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The little Bramble Cay melomys is likely the first mammal claimed by man-made climate change, report says

(Luke Leung/University of Queensland)

At first glance, the Australian island of Bramble Cay is unremarkable except for the steel lighthouse at one end. Otherwise, the small isle is dotted with a few grass clumps, shorebirds and nesting sea turtles.

Years ago, however, fishers who visited the island in the Great Barrier Reef could also spot little, rat-like rodents scurrying over the sand and coral rubble.

As mackerel fishermen Egon Stewart told Queensland scientists in a new report, around 2009 there had been “a heap of sticks and a smashed up dug-out canoe at the north-western end of the island.” When Stewart flipped over the pile, a few of the furry critters took flight across the island.

This was the last time, the researchers believe, anyone saw a living Bramble Cay melomys, a rodent round in body, long in whisker and lumpy in tail. The creatures are probably the first mammal casualty of man-made, or anthropogenic, climate change, University of Queensland researcher and study author Luke Leung said in a statement. Despite subsequent search efforts, there is no evidence the animals remain on the island, the only place they were known to live on the planet.

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The first recorded Bramble Cay melomys sightings date back to the 1800s. In 1978, researchers estimated several hundred rodents lived on the island, but the numbers dropped to the double-digits by 1998. Twelve of the rodents were caught in November 2004; in December 2011, scientists looking for them turned up empty-handed. For this report, which used survey methods consisting of nocturnal traps as well as daytime searches, no sign of a melomys was to be found — no critter, paw print or pellet.

“The results reported here, from thorough survey, confirm that the Bramble Cay melomys no longer occurs at the only site from which it has ever been reliably reported,” the scientists wrote.

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It was, in all likelihood, death from lack of resources. In the decade between 2004 and 2014, the amount of leafy plants on Bramble Cay shrunk by 97 percent, the authors say. Without plants providing food and shelter, the scientists believe rodents succumbed to local extinction. And the lack of plants, in turn, was probably caused by a rising sea that swept over the island during storms and high tides — ocean inundation, as the scientists call it.

Bramble Cay is quite flat, rising no more than 9 feet above sea level at its highest point. Based on observations of erosion, scattered driftwood and dead plants, the authors concluded, “Bramble Cay has been subjected to repeated episodes of seawater inundation.” The scientists also note that data from tides and satellites indicate the average sea level in the area has risen a quarter-inch per year.

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University of California at Berkeley climate change expert Anthony D. Barnosky told the New York Times the apparent fate of the Bramble Cay melomys is a “a cogent example of how climate change provides the coup de grâce to already critically endangered species.”

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The Bramble Cay melomys is survived by the grassland melomys and two other closely-related melomys species. There is a slim chance, Leung said, the Bramble Cay melomys still exists — perhaps on nearby Papua New Guinea — though there is no confirmation of the animals having lived anywhere except the coral island.