The effect of changes in land use on waterfowl species turnover in Finnish boreal lakes

Effects of different land-use types on nutrient and chemical run-off have been widely researched, but the total effect of changes in land use on communities of aquatic species is poorly known. We evaluated the effect of land-use change on waterfowl communities of boreal lakes. We conducted the study with topographic maps and GIS-techniques in central Finland. We compared changes in the structure of waterfowl communities with changes in land use around 15 lakes over a period of 50 years. Over the period, agricultural land and bogs were reduced in area, while ditched areas increased significantly. The numbers of waterfowl breeding pairs and species increased slightly on the majority of lakes. The largest increases in breeding pairs were for Goldeneye Bucephala clangula and Teal Alias crecca. Interestingly, Mallard Anas platyrhynchos decreased in terms of both breeding pairs and the number of occupied lakes, although it has increased nationally. We found evidence of decreasing pair numbers of Mallards on lakes where adjacent dwellings increased in number. Changes in land use correlated with those in waterfowl communities but lake size appears to affect these results. After controlling for the effect of lake size, only the number of adjacent dwellings correlated significantly with changes in the number of breeding pairs of Mallards. According to our results, changes in the area of agricultural, bog or ditched land around lakes could not be clearly linked with changes in waterfowl communities.