Conservation news

Scientists declare first mammal extinction due to climate change

  • According to a new study by scientists with the University of Queensland and the Threatened Species Unit at the Queensland Department of Environment and Heritage Protection, the Bramble Cay melomys (Melomys rubicola) is known only from a very small island with a total area of approximately 4 hectare (10 acres) called Bramble Cay in the northeast Torres Strait, between Australia and the Melanesian island of New Guinea.
  • A limited survey in March 2014 failed to find any of the rodents on the island, so the scientists returned later that year with the explicit goal of determining whether or not the Bramble Cay melomys still existed and enacting emergency measures to conserve any remaining individuals that might have been found
  • The researchers were ultimately unsuccessful in finding any of the rodents, however. They attributed the species’ extinction to sea level rise and extreme weather events driven by rising global temperatures.

Researchers in Australia say they’ve discovered the first mammal to go extinct due to human-induced climate change: the Bramble Cay melomys, also known as the Bramble Cay Mosaic-tailed rat, a small rodent found only on one small Great Barrier Reef island.

According to a new study by scientists with the University of Queensland and the Threatened Species Unit at the Queensland Department of Environment and Heritage Protection, the Bramble Cay melomys (Melomys rubicola) is known only from a very small island with a total area of approximately 4 hectare (10 acres) called Bramble Cay in the northeast Torres Strait, between Australia and the Melanesian island of New Guinea.

A limited survey in March 2014 failed to find any of the rodents on the island, so the scientists returned later that year with the explicit goal of determining whether or not the Bramble Cay melomys still existed and enacting emergency measures to conserve any remaining individuals that might have been found.

The researchers were ultimately unsuccessful in finding any of the rodents, however. They attributed the species’ extinction to sea level rise and extreme weather events driven by rising global temperatures.

“A thorough survey effort involving 900 small mammal trap-nights, 60 camera trap-nights and two hours of active daytime searches produced no records of the species, confirming that the only known population of this rodent is now extinct,” the scientists write in the study. They add that anecdotal information obtained from a professional fisherman who has visited Bramble Cay ever year for the past decade suggests that the last known sighting of the Bramble Cay melomys might have been way back in 2009.

The Bramble Cay melomys has vanished from its 350m-long cay home in the Torres Strait due to sea-level rise and extreme weather events. Photo by Queensland Government

During the August–September 2014 survey, the researchers also gathered evidence of physical and environmental processes on the island that may have driven the Bramble Cay melomys to extinction. “The key factor responsible for the extirpation of this population was almost certainly ocean inundation of the low-lying cay, very likely on multiple occasions, during the last decade, causing dramatic habitat loss and perhaps also direct mortality of individuals,” they wrote.

This finding, together with available data on sea-level rise and the increased frequency and intensity of weather events that have caused extremely high water levels and damaging storm surges in the Torres Strait region, point to human-induced climate change as the root cause of the loss of the Bramble Cay melomys, the researchers concluded.

“Because exhaustive efforts have failed to record the Bramble Cay melomys at its only known location and extensive surveys have not found it on any other Torres Strait or Great Barrier Reef island, the assertion that Australia has lost another mammal species can be made with considerable confidence,” the researchers noted in the study. That means the Bramble Cay melomys qualifies for listing as “extinct in the wild” under both state and federal Australian legislation.

“Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic climate change,” the researchers said.

But there may yet be a lifeline left for the species, as the researchers also found new information to support the theory that the melomys population on Bramble Cay might have originated in the Fly River delta of Papua New Guinea, about 53 kilometers (33 miles) northeast of the island, which would imply that the Bramble Cay melomys or a different but closely related species may occur in the Fly River region.

“Consequently, at this stage, it may be premature to declare the Bramble Cay melomys extinct on a global scale,” the researchers said. They call for the collection of DNA samples and morphological data from all melomys encountered during surveys of the Fly River delta and encourage the taking of representative specimens to be kept in New Guinean and Australian institutions in order to facilitate future taxonomic and genetic investigations of the rodent.

CITATION