Boom means bust: interactions between the El Niño/Southern Oscillation (ENSO), rainfall and the processes threatening mammal species in arid Australia

Abstract

We collated an environmental history for a 8580 km 2 study area in the Simpson Desert, Australia. Quantitative and qualitative data on climate, land-use, fire history and ecosystem dynamics were used to construct a chronology of processes threatening terrestrial mammal species. Over the last 150 years there has been the transition in land tenure from a hunter-gatherer economy to pastoralism, the loss of 11 mammal species, the cessation of small scale burning by Aboriginal people and the introduction of the fox and cat. Annual rainfall was highly variable and was influenced by the phase of the El Nin˜o Southern Oscillation (ENSO). Irruptions of rodents, marked increases in the populations of native and introduced predators and extensive wildfires were associated with the La Nin˜a phase of ENSO and occurred when rain-year (July-June) rainfall approached or exceeded the 90th percentile of the historical rainfall distribution. Large rainfall events in arid Australia have been viewed traditionally as the 'boom' times that benefit wildlife and pastoral production. However, because of hyper-predation and the risk of wildfire, we show that the years including and immediately following flooding rains should be identified as critical, or 'bust' periods for wildlife and conservation management. ENSO related climatic forecasts appear to be useful cues which can be incorporated into fire and predator management strategies in arid Australia. Studies such as this, which utilise a broad range of data types across extensive areas, can identify the timing and potential of threatening process not possible using contemporary studies alone.

Wild dog control impacts on calf wastage in extensive beef cattle enterprises

“…Rainfall influences the abundance of many wildlife species (Dickman et al 1999a(Dickman et al , 1999bLetnic and Dickman 2006;Robin et al 2009), which are prey of wild dogs. Reduced availability of alternative prey may explain the trend for calf loss to occur when rainfall had been below average.…”

Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands

“…Across diverse ecosystems including subalpine forests (4), ponderosa pine forests (5,6), and desert grasslands (7,8), interannual and interdecadal climatic variability increases fire size and extent by enhancing vegetation growth and reducing landscape heterogeneity during wet periods, subsequently increasing fire risk during the droughts that follow. This is particularly evident in Australia, where climate has been increasingly dominated by El Niño/Southern Oscillation (ENSO) and ENSO-like variability in precipitation over the last 5,000 y.…”

“…This is particularly evident in Australia, where climate has been increasingly dominated by El Niño/Southern Oscillation (ENSO) and ENSO-like variability in precipitation over the last 5,000 y. Periods of high rainfall alternating with extreme drought drive periodic pulses of fire that extend across vast expanses of the arid zone (9)(10)(11)(12), threatening habitats and facilitating predation by invasive species (8), leading to declines in the abundance of many endemic smallmammal populations.…”

Environmental effects are stronger than human effects on mammalian predator-prey relationships in arid Australian ecosystems

“…Extended periods of drought are known to exacerbate predation risks to irruptive fauna that typically persist in isolated and low-density populations (e.g. Dickman et al, 1999;Letnic and Dickman, 2006). However, there remains a dearth of studies demonstrating these expected functional relationships for many threatened fauna persisting in desert ecosystems, and identifying the strongest factors influencing prey populations has proved difficult (Holmes, 1995;Marshall et al, 2014;Peterson et al, 2014).…”