Some models no longer available: Earth enters its 6th mass extinction phase, humans accelerate the losses

Geological evidence indicates that our planet has seen five mass extinction cycles since life first appeared on the planet. While they sound like the kind of cataclysmic events that only beardy men with huge boats survive through (read that in a book once, so it must be true), they are actually an integral part of life. The cycles free up ecological niches or entire ecosystems for new species to evolve into, much in the same way wildfires clear old, dry, dead plant matter so that fresh, green, happy plants have access to enough sunlight and nutrients to grow.

And if there’s one thing we here at ZME Science know, its beer mass extinctions. We’ve seen it coming, wrote about our role in it, and about how long some systems will need to recover from such an event. But even we were surprised when a new study, headed by National Autonomous University of Mexico’s Gerardo Ceballos revealed that we had come to start the 6th wildfire not with a box of matches, but with Apocalypse-Now amounts of napalm.

“The evidence is incontrovertible that recent extinction rates are unprecedented in human history and highly unusual in Earth’s history,” the study states.

“If it is allowed to continue, life would take many millions of years to recover and our species itself would likely disappear early on,” said Ceballos.

The authors of the study, published in Science Advances, compiled data obtained from geologic evidence, modern extinction records and other sources to determine the average rate at which species disappear. They point out that the study was done using extremely conservative assumptions, such as a background extinction rate of “2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY)” -twice as high as widely used previous estimates- and stringent criteria for when a species can be considered extinct . Even working under these very restrictive conditions, they have found that our planet’s ecosystems are breaking down at a terrifying rate.

“The average rate of vertebrate species loss over the last century is up to 114 times higher than the background rate. Under the 2 E/MSY rate, the number of species that have gone extinct in the last century would have taken […] between 800 and 10,000 years to disappear” they write. “These estimates reveal an exceptionally rapid loss of biodiversity over the last few centuries, indicating that a sixth mass extinction is already under way.”

The study looks at the anthropic related extinction of species rather than the number of individuals, meaning that the data mined by the team consists of whole populations, whole species or genera of animals that go extinct, not how many individuals of which species disappear. They calculated a “highly conservative modern extinction rate” by using the data exclusively on species listed as extinct (EX), and a “conservative extinction rate” by that also includes both extinct in the wild (EW) and presumed-extinct (PE) species. In terms of biological impact and the provision of ecosystem services, they consider EW and PE species to be functionally equivalent to EX species: even if some individuals still exist, their abundance is not sufficient to have a substantial influence on ecological function and processes, and it’s unlikely that the species will recover.

The findings show that current extinction rates vastly exceed what the team considered as being the natural average. This is especially troubling as they set the average value at double what was previously estimated, and the data on vertebrate extinctions was treated in the “most conservative plausible way”. The paper goes on to say that it’s very likely that the calculations underestimate the severity of the extinction crisis, as the team aimed to place a realistic “lower bound” on humanity’s impact on biodiversity, so they were looking for the best-case scenario of what is happening to ecosystems around the world.

Problems related to this declining biodiversity and environmental degradation may already be upon on us in significant ways. Insurer Lloyd’s of London assessed the possibility of food shocks in its 2015 “Emerging Risk Report,” released before the academic study. The report determined that the global food supply is “under chronic pressure to meet an ever-rising demand, and its vulnerability to acute disruptions is compounded by factors such as climate change, water stress, ongoing globalization and heightening political instability.”

“Our analysis emphasizes that our global society has started to destroy species of other organisms at an accelerating rate, initiating a mass extinction episode unparalleled for 65 million years.”

“Averting a dramatic decay of biodiversity and the subsequent loss of ecosystem services is still possible through intensified conservation efforts, but that window of opportunity is rapidly closing.”

And we should not let it pass us by. The Starks were right, winter is coming, and if we don’t do something about it now, we’ll spend it by ourselves around the campfire. We’ll have to explain to our kids that there once really were lions living and roaring in the savannah, not rust on the Lannister coat of arms, and exactly what a “wolf” is. Because they might end up just as real to them as the dragons in the book are to us.

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  1. Pingback: Shiva- Biodiversity – fgcu colloquium

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