CONTRASTING THE EMERGENCE PATTERNS OF PAST AND PRESENT NOVEL ECOLOGICAL COMMUNITIES

Novel ecological communities emerge from environmental change, including climate warming and land use changes. While conservation efforts rightly focus on human-induced ecological change, new mixes of species arose naturally in the past from orbital, geologic and evolutionary processes. In particular, the recent warming that ended the Last Glacial Period has acted as a reference point to generate expectations for anthropogenic warming. It also provides a past baseline to establish how climate warming has driven the current, and potential future, emergence of novel ecological communities. We used 3,161 pollen time series from the Neotoma Paleoecology Database, distributed globally, to detect the emergence of novel communities using a robust standardized framework.

We found a fourfold increase in novel community emergence coincident with post-glacial warming, with legacy effects that lasted for 8,000 years after temperatures stabilized. Novel community emergence since the Industrial Revolution (1850 AD onwards) was similar to these elevated post-glacial observations, but came about six times faster. Despite this, modern novel community emergence was lower than expected based on warming, and post-glacial and modern latitudinal patterns differed. These results suggest that non-climate anthropogenic impacts are currently the dominant drivers of terrestrial novel communities, which, in aggregate, represent a press disturbance equivalent to the warming that ended the last Ice Age. Ongoing climate change may drive further increases in novel community emergence, which may persist for millennia after temperatures stabilize.