Coastal seas worldwide are being and will be impacted by climatic changes. Water temperatures have increased significantly over the past decades, the ice volume in the Arctic has decreased by 70%, the avarage sea level is rising rapidly, the frequency of hurricanes and extreme rainfall has increased, and spring has advanced in the Northern Hemisphere (Hoegh-Guldberg & Bruno, 2010; Philippart et al. 2011; IPCC 2014).
Compared to other coastal areas, the temperature in the Wadden Sea area has increased disproportionately fast in the last 25 years (Belkin 2009; Van Aken 2010). Possible consequences are an early migration of shrimp in the spring (Philippart et al. 2003), changes in success and timing of reproduction of shellfish (Philippart et al. 2014), reduced numbers of juvenile flatfish (Van der Veer et al. 2010), and immigration from southern fish and bird species (Van der Veer et al. 2015). In the northern Wadden Sea, temperature influences the spring bloom dynamics (Van Beusekom et al. 2008) and zooplankton dynamics (Martens & Van Beusekom, 2008). This kind of shift has implications for the natural values of the Wadden Sea, including its function as a nursery for fish, and as a fueling station for migratory birds.
In May 2014, the KNMI presented the current climate scenarios for the Netherlands, including higher temperatures, faster rising sea levels, wetter winters, heavier rainfall and an increased risk of drier summers for decades to come (KNMI 2014). It can be expected that these developments will have an impact on the number of species, and densities and distributions of characteristic flora and fauna of the Wadden Sea.
The size and distribution of many populations and habitats are monitored under European directives and trilateral agreements. In line with the National Adaptation Strategy, monitoring should also serve to track long-term effects of implemented measures aimed at the protection of the natural values of the Wadden Sea.