The Great Barrier Reef’s only endemic mammal is now extinct

On a tiny plot of coral off the coast of Queensland, northeast Australia, the Great Barrier Reef’s only endemic mammal used to flourish. The ecologically unique Bramble Cay melomys (Melomys rubicola) was first documented by Europeans in 1845. In the late 1970s it existed in its hundreds. But on 14 June this year it recorded a more unwelcome sort of honour as it was officially confirmed to be extinct, becoming, according to scientists, the first recorded mammalian extinction due to human-induced climate change.

Also known as the mosaic-tailed rat, the melomys’ only known habitat was Bramble Cay, a tiny four-hectare island surrounded by an oval reef, situated at the entrance of the northeast Torres Strait – the passage between northern Australia’s Cape York Peninsula and the island of New Guinea. The dynamic cay is a rich breeding ground for green turtles and a variety of seabird species, but has suffered from unrelenting man-made impacts over the past few decades.

The cay has been exploited for its biological and phosphatic rock resources since the mid-19th century, and was home to a continuous succession of navigational beacons and lighthouses since the early 1900s. The Erubam Le (or Darnley Islanders) were granted native rights over the island in 2004 and regularly harvest the fish, turtle and bird resources from the reef.

The melomys was last spotted on the island in late 2009, but attempts to detect the species since then have been unsuccessful. ‘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,’ writes Ian Gynther from Queensland’s Department of Environment and Heritage Protection, and Luke Leung and Natalie Waller from the University of Queensland. ‘On this basis, the Bramble Cay melomys qualifies for listing as extinct in the wild under both state and federal legislation.’

“The destructive effects of extreme water levels resulting from severe meteorological events are compounded by the impacts from anthropogenic climate change-driven sea-level rise”

Bramble Cay sits no more than 3m above sea level. According to scientists, the rising tides caused by climate change have seen the rodent lose a staggering 97 per cent of its habitat in just ten years. Not only did the area of the cay that sits above the high tide decrease from 4ha to 2.5ha between 1998 and 2014, but the island’s vegetation cover shrunk from 2.2ha in 2004 to just 0.065ha in 2014.

‘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,’ the researchers explain. ‘For low-lying islands like Bramble Cay, the destructive effects of extreme water levels resulting from severe meteorological events are compounded by the impacts from anthropogenic climate change-driven sea-level rise.’

The IPCC (Intergovernmental Panel on Climate Change) finds that global sea levels rose by almost 20 centimetres between 1901 and 2010, which, around the Torres Strait, occurred at almost twice the global average rate between 1993 and 2014. Darren Grover, Head of Species Conservation at WWF-Australia, says: ‘With the coral bleaching disaster, and now the extinction of the Bramble Cay melomys, the Great Barrier Reef has become the face of climate change. This crisis demands an emergency response from Australia’s national leaders. This includes committing to a plan to transition to 100 per cent renewable electricity by 2035 and to achieving Net Zero Carbon Pollution before 2050 to combat global warming and its impacts.’

This was published in the September 2016 edition of Geographical magazine.