Past and future potential range changes in one of the last large vertebrates of the Australian continent, the emu Dromaius novaehollandiae

Julia Ryeland,Ricky J Spencer,Tristan T Derham

doi:10.1038/s41598-020-79551-0

Julia Ryeland, Ricky J Spencer + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-79551-0

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Abstract

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. The emu, one of the last megafaunal species in Australia, has likely undergone substantial distribution changes, particularly near the east coast of Australia where urbanisation is extensive and some populations have declined. We modelled emu distribution across the continental mainland and across the Great Dividing Range region (GDR) of eastern Australia, under historical, present and future climates. We predicted shifts in emu distribution using ensemble modelling, hindcasting and forecasting distribution from current emu occurrence data. Emus have expanded their range northward into central Australia over the 6000 years modelled here. Areas west of the GDR have become more suitable since the mid-Holocene, which was unsuitable then due to high precipitation seasonality. However, the east coast of Australia has become climatically sub-optimal and will remain so for at least 50 years. The north east of NSW encompasses the range of the only listed endangered population, which now occurs at the margins of optimal climatic conditions for emus. Being at the fringe of suitable climatic conditions may put this population at higher risk of further decline from non-climatic anthropogenic disturbances e.g. depredation by introduced foxes and pigs. The limited scientific knowledge about wild emu ecology and biology currently available limits our ability to quantify these risks.

Highlights

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement
Being one of the last remaining Australian megafaunal species and occurring across most of the continent, the emu likely plays an important role in ecosystem connectivity and structure; a role which would be unfilled if the emu disappeared from Australian landscapes
Whilst there was more variability in the individual models predicting the Great Dividing Range region (GDR) distribution and fewer individual algorithms used for ensembles (36 and 39 for the Austral-Scientific Reports | (2021) 11:851 |

Summary

Introduction

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. Many species have experienced range shifts in response to altered fire regimes and hunting since indigenous Australian arrival, changes in the structure of habitat with megafauna extinction (with woody vegetation no longer strongly s uppressed8,10,11) and with anthropogenic influence since European settlement (e.g. increasing urbanisation, the introduction of predators and competitors, and land c learing[13,14]). The extinction of the megafauna likely altered Australian landscapes, in particular, causing expansion of scrubland steppes around 45 kyr[28] This caused significant shifts in emu diet from a predominately C4 plant-based diet prior to megafauna extinction, to an almost solely C3 plant-based d iet[28], potentially driving emus into areas with higher availability of C3 plants. The threats to the emu populations remain unclear and it is not known whether environmental and climatic changes played a role in their disappearance, nor whether emus are likely to continue to decline

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