Rare reptile all washed up through loss of rain in Australia

Nikki and Tortois

Nicki Mitchell from the University of Western Australia is working to save one of the world’s rarest reptiles – the Western Swamp Tortoise. The last surviving members of this species are eking out an existence near Perth. But Nicki has observed how thelack of rainfall in the region threatens to wipe out the small number of these animals that remain in the wild.

‘One of its main threats is climate change because of decreases in winter and spring rainfall,’ explains Nicki.‘In fact we’ve already had climate change in South Western Australia: from the 1970’s the rainfall changed fairly dramatically. We used to have annual rainfalls in winter in Perth of up to 1000 mL now we’re getting more like 500-600mL in a good year.’

The tortoise only survives naturally in two small wetlands that are right on the edge of Perth, where there has been a 15% loss in rainfall since the 1970’s. This rainfall decline – which reduceswater flow into Perth’s dams by 40% – can be linked to increases in greenhouse gases. The loss of winter rainfall in particular has been exacerbated by climate change.

The Western Swamp Tortoise is the rarest reptile in Australia and one of the top three rarest tortoises in the world. Nicki and her colleagues have catalogued the declining numbers of this species.‘We think there are between 50 and 100 adult tortoises in the wild – down on about 400 that were believed to exist in the 1960s.’

The tortoise relies on six or seven wet months during the winter and spring to feed, grow, mate and raise hatchlings. During the summer, the wetlands dry up and they hibernate. As their habitat becomes drier and drier in the winter, these reptiles struggle to fulfill their natural cycle. Hatchlings struggle to grow big enough to survive their first summer.

The tortoise is vulnerable to climate change due to human activity. ‘Because ground water is extracted to support the population of Perth, the ground water connection to some wetlands has been lost,’ Nicki explains.‘So the tortoises are relying on rainwater to fill the swamps, and the rainfall is half what it was in the past.’

Nicki says, ‘South Western Australia is likely to become drier with unabated climate change. There could be up to a 14% reduction in rainfall by 2030 alongsidea temperature increase of up to 1C.’

As the temperature increases, so will evaporation, doing further harm to the wetlands the tortoise relies upon. Nicki believes that under relentless pressure from climate change there is only one option. ‘The western swamp tortoise is a species that we think will need to be relocated to better habitat – that is the only way they’ll survive in the wild.’

Source: WWF

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