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View of the East Frisian Wadden Sea: Unique and fragile ecosystem

Photo: Sina Schuldt/dpa

The consequences of the climate crisis in the sea and on land are increasingly changing the ecosystem in the Wadden Sea, a UNESCO World Heritage Site.

This emerges from a new quality status report on climate change that the Trilateral Wadden Sea Secretariat in Wilhelmshaven recently published.

Changes can be observed in sea level, temperatures and the occurrence of extreme weather events, said Julia Busch, climate change program manager at the Wadden Sea Secretariat, to the German Press Agency.

“If important elements in this well-oiled system are missing or shifted, this has an impact on the entire system.”

In addition, there is human use of the Wadden Sea, for example for fishing and tourism.

»Give the ecosystem more time«

Since the publication of the last status report on climate change in the Wadden Sea in 2017, "unprecedented changes" have been observed in the Wadden Sea, lead author Katja Philippart from the Royal Netherlands Institute for Marine Research (NIOZ) is quoted in a statement from the Wadden Sea Secretariat.

These included a mass die-off of cockles as a result of a heat wave in 2018, a decline in freshwater flow from rivers into the North Sea and a rise in sea levels.

It is urgently necessary to take coordinated measures to combat the effects of climate change on the Wadden Sea.

“Finding ways to give the ecosystem more time to adapt to these aspects of climate change will be a major challenge for everyone involved in monitoring, research and management of the Wadden Sea,” said Philippart.

Temperature record in the western Wadden Sea

As a result of global climate changes, scientists are also registering temporary increases in air and water temperatures in the North Sea region.

The study authors point out that the highest sea water temperature in 160 years was measured in the western Wadden Sea last June at 18.5 degrees.

Some species can adapt well to higher temperatures, others less so, Busch said.

“We are already seeing a change in the species composition.” Scientists have been observing with concern for some time that the flight and resting times of migratory birds are changing.

The report cites the example of black-tailed godwits, which have to shorten their rest in the Wadden Sea in order to catch up with the earlier hatching of insects that serve as a food source in their breeding area of ​​Siberia, caused by global warming.

The report also refers to a study that suggests the lugworm could move north as a result of climate change.

The Wadden Sea is also feeling the effects of climate change on land.

Since spring and summer were drier and warmer on average recently, rivers such as the Ems, Elbe and Weser discharged less fresh water into the Wadden Sea.

The less fresh water comes into the salty Wadden Sea, the higher the salinity remains, said Busch.

"This affects the life of algae and therefore also of fish and birds in the mudflats," explained Philippart.

Fresh water contains phosphate and nitrogen, which serve as the basis for algae growth and the food chain.

Heat wave hits cockles

Extreme weather events such as heat waves are also likely to become a problem for life in the Wadden Sea, write the study authors.

Philippart refers to the large die-off of cockles in the Dutch Wadden Sea in the summer of 2018.

"In addition to the heat, this probably also had something to do with the decline in the availability 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 environmental pollution.

Scientists from all three states bordering the Wadden Sea, Germany, Denmark and the Netherlands, worked on the new report on climate change.