books science

Book review: The Human Planet, by Simon Lewis & Mark Maslin

The Anthropocene is a theme that I return to from time to time, from one perspective or another. The Human Planet: How we created the Anthropocene returns to where the notion began: in geology. Where did the idea come from, where was human influence first identified in the geological record, and what is the geological record anyway?

Although we only recently started talking seriously about the Anthropocene, the human footprint on the earth’s systems go back a long way. Earlier scientists spotted this: the Compte de Buffon identified a ‘human epoch’ in 1778. “I do not hesitate in proclaiming the Anthropozoic era” wrote Italian priest and geologist Antonio Stoppani in 1873. Russian geologists were talking about the Anthropogenic system in the 1920s. There’s nothing new about the idea, though the mounting pressure on the natural environment gives it added urgency.

Human impacts go back a long way, well before the industrial revolution, and the book spends several chapters tracking them. Our first planetary change was while humans were still hunter-gatherers. With cooperative hunting techniques and weapons, early humans wiped out large land animals everywhere they went. Mammoths and elephants, hippos and rhinos all vanish from record as humans enter it. Africa suffered the fewest extinctions, which is why we think of these creatures as African animals today. Altogether the authors estimate that a billion large animals were slaughtered for meat, and “megafauna absence can restructure whole ecosystems.”

A second big change came with the development of farming. Plants and animals were domesticated, and early farmers began to influence genetics. (If you’ve ever wondered why the zebra was never domesticated when other wild horses were, the book will tell you – one of many little asides and examples). Forest was burned off to clear it for farmland, and the loss of forest warmed the atmosphere enough to interrupt the earth’s usual cycle in and out of ice ages. “The new mode of living that emerged 10,500 years ago managed to delay the next glaciation event, a truly global environmental impact.”

The most tragic of the global changes is the age of exploration, when people from different continents met for the first time. Europeans brought diseases to South America that people had no immunity to. Millions died, with populations crashing by 90% in some places. It was this loss of workforce that led to the slave trade and the importing of human labour to the Americas. It also led to farmland being abandoned, and the regrowth of forests cooled the whole planet.

More recent changes are more familiar and more obvious – fossil fuels, invasive species, the discovery of nuclear power and the first radioactive traces in the geological record. And with so many of these impacts to choose from, where do we draw the line and declare the start of the Anthropocene? Scientists want to know where to hammer in the  ‘golden spike’ where the change first appears in the layers of rock – something that all previous geological ages have.

That’s a huge debate at the moment, and the book details the processes involved. It’s a little tortuous. Geologists think in ages, and they cannot be hurried. There are committees for these things, which in my imagination look like the Entmoot in Lord of the Rings.

‘Why does it matter?’ I found myself asking as my interest began to freeze over, but the authors have anticipated the question. “The choice of start date for the Anthropocene will inevitably feed into the stories we tell about ourselves and wider human development.” Is the Anthropocene accidental, something we blundered into? Is it about technology, or about farming? “From different stories flow different views of the world and so alternative courses of action.”

Lewis and Maslin make the case for 1610 and the birth of the modern world. That makes the Anthropocene story one of slavery and colonialism, of “domination and the resistance to that domination”. And that kind of a definition is going to get political.

Both authors are earth scientists, so their primary concern is not with politics or economics. But they do conclude with some comments that chime very well with the themes of this blog. Now that we can see the effects we are having, we have to start positively managing the planet. Reducing greenhouse gases is the first priority, though not the only one. “To achieve it, society would need to place the eradication of greenhouse gas emissions at the same level of importance as the pursuit of economic growth”, they suggest.

The Human Planet is a highly readable overview of the science behind the Anthropocene, and the implications of recognising ourselves as a force of nature. As an idea that is changing how we understand ourselves as a species, it’s well worth keeping an eye on Anthropocene debate, and this is a good place to start.


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