Meta-analysis: Does disturbance have a general positive or negative effect on consumer mediated habitat linkages and trophic subsidies?
One pervasive consequence of increasing disturbance regimes is the simplification of foodwebs. Such simplifications are having profound effects, not only within disturbed ecosystems, but others that maybe connected to the disturbed system via consumer mediated habitat linkages. Consumer mediated habitat linkages can be defined as the transport of biomass to spatially distinct foodwebs through movements of heterotrophic species. These trophic linkages across disparate foodwebs can govern processes at every ecological scale, substantially contributing to the stability, resistance capacity and resiliency of many natural systems. However, disturbance such as eutrophication, species invasions, overfishing, and other climate disturbances can alter these linkages, driving cascading changes to recipient ecosystems. Unfortunately, how disturbance functions to alter these consumer mediated habitat linkages remains understudied. In this investigation, we examined effects of functional disturbance type and disturbance severity (i.e. frequency of occurrence, duration and amplitude) on the strength of consumer mediated habitat linkages.
From our literature review, we found the magnitude and directionality of consumer mediated habitat linkages responded similarly to disturbances that were functionally similar. However, effects were more varied across functionally different disturbances, with some disturbances increasing the magnitude of trophic subsidies, while others consistently decreased biomass transfer from one habitat to the next. When considering disturbance severity, more severe and extreme disturbances largely decreased consumer habitat connectivity, while disturbances of moderate severity could both increase or decrease consumer mediated habitat connectivity. With both anthropogenic and climate disturbances expected in increase in overall severity, it is important that we develop frameworks improve our understanding of how disturbance affects this important ecosystem process in order to better predict how ecosystems that are structured by these linkages will change in the future.