Mapping changes in landscape-scale patterns of vegetation in coal seam gas development areas

Abstract

In the 15 years to 2013, the rate of coal seam gas (CSG) development in Queensland increased dramatically. Drilling of gas wells and installation of associated infrastructure sometimes requires the removal of vegetation. Although a change in vegetation cover on a small scale does not necessarily correspond to significant landscape-­‐scale change, research overseas indicates that the extent and configuration of vegetation patches in a landscape is altered in areas of concentrated oil and gas extraction. The focus of previous research has been on oil and shale gas activity, mainly in North America. There has been little work on the nature and extent of the impact of similar developments in an Australian context, or impacts due specifically to CSG activity anywhere in the world. The aim of this study is to determine the nature of land cover change in a region of southern Queensland under intense CSG development. The extent and fragmentation of vegetation in 1999, immediately before CSG development began, is compared to the extent and fragmentation of vegetation in 2013, after 1562 coal seam gas wells had been drilled. Land cover was determined by classification of a LANDSAT 4 image taken in 1999 and a Landsat 8 image taken in 2013. ArcGIS 10.2 was used for image manipulation, and vegetation patch metrics were determined using FRAGSTATS 4.2 software. For comparison, the same metrics were also calculated in hot spot regions defined in two different ways to focus more closely around drilling sites. Similarly, the same metrics were calculated on a classified image modified to ensure that known linear clearings were continuously defined despite the automatic classification. The study finds that processes causing land cover change in the study area generally have a net positive effect on the landscape. Positive changes were observed despite clear evidence that CSG activity has directly led to vegetation loss on a small scale around CSG developments within the study area. This study shows that, while CSG development has a distinguishable impact on land cover at a landscape scale in southern Queensland, other more significant drivers of change mask the effect of CSG activity

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