Novel ecosystems created by coal mines in central Queensland’s Bowen Basin

Abstract

Open-cut coal mining began in central Queensland’s Bowen Basin approximately 50 years ago. Over this period of time, mine rehabilitators have used a variety of tree, shrub, and groundcover species to create ‘novel ecosystems’ to stabilise soils and provide vegetative cover for pre-supposed final end-land uses. We examine post-mining rehabilitation from multiple soil and vegetation monitoring activities in the Bowen Basin to assess the similarity of landforms, plant composition, and trends in plant diversity compared to unmined reference communities. Rehabilitated spoil dumps and reference sites were assessed using soil and vegetation data contained in compliance monitoring reports from Goonyella Riverside, Moura, Oaky Creek, Rolleston, and Blackwater mines. Slopes, soil chemistry, and plant species mixes of rehabilitation aged from 2 to 22 years were compared to selected reference communities. Mines in this region have generally proposed one of two post-rehabilitation end-land uses: either pasture for cattle grazing or reconstructed native communities which potentially provide native fauna habitat. Landform data from a selection of these mine sites suggest that when their rehabilitation was compared to nearby reference sites median slope values were between 2.5 and 7 times steeper and soil pH, electrical conductivity, and phosphorus levels were significantly higher. The steeply sloped landforms, poor soil characteristics, depauperate native species pool, and uniform presence of exotic pasture grasses in the rehabilitation indicate that most of these newly created ecosystems should not be used for cattle grazing and also have few natural values. Legislative and community expectations have changed progressively over time and, although much of the rehabilitation is currently dominated by an assemblage of exotic buffel grass ( Cenchrus ciliaris ) and Acacia spp., recent environmental authorities suggest these ‘novel ecosystems’ will be judged against native reference sites. Upon completion of mining activities the resilience of these new ecosystems to drought, fire, and grazing will need to be demonstrated prior to lease relinquishment.