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• SSR150 - Revegetation of mined land in the wet-dry tropics of northern Australia: A review (PDF - 722 KB)

Executive summary

This review aims to assist the Alligator Rivers Region Technical Committee (ARRTC) in determining whether current practices and plans for revegetation at Ranger mine and elsewhere in the Alligator Rivers Region (ARR) are appropriate, and to establish research priorities in this region. The majority of information regarding revegetation in the wet-dry tropics (WDT) of northern Australia pertains to Ranger mine. However, there is a dearth of peer-reviewed published papers which is a significant problem that may limit effective communication and application of appropriate revegetation techniques on mines in the WDT.

The use of topsoil on hard rock mines in northern Australia is a contentious issue, with topsoil re-spreading being excluded from many rehabilitation programs. However, the experience of many WDT rehabilitation researchers indicates that use of topsoil containing indigenous microbes, valuable nutrients and organic matter increases the probability of achieving a successful, self-sustaining native ecosystem in the long term (eg Bell 1993, Hinz 1996, Tongway et al 1997). Because of the negative effects associated with stored topsoil use at hard rock mines, research is required on effective collection, handling and storage strategies for stored topsoil. Studies are also needed to determine the minimum amount of topsoil required for effective rehabilitation.

There is a paucity of literature on the long-term successional development of revegetated areas in the WDT. On disturbed sites in the WDT, the dominance by early successional species such as acacias has been found to retard successional development, with poor recruitment of eucalypts and other species to these systems (Setterfield et al 1993). Given the discrepancy between the time scales of many revegetation programs and subsequent lease relinquishment, and the time required to effect succession, accurate prediction of successional development of young rehabilitated areas is important. Research is also required to produce a body of organised, reliable theory and practice for industry on the selection, germination and establishment of a composite of species that will increase the likelihood of successional development toward a target ecosystem.

Perhaps the most important issue affecting the successional development of young rehabilitated areas towards self-sustaining native vegetation communities is fire. The existing literature pertaining to the role of fire in tropical systems focuses on mature systems rather than on young rehabilitated areas. Research is needed to establish the time required for the development of fire resistance in the various woody components of rehabilitated areas. There is also a need to quantify the frequency and timing of burning regimes that could reduce the risk of high intensity fire in younger rehabilitation and direct species composition/successional development of older rehabilitation.

Finally, there is a requirement, both during and upon completion of rehabilitation, for the redeveloped landform, soils and vegetation to be monitored and assessments made of how successful the rehabilitation process has been. This review examines five methodologies that have been used to assess the success of rehabilitation in the WDT. Success criteria based on a single or narrow set of parameters are likely to be inadequate. A study comparing the indicator value of the various monitoring methods would be valuable, with a possible outcome being the development of a 'multi-discipline' monitoring approach.

Gaps in the existing knowledge or practices that may limit the success of revegetation at minesites in the Alligator Rivers Region are identified. The most critical issues are identified broadly as: topsoil utilisation and management; fire; management/prediction of successional processes; establishment of symbiotic microorganisms; native seed collection, storage and germination; development of monitoring methodologies and acceptable success criteria; and technology transfer.