If the North Sea island of Pellworm vanishes beneath the waves it will take with it the 300-year-old family farm of Sophie Backsen, 22, who last week won a court judgment forcing Germany to take swifter action to combat climate change.

Backsen was one of a group of plaintiffs who challenged Germany’s 2019 climate law, saying that by moving too slowly to cut greenhouse gas emissions, Germany was stealing from younger generations.

“Pellworm is simply my home, my homeland. This is where I grew up. Our farm is here. And that would be a huge loss for me,” she said, walking along a dyke under a low grey sky...