THE EXPLOITATION OF WETLAND ECOSYSTEMS BY HERBIVORES ON BYLOT ISLAND

We examine the interactions between herbivores, plants and climatic fa ctors in arctic wetlands using, as a case study, results of our resear ch on grazing by snow geese on Bylot Island. During the summer, geese are the most important herbivore on the island and consume a high prop ortion of the annual graminoid production (grasses and sedges). Herbiv ores can sometimes enhance plant production by increasing the turnover rate of nitrogen, a nutrient which commonly limits growth of arctic p lants. However, we found no evidence of positive feedback of grazing o n plant growth and, on the contrary, chronic goose grazing tended to d ecrease production of these ecosystems in the long term. Geese need la rge quantities of high-quality plants to breed successfully, and negat ive effects on goose reproduction as a result of lack of food were det ected. Herbivore populations are also influenced by climatic factors, either directly or indirectly through effects on plant growth. It is l ikely that tundra plant-herbivore systems will be strongly affected by future climatic changes.