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Mass Extinctions

August 27, 2019

One of the important books I read while on vacation was Timefulness: How Thinking Like a Geologist Can Help Save the World by Marcia Bjornerud.

Geology is one of those often overlooked sciences that doesn’t have quite the pizzazz of physics, biology, or even chemistry. It’s just about rocks, right? Bjornerud, a professor of geology and environmental studies, makes a compelling (and poetic) case for  appreciating earth’s geology and the importance for thinking like a geologist–taking the very, very long perspective, even of geologic ages, not just next year’s benefits. She calls this way of thinking timefulness.

She begins by telling the interesting story of how scientists, bit by bit, figured out the age of the planet, the beginning of life, and how to date rock layers and fossils. About four and a half billion years ago the earth formed, and then began a fascinating process of geologic and atmospheric upheavals that are still continuing today. The earth and its atmosphere are not static. The continents have drifted, mountains have risen and fallen, the temperature has gone up and down drastically, and the make-up of the atmosphere has completely shifted at least four times. We human beings inhabit this planet only because geologic and atmospheric conditions have been just right for us for the tiniest sliver of earth’s time. If conditions change (and they will, and are changing even now), we may find ourselves on an inhospitable planet.

Five times life on this planet has suffered catastrophic mass extinctions, and when life re-emerged, it was quite different from the dominant lifeforms that preceded it. 440 million years ago, 86% of all species went extinct during an abrupt ice age followed by rapid warming; 365 million years ago rapid cooling killed off 75% of all species; 250 million years ago, cold and then extremely warm weather led to the extermination of 95% of all species; 200 million years ago a hot and dry period caused the extinction of 80% of all species; and 65 million years ago an abrupt cold spell killed off 76% of all species. The climate change that brought about this last mass extinction was caused almost certainly by a large asteroid striking the earth. But so far there is no evidence that asteroid or comet strikes caused the previous mass extinctions; rather, it is more probable the drastic climate changes were caused by geologic factors on the earth.

The sobering news is that climate is once again changing rapidly. Carbon dioxide, which is a heart-trapping gas, has been stable in our atmosphere for the last twelve thousand years, at about 255 parts per million. This stable level gave humans a comfortable and dependable temperature for flourishing and coincides with the rise of human civilizations. By 1800 the level of carbon dioxide had very gradually risen to 280 ppm. But then came the industrial revolution and the ever-increasing burning of fossil fuels (coal, oil, natural gas), concrete production, and deforestation, which release carbon dioxide into the atmosphere. By 1960 the level was 315 ppm–rising as fast in 160 years as it had in the previous eleven or twelve thousand years. In 1990 we passed the 350 ppm mark, which many climatologists consider the upper threshold for maintaining climate stability favorable to humans. By 2000 we reached 370 ppm, and as of today we are well over 400 ppm. There hasn’t been this much carbon dioxide in the atmosphere in over four million years–when the climate was quite hotter. We humans are rapidly changing the climate of the planet.

Bjornerud puts all of this change into geologic perspective, looking for analogies in the geologic record. We may not be in the midst of a mass extinction like the one 65 million years ago, but species are still disappearing at an alarming rate. For instance, the average extinction rate for amphibians over tens of millions of years is about one species per hundred years. Today, the extinction rate for all animals is at least 100 times, and perhaps 10,000 times, the geologic average. We may not be facing imminent extinction ourselves, but we are in for much more volatile and destructive weather, and a planet with rapidly decreasing biodiversity.

What can be done? The short answer is to achieve carbon emission neutrality as soon as possible. This is politically and economically controversial, but the longer we put it off, the more costly will be the consequences. Because cutting carbon emissions is so difficult, many scientists have suggested finding ways to get the carbon out of the atmosphere or block the heating rays of the sun. Bjornerud goes through each of these proposals one by one, demonstrating how unfeasible they are, or how the costs would be impossible. One approach–massive reforestation of the planet wherever possible–would indeed help to soak up carbon, but it does so only temporarily since decaying trees would then re-release the carbon. Another approach–injecting massive amounts of sulfates into the atmosphere to deflect some of the warmth of the sun–might work but would require international cooperation for centuries (a highly unlikely prospect) and turn the sky permanently white.

Bjornerud concludes: “An irony of our technological advancement is that it has created a society that is in many ways scientifically more naive than the preindustrial world, in which no citizen who learned physics through backbreaking work and understood climate through subsistence agriculture would have assumed that he or she was exempt from the laws of nature. The ‘modern’ kind of magical thinking is characterized by the belief that repeating falsehoods like incantations can transform them into scientific truth. It is also yoked to a quasi-mystical faith in the free market, which, according to the prophets, will somehow allow us to live beyond our means indefinitely.”

Bjornerud says we need the “Seventh Generation” approach–an idea advocated by Iroquois Indians over three hundred years ago “that leaders should take actions only after contemplating their likely effects on ‘the unborn of the future Nation … whose faces are yet beneath the surface of the ground.'” Thinking in terms of seven generations goes beyond our own lifetimes, and prevents us from “stealing from the future.”

This is just a taste of the rich information and challenges in this book. I cannot think of a subject that will have more profound effects for our future wellbeing than this one. We owe future generations a decent chance to survive and flourish.

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