Beware, cranberry! How the North-American berry has taken over a German island

Conservationists on the German island of Sylt are fighting a decade-long battle against an unwelcomed intruder. The culprit? The North American cranberry, which has been overrunning the dune valleys and displacing native plant species. To free the local flora, the conservationists have been conducting a special “weeding” operation in a small area of southern Sylt.

It appears they are winning the fight. "The sundew is back and there is also room again for dwarf bulrush and marsh clubmoss," said Angela Schmidt, a biologist and head of the Wattenmeer Conservation Station on Sylt. 

According to Schmidt, these plants are all highly endangered and only grow on Sylt in the moist dune valleys, being found in only a few other places in North Germany.

The cranberry plant spreads not only through its berries but more so through its runners. "The main goal is to bring in the runners so that they do not wander from dune valley to dune valley - this is best done by hand," said Schmidt. The invasive nature of the cranberry, with its ability to spread aggressively via runners, makes it particularly challenging to control. 

The "Cranberries-Pulling-Out" action takes place six times a year in October and November in Hörnum, Sylt, when the berries are ripe. Up to 20 locals and vacationers help with the cranberry pulling action, contributing to the preservation of the island's unique ecosystem. 

The invasive cranberry is particularly problematic because it prevents native species from growing, threatening the biodiversity of the island's unique habitats. By outcompeting the indigenous plants, the cranberry disrupts the natural balance of the dune ecosystems, leading to a decline in native biodiversity.

Sources: Süddeutsche Zeitung, Die Welt, Die Zeit

This article was written in collaboration with generative AI company Alchemiq