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Planet Earth May Have a Metabolism Problem

Yadvinder Malhi presenting his talk on Earth metabolism at Columbia University.
Yadvinder Malhi presenting his talk on Earth metabolism at Columbia University. Photo: Katy Coomes

Many of us learned in high school about the metabolism of the human body. This is how we convert food into energy in order to maintain life. In other words, it is the flow of energy throughout a system. This concept is one that Yadvinder Malhi, a visiting scholar at the Earth Institute and a professor of ecosystem science at the University of Oxford, explores in a system much larger than the human body: the Earth. On November 12, Malhi presented his thoughts in a lecture titled ‘The Metabolism of Planet Earth.’ He presented Earth’s metabolism as a way of quantifying the impacts of human activity on the Earth.

Yadvinder Malhi, fellow of the Royal Society, past president of the Association for Tropical Biology and Conservation, and an awardee of the Patrons’ Medal of the Royal Geographical Society, has a PhD in meteorology, which he received from the University of Reading for his research on the Earth’s energy budget and heat fluxes. During fieldwork in Amazonia, Africa, and Asia, he has studied tropical ecosystem processes and climate change. However, his main interest is in how to sustain a healthy biosphere under the changing state of the global climate.

To Malhi, the Earth is an organism unto itself, living and breathing. There is a give and take of energy between all living things that must stay in balance for the Earth to thrive. Malhi measures this energy through the transfer of CO2 between the atmosphere and all plants on land and in the ocean. If you map the planet’s production of CO2, Earth appears to have a heartbeat:

Malhi uses the simple equation for photosynthesis to convert CO2 into units of energy which he can then apply more broadly across all living organisms. Comparing the amount of energy consumed by humanity to the amount of energy produced by the Earth, he reveals that post-industrial revolution we are using more energy than the Earth is able to continue providing. Or, to relate it back to the metabolism of the human body, we are burning more calories than we’re consuming. If we don’t fix the balance, eventually we’ll starve.

Prior to the industrial revolution, humans only drew energy from that which was directly supplied by other organisms currently living on the Earth (think: hunter gatherer lifestyles). With the discovery of fossil fuels, humans created a so-called energy time machine. We could now access energy that had been produced from the Earth thousands of years ago. Because of this, the energy use of humanity became more than the current planetary biosphere could support. Malhi shows that the energy flow of Earth has been thrown out of balance, resulting in harmful repercussions for the organism as a whole (i.e. climate change).

The interaction of humanity’s metabolism and the planet’s metabolism is displacing other life on Earth, said Malhi. On the other hand, our surge in metabolism through advances in technology, medicine, food systems, and more has also resulted in improvement of the human condition. For example, the number of people living in extreme poverty is declining and child mortality has reduced. The question is, how do we balance maintaining these improvements while also reducing our negative impact on the world?

This is a problem that is being tackled by the Earth Institute as well as many of Malhi’s colleagues, notably Oxford economist Kate Raworth, who coined the term Doughnut Economics. This concept outlines the planetary boundaries we need to stay within to prevent further damage to the biosphere, while not backtracking on improvements to humanity.

The final thing Malhi noted is that those who are most benefitting from these social improvements and would hurt from backtracking are also those contributing the least to global climate change. “We” is often said when discussing the effects humanity have on the Earth, assuming a collective contribution across the globe. The reality is that over half of the global climate challenge is being caused by North America and Europe alone. Although Malhi acknowledged that his metabolic model does not take this into consideration, it still serves as a good basis for exploring of how the effects of certain behavior changes within humanity would affect the biological metabolism of the Earth. It is only further proof that our hunger for social improvement has outgrown what our home, the Earth, can sustain. We must figure out a balance if we want to continue to live here without consequences.

Science for the Planet: In these short video explainers, discover how scientists and scholars across the Columbia Climate School are working to understand the effects of climate change and help solve the crisis.
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