Avoiding another Great Dying – learnings from the world’s greatest extinction event

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Planet Earth, a quarter of an aeon ago. A series of volcanic eruptions in what we now call Siberia has put huge amounts of carbon dioxide into the atmosphere, and covered the world in a layer of ash. CO2 concentrations have increased by 17 times, and sea surface temperature averages 40°C.1 The oceans are acidic and deoxygenated; marine life is choking to death. This is fireball earth.

Though it might sound like an apocalypse movie, this was earth’s grim reality at the end of the Permian period. Before we dismiss it as a freak event, let’s look at what caused it. It was driven by the same thing we’re tackling today: increasing CO2 emissions into the atmosphere. Over the course of approximately 60 thousand years, the blink of an eye in geological terms, the earth took on a hot and dry climate.

These changes saw the archosaurs rise to dominance (reptile ancestors to the Jurassic dinosaurs) and the appearance of the first mammal ancestors (the therapsids). We also lost the largest insects the world had ever seen – which many would count as a win. However the most dramatic losses were seen in our oceans: most sedentary, calcified organisms (like shellfish) were unable to adapt to the dramatic change in conditions, and a new age of ocean life resulted: mobile species such as snails, sea urchins and crabs.2

We talk about the sixth major extinction event that we are in the middle of today (the Anthropocene), but just how similar is it to the one 250 million years ago? Before The Great Dying, as the Permian extinction has been termed, CO2 concentration was at around 440 ppm (parts per million) – only slightly higher than the 415 ppm we are experiencing today. By the end of The Great Dying however, the concentration is estimated to have reached 7,390 ppm. This concentration was achieved by releasing 4.5 gigatonnes of carbon each year, which is only half of our modern rate of production.4 Modern simulations of our carbon emissions estimate that in a non-intervention scenario we may reach 1,000 ppm before the turn of the century, a rate of increase in carbon emissions much faster than seen during the earth’s most deadly extinction event.

Source: https://www.maxpixel.net/photo-613319

Will history repeat itself? As the effects of increased temperature and acidification begin to take hold, we’re seeing the mass bleaching of coral reefs across the globe. Much like 250 million years ago, the effects of climate change disproportionately impact stationary marine organisms. Corals have symbiotic algae which give them their characteristic colour and allow them to photosynthesise. But when coral gets stressed, it gets rid of this algae resulting in bleaching. Massive bleaching events, affecting 90% or more of coral reefs, are expected by 2050, even under the most optimistic IPCC emissions scenarios.5 If warming is inevitable, science must instead turn to active interventions that will protect corals and make them more resilient to our changing climate. 

Adaptation is key to survival

Nature adapts to changing climates — the main question is how quickly. One study found that warming will expand suitable coral habitat into sub-tropical areas, creating refugia for many species6. The main concern is that the complex reef systems will not have enough time to build up large enough populations in fringe habitats before their primary habitat becomes unliveable. So adaption alone will not be enough to save the worlds coral.

Credit: James Gilmour / Australian Institute of Marine Science
Source: https://www.aims.gov.au/docs/research/climate-change/coral-bleaching/bleaching-events.html

Harnessing evolution may present a solution. One study found that corals that have been bleached in the past have different ‘metabolomic indicators’ – small particles related to cell function (a technique honed by medical science). Using this technology, the study identified more resistant coral who had, due to environmental, genetic, or biotic factors, been able to escape bleaching7. This process of survival of the fittest can be stimulated experimentally in a lab through accelerated evolution, where the coral symbionts (algae and bacteria) are exposed to the stressful conditions to fast-track evolution into creating a more resistant symbiont8. Identifying stronger and more resilient corals and symbionts may save some species of coral, but there are concerns over what repercussions we’d see after losing species that can’t adapt, and whether taking evolution into our own hands may have unforeseen ecological consequences9.

Altering the course of history

Evidently, active intervention strategies that create climate change resistant organisms are a growing and evolving field. Climate change research is becoming more and more important, especially if what we see today is anything like the climate change events of our past. The crucial difference between today’s emissions and the volcanic eruptions that caused The Great Dying is that we have the power to do something about it . We can intervene, and change course before it’s too late.

This time perhaps prehistory won’t repeat itself.

Article by Rachel Nicholls, Colette Blyth and Andrew Lowe

Feature image: composite by Rachel Nicholls, including: Smoke sky Credit USFWS; Eruption Credit Peter Thoeny; Ocean surface; Big fish Credit Kate Gardiner;  Smaller fish Credit Derek Keats.  

References

  1. Brand, U. Posenato, R. Came, R. Affek, H. Angiolini, L. Azmy, K. Farabegoli, E. 2012. The end‐Permian mass extinction: A rapid volcanic CO2 and CH4‐climatic catastrophe. Chemical Geology, 322–323, 121-144. http://dx.doi.org/10.1016/j.chemgeo.2012.06.015
  2. Wagner, P. Kosnik, M. Lidgard, S. 2006. Abundance Distributions Imply Elevated Complexity of Post-Paleozoic Marine Ecosystems. Science. 314 (5803): 1289–1292. https://doi.org/10.1126/science.1133795
  3. Li, H. Yu, H. McElwain, J. Yiotis, C. Chen, Z. 2019. Reconstruction of atmospheric CO2 concentration during the late Changhsingian based on fossil conifers from the Dalong Formation in South China. Palaeogeography, Palaeoclimatology, Palaeoecology. 519, 37–48. https://doi.org/10.1073/pnas.2014701118
  4. Cui, Y. Li, M. van Soelen, E. Peterse, F. Kürschner, W. 2021. Massive and rapid predominantly volcanic CO2 emission during the end-Permian mass extinction. Proceedings of the National Academy of Sciences. 118 (37) https://doi.org/10.1073/pnas.2014701118
  5. Frieler, K., Meinshausen, M., Golly, A. et al. 2013. Limiting global warming to 2 °C is unlikely to save most coral reefs. Nature, Climate Change 3, 165–170. https://doi.org/10.1038/nclimate1674
  6. Bleuel, J. Pennino, M. Longo, G. 2021. Coral distribution and bleaching vulnerability areas in Southwestern Atlantic under ocean warming. Nature, Scientific Reports 11, 12833. https://doi.org/10.1038/s41598-021-92202-2
  7. Roach, T., Dilworth, J., et al. 2021. Metabolomic signatures of coral bleaching history. Nat Ecol Evol 5, 495–503. https://doi.org/10.1038/s41559-020-01388-7
  8. Maire, J & van Oppen, M. 2021. A role for bacterial experimental evolution in coral bleaching mitigation?Trends in Microbiology. In Press, Corrected Proof. https://doi.org/10.1016/j.tim.2021.07.006
  9. Cunning, R. 2021. Will coral reefs survive by adaptive bleaching? Emerging Topics in Life Sciences. https://doi.org/10.1042/ETLS20210227

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