Research

Big Picture Ecology: The Patterns of Ecosystem Structure and Function

Ecosystems vary enormously: in how many species they contain, in what kinds of species occur, in how abundant organisms are, in how productive they are, etc. Many of these characteristics are critically important to humans. Many are also potentially affected by human activities. The goals of my research program are: 1) to describe the gross patterns of biological structure and function of ecosystems, 2) to determine which variables exert the strongest control on those properties, and 3) to determine how human activities influence them.

For example, one of my main areas of interest is biodiversity: why are there lots of species in some places and few in others? Which ecosystem characteristics are most closely related to the kinds of species occur in specific areas? My colleagues and I have shown that broad-scale patterns of biodiversity are very strongly related to two key climatic variables: heat and water. Both of these variables are also related to organisms' productivity and/or energy balance. This leads to a host of other questions. What mechanism links diversity to climate? Do climate changes leads to diversity changes?

On regional spatial scales, which human activities have the greatest impact on ecosystem structure and function? Habitat destruction or fragmentation? Human population density? Industrial pollution? My colleagues and I have examined these questions in several contexts. For example, in Canada's national parks, are patterns of species richness and extinctions related to development and landscape fragmentation? Surprisingly little. Similarly, across gradients of deforestation in southern Ontario, we asked whether patterns of bird species richness were related to vegetation cover (e.g. agriculture vs. forest), as assessed from satellite images. Again, surprisingly little. So what permits lots of species to coexist under some circumstances and not others?

My colleagues and I do similar broad-scale work in a variety of other systems. We look at the history of the evolution of life: are there predictable patterns? Yes! (Stay tuned!). We look at patterns in the structure of aquatic systems: for example, to what extent does the abundance of predators (such as fish commonly stocked in lakes) affect the abundance of other groups of organisms. Some of my students have also been involved in broad-scale patterns of human health and how they relate to the use of pesticides.