Bauxite Mining Rehabilitation
Alcoa mines and rehabilitates around 600 hectares of jarrah forest each year in the Darling Range south of Perth. To date, 14,500 hectares have been revegetated and restored. We mine around 32 million tonnes of bauxite each year and have cleared just one per cent of Western Australia’s jarrah forest since 1961. Our rehabilitation objective is to re-establish a functional ecosystem that will fulfil the pre-mining forest land uses including conservation, timber production, water catchment and recreation.
The jarrah forest in Western Australia, where our Huntly and Willowdale mines are located, is renowned for its diverse flora, being one of the most plant species-rich forests in the world. Therefore restoring botanical richness in the new forests on mined areas is a critical objective for Alcoa.
We are committed to high standards of environmental performance and aim to return 100 per cent of plant species richness in our rehabilitated mine site areas, compared with pre-mined jarrah forest. We achieved this milestone in 2001, becoming the first mining company in the world to reach that goal. In that year, we returned an average of 101.4 per cent of botanical species to our rehabilitated areas across our Huntly and Willowdale mine rehabilitation sites in Western Australia. A number of challenges since 2001 (including years of low rainfall which has resulted in decreased natural soil seed banks as a result of poor flowering and seed set, and early autumn rains meaning soil ripping operations were not completed in dry soil conditions) prevented us from reaching this target again until recently. Results (complied in 2008) from our rehabilitation that was planted in the 2006/ 07 season showed our highest ever return of botanical richness - equal to 108.2 per cent. This result means that on average there are more species found in a rehabilitated area, compared with an equivalent area of existing unmined forest.
The species richness results obtained from our rehabilitation monitoring are fully analysed each year and the factors contributing to the results are fully investigated. Our investigations have lead to modifications to our rehabilitation procedures, with the aim of improving future rehabilitation.
The ability to restore a piece of altered land relies heavily on a good understanding of the area’s ecology. Alcoa’s environmental departments work in collaboration with local universities, government agencies and private researchers in understanding the forest ecosystems to ensure Alcoa’s rehabilitation is second to none.
In 2007, our bauxite mining operations received a prestigious Golden Gecko award, recognising environmental excellence in the closure, remediation and rehabilitation of our first bauxite mine at Jarrahdale. This was our second Golden Gecko award, having also been recognised in 2002.
The bauxite mine rehabilitation program involves:
- reshaping mined areas to blend with the surrounding landscape;
- building earthworks to control run-off from the rehabilitated area;
- returning topsoil and logs to help in flora and fauna return, and to maximise soil nutrients;
- contour ripping subsoils to assist in tree root penetration, maximise water infiltration and assist in erosion control;
- seeding tree, understorey and other species indigenous to the jarrah forest; and
- a once-off application of nitrogen and phosphate fertiliser, usually by helicopter.
The jarrah forest is home to a rich array of fauna, many of them unique to the South West of Western Australia. Re-colonisation by mammals, birds, reptiles and invertebrate group into newly rehabilitated forest after mining is one the key success indicators of rehabilitation.
Fauna management activities undertaken by Alcoa include:
- pre-mining fauna surveys;
- fauna monitoring in rehabilitated areas and the surrounding unmined forest;
- return of large logs as fauna habitats to rehabilitated areas;
- translocation of rare or endangered animals into rehabilitated regions; and
- funding fox baiting of the broader forest.
We undertake pre-mining fauna surveys before entering a new mining region. If rare or protected species are found during the surveys, management plans are developed to minimise any impact on them.
Results from monitoring and research projects have shown that 100 per cent of mammal species, 90 per cent of bird species and 89 per cent of reptile species that inhabit upland parts of the forest where mining occurs have recolonised rehabilitated areas within 10 years.
Current research is focusing on reptile species that have more specialised requirements for food or shelter and which are slower to return to rehabilitated areas, to determine how their return may be accelerated.
Read more about bauxite mining.