Like many genera, the short faced bear (Arctodus) met with its demise during the Last Glacial Maximum (LGM), an ice age that covered North America, Northern Europe and Asia with vast ice sheets between 26,500 and 19,000 years ago. Due to prey variety contraction as a result of the drastic climate change, competition from other predators that shared Arctodus’s predilection for reindeer (Rangifer) drove Arctodus to a diet primarily of yak (Bos) before disappearing from the fossil record for good around 11,000 years ago.
These and other impacts of an extreme climate change were revealed in a recent study in Proceedings of the Royal Society B by Yeakel et al., which used stable isotope measurements to study the impact of the LGM on ecosystems across the Mammoth Steppe, specifically in Europe and Beringia (consisting of Siberia, Alaska, and the Yukon). The authors ultimately hoped to provide data that will contribute to the study of how ecosystems react to climate change, a timely topic. Among other aspects of ecology the study analyzed the modularity of food webs and specialization of predators. While modularity, or compartmentalization of groups within a food web, generally portends ecosystem survival – preventing extinction cascades by isolating branches of the food web – specialization can have negative effects by limiting a predator’s choices.
The study showed that Beriginan food webs were more compartmentalized than those of Europe. The major hypothesis put forward to explain this difference is that the Beringia region was more isolated and thus allowed for the establishment of stable and well-defined predator-prey relationships. In contrast Europe’s food webs were more interconnected, perhaps as a result of the region’s more centralized location, allowing for frequent invasion and reorganization of the ecosystem. The relative differences in modularity were maintained during and after the LGM, highlighting that climate is just one of many factors influencing ecosystem structure. However, both ecosystems showed significant increase in specialization, or increased reliance on a smaller variety of prey.
The findings of this study are consistent with the idea that climate change was but one factor leading to end-Pleistocene extinctions. As for predicting impacts of current global warming, Dr. Yeakel emphasizes that, let alone determining the impacts of modularity, determining the extent of modularity of a modern ecosystem is “a hot topic and difficult to address.” The LGM did, however, impact ecosystems and drive many species to extinction. Arctodus was reportedly a brutish predator and was perhaps not mourned. To what extent today’s climate change claims more likeable – or integral – species remains to be seen.
The complete study, The impact of climate change on the structure of Pleistocene food webs across the mammoth steppe was published May 8, 2013 in the journal Proceedings of the Royal Society B.
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