Closing the temporal gap: ecological responses to past extinction events

Rising carbon dioxide levels and human activities are pushing Earth's ecosystems to a state that they have previously only experienced during warming-induced mass extinctions of the past. The fossil records of these ancient warming events provide us with direct evidence of how our planet's ecosystems were structured and functioned at times of climate change and biodiversity loss, how they responded to such changes and, most importantly, how they recovered. Information locked in the fossil record should help us better understand how Earth's present-day ecosystems will respond to continued warming, and help us test predictions of future change.

One problem with using the fossil record in that way is that most studies look at past changes that occurred on long timescales of tens of thousands or hundreds of thousands of years, but ecologists and biologists today are more interested in what will happen in years, decades and centuries. This project seeks to try and close this temporal gap so that we can make more meaningful comparisons between the past and present. Can we look at changes that happened millions of years ago on similar timescales that we are interested in today?

We think we can. Dating techniques have improved over the years and we have much more precise measurements for the ages of extinction events. Also, climate change tends to cause more weathering, which leads to more mud and silt being washed off the land and into the shelf seas. This accumulates in great thicknesses of sediment which preserve alot more detail about the past. Finally, climate change also leads to expanding 'dead zones' on the seafloor - areas without oxygen that cannot support any burrowing animals. The lack of burrowing animals means a better preserved seafloor.

We have identified two extinction events - the Late Permian and the Early Toarcian - that were caused by global warming and which are well-dated, with thick rock successions that were deposited on the seafloor under low oxygen conditions. We aim to collect samples from those fossil records and to count and identify the microscopic plankton and spores and pollen of land plants in those samples, to understand how communities on land and in the sea were changing through time. We hope to be able to see responses that took place on the scale of millenia or centuries, and we will analyse those changes in the same way that ecologists analyse modern ecosystems. Our study will generate hundreds of samples and it would take many years to look through all of them, so we are also going to try to harness artificial intelligence (machine learning) to speed up the process for us.

If we're successful then we will have the most detailed study ever made of these two past extinction events, and will be able to use the fossil evidence alongside data from modern ecosystems to help inform our understanding of future ecological responses to present-day warming.