restoration standards,” Dr Cross said.
“That is changing, albeit slowly in some industries, and we are seeing that some industry champions are now going above and beyond and striving to meet very high standards of restoration.”
He said it was a fallacy that completing mine rehabilitation properly was more costly.
“I would say that it is more expensive to come back and reattempt restoration once you have failed initially,” Dr Cross said.
“What we have seen throughout the state is legacy sites where restoration has never occurred in 60 or 80 years and for companies to now return and redress that will be very expensive indeed.
“The estimates that have been put at the restoration of abandoned mine sites, for example, where problems in regard to substrate chemistry and things like that are quite extreme are in the tens of millions of dollars.
“So really, getting it right the first time probably represents the cheapest option for any company when undergoing their restoration.”
The environmental and social costs are also high, with the Senate inquiry finding incomplete or inadequate mine-site rehabilitation led to changes to water quality, disrupted communities, changed biodiversity and permanent impacts on surface and groundwater pathways.
Dr Cross said Australians lived and work in one of most biodiverse places on earth and had a duty to protect it.
“Industry has a real responsibility not to just walk away from the responsibility to reinstate that biodiversity after they reap a profit from iron ore extraction or any other industry and I think it’s really fantastic that we are seeing industry supporting research to ensure we are able to assist them in meeting those requirements,” he said.
