Abstract
The koala (Phascolarctos cinereus) is currently listed by both the IUCN and the Australian Governments’ Threatened Species Scientific Committee as vulnerable to extinction with an overall decreasing population trend. It is unknown exactly how many koalas remain in the wild, but it is known that habitat fragmentation and bushfires have ultimately contributed to the decline of the koala all over Australia. This novel study is a retrospective analysis of data over a 29-year period (1989–2018) using records for 12,543 sightings and clinical care admissions for wild koalas from the major koala hot-spots (Port Stephens, port Macquarie and Lismore) in New South Wales, Australia. This study aims to understand the long-term patterns and trends of key stressors that are contributing to the decline of koalas in New South Wales, and the synergic interactions of factors such as rescue location, sex and age of the koala, and if their decline is influenced progressively by year. The main findings of this retrospective analysis indicated that between all 3 rescue sites, the most common prognosis was disease, the most common disease was signs of chlamydia, and the most common outcome was release. The location where the highest number of koalas were found prior to being reported as sighted or admitted into clinical care was within the regional area of Lismore. Furthermore, sex was not a discriminating factor when it came to prognosis or outcome, but age was significant. Finally, incidents of disease were found to increase over long-term, whereas release decreased over time and euthanasia increased. The wealth of data available to us and the retrospective analysis enabled us in a way to ‘zoom out’ and reveal how the key environmental stressors have fluctuated spatially and temporally. In conclusion, our data provides strong evidence of added pressures of increased human population growth in metropolitan zones, which increases risks of acute environmental trauma and proximate stressors such as vehicle collisions and dog-attacks as well as increased sightings of virtually healthy koalas found in exposed environments. Thus our ‘zoom out’ approach provides support that there is an urgent need to strengthen on-ground management, bushfire control regimes, environmental planning and governmental policy actions that should hopefully reduce the proximate environmental stressors in a step wise approach. This will ensure that in the next decade (beyond 2020), NSW koalas will hopefully start to show reversed trends and patterns in exposure to environmental trauma and disease, and population numbers will return towards recovery and stability.
Highlights
In theory, Australia should have relatively few conservation concerns; its national population density is low (~3km2) by global standards (~50km2), most of the continent remains sparsely settled and little modified, and the nation is relatively affluent [1]
It is hypothesised that there will be no difference between the factors, but that there will be a significant difference in year admitted into care [1989–2018], as bushfires and habitat fragmentation are major threats that have increased in severity over time with an increase in human population
Prognosis refers to the reason that each koala was recorded as a sighting or the reason that the koala was admitted into clinical care
Summary
Australia should have relatively few conservation concerns; its national population density is low (~3km2) by global standards (~50km2), most of the continent remains sparsely settled and little modified, and the nation is relatively affluent [1]. Since European Settlement in 1788, 30 mammal species endemic to Australia have become extinct, with 55 others experiencing a worsened conservation status [2]. This statistic is primarily attributed to the fact that humans alter areas of pristine habitat that is rich with biodiversity, so as to accommodate rapid population growth [2]. In late 2019, Australia experienced unprecedented bushfires, and there is no evidence yet to suggest how many koalas were affected by this fire, it is estimated that the effect to New South Wales koala populations was catastrophic. It is demonstrated that both habitat fragmentation and bushfires have contributed to the decline of the koala species all over Australia [3,4,5,6,7,8]
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