Historic canals turn green in Belgium’s Ghent amid autumn warmth

A canal of the River Lys in the Belgian city of Ghent, choked with duckweed on Oct 1. Duckweed has proliferated due to a lack of rain and record-breaking temperatures.

GHENT, Belgium – A bright green film carpets the historic canals in the medieval Belgian town of Ghent, as tourists and students relax along its edge in the unseasonable autumn warmth.

The blanket of duckweed covering the water has proliferated dramatically due to a lack of rain and record-breaking temperatures.

Like much of Europe, Belgium in recent months experienced an exceptional series of heatwaves, with the summer of 2026 being declared the hottest in its history.

“We’ve never seen anything like this here in Ghent,” Davide Siddi, who captains a boat giving tours of the canal, told AFP.

“It’s been like this for three weeks to a month.”

The lack of rainfall coupled with the unusually warm weather – with temperatures in September still regularly exceeding 20 deg C – provide the ideal conditions for the duckweed to flourish.

“Normally, the plant is found where water is stagnant, but at the moment it is spreading everywhere,” Geert Weymeis, head of Flanders Waterways, told AFP.

“This is the first time we have seen it grow on such a massive scale here.”

Weymeis said the phenomenon mainly affects the Lys, a river that flows from the north of France and empties into the Scheldt river which runs through Ghent’s centuries-old canals.

“It could last for a few more weeks if the temperature does not drop significantly,” Weymeis said.

Duckweed deprives the flora and fauna in the water of sunlight, but the plant is harmless for humans.

Tourists can still safely board the boats that wind their way past the churches and historic buildings in the city centre.

Against the blue sky, the pea green coating creates a striking image that passersby stop to photograph.

But there is also a sense of worry over the impact that man-made climate change is having on the environment around them.

“It’s both beautiful to look at and a cause for concern,” Ramzi Salhi said, after capturing the image.

For boat owners like Siddi, the problem is most practical.

The duckweed can clog up the engines of the tourist boats plying the canals and cause them to overheat.

“Over the past month, a few boats have already broken down,” he said. AFP