Bramble Cay is so small; it’s not technically an island, but a cay, at 340m by 150m which is a 20-minute walk from end to end or about the size of three cricket grounds. It juts out three metres or less above the water between Queensland in Australia and Papua New Guinea. However, this island was the only habitat of an Australian rodent which has now been declared extinct due to human-caused climate change!
Bramble Cay melomys, endemic to this island in the Great Barrier Reef in the eastern Torres Strait was first recorded by Europeans in 1845. They were seen in large numbers in 1978 as well. The last mosaic tailed rat, as it is also known, was spotted in 2009. However, a thorough survey using small animal traps, camera traps and daytime searches from August and September 2014 failed to detect any of the animals, says a new report written by Ian Gynther from Queensland’s Department of Environment of Heritage Protection and Natalie Waller and Luke Leung at the University of Queensland. Thereafter, its status was changed from “endangered” to “extinct”.
The report goes on to highlight that the “key factor” responsible for killing off the animals was flooding of their island on multiple occasions during the last decade, “causing dramatic habitat loss” and possibly killing some individuals directly. “Available information about sea-level rise and the increased frequency and intensity of weather events producing extreme high water levels and damaging storm surges in the Torres Strait region over this period point to human-induced climate change being the root cause of the loss of the Bramble Cay melomys,” the researchers added. “Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic (human induced) climate change.” Shocking!
John White, an ecologist from Deakin University in Australia commented that this is likely just the tip of the iceberg. Climate change is exerting survival pressure on species everywhere. Species restricted to cold climate habitats, such as the Earth’s poles or mountain tops, as well as habitats that can only tolerate a narrow range of temperatures, such as tropical coral reefs, are considered most at risk. A study earlier this year also estimated that “one in six of world’s species faces extinction due to climate change”.
The Bramble Cay melomys is a type of mosaic-tailed rat — a group that has a mosaic pattern on scales on its tail instead of the parallel rings found on the tails of most rats and mice. The animals grew to be about 14- to 16-centimetres long, with a tail of about the same length as its body. They were thought to eat mostly plants, especially a succulent herb called Portulaca oleracea that’s common on Bramble Cay, and possibly turtle eggs.
The land area of the cay decreased from 4ha in 1998 to 2.5ha in 2014. Within a span of 10 years melomys lost 97% of their habitat. The vegetation cover declined from 2.2ha in 2004 to just 0.065ha in 2014. “The vegetation has died out due to the salt water. Unlike the birds and turtles that live there, they had nowhere else to go,” explains Dr Leung, co-author of the report. “This poor little native rodent didn’t draw much attention. If it was a panda bear it would be a very different story.”
WWF-Australia spokesperson Darren Grover raised alarming concerns, “Australia’s species extinction crisis is not something that occurred hundreds of years ago, it’s happening right now — Australia officially has the worst rate of mammal extinction in the world.”
The authors, nonetheless, mention that all hope is not lost. They believe that there is a possibility that a population of these rats exist undiscovered in Papua New Guinea. According to them, melomys might have been introduced to this island on rafting debris from mainland. However, targeted surveys need to be carried out, to see if they are there.