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Friday, July 22, 2011

Platypus feeling the heat of Climate change

Some of Australia's most iconic animals are feeling the heat of climate change and global warming. Scientists have already reported that Koalas face starvation, extinction due to climate change and now it seems the Platypus is under threat due to increasing summer temperatures.

The video above of a platypus seen feeding mid-afternoon surrounded by half a dozen people watching is unusual. Platypus are generally nocturnal and shy creatures usually glimpsed at dawn feeding in streams and rivers.

The new research - Early response of the platypus to climate warming (abstract) - to be published in the international scientific journal 'Global Change Biology' later this year.

PhD student Melissa Klamt with Professor Jenny Davis and Dr Ross Thompson from Monash University examined platypus population data from the early 1800s to the present and combined it with climate data to show the range of the platypus is shrinking due to warmer summer temperatures rather than the loss of availability of habitat. This trend is clear from just a 1ºC rise in global average temperature.

"Platypus are amazing animals that we think of as being quite adaptable" Ms Klamt said in a media release, "But we found evidence that recent warming of the climate is really affecting their distribution."

Platypus have an extremely efficient fur which keeps them warm in the cold and sometimes icy temperatures of the creeks and rivers that are their main habitat. But hotter summers warm the waters and the efficient platypus fur means they cannot get rid of excess heat and moderate their body temperature. During extreme heat they retreat to their burrows for refuge. During prolonged warm periods foraging opportunities would be greatly reduced.

"Platypus have only a limited capacity to moderate their body temperature," said Professor Jenny Davis from Monash University's Australian Centre for Biodiversity. "When summer temperatures become too warm they are very vulnerable."

Research by the Bureau of Meteorology and CSIRO has identified a long-term drying and warming of the climate in south-eastern Australia. The researchers have identified that this will directly reduce suitable platypus habitat by more than 30 per cent over the next 60 years. The increased extraction of water for human and agricutural use will also increase the loss of suitable platypus habitat.

If substantial cuts to greenhouse gas emissions aren't made globally Australia could see a 4ºC warming by the end of this century. CSIRO have warned this would result in temperature increases of about 3ºC to 5ºC in coastal areas and 4ºC to 6ºC in inland areas; likely declines of annual rainfall in southern Australia, particularly in winter, of up to about 50% but uncertain rainfall changes in other regions; marked increases of potential evaporation of about 5% to 20%; and more droughts in southern Australia. The decreased rainfall will result in decreased stream runoff and a contraction of aquatic habitat. These effects would be lethal over much of the range of the platypus.

"Rapid global warming of 4ºC would be unlike anything experienced before by modern human societies - presenting us with huge challenges in terms of our ability to adapt," said CSIRO Climate Adaptation Flagship climate researcher, Dr Penny Whetton.

Platypus can be found from North Queensland through New South Wales and Victoria and in Tasmania in freshwater ecosystems. It is no longer found in South Australia and populations have declined in the lower reaches of the Murray and Murrumbidgee Rivers in Victoria and NSW. It is usually nocturnal and most often seen by humans at dawn or early morning feeding in freshwater pools and streams.

"This is just another piece of evidence that climate change is a real factor affecting our native biodiversity now," said Dr Ross Thompson, Deputy Director of the Australian Centre for Biodiversity, where the research was conducted. "It reinforces the need to act decisively on climate change issues."

Platypus are a unique mammal species. The platypus and four species of echidna are the only living examples of the egg laying monotremes. The platypus genome has recently been sequenced to reveal a combination of reptilian and mammalian unique characteristics. In foraging for food it uses 'electroreception', a feature exclusive to the platypus and some fish.

"While the platypus has proven robust to many anthropogenic stresses, their specialized habitat requirements and limited dispersal ability may render them highly vulnerable to the impacts of a changing climate, particularly from loss of aquatic habitats due to drying and elevated water temperatures." the research paper says.

The researchers do provide some ways to limit the damage to platypus and other freshwater aquatic species through the provision and protection of 'refugia' - biological refuge islands which can support a range of micro-climates and micro-habitats. Habitat restoration by replanting trees and shrubs along waterways across a catchment may help to keep water temperatures from warming too much. Maintaining environmental flows during drought periods could also assist in maintaining platypus food sources and aquatic environment health through stressful periods.

There are signs that restoration of riparian habitat along Melbourne's waterways like Merri Creek may be assisting return of platypus to habitats within an urban environment with sightings in recent years increasing.

The IUCN redlist puts the platypus as of least concern in terms of global conservation status, with the species still found in much of its historic range. But the researchers warn that "our modeling shows that their vulnerability should not be underestimated".

"The apparent crossing of a threshold from aquatic habitat limitation to physiological limitation signals an early response to climate warming. The next step may be an 'ecological surprise' in the form of a catastrophic decline in platypus distribution and abundance. Facing this scenario, climate adaptation strategies must give highest priority to ensuring the enduring conservation of this globally significant animal." the research paper concludes.


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