Do Top Down or Bottom-up Processes Control Productivity in Arctic Ecosystems?
Prof. Robert L. Jefferies 2007/2008 is International Polar Year and Canada is mounting an intensive research programme in the Arctic. One project to which a number of scientists are contributing is to determine whether the trophic structure of Arctic ecosystems is primarily driven by top-down processes (predation) or by bottom up processes (net primary production). We have been examining this general question in the coastal systems of the Hudson Bay Lowlands on the Arctic/sub-Arctic boundary for a number of years. Here, large numbers of migratory geese of different species breed each summer in the wetlands. Most intertidal marshes in the region have been lost as a result of the foraging activities of large numbers of geese. As a result the birds have moved into the freshwater sedge meadows inland from the coast. However, for various reasons the families of birds are forced to forage over wide areas, and as a consequence the birds are widely dispersed in the sedge meadows. In these fres
