“About 74,000 years ago,” Lynas began, “a volcanic event nearly
wiped out humanity. We were down to just a thousand or so
embattled breeding pairs. We’ve made a bit of a comeback since
then. We’re over seven billion strong. In half a million years
we’ve gone from prodding anthills with sticks to building a
worldwide digital communications network. Well done! But…
there’s a small problem. In doing this we’ve had to capture
between a quarter and a third of the entire photosynthetic
production of the planet. We’ve raised the temperature of the
Earth system, reduced the alkalinity of the oceans, altered the
chemistry of the atmosphere, changed the reflectivity of the
planet, hugely affected the distribution of freshwater, and
killed off many of the species that share the planet with us.
Welcome to the Anthropocene, our very uniquely human geological
era.” Some of those global alterations made by humans may be
approaching tipping points—-thresholds—-that could destabilize
the whole Earth system. Drawing on a landm