Advanced science is being applied to the reclamation of mines and polluted industrial sites, returning them to pristine condition, writes PADDY WOODWORTH
IF YOU KNOCK down a forest and strip the minerals beneath it to a depth of several metres, can you really put the forest back again afterwards, with all its constituent species?
Scientists working for Alcoa's bauxite (aluminium) mines near Perth in Western Australia (WA)claim to have shown that they can indeed restore the rich biodiversity of the threatened Jarrah ( Eucalyptus marginata) forest after mining, at least in the short term, right down to the last obscure species of sedge or sundew, many of which are endemic to the region.
And the news gets better: senior research scientist Dr John Koch told me on a visit to the forest this month that recent data indicate restored areas are significantly more resistant to "die-back", a devastating disease caused by an introduced soil-borne pathogen ( Phytophthora cinnamomi), than are unmined parts of the forest.
Further research in this field could make a contribution towards combating the disease in other threatened regions of south-west Australia, a biodiversity hotspot.
Two years ago, the journal Restoration Ecologyreported that the restoration of the Jarrah forest has been remarkably successful. Last month, a conference of the Society of Ecological Restoration International in Perth heard another series of papers delivered that confirmed these findings.
Still, it’s hard not to be just a little sceptical. Putting a positive spin on stories of deep environmental degradation, or “Greenwashing”, is a notorious technique of corporate PR in the mining industry. “Rehabilitation” often translates into a monocultural plantation, or a golf course.
And indeed, had you visited Alcoa’s “rehabilitated” sites in the Darling Scarp Jarrah forest in the 1960s, you would have seen barren rows of pines replacing the rich Jarrah plant communities.
A combination of public protests and a change of heart by local management appears to have propelled Alcoa in WA to the forefront of restoration ecology. The company’s record elsewhere still leaves a great deal to be desired, and even in WA there are still big problems with refining residues, but these are outside the forest.
Over the past 30 years, a team of ecologists, led first by John Gardiner and now by John Koch, has pioneered a series of meticulous techniques to achieve their current results in WA.
These include “double-stripping” of topsoil prior to mining. The first five centimetres, rich in seed and microbes, is lifted off first, and within days it is laid on an adjacent area undergoing restoration. The second, deeper layer of “overburden”, with much less organic life, can be stored for longer without ill effects.
Mining removes up to four metres of bauxite below the overburden. Before restoration, the site is re-contoured by heavy machinery to mimic local topography, and then deep-ripped to break up compaction and give the plants access to water. Seeds of every species previously found in the area are then planted, where possible. But some plants won’t propagate by seed, and Alcoa has built a $3 million (€2.2m) laboratory to germinate them by tissue culture, after which they are planted individually.
A layman must wonder if the removal of the bauxite itself will have negative effects in the long term, even though there is no evidence – so far – that any of the plants need it for nutrition.
“The trees seem to respond to all the same factors as an unmined forest,” responds Koch. “Call me in 2020 and I will let you know how the 50-year-old Jarrah is going!”
Paddy Woodworth is researching a book on ecological restoration projects worldwide. Titled Restoring the Future, it is due to be published by Chicago University Press next year