YSM Issue 93.4 Full Magazine

OINT
CLIMATE CHANGE IS WORSE
THAN YOU THOUGHT
BY CHARLOTTE LEAKEY
IMAGE COURTESY OF PIXABAY
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 highresolution
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 as species interbreeding and
competition with Homo 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.
www.yalescientific.org
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. https://doi.
org/10.1016/j.oneear.2020.09.007
December 2020 Yale Scientific Magazine 35