Humans, megafauna and environmental change in tropical Australia

Abstract

Debate concerning the environmental impact of human arrival in Australia has continued for more than a century. Here we review the evidence for human impact and the mechanisms by which humans may have affected the environment of tropical Australia. We limit our review to tropical Australia because, over three decades ago, it was proposed that the imposition of an anthropogenic fire regime upon human occupation of the Australian continent may have resulted in profound changes in regional vegetation and climate across this region. We conclude that ecological processes and vegetation-fire-climate-human feedbacks do exist that could have driven a significant shift in boundary conditions and ecosystem state at the sub-continental scale through the sustained imposition of an anthropogenic fire regime over tens of millennia. These potential feedbacks operate through the inhibition of forest expansion both directly, by targeted burning at established forest edges and newly irrupted forest patches, and indirectly, through lengthening of the dry season because of changes to the timing of burning. However, the impact of any such anthropogenic forcing may have been entirely overshadowed by the effects of natural climate change and variability, as well as the generally low nutrient status of Australian soils. A robust assessment of the degree to which the environment of tropical Australia at the large scale has been modified from its 'natural' state because of human occupation will require new, coordinated collaborations between indigenous traditional landowners, archaeologists, anthropologists, geochronologists, geoscientists, ecologists, climatologists and modellers.

The deep human prehistory of global tropical forests and its relevance for modern conservation

“…This may reflect reliance on starchy forest edge plants and bearded pig attracted to canopy openings 12 . In tropical Australia, the decline of Araucaria and rise of Eucalypts and Casuarina has been correlated with the advent of anthropogenic biomass burning after 40 ka [46][47][48] . Human landscape impacts have also been documented in the montane tropical forests of Highland New Guinea from 45-35 ka, even retarding vegetation re-colonization in the region following the Last Glacial Maximum 49 .…”

What caused extinction of the Pleistocene megafauna of Sahul?

“…However, it is generally accepted that people were widespread over the continent by 45 ka or a few millennia earlier [13,14,27,28]. There is as yet no obvious geographical pattern in first-appearance dates to indicate the progress of a wave of colonization across Sahul.…”

Palaeoecology of the South Wellesley Archipelago. A history of human occupation and environmental change

“…Anthropogenic fire regimes in tropical northern Australia are different from 'natural' pre-human fire events (Bird et al, 2013). Removing Indigenous land owners from northern Australia in the early to mid-20 th century ended the setting of several small fires in the early dry season, and was replaced by larger and more intense naturally set fires at the end of the dry season (Bowman et al, 1990;Braithwaite, 1991;Price et al, 2012).…”