Funded Grants

Spatio-temporal climate impact on complex ecosystems

In many hierarchical dynamical systems, synchrony between multiple signals is more important than the individual signals themselves. For instance, a neuron may fire only when its input neurons fire simultaneously, and the electrical grid may crash only when demands of multiple users become synchronized, producing total-usage spikes. Only synchronous components of signals matter in the average signal that affects the next hierarchical level.

Complex ecosystems are of this type. Ecosystems include multiple trophic levels, with population-dynamical signals from lower levels often being spatially aggregated to affect higher levels and human concerns such as fisheries and agriculture. For instance, predators are only harmed if prey populations are simultaneously low over a whole hunting area. And human fish exploitation is only reduced if fish populations decline synchronously over all accessible fishing locations. Thus spatial synchrony of population dynamics is crucially important to ecosystem dynamics.

Population synchrony is widely observed and studied. Correlations between population time series from different locations are seen in organisms as diverse as mammals and protists, at distances up to thousands of kilometers. Synchrony is related to large-scale outbreaks and shortages. Causes of synchrony include dispersal between populations, and, crucially, synchronized climatic drivers.

In spite of the importance of synchrony, impacts on synchrony of global climate change are virtually unstudied. Climate change will worsen, and much research has already documented the ecological impacts of climate change, including poleward species range shifts and phenological changes. But historic difficulties in determining specific climatic drivers of population synchrony have prevented research on possible impacts climate change could have on synchrony if it modifies those drivers. Climate change constitutes not just warming, but also changes in other aspects of environmental signals. Synchrony can also be transmitted through trophic interactions, e.g., a synchronized predator can induce synchrony in its prey. The extent to which climate-induced changes in synchrony may cascade through complex interaction networks is unknown.

My lab recently developed new ways to help identify environmental drivers of synchrony, and we showed that changes in drivers occur, and can have important population impacts at large spatial scales. For instance, changes in winter temperature synchrony caused changes in the synchrony of aphid pest populations which influence agriculture across Britain. We also have and continue to develop new techniques and models for understanding the transmission of synchrony through trophic networks.

We will therefore explore the important question: How will climate change modify the spatial synchrony of population dynamics, and how will these modifications cascade through complex ecological communities and impact human concerns? My research approach has several components: 1) new statistical methods using wavelet transforms; 2) analysis of multidecadal, multispecies, insect, plankton, fish, and environmental datasets from European and North American sampling programs; 3) mathematical models and stochastic process theory in a network context; and 4) analysis of climate scenario data from global circulation models. This research will open the first windows into understanding a previously unrecognized and complex but important way in which humans are affecting their environment and thereby their own interests.