Are lizards toast? Climate warming, fire and lizard extinctions in the Australian arid zone

A collaborative project undertaken by The University of Melbourne and Australian Wildlife Conservancy and supervised by Michael Kearney

There is correlative evidence for recent range shifts and local extinction in association with climate warming. However, our understanding of the underlying mechanisms remains poor, making adaptive management difficult. One potential mechanism is restrictions on activity imposed by high temperatures. This mechanism was recently proposed to explain a spate of local extinctions in lizards across the globe, including the Great Desert Skink in Australia. However, the effects of climate change will likely be both direct and indirect, and will involve interactions with other threatening processes. What is lacking in this field is a means to fully integrate connections between climate change, habitat change (e.g. fire, food), individual responses (behavioural and energetic) and population responses (dispersal, inbreeding, population growth). Such an approach could provide key information for climate-relevant management decisions such as fire management, translocations, and where and when to survey for new populations. Our research will fill these gaps with novel and taxonomically generalizable techinques, which we will apply to better manage populations of arid zone lizards, with a specific focus on the Great Desert Skink.

In this project we will develop and apply an integrated approach for managing endangered arid-zone lizards in the context of climate change in interaction with other threatening processes, especially fire. We are achieving this by building a mechanistic model connecting thermal sensitivities, climate and habitat features, and integrating it with population dynamics models that can simulate different fire regime management strategies. We are applying the model to the Great Desert Skink at Newhaven Wildlife Sanctuary, a species thought to be vulnerable to extinction through changed climate and fire regime.

The aims of our study are:

  1. To estimate parameters for a mechanistic niche model of climatic constraints on the Great Desert Skink as a function of fire-induced vegetation change;
  2. To measure habitat suitability and as a function of fire history and to field-validate the predictions of the mechanistic niche model through microclimatic studies of Great Desert Skinks and their habitats under natural different fire successional stages;
  3. To integrate GIS-mapping and population dynamics approaches to understand the metapopulation dynamics of the Great Desert Skink in terms of the effects of climate and fire on habitat patchiness;
  4. To integrate the above knowledge into a decision-theory-informed management strategy of the Great Desert Skink at Newhaven Wildlife Sanctuary in the context of climate change.
Outcomes to date

In the population modelling study (Cadenhead et al., 2016) we propagated fire regime and species’ response uncertainties through a 50-year viability analysis of the great desert skink at Newhaven Sanctuary, characterizing fire regime change under three scenarios. The species’ response uncertainty was characterized with three competing models based on fire and habitat variables, fitted to 11 years of occupancy data. We evaluated fire management options for conserving the species, based on their robustness to uncertainty about fire and species’ response. Efforts to minimize the frequency and size of fires provided the most consistent improvements to species’ persistence.

In the experimental burns study (Moore et al., 2015) we simulated different fire types (clean burn, patchy burn and no burn) at 30 great desert skink burrow systems at Newhaven Wildlife Sanctuary. Burrow-system occupancy was monitored daily for 1 month, then monthly for an additional 3 months. We also made observations of burrow occupancy and breeding success at a number of sites elsewhere in the Sanctuary that had been burnt to some extent 2 years earlier. There was no significant effect of fire on burrow-system occupancy 1 month after experimental burns; however, burrow-system occupancy was significantly higher at unburnt sites 4 months after experimental burns and 2 years post-fire. Breeding success was significantly higher at unburnt sites than at clean-burnt and patchy-burnt sites. From these findings we concluded that fire adversely affects great desert skinks. Because fire is an inevitable and natural process within arid-zone spinifex grasslands, the primary habitat for the great desert skink, we recommended prescribed-burning practices that aim to maximise ground cover by reducing the frequency, intensity and size of fires. More specifically, we recommended fire exclusion from key sites within distinct localities where great desert skinks are known to be locally abundant. Depending on the size of these key sites, there may also be a need to construct strategic fire breaks within sites to ensure that any unwanted ignitions do not result in the loss of all vegetation cover.

We are in the process of collating and publishing further work on: 1. the thermal behaviour and sensitivity of the species, showing how important the burrow system of the great desert skink is for their ability to buffer extremes of temperature and dryness, and; 2. identifying key predators and how predation pressure at the burrow system is influenced by fire.

Publications

Cadenhead, N. C. R., Kearney, M. R., Moore, D., McAlpin, S., and Wintle, B. A. (2016). Climate and Fire Scenario Uncertainty Dominate the Evaluation of Options for Conserving the Great Desert Skink: Resolving uncertainty in fire management. Conservation Letters 9, 181–190. doi:10.1111/conl.12202

Moore, D., Kearney, M. R., Paltridge, R., McAlpin, S., and Stow, A. (2015). Is fire a threatening process for Liopholis kintorei, a nationally listed threatened skink? Wildlife Research 42, 207–216. doi:10.1071/WR14227

Figure 1. Prescribed burning within semi-saline spinifex plains, preferred Great Desert Skink habitat on Newhaven Wildlife Sanctuary, a property managed by the Australian Wildlife Conservancy.
Credit: Josef Schofield/AWC

Figure 2. Great Desert Skinks are listed as Vulnerable under the EPBC Act.
Credit: Josef Schofield/AWC