More mild winters in the Wadden Sea: What happens to the ecosystem?
Severe winters with ice cause dramatic breaks in the ecology of the Wadden Sea. Freezing initiates mass escapes in birds, fish descend to deeper waters, and many bottom animals die. Ice floes plough with the tides through sediments and disrupt benthic fauna.
In the summer following an extreme winter, strong year-classes of tidal flat shellfish arise. Crabs and shrimp, the main predators on shellfish spat, were diminished by the winter. Their absence enriches the tidal flat foraging grounds for birds and fish in subsequent years. Formerly, one to two severe ice winters occurred per decade, while in the last 5 decades cold winters were few and less strong.
If severe winters will fail to happen, food supply for birds and fish might decline. However, caution is advised with ecological projections in this regard. In addition to climate warming, also introduced species from overseas alter the ecological web with novel interactions.