Ghent canals turn green after Belgium's hottest summer

A bright green layer of duckweed has spread across historic canals in Ghent after Belgium's hottest recorded summer and weeks of unusually warm, dry weather.

The plant has covered parts of the medieval Belgian city's waterways for about three weeks to a month, according to Davide Siddi, a boat tour captain in Ghent.

Geert Weymeis, head of Flanders Waterways, said the lack of rain and warm weather had created conditions for duckweed to spread widely. He said the phenomenon mainly affects the Lys, a river that flows from northern France and empties into the Scheldt, which runs through Ghent's canals.

Weymeis said duckweed is normally found where water is stagnant, but is now spreading more widely. He said it could remain for several more weeks if temperatures do not fall significantly.

Duckweed blocks sunlight from reaching plants and animals in the water, but it is harmless to humans. Tourists can still board boats in the city centre.

For boat operators, the plant has caused practical problems. Siddi said duckweed can clog tourist boat engines and make them overheat, and that a few boats had already broken down over the past month.