Bramble Cay melomys are the chubbiest brown mice you’ve never heard of. They lived on a small island on the northern tip of the Great Barrier Reef until they met their unfortunate demise in the early 2000s. Scientists worldwide grieved the extinction of these elusive critters, both for the ecosystems they left behind and for the dire situation that their extinction brings to light. “Significantly, this probably represents the first recorded mammalian extinction due to anthropogenic climate change,” a 2016 Queensland Government report postulated. As modern-day anthropogenic (human-caused) climate change progresses, other fauna of the Earth are also projected to suffer immensely. Alas, if climate-driven extinctions of ancestral human species thousands of years ago give any indicators about the present, the situation might be even worse than we thought.
Pasquale Raia’s group at the University of Naples Federico II studied the fossil records of five extinct human species, such as Homo erectus and Homo neanderthalensis, in addition to our own, to see how they reacted to natural changes in climate. The researchers looked at climatic niches, the conditions in which a species can survive and thrive. By studying fossil records with a climate emulator, a computational tool that supplies high-resolution temperature and rainfall data, the researchers estimated the climatic niches during the time period and in the regions in which each human species lived. After distributing each species’s fossil record into respective consecutive time bins—a statistical technique for discretizing large sets of data—they compared the niche of each bin to the fully realized climatic niche that the species encompassed throughout its evolution.
Right before their extinction, in the last time bin, three human species lost a significant proportion of their climatic niche. These results were consistent across different fossil records and with controls for various confounding factors, such species interbreeding and competition with H. sapiens. “If you consider the entire history of a species as a sphere, we thought that the diameter of the sphere of each bin would be a constant proportion of the entire sphere because humans are so good at modifying their climatic conditions,” Raia said. “[Instead], in the last bin, that sphere became very tiny.” Additional statistical analysis further confirmed that climate change in particular caused the shrinkage of the bin sphere, accelerating the extinctions.
What does this mean for us, the last prevailing Homo species, as we face a climate crisis today? There’s good(ish) and bad news. The good: “I do not feel that we as humans really risk going extinct because of future climate change,” Raia said. Though we face drastic damages to our lifestyle, as a species, we have the ability to create technology that can let us at least survive just about anything that climate change has to throw at us. Floods, droughts, drowning cities, tropical storms, or even ice ages would be devastating, but they would not be at a scale to completely wipe out the human race, unlike the fate of the hapless hominids of the past.
The bad news concerns other life on Earth. “[The Homo species] were endowed with a lot of skills that were quite unnatural, quite rare. They were able to master fire, produce clothes and spears, and move over very large distances,” Raia said. “Despite this, climate change that was not as fast and not as extreme as the current climate change was enough to wipe them extinct.” This is very concerning: given this result, it is difficult to envision how the fauna of the Earth, which are far less technologically advanced than any Homo species, could possibly survive anthropogenic climate change — especially considering that it is occurring at a rate orders of magnitude more quickly than past events.
Exactly how vulnerable are our precious fauna? The preliminary results look grim. “They have not enough space, the populations are too small, too isolated, too fragmented,” Raia said. And humans have been frustratingly slow to help. “We are doing almost nothing — we are thinking a lot, studying a lot, trying to do a lot of things,” Raia said. “I think probably a teenager from Sweden is doing more than politicians have done in the past twenty years or so.” If these patterns continue, we are looking towards a disaster, both for the fauna of our planet and for the modern lifestyle we hold onto.
Gynther, I., Waller, N. & Leung, L.K.-P (2016). 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.
Raia, P., Mondanaro, A., Melchionna, M., Febbraro, M. D., Diniz-Filho, J. A., Rangel, T. F., . . . Rook, L. (2020). Past Extinctions of Homo Species Coincided with Increased Vulnerability to Climatic Change. One Earth, 3(4), 480-490. doi:10.1016/j.oneear.2020.09.007
Xu, C., Kohler, T. A., Lenton, T. M., Svenning, J., & Scheffer, M. (2020). Future of the human climate niche. Proceedings of the National Academy of Sciences, 117(21), 11350-11355. doi:10.1073/pnas.1910114117