Keynote Speakers

Sergei Petrovskii is a Chair in Applied Mathematics in the School of Computing and Mathematical Sciences, University of Leicester (UK). He is an applied mathematician with over 30 years of research experience in mathematical ecology and ecological modelling, with a special focus on modelling complex multiscale environmental and ecological systems. His research on the effect of global warming on ocean deoxygenation where he discovered a new type of ecological catastrophe potentially leading to a mass extinction has been published in high-ranked scientific journals and highlighted by media around the world. Other topics include biological invasions, mass extinctions in Earth’s deep past, and anomalous long transient dynamics in ecologically-inspired dynamical systems. He published five books and 170 papers in peer-reviewed journals. He is the “Mathematical Biology” Section Editor of Mathematics, an Associate Editor of the Journal of Mathematical Biology and an editorial board member of Physics of Life Reviews.

Plankton, Oxygen, Climate Change and Mass Extinctions: a Journey through Time, Space, and Bifurcations

Global climate change is arguably the greatest challenge that humankind has ever been facing. Not only it is likely to cause numerous adverse effects on  environment, ecology, economy and society – in fact, it may even bring some existential risks to humanity as a whole. An indication of the latter can be seen in the well-known observation that average species extinction rates over the last few centuries have been 10-100 times higher compared to the background extinction rates. This has been used as a basis to suggest that we are witnessing the beginning of the Sixth Mass Extinction.

Mass extinction is a global event, so that for it to happen, there must be some global changes in the Earth system. In turn, a global change (e.g., global warming) can lead to a mass extinction through a cascade of processes on smaller spatial scales - “extinction pathways” [1]. One such pathway predicts, using mathematical modelling [2,3], a global anoxia resulting from global warming. Apparently, if the global stock of oxygen becomes depleted, that would inevitably lead to extinction of humans as well as animals. Interestingly, there is paleontological evidence showing that some big extinction events of the past were indeed caused by anoxia which was preceded by an increase in the average Earth temperature.

A big question is how close we may be to the oxygen depletion catastrophe. Since about 70% of atmospheric oxygen is produced in the ocean (in phytoplankton photosynthesis), for early warning signals one could look at the dynamics of the dissolved oxygen in the ocean. There has been growing evidence that the Oxygen Minimum Zones showed tendency to grow over the last few decades. By considering a model of plankton-oxygen dynamics [4], I will argue that such OMS growth may be an indication that the global Earth system has already passed the saddle-node bifurcation (leading to disappearing of the ‘safe’ steady state) and is now in a stage of long transient dynamics [5]: a slow free fall to the final stage of global anoxia.

There have been many mass extinctions in Earth’s deep past. Most well-known are the “Big Five” when about 50-90% of life was wiped out. However, there were many events of smaller extinction magnitude ranging between 10-50%. While each mass extinction is in some sense unique, their ultimate reasons or “triggers” are not too many [1]. Therefore, one can ask if it might be possible to describe all mass extinctions in a unified way. In the last part of my talk, I will consider two mathematical model that give examples of such description across the whole multiplicity of extinction events [6]. Interestingly, in spite of conceptual, rather schematic nature of the models, their predictions are in a reasonably good agreement with the fossil data.

[1] Sudakow I, Myers C, Petrovskii S, Sumrall CD, Witts J. (2022). Knowledge gaps and missing links in understanding mass extinctions: Can mathematical modeling help? Physics of Life Reviews 41: 22--57.
[2] Sekerci Y, Petrovskii SV (2015) Mathematical modelling of plankton-oxygen dynamics under the climate change. Bull. Math. Biol. 77, 2325-2353.
[3] Petrovskii SV, Sekerci Y, Venturino E (2017) Regime shifts and ecological catastrophes in a model of plankton-oxygen dynamics under the climate change. J. Theor. Biol. 424, 91-109.
[4] Alhassan, Y., Petrovskii, S. (2024) Standing on a cliff: OMZ growth may indicate the approach of a global anoxia. Mathematics, submitted.
[5] Morozov A, Abbott KC, Cuddington K, Francis T, Gellner G, Hastings A, Lai YC, Petrovskii SV, Scranton K, Zeeman ML. (2020) Long transients in ecology: Theory and applications. Physics of Life Reviews 32, 1-40.
[6] Alsulami A, Petrovskii SV. (2023). A model of mass extinction accounting for species's differential evolutionary response to a catastrophic climate change. Chaos, Solitons & Fractals 175, 114018.