Patterns of Food Web Structural Shifts Under Rapid Global Change

Background/Question/Methods

Anthropogenic activities are altering the structure and function of food webs. Macroscopic food web properties, such the trophic position of top predators, and the extent of resource coupling by consumer species are frequently examined across space and time to explore the impact of environmental stressors on the structure of ecological communities. However, general patterns of such food web responses across various drivers of global change, and across different ecosystems, have yet to be elucidated. Here, we synthesize literature on macroscopic food web structural shifts in response to global change and evaluate the common mechanisms that initiate modifications in these fundamental properties. Meta-analysis techniques are used to examine changes in the trophic positioning of top predators and the degree of resource coupling by consumer species across a suite of anthropogenic stressors to fill knowledge gaps surrounding the empirical patterns of community responses to global change.

Results/Conclusions

We find that while there are coherent responses in the major flows of energy to various drivers of global change, there is also noise in this signal that is not yet well understood. Specifically, there is a tendency for food webs to truncate and decouple from alternative resources, but this tendency appears to be upset under certain conditions (e.g. dams, species invasions). In addition, future research is needed to better understand food web structural responses to global change in particular ecosystems. We argue that tracking alterations to the backbone structures of food webs through biomonitoring techniques, such as stable isotope analysis, is a promising avenue for researchers to understand and predict the future state of global ecosystem function.