Australian rodent first mammalian victim of climate change

Bramble-cay-melomy

Tucked away on a small island off the coast of Queensland, Australia, the rat-like animal would have stared up at you with dark, beady eyes from the safety of some scattered shrubs.  No more than 15 centimeters long, the rodent would have been covered with light red fur, its tiny ears tucked tightly against its head, its pale underbelly barely visible.  You would have probably noticed the odd tail, as long as its body and lumpy with scales.

You may have seen this mosaic-tailed rat, melomys rubicola, had you traveled once upon a time to Bramble Cay, a small island built upon a the Great Barrier Reef.  But no longer.  After a fairly exhaustive search using traps, cameras, and searches on foot, Australian scientists have pronounced with confidence that the melomys is likely extinct [1].  The probable cause?  Evidence suggests dramatic weather conditions in the region combined with rising sea levels due to anthropogenic climate change  While a faint glimmer of hope remains that a small colony may still exist on poorly studied region of Papua Guinea, this is likely the first of many mammals to fall victim to the complex weather systems created by global warming.

The future, now

Why should we care?  Some will immediately sense the emotional connection: those cute little eyes and ears a victim of shameless human expansion across the globe.  And I don’t believe this sentiment can be overstated in these times, when we are moving farther and farther away from understanding our connection to the environment the effects of our industry on it.

But there is more to this loss than dealing with accomplice’s guilt.  The present weather systems bombarding Bramble Cay and their effects on the local ecosystem play out our future in fast-forward.  The island rests only 3 or 4 meters above sea level, leaving it susceptible to any slight changes in climate.  Whereas global sea levels have risen 20 centimeters over the last century, the oceans have risen at twice the average rate near Bramble Cay.  As a result, the area of the island consistently above high tide has shrunk since 1998 from 9.8 to 6.2 acres, eliminating the spread of vegetation, low-lying rock overhangs, and 97% of available habitat for the melomys.

As a group of scientists from the Department of Environment and Heritage Protection and the University of Queensland thoroughly documented the island, they found flattened, dead sedge along the coastlines, erosion, and the loss of soft substrate along rock formations.  All these signs point to dramatic weather systems recently hitting the cay.  In 2005, Tropical Cyclone Ingrid blasted the island, destroying up to half of all vegetation by 2011.  Harsh winters during the same time also brought more severe storms through the area.  Increased cyclonic activity near Queensland has already been associated with intensity in the La Nina cycle, which occurs with higher global mean sea surface temperatures due to anthropogenic global warming.  The melomys didn’t stand a chance given the loss of the vegetation and habitat.

“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,” writes Gynther et al [1].  Such an explanation points to resilience, or the lack thereof: as sea levels rise, ecosystems near the coast or on islands cannot survive such severe storms as easily.

Here it is straight: human-induced global warming leads to changes in El Nino/La Nina oscillations leads to more severe storms leads to dramatic punishment to nearby ecosystems.  The melomys was caught in the middle.  All this happened quite quickly due to the low elevation of Bramble Cay, but this is an omen of what is in store for more heavily populated coastal regions as sea levels continue to rise and storms intensify.

Hope in Papua New Guinea

Australian scientists placed 900 small-mammal traps, set up 60 cameras, and combed the island for any sign of the mammal.  Usually these efforts turn up something, so the lack of a sighting indicates extinction.  But there may still be hope.  Some scientists believe the melomys living on Bramble Cay originated from the Fly River delta region of Papua New Guinea just to north, a less explored habitat that could be housing the last remnants of the species.  The scientists have recommended exploration of this area (if funding is available, of course).

The melomys is the first but not the last.  I never knew of this little creature before news of the search for their existence, but now the rodent serves as another reminder that the effects of global warming are happening now.  Scientists believe the finality of extinctions like these can be prevented if more resources are used to identify at-risk regions and relocate wildlife, not to mention reducing greenhouse gas emissions as quickly as possible.  The success of such a mission usually rests with finding enough money from politicians and governments who see the urgency of such pursuits.

References

Gynther I, Waller N, and Leung LK-P. “Confirmation of the extinction of the Bramble Cay melomys Melomys rubicola on Bramble Cay, Torres Strait: results and conclusions from a comprehensive survey in August-September 2014.” Unpublished report to the Department of Environment and Heritage Protection, Queensland Government, Brisbane, 2016.

Howard BC. “First mammal species goes extinct due to climate change.National Geographic, June 14 2016.

Figure Credits

Figure of Bramble Cay melomys courtesy of Ian Bell via Wikipedia

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