Saturday, November 24, 2018

Life Goes On

Cambrian ocean scene, featuring an Anomalocaris canadensis ("anomalous Canadian shrimp") chasing trilobites. Image by diorama artist Ken Doud.

In fact it's likely she meant the Cambrian, and I think it's very likely that a system of global warming, rising sea levels, and coastal erosion, worked in at least as disruptive fashion as it does now, if I'm getting this great post from Science News for Students and a Britannica article right. In a sense, I'll show, conservatives are right in their claim that the climate change phenomena we're experiencing now aren't that different from the climate change phenomena that have been around forever, and they certainly weren't caused by humans then. But don't get too comfortable, conservatives.

Because they were caused, in part, by biological organisms, through their production not of greenhouse gases but of atmospheric oxygen. In the late pre-Cambrian, around 830 million years ago, the earth's atmosphere was up to around 2% oxygen, and by the start of the Cambrian 540 million years ago it was up to between 10% and 16%, close to the 21% it is today, and it was early life that made that happen. And there was also a period of intense global warming, up to year-round global average temperatures of around 22 degrees (72º F), caused not by greenhouse gases but the drift of the continents around the circumference, leaving a long period when there were no polar icecaps, because no land (as in Antarctica) or land-enclosed sea (as in the Arctic) provided the conditions for an icecap to form. This meant ice sheets in the interior of large land masses melting and big rises in sea level attacking those coastline areas with their hyperoxygenated water, bashing and tunneling and flooding vast areas of land.

In these shallow waters the first true animals—creatures capable of moving independently and seeking food in the form of the first photosynthetic plants, single-celled plankton and algae—evolved, putting the previously dominant life form of the Ediacarans, the first multicellular creatures, a big family of mostly immobile discs, tubes, fronds, and mattresslike packages, under intolerable pressure by the wholesale changes they brought to the environment, and these new creatures brought on the first of the five great mass extinctions, the Ediacaran Event, possibly killing most of themselves as well (the evidence isn't clear). Which in turn made room for the Cambrian explosion of the metazoans (Annelida, Arthropoda, Brachiopoda, Chordata, Ctenophora, Echinodermata, Hemichordata, Mollusca, Onychophora [velvet worms], Porifera, Priapulida, and more).

And 50 million years after that the Ordovician and Silurian events brought 85% of all species to extinction, and all that extraordinary creativity was kind of wiped out in turn, and another boatload of species took its place. So it goes, as Kurt Vonnegut, Jr., used to say.

Anyway what I wanted to say was that climate change deniers are quite right, in their own terms, when they say what's going on with the climate is perfectly natural. It's entirely normal for some hotshot young species to think it it can totally transform the ecology without any adverse consequences, and lead itself and all its neighbors off the planet's surface and into the fossil record. You don't blame those first metazoans for the trouble they made, and you shouldn't blame humankind either, if we're busy making the planet uninhabitable for ourselves and practically everybody else. Life goes on! Even if it doesn't go on for us. Some breed of kudzu-eating cockroach will take over the land, and the sea will devolve on creatures that can eat plastic. When they've eaten all the plastic, they'll die and something else will turn up. And at least the Koch brothers and Megan McArdle will be as dead as we are. We like humans on the whole, and polar bears and redwoods and so on, but maybe we're just being sentimental.

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