Ecosystem transformation following the mid-nineteenth century cessation of Aboriginal fire management in Cape Pillar, Tasmania

Abstract

Ongoing European suppression of Aboriginal cultural land management since early-nineteenth century colonisation is widely thought to have caused major transformations across all Australian landscapes, including vegetation thickening, severe fires and biodiversity declines. However, these effects are often confounded in the densely settled southern Australia due to European land transformation. Landscapes currently under conservation and national park management in Tasmania are generally less disturbed, providing an opportunity to track ecosystem changes caused by the removal of Aboriginal peoples following colonisation in southern Australia. We use a multi-proxy palaeoecological technique and the analysis of historical aerial photography to investigate these changes in Cape Pillar, southeast Tasmania. Results reveal a major ecological shift following European colonisation, with the replacement of stable, open wet heathland characterised by minor fires (active cultural land use) with dense dry scrub characterised by major fires (cessation of cultural land use). We also discuss potential background role of regional climatic shifts in the observed ecological changes. Management programmes designed to restore open heathland pre-colonial cultural ecosystem would help reduce the risk of large fires in Cape Pillar.

What did it used to look like? A case study from tall, wet mainland Mountain Ash forests prior to British invasion

“…Evidence of changes in forest cover and forest structure in the absence of cultural burning has also been interpreted in contrasting ways. For instance, some sources hypothesized that changes in forest structure and cover resulted from a reduction in fire frequency (e.g., Bowman, 1999;Howitt, 1890a), while others noted that they coincided with an increase in frequent fire, as indicated by charcoal deposition (Adeleye et al, 2022;Mariani et al, 2022). Others suggested that increasing understorey density or loss of mesic species coincided with observed increases in burning frequency by British invaders in some forests (Helms, 1896;Lane-Poole, 1921;Stretton, 1939;Wakefield, 1970).…”

Fire Cycles and the Spatial Pattern of the Scrub–Sedgeland Mosaic at Blakes Opening in Western Tasmania, Australia

“…We resampled those images to a common resolution of 1 m and converted them to panchromatic to maximize comparability. The images were classified by combining spectral and textural information, which has been shown to provide accurate vegetation classification in Tasmanian habitats [12,16]. Following the approach described in Bowman et al [12], we first used the package glcm [17,18] to calculate a Gray-Level Co-Occurrence Matrix (GLCM) [19,20], which provides information on texture parameters, representing measures of the smoothness, coarseness, and regularity of an image.…”

More than dirt: sedimentary ancient DNA and Indigenous Australia

“…Ecological management practices that utilise fire are integrated in many cultures around the world, including Aboriginal Australians (Coughland & Petty, 2012). Also referred to as cultural burning, the fire-based ecological practices of Abo-riginal peoples go as far back as the early Holocene (Matthew A Adeleye, Haberle, Connor, Stevenson, & Bowman, 2021) and have had clear ecological impacts on animal and plant populations (Matthew Adesanya Adeleye, Haberle, Ondei, & Bowman, 2022;Bowman, 1998). Associating ecological communities identified by sedaDNA in stratigraphic horizons with the concentration of charcoal in the sediment can elucidate the effects of fire on the local environment.…”