SCHRÖDER JJ (2015) Does ice coverage in the Baltic Sea affect numbers of diving ducks wintering in the Netherlands?. LIMOSA 88 (1): 22-30.

In the Netherlands quantitative targets have been defined to evaluate effectiveness of the management of Natura 2000 sites. Targeted numbers of Goosander Mergus merganser, Smew Mergellus albellus, Tufted Duck Aythya fuligula, Pochard Aythya ferina and Goldeneye Bucephala clangula are not always realised in the Netherlands as a whole and in the Veluwerandmeren in particular (Tab 1). It has been argued that this should not be attributed to failing management but to external factors, among which climate change. Diminished ice coverage in the Baltic Sea may have taken away the incentive for ducks to move and winter in more southern regions including the Netherlands. An analysis of data of the Swedish Meteorological and Hydrological Institute confirms that the extent and duration of ice coverage in the Baltic has decreased by, on average, about 50% over the last 36 years (Fig. 1). However, annual changes in duck numbers in the Netherlands could only partly be linked to annual changes in ice coverage in the Baltic Sea for Goosander, Smew and Red-breasted Merganser Mergus serrator (Figs. 2 and 3), but not for Greater Scaup Aythya marila, Common Eider Somateria mollissima, Tufted Duck, Pochard and Goldeneye. This implies that other factors, including a declining carrying capacity due to diminished anthropogenic nutrient inputs, should be considered as an explanation for not realizing targets in the Natura 2000 sites.

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