Moriarty Science Seminar: Dead shells speak: detecting unsuspected ecosystem change without being there

R.W. Moriarty Science Seminar Presents: Dead shells speak: detecting unsuspected ecosystem change without being there

Speaker: Susan Kidwell, University of Chicago

Abstract:One of the major challenges for environmental management and conservation biology is simply discovering ‘what was natural’ before human impacts. This problem is especially pressing in marine systems, where biological monitoring and other records are brief or lacking. This question can be tackled locally in a geologically common-sensical way. First, we compare local dead-shell assemblages — sieved from the surface mixed layer — to a census of the local living community, identifying which species occur only as dead individuals (suggesting their populations have waned) and those that occur only alive, despite having mineralized tissues that should leave a trace, suggesting they are new arrivals to the habitat or region. We can then “age un-mix” the dead-shell assemblage using radiocarbon or other methods, which permits us to establish when taxa declined (or increased) relative to local timelines of natural and cultural stressors. This simple approach, strongly supported by meta-analysis and mechanistic modeling, provides a powerful tool for recognizing ecological change retrospectively. Importantly, it has the power to exonerate as well as to incriminate human activities. The method will be illustrated with some case studies from around the world.
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