Welcome by the Royal Society and lead organiser
Testing the effects of multi-stressor global change in deep time
Professor Matthew Clapham, UC Santa Cruz, USA
The oceans are being transformed as temperature, pH, and oxygen content all change at rates unprecedented in the recent geological past, but predicting vulnerability to these stressors remains a challenge. However, similar events of rapid climate change have occurred repeatedly in Earth’s deep time past. As a result, the fossil record provides opportunities to test hypothesized effects of climate change on the marine biosphere. For example, are more active organisms less vulnerable to climate change stressors? Are tropical organisms at greater risk of extinction, or does environmental variability influence survival? Can direct physiological stresses from temperature be reconstructed at the level of an individual organism? The nature of the fossil record limits the types of questions that can be asked, but its record of biotic change over evolutionary timescales and at global scales provides a complementary perspective that is difficult to obtain from experiments or observations on the extant biota. Extinction patterns in the fossil record help constrain the mechanisms through which climate change disrupts the biosphere and provide clues that reveal, at a broad scale, the groups that may be especially vulnerable during the coming decades.
A conservation paleobiological perspective on Chesapeake Bay oysters
Professor Rowan Lockwood, College of William & Mary, USA
The eastern oyster (Crassostrea virginica) plays a vital role in Chesapeake Bay habitats, acting as an ecosystem engineer and improving water quality via filtration. Populations of bay oysters have declined precipitously in recent decades, primarily due to human harvesting and disease. By the time oyster monitoring was established in the 1940s, reefs were already decimated, suggesting that scientists have never actually observed a healthy reef in the Chesapeake Bay. The fossil record, which preserves 500,000 years of once-thriving reefs, provides a unique opportunity to study pristine reefs and a possible baseline for oyster mitigation.
For this study, over 4000 fossil oysters were examined from 11 Pleistocene localities in the mid-Atlantic US. Data on oyster shell lengths, lifespans, growth rates, and population density were assessed relative to data from modern oyster monitoring surveys, in addition to archeological and historical sources. Comparisons to modern C. virginica, sampled from similar environmental conditions, reveal that fossil oysters were significantly larger, longer-lived, and an order of magnitude more abundant than modern oysters. This pattern results from the preferential harvesting of larger, reproductively more active females from the modern population.
These fossil data, when combined with modern estimates of age-based fecundity and mortality, make it possible to estimate biological function in these long-dead reefs, including carbonate production and filtering capacity. Conservation paleobiology can provide us with a picture of what the Chesapeake Bay looked like, but also how it functioned before humans.
Marine ecosystem responses to temperature-related stressors through time
Professor Wolfgang Kiessling, Friedrich-Alexander-University of Erlangen-Nürnberg, Germany
We know that current climate change is already affecting biological systems at global scale, and temperature-related stressors (TRS) are often invoked to explain ecosystem changes in deep time. Without the direct anthropogenic stressors complicating responses, we can (1) potentially better isolate the impact of TRS in the past than today and (2) see under which circumstances TRS lead to ecosystem collapse or mass extinctions. There are many complicating issues such as the vastness of geological time, implying large uncertainties about rates of change, the scarcity of non-skeletal organisms in fossil ecosystems, and different players, which perhaps did things differently in the past. However, simulations and new analytical approaches may help reveal time-invariant principles.
Insights from past responses to TRS may then allow going beyond current approaches in conservation paleobiology and predict the fate of ecosystems under increasing TRS. For example, tropical reef systems have always collapsed under acute global warming rather than cooling and traits of reef corals are significantly linked to their extinction risk. Focussing on marine systems, Kiessling will first summarise the lessons we have already learnt from the past and then provide some guidelines towards a better integration of palaeobiological knowledge in conservation biology.
Are “living fossil” taxa likely to contribute to future evolutionary potential?
Dr Dominic Bennett, University of Gothenberg, Sweden
Are evolutionary distinct species – what may fancifully be called “living fossils” – more or less likely to diversify in the future? The various forms of evidence and argumentation for how evolutionary distinctness may be a predictor of evolutionary potential are mixed. Depending on the scientific discipline and the data, these taxa may either be doomed to extinction or primed for future diversification. With an increasing focus of conservation effort towards the evolutionary distinct, such a question is of growing importance. If it is shown that these “living fossils” have higher rates of extinction and lower rates of speciation, then it may be argued that time and resources should not be spent on these evolutionary dead-ends. Conversely, if these groups can be identified as evolutionary fuses then it may be argued that their conservation is key to safeguarding future biodiversity. Here we map the fates of mammalian clades through time to their evolutionary distinctnesses. We find that taxa that are evolutionary distinct have increasing measures of evolutionary distinctness through time. This indicates that these groups have lower rates of speciation but also lower rates of extinction and, as such, represent neither dead-ends nor fuses. Our finding recasts the conservation arguments: protecting the evolutionary distinct will not secure the future of life; it will, however, not be a wasted effort either.