Effects of large herbivorous waterfowl in aquatic ecosystems

Effects of large herbivorous waterfowl in aquatic ecosystems

The dramatic increases of geese and swans in northern Europe do not only cause conflicts due to crop damage, but also raise concerns about consequences to ecosystems in general. The role of these birds in aquatic ecosystems is especially urgent to investigate since many wetlands are facing concurrent and drastic changes, e.g. brownification, eutrophication and in species composition. This is worrying, as wetlands normally are among the richest habitats in terms of productivity and biodiversity. It is not known if geese and swans are prime agents behind these changes, or alternatively, if they are just benefiters. Nonetheless, it is not unlikely that the growing numbers may catalyze changes throughout wetland ecosystems, since geese and swans often constitute a large share of the total biomass of aquatic consumers. The project proposed in this application will thus address the hypothesis that geese and swans may be drivers of the ongoing changes in wetland ecosystems. As a PhD project this will be studied descriptively as well as experimentally over several years, and include several trophic levels in the ecosystems, from direct grazing effects on vegetation to indirect effects (cascades) on invertebrates and other waterbirds. Results will have high universal applicability since the studies will cover a large spatial scale and include wetlands along the nutrient gradient. Outcomes will be of great value for wetland management, but also for the "players" in aquatic ecosystems. This includes hence not only the ecosystem as a whole, but also specific taxa such as important avian game, for example geese. Although there are previous studies on wetland ecosystems, new knowledge based on current conditions is needed to be able to draw comprehensive conclusions about the consequences of the increasing populations of geese and swans.

Gunnar Gunnarsson, Kristianstad University

4 810 000 SEK