Coal mining and agriculture have repeatedly come into conflict when they co-occur. Although seemingly benign when compared with surface mining, underground coal extraction techniques (including longwall mining) cause subsidence of agricultural land and loss of productivity. Despite growing concerns for global food security and increasing demand for coal resources, there is little peer-reviewed literature on the impacts of longwall mining in prime agricultural areas. In this paper, we examined the present knowledge of subsidence impacts of longwall mining on agriculture and how this may be interpreted for specific locations such as Australia. The review found that subsidence affects soil properties, hydrology and topography. The main impacts on agriculture are altered soil and groundwater hydrology, modified topography associated with increased erosion or waterlogging risk, and zones of compaction or cracking that cause soil physical and chemical changes. Agricultural productivity is also reduced through altering the types of farming practices that are suited to subsided non-uniform landscapes, decreasing farming efficiency through increasing paddock heterogeneity and decreasing ease of workability. There is a need to consider these multiple impacts under local conditions, with particular regard to the interaction of mine subsidence-associated disturbances with farming practices. We conclude by describing future research directions required for Australia and other countries outside of the USA-where most of the research has been conducted. Australia has unique soil and climatic conditions making extrapolation of studies from the USA on subsidence impacts and mitigation problematic. Figure 7. Australian wheat yield (with the trend over time removed) has fluctuated with variations in the southern oscillation index (Adapted from BOM, 2013a). This figure is available in colour online at wileyonlinelibrary.com/journal/ldr. 1661 LONGWALL MINING REVIEW
Introduction: This study depicts broad-scale revegetation patterns following sand mining on North Stradbroke Island, south-eastern Queensland, Australia. Methods: Based on an ecological timeline spanning 4-20 years post-rehabilitation, the structure of these ecosystems (n = 146) was assessed by distinguishing between periods of 'older ' (pre-1995) and 'younger' (post-1995) rehabilitation practices.
Summary
This pilot study of the rare Pagoda Rock Daisy (Leucochrysum graminifolium) in the western Blue Mountains of New South Wales (Australia) proposes a simple survey method combining timed meander and grid‐cell survey design to improve the survey effort required for monitoring of species growing in remote and/or inaccessible field locations. Where Pagoda Rock Daisies were known to be present, detection time was both rapid and effective (mean of 4.9 min for each 1 ha grid). Notably, the total survey effort remained constant for all grids, even though Pagoda Rock Daisies were unevenly distributed in the landscape (approximately 17 min/ha). Ultimately, the time required to traverse the landscape was deemed to be the primary limiting factor affecting survey effort. The application of this method is not restricted to challenging locations such as cliff edges; this method could be scaled according to the landscape or organism under investigation, providing a rapid method for surveying and monitoring rare, introduced or other plants from a site‐based scale to a broader geographic area.
Summary
Landscape rehabilitation following mining is required to be resilient to disturbance impacts such as fire, drought and disease. As mining companies undergo the process of rehabilitation certification and mine closure, there are notable knowledge gaps on the ecological risks associated with mature rehabilitated landscapes, based largely on the assumption that rehabilitation is analogous to reference communities. However, the response to fire disturbance across a range of landscapes remains largely untested and in particular there is limited understanding of recovery traits of plant species that occur naturally or are commonly seeded into rehabilitation. In August 2018, a controlled fire was applied to 37 hectares of 12‐year‐old coal‐mine rehabilitation in central Queensland, Australia. We used a combination of (i) ground plot surveys and (ii) drone imagery to compare the vegetation response of burnt woody species to unburnt controls prior to, and for, two years following the fire. The survival of the most dominant shrub species found on the rehabilitation site was significantly impacted by the fire. Old Man Saltbush (Atriplex nummularia Lindl. subsp. nummularia) recorded significant post‐fire mortality, with ground surveys recording an average reduction of 89% of stems per hectare across the burnt site, while unburnt controls remained unchanged. The plot data analysis was supported with high spatial and temporal resolution drone imagery, classified using a Random Forest machine‐learning approach. Change analysis of these maps showed a significant decline of 82% in Old Man Saltbush plant density and 92% reduction in foliage cover following the fire. In addition, the mean canopy area of individual Old Man Saltbush shrubs reduced significantly from a pre‐fire mean of 11.3 to 4.8 m2 two years following the fire. A spatial proximity analysis showed that those individuals that survived the fire were located significantly closer to unburnt areas and bare spoil, indicating that discontinuous ground fuel loads can greatly improve the survivability of individuals. This study provides new evidence on the contested fire sensitivity of Old Man Salt bush and demonstrates the risk that future climate‐driven extreme events may have on the resilience of novel ecosystems.
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