Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Friday, June 17, 2011

Man vs. Gaia

Image from ""

This cartoon, signed by "humon," shows one aspect of the fight between humans and their environment; also known as "Gaia". The concept is the same as that expressed by George Carlin as, "The planet is fine, the people are fucked".

But even Gaia herself, poor lady, might not emerge unscathed from the fight. She may be robust, but she is not eternal. Look at this graph, from a paper by Franck, Bounama and Von Bloh,

As you see, the earth's biosphere, Gaia, peaked with the start of the Phanerozoic age, about 500 million years ago. Afterwards, it declined. Of course, there is plenty of uncertainty in this kind of studies, but they are based on known facts about planetary homeostasis. We know that the sun's irradiation keeps increasing with time at a rate of around 1% every 100 million years. That should have resulted in the planet warming up, gradually, but the homeostatic mechanisms of the ecosphere have maintained approximately constant temperatures by gradually lowering the concentration of CO2 in the atmosphere. However, there is a limit: the CO2 concentration cannot go below the minimum level that makes photosynthesis possible; otherwise Gaia "dies".

So, at some moment in the future, planetary homeostasis will cease to be able to stabilize temperatures. When we reach that point, temperatures will start rising and, eventually, the earth will be sterilized. According to Franck et al., in about 600 million years from now the earth will have become too hot for multicellular creatures to exist.

Of course, the extinction of the biosphere is not for tomorrow or, at least, the calculations say so. But it is like estimating one's lifespan from statistical data. Theoretically, the homeostatic mechanisms that operate your body could keep you alive until reach a respectable age; sure, but homoeostasis is never perfect. For instance, there are mechanisms in your body designed to reverse the effects of traumas. You may expect these mechanisms to work well if you are young but, if you are hit by a truck at full speed, well, you end up on the wrong side of the life expectancy statistics.

Similar considerations apply to Gaia. Theoretically, the planetary homeostatic mechanisms should keep Gaia alive for hundreds of millions of years, but what about major perturbations, some planetary equivalent of being hit by a truck? Would Gaia be able to recover from a human caused runaway greenhouse catastrophe?

We cannot say for sure. What we can say is that we are living in a period called the "sixth extinction," similar to other major past extinctions. In most cases, these extinctions appear to have been caused by an increase in the concentration of greenhouse gases in the atmosphere. The sixth extinction, too, is taking place in correspondence to a rise of the concentration of carbon dioxide in the atmosphere that may never have happened so fast in the history of the planet. This rapid rise is also taking place under a solar irradiation that has never been so high as it is today. We can't rule out that the sixth extinction will be the last one.

So, in the fight of man vs. Gaia neither one might be left standing. That's just a possibility, of course, but one thing is certain: in this fight, the enemy is us. 

Thanks to Antonio Turiel for the link to humon's cartoon and to Weissbach for the link to George Carlin's movie


  1. Well said, and keep in mind that it's not just the carbon cycle that humans have perturbed on an unprecedented scale; it's the other great biogeochemical cycles that support the biosphere, e.g., nitrogen and phosphorus, which are undergoing immense rate excursions, on the order of several gigatons per year.

    Together with the other insults to the negative (stabilizing) feedbacks in the biosphere (e.g., deforestation, overfishing), you have your speeding truck. I have no doubt that microbes will do well; in the words of Jeremy Jackson, "The future is bright for dinoflagellates", but multicellular life may end up pasted on the grill, and in the very near future -- on the order of several decades.

  2. Nice post and cartoon ! Even though I'm not a big fan of the Gaïa term, thanks Ugo

  3. Thanks, Antonio. Your blog is a great source of ideas. I posted also the spanish version of the cartoon here.

  4. According this study (, we are "almost" in "Sixth mass extinction", not yet.
    However, I agree with you.

    Dario F.

  5. Thanks, Ugo. Your translation was better than mine, I have taken some points of your Italian version to improve my Spanish one.

    Since recently I'm engaged in an intense public discussion with a broker specialized in energy commodities, mainly oil and gas, and it's very funny to observe their denial strategies in action, sometimes incurring in evident contradictions. Very instructive, and of course one of the ingredients in our blindness as species.


  6. Note : one could link this cartoon to below saying from Cioran (somehow a Romanian Shopenhauer writing in french) :
    "En permettant l’homme, la nature a commis beaucoup plus qu’une erreur de calcul: un attentat contre elle-même."

    "In allowing humans, nature has commited much more than a calculus mistake : a terrorist act against itself"

  7. Thanks, Ugo. I had been wondering if anyone had taken the broad view of biomass history over time; I'll read the paper with great interest.

    The cartoon reminded me of Ray Bradbury's evocative story There Will Come Soft Rains based on the Sara Teasdale poem of the same name. It made such an impression on me that I remember the final couplet without even making an effort to memorize it:

    "And Spring herself when she woke at dawn
    Would scarcely know that we were gone."

  8. Yes, Andrew, it is the greatest history in the world; the life and death of Gaia!

  9. 'Shocking' state of seas threatens mass extinction, say marine experts

    The international panel of marine experts said there was a "high risk of entering a phase of extinction of marine species unprecedented in human history". They said the challenges facing the oceans created "the conditions associated with every previous major extinction of species in Earth's history".

    "The findings are shocking," said Alex Rogers, scientific director of Ipso. "As we considered the cumulative effect of what humankind does to the ocean, the implications became far worse than we had individually realised. This is a very serious situation demanding unequivocal action at every level. We are looking at consequences for humankind that will impact in our lifetime, and worse, our children's and generations beyond that."



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)