Climate change threatens the ecosystem in the Wadden Sea Unesco World Heritage Site

Some species can adapt well to higher temperatures, others less so, said Busch. "We are already seeing a change in species composition." Scientists have been concerned for some time that the flight and resting times of migratory birds are shifting. The report cites the example of black-tailed godwits, which have to shorten their resting period in the Wadden Sea in order to catch up with the earlier hatching of insects, which serve as a food source, in their breeding area of Siberia as a result of global warming.

The report also refers to a study according to which the lugworm, for example, could also move northwards as a result of climate change and thus decline in abundance.

Rivers transport less freshwater into the Wadden Sea

The Wadden Sea is also feeling the effects of climate change on land, for example through increased consumption of freshwater resources on land, said Busch. "This is a point that has perhaps received little attention so far." One example is changes in salinity. The less freshwater enters the salty Wadden Sea, the higher the salinity remains, said Busch. The water is therefore less diluted.

As spring and summer have recently been drier and warmer on average, rivers such as the Ems, Elbe and Weser have been discharging less freshwater into the Wadden Sea. "This affects the life of algae and therefore also fish and birds in the mudflats," explained Philippart. This is because freshwater contains phosphate and nitrogen, for example, which serve as the basis for algae growth and thus for the food chain.

Heatwave hits cockles

Extreme weather events such as heatwaves are also likely to become a problem for life in the Wadden Sea, the authors of the study write. Philippart refers to the large-scale death of cockles in the Dutch Wadden Sea in the summer of 2018. "In addition to the heat, this probably also had to do with the decline in the supply of freshwater algae as a food source for these mussels."

The new report is part of a collection of reports that reflect the assessment of the ecological status of the Wadden Sea. Other status reports, which are also regularly updated, deal with species and pollution, for example. Scientists from all three countries bordering the Wadden Sea - Germany, Denmark and the Netherlands - worked on the new report on climate change.

• Release from the Royal Institute of Marine Research
• New quality status report on climate change
• Collection of quality status reports on the Wadden Sea
• Communication from the Wadden Sea Secretariat

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