SOME LIKE IT HOT: META-ANALYSIS OF MICROFOSSIL COMMUNITY RESPONSES TO RAPID GLOBAL WARMING

Climate change is one of the biggest scientific buzzwords of recent decades. The fossil record provides an ideal analogue for examining biotic response to climate change, especially as predictions about the effects of global warming on modern taxa are varied and sometimes contradictory. This study examines the response of marine microfossil communities by analyzing assemblage data for four common groups (ostracodes, calcareous nannoplankton, benthic and planktic foraminifera) from three extreme thermal maxima (Paleocene-Eocene thermal maximum, mid-Paleocene biotic event, and the late Maastrichtian thermal maximum). To assess biotic response, two assemblage characteristics are investigated: 1) changes in species diversity, measured using a series of meta-analyses to investigate whether the species richness of communities increases or decreases, and 2) changes in community structure, measured by quantifying changes in the species abundance distributions via the shape of rank-abundance curves.

Combining all taxa from all events results in an overall increase in species richness (in the interval preceding the thermal maxima diversity is lower than during the thermal maxima). When considering each event separately, both the Paleocene-Eocene and late Maastrichtian thermal maxima caused a significant increase in species diversity, although the mid-Paleocene biotic event did not show a significant change in community diversity. Planktonic communities display a significant increase in diversity during all three thermal maxima, while benthic communities experienced a significant loss of diversity. Community structure (as measured by evenness, rank-abundance curves, and ordination techniques) changes during thermal maxima, regardless of event or taxonomic group, and is not directly related to changes in diversity. The results of this study reveal that communities will respond in different, but potentially predictable, ways to global warming. This highlights the importance of understanding an ecosystem before making conservation decisions or predictions about changing biodiversity in response to climate change.