For Part I of this essay see here.
4. Our current context: the adaptive cycle, conservation, and release
As we’ve seen, predator-prey relationships shape the flow of energy through ecosystems. But what happens in either a natural ecosystem or a human social “ecosystem” when energy flows increase? As long as sufficient basic nutrients are available and other conditions (such as climate) are stable, the system tends to grow in size (in terms of biomass) and/or complexity.
And that is exactly what has happened within the human “ecosystem,” especially during the past century or so. We humans learned to use exosomatic energy (that is, energy apart from what is released from food through metabolism) when we started using fire several hundred thousand years ago. The domestication of draft animals (primarily horses, oxen, and mules), and the harnessing of waterpower and wind power (at first with sails, later windmills) increased our access to exosomatic energy. More recently, technological developments including metallurgy and the invention of the steam engine opened the way to our use of fossil fuels—coal, oil, and natural gas.
Fossil fuels, representing tens of millions of years’ worth of chemically stored sunlight, enabled our global per-capita use of energy to grow by more than 800 percent in the past 150 years. With the confluence of science, technology, and fossil energy, many things became possible that were barely dreamt of previously—including aviation, global electronic communications, the mass production of goods, and a way of life (for some, at least) characterized by lavish consumption. Human population grew from under a billion two centuries ago to 7.5 billion today; cities and nations exploded in size; trade soared in volume, speed, and distance; and the destructive power of weaponry became global in scope.
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