Resilience and climate change extinction: The sad tale of the Bramble Cay melomys

A few weeks ago the world learnt of the disappearance of the Bramble Cay melomys, a small Australian rodent only known to occur on a tiny coral cay off the northern tip of Australia. The finding is noted in a government report that documents how a comprehensive search for the species in 2014 had failed to detect a single animal.

The report’s authors state that the population had “almost certainly” disappeared because its habitat had been destroyed by the ocean stripping vegetation from the low-lying cay. Indeed, so close to sea level is the tiny island that it probably provided little refuge to the melomys from big weather events. The authors even suggested ocean inundation could have directly killed or carried away individual animals! It’s a tragic situation to contemplate, the final specimen of a species being washed away by a rising sea.

Thousands of species around the world are on the lip of extinction but the loss of the Bramble Cay melomys is particularly poignant in that human-induced climate change has been identified as the root cause of its demise. Sea-level rise and increased frequency and intensity of weather events have been noted as the cause of the loss of its island home.

TorresStraitIslandsMap with Bramble Cay
Bramble Cay melomys were only known to occur on a tiny coral cay off the northern tip of Australia. Map via Wikimedia Commons

The loss of a species of island rat does not overly concern everyone, something that is clear if you peruse the discussion threads following some of the articles on this event (for example, see Nature and The Washington Post) and many simply deny the existence of climate change (read those same discussion threads). And yet the loss of the Bramble Cay melomys should be ringing alarm bells everywhere. It’s a symbol of clear and present danger, an example of irreversible consequence and a portent of things to come.

The Bramble Cay melomys has crossed an irreversible threshold. It’s gone with no possibility of return. And with its passing, the system it was a part of has lost a natural component making it less able to cope with change and disturbance; such is the consequence of biodiversity loss.

Scientists across multiple disciplines have identified what they believe is a ‘safe’ level of greenhouse gas concentration in the atmosphere. It is 350 parts per million of carbon dioxide. This year we crossed 400 ppm. The consequences of transgressing this ‘planetary boundary’ is climate change, rising sea levels and more extreme weather events. This increase in disturbance threatens to overwhelm the resilience of many species, especially those living in low areas, and the loss of the Bramble Cay melomys is but the start of this process.

Bramble cay melomy Melomys rubicola. Photo Credit: Government of Queensland, Australia, via Wikimedia Commons

Given the already devastating change to Bramble Cay it’s unlikely that the loss of melomys will have any effects on what’s left of its ecosystem. However, in more-or-less intact ecosystems the loss of species serves to erode the system’s resilience to climate change. It’s a synergistic set of secondary feedback effects making things progressively worse. Biodiversity loss makes us more vulnerable to climate change, less able to absorb the disruption it brings.

Resilience thinking helps us engage with the complexity of the world, guiding our management of ecosystems. Part of that complexity is the strength of policy feedbacks to change. Some have suggested we should have moved the last Bramble Cay melomys to some safe harbor before they were swallowed by the hungry sea. And, indeed, we should have; we’ve known they were at risk for many years. That we didn’t suggests our feedback to the challenge of climate change are inappropriate. They need to be tighter. In this case it’s resulted in the irreversible loss of a mammal species. And maybe we should seeing this rodent as a canary in the coalmine.