Vast lands and variable data: systematic analyses to understand the patterns and processes of mammal decline

Australia has the unenviable record of the highest rate of mammal extinctions in the world. There is increasing concern that there is a new wave of extinction imminent in Australia, with scattered data and anecdotal reports suggesting that the mammals northern Australia are particularly at risk. The causes of these extinctions have been much debated, and it is possible that many factors contributed, but there is strong evidence that predation by introduced red foxes and cats was the primary cause in the majority of cases; however this is intertwined with circumstances of changed fire regimes, and extensive, long term cattle grazing, and there is strong evidence that these factors exacerbate declines. For example, monitoring in places such as Kakadu National Park shows dramatic recent falls in the abundance and species-richness of mammals, without a single clear cause. Elsewhere mammal populations have recovered with the removal of cattle grazing and repatriation of pre-European fire regime. What is lacking from an Australian perspective is a coherent synthesis of the hypotheses and causes of small mammal population pattern, a thorough evaluation of all existing data, and a systematic meta-analysis of all the evidence of different effects. Without this well targeted management, policy and restoration actions are not possible. This project will: (a) systematically collate, review and analyse all available data; (b) re-evaluate existing hypotheses of decline and formulate new hypotheses for testing with the data available; (c) apply traditional and novel methods of analysis of disparate data sets of varying quality and varying temporal and spatial scales in the light of new hypotheses; and (d) define new policy and management actions for government and community.

The Black-footed Tree-rat Mesembriomys gouldii; rarely seen in Queensland and though once common in the outskirts of Darwin, now declining. Photo by Eric Vanderduys.

The Desert Mouse Pseudomys desertor has disappeared from most of its former southern range. Photo by Eric Vanderduys.

The Feral Cat Felis catus is a significant predator of native fauna, and is linked with the extinction of many small mammals across Australia. Photo by Eric Vanderduys.

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Report of meeting one (30 November - 4 December 2010)

The first meeting of fourteen participants at the ACEAS rooms in Brisbane comprised 5 intensive days of data review, hypothesis generation, and planning for re-analysis of data to test new ideas about the causes of mammal decline. Key participants were Professor Chris Johnson, one of Australia’s most eminent mammal ecologists and author of 50 000 years of Mammal Extinctions, Dr Sarah Legge the National Conservation Manager of the Australian Wildlife Conservancy, an organisation with keen focus on mammal conservation and reintroductions, and Dr Alaric Fisher from the Northern Territory government, whose long term monitoring in Kakadu drew attention to troubling signs of mammal decline in northern Australia.

New techniques for developing critical thinking and mapping ideas and hypothesis were utilised through the software bCisive, assisted by Dr Tim van Gelder from Austhink. Though such concentrated work is gruelling at times, the opportunity to spend 5 clear days in a room full of experts in the field of ecology and conservation was a unique opportunity that is rarely afforded to researchers and can only be provided by funding agencies such as ACEAS. All participants were unanimous in agreement that the meeting was a resounding success and provided new insight and an impetus to tackle mammal conservation issue afresh.

The outcomes at the end of the first working group were exciting and included the development of a continent-wide data base to explicitly re-test the intrinsic and extrinsic correlates of decline, create species distribution models based on weather and environmental factors and a temporal meta-analysis to examine historical causes and synchronicity in the patterns of change.  Dr Nicky Thurgate (Dept SEWPC) will be working closely with the researchers to ensure that the outcomes are relevant for policy and management objectives and this is a significant component of the project.   The second workshop to be held in June 2011 will draw the same participants together but also include some delegates from overseas expert in North American and European mammal conservation research. These new perspectives will enhance some of the more parochial views of the issue.

ACEAS workshop 2, (June 13th – 17th 2011)

Vast lands and variable data: systematic analyses to understand the patterns and processes of mammal decline

The second meeting comprising twelve participants was held at the Linnaeus resort, a private conservation and education facility at Lennox Heads. The venue itself was an architecturally funky recycled timber board room, appropriately shaped like an ark as: (a) the meeting coincided with a classic east coast rain depression that pounded the meeting for the first few days, and (b) maybe one of the solutions for mammal conservation in Australia is chuck all our mammals on islands, arks and fenced compounds free from the perils that plague them. To continue the theme of pestilence, the Chilean volcano Puyehue was merrily spewing forth that week unfortunately prevented some participants from getting to the meeting. However the core team was there, along with some new members (Diana Fisher UQ, Susanne Fritz, Biodiversity and Climate Change Research Centre, Frankfurt) and special day guests (Peter Latch DSEWPaC, Andy Sheppard CSIRO)

This was our second and last meeting, and an opportunity to report on our progress towards the first workshops aims and outputs and to plan for finalisation of some of the ambitious tasks we set ourselves. Key new activities was to extend the critical thinking mapping exercise to review the policy and management successes, failures and opportunities for mammal conservation in northern Australia. This information, along with the hypothesis mapping exercise in the first workshop, now provides a nice foundation for a review paper, one of the key outcomes proposed for the working group. The mapping exercise relating to policy was also of great interest to DSEWPaC, and they are keen to extend the exercise and methodology to a policy focussed workshop in future. The second key exercise was to initiate the application of the common cause framework by reviewing and weighting the epidemiological criteria with respect to its application to mammal declines.

Other key outputs that are being worked on are the extrinsic and intrinsic correlates northern Australian marsupial and rodent decline (in comparison to southern Australian patterns), an analysis of the change in distribution (environmental suitability) over the recent past using weather data and the directions of these changes (i.e. are they coincident with the declines). This will include analysis of changes at key time slices (i.e. pre and post 1970) and the differences between rodents and marsupials, and species of different body size. Finally as mentioned above, there will be a review of the hypothesis, policy and management successes and failures. As a group we recognised that one of the main challenges facing biodiversity conservation is the inability to get long term traction in the consciousness of the public and to some degree governments, and we resolved to try and sustain a coordinated information stream to the media and journals using key messages from this working group to keep hammering the message home; the ark is sinking.

Vast Lands and Variable Data FINAL REPORT available for download