Oxford Martin School: Metabolism of a Human-Dominated Planet

The first event in Oxford Martin School for Hilary term featured Yadvinder Malhi who works at the Environmental Change Institute in the University of Oxford. He is an ecosystem scientist who studies the interactions between the biosphere and the atmosphere. In his talk he discussed the bigger picture of the human impact on the planet and what it bodes for our future.

“How do we measure how big humanity is relative to the Earth?” The answer to this question lies in metabolism. Metabolism is divided into two categories: biological and social (embodied) metabolism. The biological metabolism of humans has not changed much since pre-agricultural times. It still equals 120 W per person, the energy needed to power two light bulbs.

Our social metabolism, however, has undergone a dramatic increase. It entails all the energy used to sustain our contemporary reality – charging our computers, propelling our cars, boiling water for tea, illuminating the library at night…  Pre-agricultural humanity had an extended metabolism of  300 W. Nowadays it has risen up to 400 GW, which is twice the amount of energy flowing through the ecosystem. This means that we represent 200% of the total energy consumption of our ecosystem.

According to Kleiber’s law, the biological metabolism rate of an organism is proportional to its mass. If this law is applied to our extended metabolism, then our size as individuals should be 15 times that of King Kong. Our current lifestyles, however, cannot be maintained for long.

“The industrial revolution opened up access to previously unavailable energy from deep time ecosystems. We are still in a period of metabolic inflation that we have come to regard as normal, but is only a few generations deep. This period is now hitting constraints on both resource supply and waste reduction, constrained by the size of the planet’s systems.”

Climate change is just one of the disastrous consequences of our metabolism reaching the planetary constraints. Yadvinder Malhi suggests that the only way we can deal with this high metabolic energy demand is to look for energy sources that are not as deleterious as fuel energy and to establish a “governance across boundaries”.