Loading...
Nature

Has the ‘Human Epoch’ Begun and is a Mass Extinction Near?

As we near 2011, I know I must try to prepare myself for 2012, and the (next) wave of apocalyptic doom-saying that, according to the ‘fin-de-cyclists’, was predicted by the ancient Mayan mathematicians over 3 thousand years ago. Of course, they never predicted an End, per se, it’s just that they only extended their 260 day, cyclical calendar* to December 22, 2012 (near the winter solstice, a fitting day to be sure); they probably thought that was just plenty.

It’s easy to dismiss such cataclysmic claims as being the product of mis-educated, or under-informed, mystical types, but I remind myself that science too has fanned its share of doom and gloom scenarios…Consider the Y2K hysteria of but a decade ago. The predictions surrounding Y2K (the “millennium bug”) ranged from peoples’ bank accounts being frozen to failed air traffic control to mass power outages and the collapse of human civility, if not civilization (how would we ever get along without computers?).

So OK, both science and pseudo-science have had their end-of-life-as-we-know-it predictions (science veils its doom saying in purely “what if?” terms; pseudo-science selectively edits out what doesn’t fit the predictions), but, as a student of geology as well as biology, I still have to wonder: could we be entering (or already in) a new Mass Extinction phase? What evidence supports, or  refutes, this possibility?

Mayan Month Glyph: black storm, Ch’en

Our methods for counting our planet’s biodiversity — both in the past and in the present — are getting better. But in truth, the only way we can make accurate guesses about the future is to look for evident trends over vast stretches of geologic time, and make the best estimates that we can. Looking at the fossil record, we see that  the Earth (its biosphere) has experienced quite a few “mass” extinctions in its history– some more massive than others — such as the Permian Extinction (about 260 million years ago [mya], which ended existence for 90% of the world’s lifeforms), and, the famous KT extinction that brought about the end of the dinosaurs’ dominance (about 65 mya).

But how does the present measure up against the past?

An IUCN report from 2007 estimated that each year, some 400 species of plants and animals go extinct (in the wild). That’s a little over one species per day. But to understand the significance of that number, one has to compare it to the “normal” rate of extinction, what’s known as the background extinction rate. Analyses of the fossil record have shown that this background rate has remained relatively consistent over the eons.

Different estimates of this rate have been attempted, with the most recent ones utilizing data from the Paleobiology Database (PaleoDB).  Typically, a researcher will take a random sample from each time period and extrapolate from these counts. Critics of these estimates say that less populous species get left out of the count, so the arrived-at extinction rate is an under-estimation. A new approach to data sampling called “shareholder sampling” was utilized by paleobiologist John Alroy (Sept 3, Science). This method tracks how frequently certain groups appear in each geologic period and calculates a target number of counting samples that are representative of that proportion.

These older and newer estimates give us a range for our current epoch’s extinction rate of 10 to 100 times the background extinction rate. Much of this can be attributed to human activities such as over-hunting/harvesting, development, and pollution.

In each case of mass extinction, in each long era or eon of evolutionary change, the extinction was never total; some species adapted and survived, just barely, and some new species (or clades of species) arose, flourished and re-diversified. At some points in the fossil record, such as during periods of dramatic climate change, biodiversity in some taxonomic groups clearly declines, while in others, biodiversity actually increases.

Strophomenid brachiopod with attached cornulitid worm tube (Upper Ordovician, SE Indiana, USA). Brachiopod valves often serve as substrates for encrusting organisms.

Some groups can have sudden diversity spurts lasting tens or hundreds of millions of years, and then, suddenly, their diversity numbers just crash. An example of this is the ancient group of bivalves called brachiopods, which flourished from 540 to 250 mya, surviving through the Permian Extinction. But some time after 250 mya, their numbers took a steep dive. Despite this, though quite rare, some forms of the ancient brachiopod persist to this day.

It’s as if evolution wants to create, to preserve, life, despite it’s annihilating tendencies. Another example of this would be tiny sponge-like creatures called Ponifera, which survived the ancient ice age known as the Cryogenian, that ended about 635 mya. Descendants of these primitive sponges remain with us, continuously filtering plankton and providing in turn a food source for many other marine life forms.

However, in examining the fossil record, paleobiologists will note that the biodiversity of large taxonomic groups (such as marine plankton) has tended to arrive at an equilibrium point, in which total species’ biodiversity levels off, neither increasing or decreasing significantly.  And the thing is, there’s no way to predict with certainty if any given group has attained, or will attain, its biodiversity “cap”, or upper/lower limit. Further, this diversity limit is not fixed; apparently, this limit changes, spontaneously, every 200 million years.

Despite these uncertainties and fluxes in diversity, paleobiologists will also point out that the background extinction rate for individual species has in fact remained consistent; the average species evolutionary time span lasts but a few million years. Well, that was before the rise of homo sapiens sapiens, anyway.

This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga.[1
Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The two million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.
Geologists will tell you that we currently live in the Holocene Epoch, which commenced with the retreat of the last Ice Age, about 11 to 12, ooo years ago (which was the end of the Pleistocene epoch). If one watches the TV documentaries or dares to explore Nature on your own, one may be struck with the seemingly vast spectrum of biodiversity that characterizes our biosphere (yet consider how many species have gone extinct since just that last Ice Age, or the fact that most of the creatures that have ever lived, have gone extinct). Indeed, of the unknown number of millions of species on this “pale blue dot,” scientists estimate that maybe ten percent have been fully described, or identified.

And we might never get the chance to describe many of these, given the accelerating rate of negative human impacts on biodiversity (overall biodiversity is declining), and the current rate of extinction that’s well above the background rate; one could readily make the claim that we are indeed experiencing a mass extinction.

For this reason primarily, some scientists are suggesting that the Holocene Epoch may be over, and that a new epoch — the Anthropocene — may be officially upon us.

Perhaps, in naming this epoch after our kind, we might grow more self-conscious about what we are doing in it. What we do clearly impacts diverse ecosystems. These ecosystems drive the biodiversity and evolutionary fitness of countless animals and plants. There are some points in geologic time in which failed ecological conditions prevented recovery of species richness.  There are critical thresholds beyond which biodiversity cannot recover. Despite the resilience of some, many more will die out, never to be replaced. Our ocean’s coral reefs seem to be one type of ecosystem that is facing this evolutionary challenge.

But I believe, if we can take away biodiversity, then we also have the power to restore it. We can assist nature, perhaps, in finding a new equilibrium point for those critical species upon which our precious, life-giving ecosystems depend. We can become a positive force for planetary biodiversity. This will benefit our survival, in the long run. And, in so doing, we would truly bring honor to the title: the Anthropocene Epoch

.
Mayan Month Glyph: new sun , Yaxk’in’
* According to Wikipedia, the Mayan Calendar is actually a composite of two calendrical systems: the Tzolk’in and the Haab’ systems; 260 and 365 days, respectively. Neither system numbered years. Years were arrived at by adding the two systems together. A full cycle (“calendar round”) ends/begins (repeats) every 52 years. The end of any calendar round was generally viewed as a period of disorder and “bad luck”.

All Images: public domain

Top Image: Dutch school, 17th Century illustration, “Dronte” (Dodo)




7 comments
  1. Earl_E

    Humanity is the 800 pound gorilla we are chained to..

    The LA riots prove that man can quickly turn civilization on it’s head. If the banks hadn’t pre-coded the solution, you can’t prove society would have survived.

    We are only 8 meals from anarchy. If your bank had no record of your account, how many meals would you have missed?

    Yes we are chained to the 800 pound gorilla, but he doesn’t even have the time to watch the news, let alone dig into climate science.

    This gorilla invaded Iraq and is now stealing their oil and the most important thing is when he gets his next banana.

    People who are actually educated about climate science are probably 1 in 100,000 at best.

  2. Michael R.

    Apples to apples:

    The article was not meant to deny a real biodiversity crisis, but rather, to address this crisis (which is denied by many skeptics), starting from the objective acknowledgment that “doom and gloom” scenarios are promulgated, historically, by both science and pseudo science (both are prone, in the context of their “truth systems”, to hyperbole), and then, from that point, take a scientific look at the idea of mass extinction.

    So, yes, thanks for making that point about Y2K…efforts were made to forestall…something, possibly a major crisis in financial transactions, etc…but your subjective work experience and (now) ire may be preventing my point from being acknowledged.

    My point in using this example was that the “technorati” who were informing us about this “crisis”, were themselves in disagreement over whether there was anything to worry about…at all. On different days of the week, a new theory, or refutation of one, would appear in the mainstream press…with some predicting, at most, a big nuisance, while others asserted a larger (but not clearly defined) catastrophe.

    It is the nature of mass media, and human minds in fear mode, to distort. But this is/was confusing and stressful to many.This has the very real potential to create a backlash (as is happening now with CC), and consequently, a resistance to change and to taking rational/sensible steps to prevent/forestall the most plausible (negative) outcomes (note: recent study showing that people ‘tune out’ fear-based climate change news.)

    As to Y2K: Even if all the computers (somehow) failed to continue functioning as programmed (though the exact logic of this failure was never satisfactorily articulated, only speculated about), society would not have collapsed, mass chaos would not have ensued.

    Further, a great many computers that were never “fixed” (to avert the possible Y2K changeover glych) went right on working just fine (my computer certainly did) after midnight 2000…Further still, a great many companies were still scrambling to be “y2K compliant” right up until the last moment, some failing to do so, only to find that things didn’t fall to pieces in the aftermath.

    Donald Rumsfeld Summation:

    Was there a real crisis? Surely. Could it have been really bad? Yes, it could have been. Was there a bit too much fear-mongering in proportion to the outcome? Definitely. Could this past hype vs. outcome differential make people shut out future warnings of a pending crisis? Yes, it seems quite likely.

    I perhaps should not have used this example (Y2K) since it conveys the erroneous idea that the comparison was one of substance, instead of one of kind, as it was meant to be.

    I guess what seemed like an apple at the time, may have been an orange.

    Oh, and yes, I would get out of the way of that truck, but what if I am chained to a very large person in the middle of the road who is blind and deaf, and who has been manipulated by science hype one too many times to believe it’s true? In many ways, we are chained to to such a metaphorical person.

    happy new year, M.R.

  3. Earl_E

    Bluefin Tuna are 85% gone. Being one of the ocean’s apex predators, their demise means population explosions of the tuna’s food chain.

    Chinese now eat cow. 6.5 billion hamburgers per day will require two additional Earth’s full of cattle feed.

    What happen’s when you burn a forest to grow corn?

    A regional mass extinction of the ecosphere replaced with mono-culture.

    Mass extinction will continue until the moral improves.

  4. Earl_E

    Just wanted to mention my bank spent two years redoing the code on the mainframes to make sure when Y2K hit that our systems would be able to continue.

    Had we not, things would have ground to a halt. So when you used this Y2k effort to draw a parallel to something, you should compare apples to apples.

    Here is a better one:
    If there is a 90% chance that bus is going to hit you, are you going to get out of the way?

    Maybe you’d bet on the 10%, but I’d definately recode the mainframe before Y2k as did all banks and data-centric operations.

  5. Natalia

    This is a fascinating article! I really enjoyed it. Working at the museum with scientists, from taxonomists to captive breeders and seeing all the different perspectives about how to best maintain the world’s biodiversity. And it just makes me realize more everyday that the more I know, the more I realize how very little we know about the earth’s other inhabitants, how difficult it is to gauge what is being lost (or what was ever there). What a strange world. Thanks for the article!

Leave a Reply

Your email address will not be published. Required fields are marked *