This post briefly reviews the demise of the Bramble Cay melomys, a rat-like mammal that is no longer to be found on Bramble Cay, a tiny coral atoll between Australia and Papua-New Guinea and the animal’s only known habitat. The acknowledged cause of the extinction – which appears in this case to be real – was a series of storm surges that inundated Bramble Cay and killed off the vegetation. There is, however, no evidence linking these storm surges to human-induced climate change. The University of Queensland’s claim that the Bramble Cay melomys ….. is the first mammal to go extinct due to human-induced climate change must therefore be considered invalid as well as grossly misleading.
For years now CAGW proponents have been relentlessly searching for an example of a species that has incontrovertibly been driven extinct by man-made climate change, but so far without success. Discredited examples have included the Harlequin Frog and the Golden Toad in Costa Rica, the European Land Leech in Europe, the White Possum in Queensland and the Aldabra banded snail (discussed earlier in this post), which after being declared extinct in a Royal Society paper was later found alive and well in a different part of Aldabra Atoll. (The RS nevertheless refused to withdraw the paper). Now, however, we have a new candidate – the Bramble Cay melomys, and this one really has the AGW people stirred up (a Google search for “Bramble Cay melomys extinct” generated 176,000 hits). There’s no shortage of hand-wringing either. As the Guardian puts it:
Farewell, Bramble Cay melomys. We killed you and you will be remembered as the first mammalian extinction caused directly by climate change: wiped off the planet by rising seas ….. It is the beginning of a new wave of loss and we need to start to prepare ourselves for the grief that will inevitably follow.
Here we will look into the question of whether “we” really did kill the unfortunate animal.
Figure 1 shows the location of Bramble Cay off the northeast tip of Queensland and the south coast of Papua-New Guinea along with the locations of four tide gauge stations discussed later:
Figure 1: Location map
And the following photos indeed make one wonder how a mammalian population could continue to survive on a postage stamp-sized (about 4 hectares), barren atoll like Bramble Cay:
Figure 2: Recent photographs of Bramble Cay. The structure in the first photo is a disused lighthouse. The second shows a trap set next to one of the last remaining patches of vegetation.
So is the melomys really extinct? No one knows for sure because there’s a possibility that it may still be present in the Papua-New Guinea rain forest. But a detailed study conducted by the University of Queensland entitled Confirmation of the extinction of the Bramble Cay melomys leaves little doubt that it is no longer present on Bramble Cay.
And what does the study say about the causes of the extinction? It looks into rainfall and temperature and concludes that neither had a significant impact:
With no trend in the annual rainfall data apparent over recent decades, this climate variable is unlikely to be a causative factor in the decline in vegetation cover on Bramble Cay during the decade prior to 2014. By contrast, the small, gradual increase in air temperature evident in the climatic record for Torres Strait could conceivably have affected plant health on Bramble Cay negatively over the past ten years, perhaps contributing to a reduction in the area of vegetation on the island. However, the relatively small change in average temperatures is unlikely to account for the large magnitude of change in vegetation extent that has taken place over such a relatively short time span.
…. goes on to identify the real cause:
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.
…. and concludes by paying the requisite obeisance to human-induced climate change:
Available information about sea-level rise and the increased frequency and intensity of weather events producing extreme high water levels and damaging storm surges in the Torres Strait region over this period point to human-induced climate change being the root cause of the loss of the Bramble Cay melomys.
I’m taking the first conclusion on trust because I have no usable data on rainfall and temperature in the area around Bramble Cay, but I do have some data for sea level rise and cyclones/typhoons. First, is Bramble Cay routinely affected by typhoons and cyclones? Figure 3 leaves no doubt that it is:
Figure 3: Typhoon/Cyclone tracks, 1990-2010, data Australian Bureau of Meteorology
And has the frequency of typhoons/cyclones in and around Australia been on the increase, as one would expect if storm surges are becoming more common? According to the Australian BOM it has not:
Trends in tropical cyclone activity in the Australian region (south of the equator; 90–160°E) show that the total number of cyclones appears to have decreased to the mid 1980s, and remained nearly stable since. The number of severe tropical cyclones (minimum central pressure less than 970 hPa) is dominated by variability with periods of lower and higher frequencies of occurrence.
The data are shown in Figure 4:
Figure 4: Number of cyclones around Australia, 1970-2010.
Despite what the BOM claims there has been an obvious decrease in the total number of cyclones around Australia since 1970.
And what about sea level rise? Figure 1 showed the locations of four PSMSL tide gauge records on the northern tip of Queensland, about 250km away from Bramble Cay and the closest I can find. From west to east they are Booby Island, Goods Island, Turtle Head and Ince Point. All of them have data from 2000 through 2013 and Figure 5 plots them up:
Figure 5: The four tide gauge records
Figure 6 shows the average of the four records:
Figure 6: Average of the four tide gauge records
If one can believe a trend line drawn through data like these then relative sea levels in the area rose by 65mm, or about 2 ½ inches, between 2000 and 2014, the period over which the melomys died out. Clearly this would not have inundated Bramble Cay, which reaches a height of nine feet above sea level. Not even the +/- 400mm seasonal range – note that sea levels are highest in the cyclone season – would have made that much difference, and being in the open ocean the seasonal range at Bramble Cay could well be lower than this. Yet there is abundant evidence that the island was inundated, and more than once, in recent years. From the University of Queensland report:
A significant weather system in July 2005 during which “waves were reported being thrown up over the cay as a result of gale force winds pounding the cay for several days coupled with very high tides” was probably responsible for, or at least contributed to, the 49% reduction in vegetation cover on the island in December 2011, as compared to the previous assessment in November 2004…. seawater inundation resulting from one or more extreme weather events over the two and a quarter years following December 2011 (was) the most likely cause of the further 94% loss of vegetation cover that occurred by March 2014. Observations made during the August–September 2014 visit provided strong evidence of additional episodes of seawater inundation or wave penetration of the cay’s interior during the five-month period between the two trips made to the island in 2014.
So there you have it. The demise of Melomys rubicola had nothing to do with temperature, rainfall or sea level rise. The animal was a victim of storm surges that progressively destroyed its habitat. No evidence – not even a climate model – is presented to support the claim that these storm surges had anything to do with increasing atmospheric CO2. It’s also questionable whether storm surges at a remote atoll even qualify as “climate change” – note that they are described in the above quotes as “weather events”. Yet in its press release the University of Queensland has no compunction in confirming that the extinction was a result of man-made climate change:
University of Queensland and Queensland Government researchers have confirmed that the Bramble Cay melomys – the only mammal species endemic to the Great Barrier Reef – is the first mammal to go extinct due to human-induced climate change.
Usually I like to conclude a post with a pithy comment, but in this case words fail me.