Frank Batini

Probably the world’s largest mine, in terms of area, is Alcoa’s bauxite mine, located in the northern jarrah forest, within a biologically rich area, close to the State’s capital city (Perth) and on its domestic water supply catchments. In the past 60 years some 30,000 ha have been cleared and mined and about 25,000 rehabilitated. Because the individual mine-pods are scattered, a total of 90,000 ha of native forest has been impacted by mining.

Mining is not subject to the WA Forest Management Plan and, while the Government has decided that timber harvesting will stop at the end of 2023, mining of jarrah forests will continue, at least until 2045, when Alcoa’s 84 year lease will be re-negotiated. By this time, I expect that most of the high-rainfall, high-quality forest between Perth and Collie will have been mined.

These activities are supported by Government, even though mining and refining to alumina is energy intensive, producing vast volumes of carbon dioxide. Alcoa is the largest user of natural gas in the south-west and pays far less for each unit of gas than do other consumers. Alcoa has recently announced a $1.3 billion profit to its American and Australian owners.

After removal of timber products, the area to be mined is cleared, the topsoil and subsoil are removed separately, then 2-5 m of bauxite is blasted and trucked to a crusher, the subsoil and topsoil are returned, the area is shaped to retain water, it is deep-ripped to encourage infiltration and is then fertilised and seeded with a mixture of native overstorey and understorey species. The emphasis is to produce a self-sustaining ecosystem and to minimise erosion. In addition to the mine pits, areas that were affected by dieback disease are replanted. Because access is more difficult, there is a reduction in the areas that are prescribed-burnt. All of these steps increase crown cover.

As crown cover increases, water yield decreases. The greater the area mined and rehabilitated to tree plantations, the greater is the water loss. In 2007, Alcoa reported that the loss in yield from five monitored catchments, where mining had occurred on part of the landscape, was 40-50 mmpa greater than in the un-mined forest. In the intervening 16 years the trees have grown and would now be using much more water. If we apply a conservative reduction in yield of 50 mm/ha to the area now impacted by mining (90,000 ha) the “loss” in water yield from catchments harnessed for water supply is at least 45 Gl (billion litres) each year. This volume of water would fill 30 MCG’s.

This water is no longer available for stream-flow and other essential ecosystem processes.  To replace it with desalinated drinking water costs the Water Corporation $2-$3 per Kilolitre, or $90-135 million each year. This additional cost is then passed on to the taxpayer. Yet the royalty paid to the State in 2022 was only $78 million.

Professional foresters have, for decades, proposed a solution. Having established these stands of trees, it is essential that Alcoa provide some money for their maintenance. There is a need to thin the dense tree plantations to a desirable density; to control any coppice from the stump and to undertake more regular prescribed burning. These activities are estimated to cost between $1500 and $2000 per hectare, or $37-50 million in total. Once the first thinning/burning has been completed, the areas could be handed-back to the State, and Alcoa’s responsibilities would cease.

The draft Forest Management Plan (2024 -2033) foreshadows an annual thinning program of up to 8000 ha. Yet the FMP fails to specify: where these areas are, the species available, their size-class distribution, whether the product can be offered for sale and if not, who will pay for the cost of thinning. The forest managers (Parks and Wildlife) clearly do not have sufficient funds and Alcoa argue that all rehabilitated areas are no longer their responsibility. While this impasse exists nothing is done and the annual loss of at least 45 billion litres of water continues.

References
Water Corporation (2005), Wungong Catchment Environment and Water Management Project.
J T Croton and A J Reed ( 2007). Hydrology and bauxite mining in the Darling Range. Restoration Ecology 15 (4) p S40-S47.

Frank Batini MSc (Oxon), BSc (UWA), Dip For (AFS), previously an Adjunct Professor of Environmental Science at Murdoch University has 60 years of  experience as a forester, environmental manager and consultant in the management of natural resources.