Forgotten impacts of European land‐use on riparian and savanna vegetation in northwest Australia

Abstract

Questions Fire and livestock grazing are regarded as current threats to biodiversity and landscape integrity in northern Australia, yet it remains unclear what biodiversity losses and habitat changes occurred in the 19–20th centuries as livestock and novel fire regimes were introduced by Europeans. What baseline is appropriate for assessing current and future environmental change? Location Australia's Kimberley region is internationally recognized for its unique biodiversity and cultural heritage. The region is home to some of the world's most extensive and ancient rock art galleries, created by Aboriginal peoples since their arrival on the continent 65,000 years ago. The Kimberley is considered one of Australia's most intact landscapes and its assumed natural vegetation has been mapped in detail. Methods Interpretations are based on a continuous sediment record obtained from a waterhole on the Mitchell River floodplain. Sediments were analysed for geochemical and palynological proxies of environmental change and dated using 210Pb and 14C techniques. Results We show that the present‐day vegetation in and around the waterhole is very different to its pre‐European counterpart. Pre‐European riparian vegetation was dominated by Antidesma ghaesembilla and Banksia dentata, both of which declined rapidly at the beginning of the 20th century. Soon after, savanna density around the site declined and grasses became more prevalent. These vegetation shifts were accompanied by geochemical and biological evidence for increased grazing, local burning, erosion and eutrophication. Conclusions We suggest that the Kimberley region's vegetation, while maintaining a ‘natural’ appearance, has been altered dramatically during the last 100 years through grazing and fire regime changes. Landscape management should consider whether the current (impacted) vegetation is a desirable or realistic baseline target for biodiversity conservation.

Interactions among threats affect conservation management outcomes: Livestock grazing removes the benefits of fire management for small mammals in Australian tropical savannas

“…Increased fire prevalence could affect mammal populations in a variety of ways: in the short term, fire removes grass cover (exposing small mammals to greater predation risk; Leahy et al, 2016), and removes food resources including grass seed and grass stems (Andersen et al, 2005) including fleshy fruited shrubs, flowers, and some grasses (Atchison, 2009;Connor et al, 2017). The abundance of shelter sites such as hollow logs and tree hollows are also reduced by high intensity fire, especially if these fires recur frequently (Firth, Woinarski, Brennan, & Hempel, 2006;Williams, Cook, Gill, & Moore, 1999;Woolley, Murphy, Radford, Westaway, & Woinarski, 2018).…”

Long-unburnt habitat is critical for the conservation of threatened vertebrates across Australia

“…It is crucial that we adequately consider the implications of novel environmental contexts when managing landscapes for threatened vertebrates, particularly in light of how little is known about historical conditions, including Indigenous burning practices, in many locations (Connor et al 2018;Ross et al 2020). The concepts of historical baselines, reference conditions, and benchmarking are entrenched in restoration and management practices around the world (Parkes et al 2003;Stoddard et al 2006;Jakobsson et al 2020), so careful evaluation of the metrics and methods used for landscape management of biodiversity is critical (Kopf et al 2015;Ruaro et al 2021).…”

Landscape-Scale Effects of Fire, Cats, and Feral Livestock on Threatened Savanna Mammals: Unburnt Habitat Matters More Than Pyrodiversity

“…Due to the annual cycle of a wet season followed by an extended dry season (>6 months) in which grasses cure, savannas in the region are subject to annual grass fueled fire regimes (Russell-Smith et al, 2003b). The Northern Kimberley region has not been subject to extensive vegetation clearing; however, fire regimes changed to highintensity wildfire dominated fire regimes during the 20th century with the breakdown of traditional Indigenous fire management (Russell-Smith et al, 2003b;Connor et al, 2018). Introduced herds of cattle, horses, and donkeys are widespread throughout the region as an additional critical disturbance factor.…”