Book Review: A New History of Life, by Peter Ward and Joe Kirshvink
At the present moment, we are concerned about the rise of CO2 in the atmosphere and its disrupting effects on planetary temperature and life. It is a reasonable fear. Of the ten or so mass extinctions in our planet’s history, most have involved greenhouse gas events as major perpetrators. In the long run, though, the problem may be in the other direction.
The long-term prediction for carbon dioxide is that it will continue in the same trend it has shown over at least the last billion years—a slow but inexorable decrease. The lowering levels are because of both life and plate tectonics: as more and more CO2 is used to make the skeletons of organisms, especially in the oceans, CO2 is consumed. If these skeletons stay in the oceans, the skeletally confined CO2 (now in calcium carbonate) will recycle. But plate tectonics makes the continents ever larger, and an increasing amount of limestone, which is the grave of atmospheric CO2, becomes locked to the continents as sedimentary deposits.
Ward, Peter. A New History of Life (pp. 347-348). Bloomsbury Publishing. Kindle Edition.
For this long term (several hundred million year) prediction the upward excursion of a couple or three hundred thousand years caused by us burning all the fossil fuels is a blip. Without CO2, plant life will die, continents and seas will become deserts, and atmospheric oxygen will drop to a tiny fraction.
I’m not too worried though. If human or some other kind of high technology survives, we ought to be able to find some ways lengthen the playing field for another couple of billion years or so. Eventually, though, the Sun will expand and consume the Earth, so we, or whomever, will need to get out or die.
Mass extinctions are a major theme of life, and are a continuing theme on our planet. The rise of oxygen killed most of Earth’s microbial life, or at least that on the surface or in the oceans, but it also made possible eukaryotes and multicellular life. A couple of snowball Earth events were similar catastrophes. Extinction kills off dominant forms and makes way for new ones. Would mammals have become the dominant class if an asteroid had not committed dinosaur genocide?
These are the stories Ward and Kirshvink tell, and I found the tale fascinating. I have long been interested in the subject, but much of the tale was new to me.
I highly recommend the book for those interested in the subject.