The causes and consequences of species extinctions in food webs

The Earth is currently experiencing its sixth mass extinction event. All previous extinction events have been driven by global catastrophes that have resulted in massive reorganization of ecological communities. Today however extinction is driven by humans leading to a very different set of pressures on ecosystems than the mass extinctions of the past. There are no ecosystems on Earth that have been unaffected by human-mediated disturbance. Species invasions, pollution, eutrophication, climate change, and harvesting of resources have led to massive losses of biodiversity, changes in ecosystem functions and services that are necessary to human well-being, and changes in how ecological communities are structured. The consequences of these types of disturbances have been explored for decades and for some disturbances, such as the effects of eutrophication in lakes, are very well-understood. It is somewhat surprising however how little we understand about how disturbance affects ecological communities in general. We know that communities heavily impacted by human disturbances contain fewer species and different species than communities that are less heavily impacted; however we lack a predictive framework for the consequences of human disturbance. The objective of this research is to develop such a framework focusing on two main questions. First, how does the magnitude of species loss following disturbance differ based on the type of disturbance, the habitat type that is being disturbed, and the life history traits of species? Second, given that different disturbances will affect ecological communities differently, what general trends exist in the types of species that are lost from various communities when they are disturbed? Answering these questions is important so that we can predict the consequences of disturbances. Given information about the extent and type of disturbances that various habitats are experiencing and the answers to the questions above we can begin to make predictions about which disturbances, which habitats, and which species need the most conservation and management attention.