I don’t know whether this is cause for optimism or despair

Doug Erwin argues that we’re not in the middle of a 6th mass extinction. It’s not because we haven’t decimated life on planet Earth; it’s because if we were, the catastrophe would be immense, and we ain’t seen nothin’ yet.


This is because by the time a mass extinction starts, the world would already be over.




The good news is that we aren’t dead yet! The bad news is that when the end comes, it will be rapid and non-linear and unimaginably devastating. Just to put it in perspective, this is small potatoes compared to a real mass extinction:


The oceans have endured a similar transformation in only the past few decades as the industrial might developed during World War II has been trained on the seas. Each year fishing trawlers plow an area of seafloor twice the size of the continental United States, obliterating the benthos. Gardens of corals and sponges hosting colorful sea life are reduced to furrowed, lifeless plains. What these trawlers have to show for all this destruction is the removal of up to 90 percent of all large ocean predators since 1950, including familiar staples of the dinner plate like cod, halibut, grouper, tuna, swordfish, marlin, and sharks. As just one slice of that devastation, 270,000 sharks are killed every single day, mostly for their tasteless fins, which end up as status symbol garnishes in the bowls of Chinese corporate power lunches. And today, even as fishing pressure is escalating, even as the number of fishing boats increases, even as industrial trawlers abandon their exhausted traditional fishing grounds to chase down ever more remote fish stocks with ever more sophisticated fish-finding technology, global fish catch is flatlining.

Related concept: error catastrophe. One of the properties of organisms and food webs is that they’re surprisingly robust — you can punch holes in them and take out pieces and they just keep going until suddenly, the network can’t compensate and the whole thing just collapses. We’re cheerfully battering whole ecosystems and cheerfully telling ourselves how tough and resilient the world is, and it’s true…until one last damaging blow causes an abrupt disintegration.

Oh, did I say I didn’t know whether to be optimistic or despairing? I lied. I know which one I feel most.


  1. chigau (違う) says

    I used to think I’d be dead of old age long before the final collapse.
    Now I’m not so sure.

  2. kestrel says

    Whenever people tell me how the ocean can’t be damaged, it’s too big, I challenge them to set up a salt water aquarium and keep the organisms alive for 6 months. Just 6 months. I wish all people who make decisions regarding the use of the ocean had to do this.

    On the other hand in the US we can’t even get a lot of people to accept climate change, even right after they’ve just said “Wow, the weather sure is weird! It’s never been like this before!”. head/desk

  3. Dunc says

    We’re also not in a new geological era called the “anthropocene”: the changes involved can’t possibly last long enough to qualify as an era. We’re just laying down a boundary layer… I wonder what the cockroach geologists will call it?

  4. felicis says


    That’s not really true – there are mathematical biologists. Electrical engineers who specialize in power systems know quite a bit of math. And math is how one explains how such things work.

  5. Stray Cat says

    It’s been so long since I checked in on this blog. Years really. Glad to see PZ is still buzzing. Maybe I’ll stick around.

    I guess I’m…. glad y’all have a vision of the future as dour as mine? The world is unstable and unsustainable in so many ways. Who knows what the hard times that come will look like exactly, but you better believe they’re coming.

  6. rietpluim says

    So we’re not in the middle of a mass extinction?
    I guess all is all right then.
    It’s a relief, thank you.

  7. brett says

    Trawling is an ecological abomination, and needs to be banned outright. Instead, we struggle to even get sustainable catch limits on stuff, and there are folks willing to simply ride out the destruction of vast swathes of ocean habitat because it isn’t in their national borders (I remember when Bluefin Tuna started becoming endangered, the price actually went up because of stockpiling for when they went extinct).

    As for the broader point, it’s going to fall out in uneven fashion, of course. People living closer to the subsistence line, with fewer resources to deal with the change and ineffectual governments to deal with it, will suffer the most despite being the least responsible. Hell, I remember someone arguing outright that since disaster was inevitable, you might as well go full force on development and hope to be a rich country with more resources when the situation turns sour.

  8. chrislawson says

    Hmm. I agree that we can’t be sure we’re in a sixth extinction, but that’s down to (1) a lack of general agreement on what exactly counts as a mass extinction, and (2) that past extinctions have only been identified in hindsight, so it’s hard to tell how well the model applies when we’re in the middle of living it.

    But the other arguments don’t hold up for me. What we’re seeing is still incredibly rapid in geological time. Some estimates have us losing species faster than at any time since the KT extinction…and the modern extinction is accelerating due to self-reinforcing habitat loss and overexploitation and now global climate change (which looks like it’s about to destroy the Great Barrier Reef and its huge reserve of biodiversity). The fact that 97% of the biomass of land animals has been captured for human use is to me good evidence for us being in a mass extinction, not against it. We can’t measure biomass changes from the fossil record, only species frequency. From a geological perspective, anyone looking at the fossils we’re leaving behind today will see a huge dropoff in the diversity of land animal species starting around 300 years ago. This is what the known extinctions look like. (And I would also bet there are similar concerns with plant diversity as we continue to narrow down our agricultural range in pursuit of maximal profitability of the crops we choose to plant).

    Finally, of all the mammals, rats are the ones I’m least worried about. They’re an incredibly adaptive species. If rats are on the verge of extinction, humans will have been long gone.

  9. Reginald Selkirk says

    Sorry, got the wrong thread.
    Although, I gues that Mark Twain is extinct, so it’s relevant.

  10. A Masked Avenger says

    I’m not a biologist or ecologist so I have to ask: is he right?

    AFAICT, he’s only half right. The previous five major extinction events were spread over millions of years, with the shortest being ~500ka and the second-shortest being ~1ka. It seems plausible to my non-expert mind that ecosystems managed to adapt for a while, but then suddenly collapsed once losses became critical in some way.

    If so, it’s entirely possible that we’re in a period of accelerated extinction rates characteristic of mass-extinction events, but haven’t yet reached the critical point at which collapse becomes unavoidable. If so, I wouldn’t say that we’re NOT entering an extinction; at most I would say that we may not have reached the point of no return yet.

    Though again to my non-expert mind, indications seem to be that we’re on the brink of runaway global warming, as things like CO2 outgassing from permafrost regions has been observed sooner than expected, and that we may be on the cusp of a point of no return.

  11. weylguy says

    “Dog and cats living together, mass hysteria!” — Dr. Peter Venkman

    What kills me is that when it finally happens, we’ll all be asking ourselves how we could have ever believed that our over-consumptive, unsustainable way of life would last forever. Then we’ll start killing each other over scraps of road kill, bottled water, bullets and penicillin tablets.

  12. chrislawson says

    Pierce: it wasn’t the percentage of the Earth’s biomass, it was specifically the percentage of land animal biomass. So microbes are not included, and neither are aquatic critters.

    (I have to admit, I find that figure somewhat dubious even if he is limiting himself to land-based animals — the biomass of insects alone should be huge.)

  13. says

    Something about all that land being converted to farmland that you overlooked. As cities expand they convert the best farmland into housing lots and asphalt.

  14. says

    it’s because if we were, the catastrophe would be immense

    Oh, then wake me up when that happens and it’s too late to worry about it.

  15. A momentary lapse... says

    That 97%/3% split seems to match xkcd 1338 – a visualisation of the biomass of land mammals.

  16. komarov says

    Oh, good, so when it happens it will be over very quickly. That should save our species – and many others – some pointless thrashing about, trying to cling to life. Sorry, I’m new at this optism.. optimim … thing. Frankly, I doubt it’ll catch on.

    Re: Dunc (#3):

    I wonder what the cockroach geologists will call it?

    The slightly radioactive carbonaceous band? I’d be more curious to know if they ever figure it out, or if they keep asking themselves what kind of natural disaster could have left it behind* until they lay down their own slightly radioactive layer.

    *Leading theory: “Big natural reactor formed right next to a budding supervolcano. Those planet-roaming apes we keep finding everyhwere probably didn’t even have time to fall out of their trees, it was over so quickly.”

  17. says

    Chrislawson @ 8:


    As a person with a horde of rats, all I can say to that is: Truth.

  18. unclefrogy says

    I am not sure if despair is correct, The earth and it’s biosphere will likely get through this period but there will be many that won’t indeed many that have already
    perished utterly and will be seen no more. That it is not caused by cosmic forces or huge geological events but by the action of man and is continuing makes me very sad.
    there are some who are making valiant efforts to save somethings and change direction. I hope it works or at least helps.
    uncle frogy

  19. ginckgo says

    I think I see where Erwin’s gripe lies: as a palaeontologist, he defines ‘mass extinction’ as the completed event; while ignoring the ‘middle’ in the phrase “we’re in the middle of a mass extinction”. He even says that his research shows that M.E.s start with a killing of if a critical, but smaller % of species initially, up to the point where entire food webs and ecosystems collapse, taking the rest of species with them.
    So we are currently in the first stage of an ME, and need to act before the ecosystem collapse stage is reached – but we are nonetheless in the ‘middle’ of a mass extinction.
    The fact is that none of the Big Five (let alone the dozens of smaller mass extinctions) are the same. Each one has completely different set of causes, and different patterns of extinction, as well as time frames over which it happened. For him to assert that there is a single pattern to look for is frustratingly ignorant for someone that should know better.

  20. brett says

    @21 ginckgo

    I was thinking that too after I looked up some of the Mass Extinction Events. He brings up the Permian Extinction, the worst of them all, but the Permian Extinction lasted roughly 60,000 years. That’s a brief time in geological terms, but quite large by human ones – it’s one-fifth as long as Homo Sapiens appear to have existed period. The K-T Impact was obviously much more sudden, but that was an impact.

    I’m more worried about something like the Younger Dryas Period. Major, sudden global climate shift happening over a period of time measured in decades (maybe even as little as a decade). I remember years ago the US military did some scenario-playing about what the effects would be if we went through something like that, and it wasn’t good (not civilizational collapse, but bad stuff in terms of conflict, shortage of food and resources, etc).

  21. katkinkate says

    I think any investigation of the fossil record in the far future will show the beginning of this mass extinction event was back when we left Africa and systematically killed off most of the megafauna as we went. I think we are closer to the end stages of this event than we would like to think.

  22. ajbjasus says

    Two analogies:

    Trawling – if people saw that their farm produce was “harvested” using a pair of giant helicoptors dragging nets behing them that scooped up all crops, soil, farmhouses and “by-catch” (all the other species), they would soon ask it to be stopped.

    As for the ecosystem “surviving” it’s a bit like someone jumping off the empire state building, and thinking for a short while it’s going well, beacause all that is happening is that they are accelerating.

    I’m not sure how we will realise that our modern lifestyle, and numbers of humans on the planet are incompatible, until it’s too late.

  23. unclefrogy says

    As for the ecosystem “surviving”

    unless we some how manage to sterilize the whole planet a very difficult thing to do given the existence of extremophiles, the ecosystem and its processes will continue in some form possibly with a completely different mix of species.
    uncle frogy