Exploring biophysical limitations and post-mining native ecosystem rehabilitation outcomes in Queensland

Abstract

In Queensland, Australia, the objective of mine rehabilitation is for land disturbed by mining to attain a ‘stable condition’, which is defined as land that is, safe, stable, non-polluting and able to sustain a post-mining land use (PMLU). Mining companies need to articulate achievable and measurable rehabilitation milestones and milestone criteria to demonstrate progress towards these rehabilitation objectives via Progressive Rehabilitation and Closure (PRC) plans. A commonly proposed PMLU is native ecosystem, though there is not a state-wide definition of ‘native ecosystem’ for the purposes of rehabilitation, and existing rehabilitation milestone criteria for this very broad PMLU vary considerably between sites. It is in this context that the Office of the Queensland Mine Rehabilitation Commissioner is undertaking research to define and understand the drivers for various native ecosystem rehabilitation outcomes and describe best practice with respect to planning for and evaluating the success of native ecosystem PMLUs in Queensland. In Queensland, rehabilitated ecosystems that develop in highly disturbed landscapes often produce one of the following outcomes: they may be natural (restored to the extent of historic succession trajectory); hybrid (have some but not all characteristics of the natural/historic landscape, and some novel attribute); or novel (a new assemblage of abiotic and biotic attributes resulting in a stable alternative ecological form). This natural–novel paradigm, is a useful tool for evaluating rehabilitation options on mine sites. However, the natural–novel concept is not without controversy or criticism. For example, it raises the question: does accepting ecosystem novelty equate to a ‘lowering of the bar’ with regards to ecosystem rehabilitation goals? Or, conversely, is ecosystem novelty an opportunity for innovative delivery of ecosystem services in otherwise degraded landscapes? In the present work, we extend on the natural-hybrid-novel framework to include substitute natural ecosystems as a rehabilitation outcome that should be considered when biophysical limitations preclude establishment of the pre-mining natural ecosystem. We also articulate the distinction between planned novel ecosystems (i.e. ecosystems designed to deliver beneficial environmental outcomes) and unplanned novel ecosystems (the inadvertent result of rehabilitation attempts when biophysical limitations preclude natural ecosystem establishment) and suggest that these, and hybrid ecosystems, be evaluated in light of the environmental, biological and human-centric ecosystem services they deliver.