Thursday’s Volkskrant looks at the difficulties the Netherlands faces in getting rid of the ‘foreign’ animals and plants which are setting up home on its waterways.

Unwanted immigrants number one are the coypu and the muskrat, first introduced for their fur, and now nationwide pests because of their habit of digging under dykes and river banks, causing them to weaken.
Number two on the least-wanted list is the zebra mussel which came from the Black Sea region and now causes considerable damage at power plants by clogging up water intake pipes.
The giant pennywort, an aquatic plant and a relatively recent arrival from the US, is also causing water boards a lot of trouble, with some areas threatening to grow full of the weed.
Then there’s the Chinese mitten crab which destroys fishing nets and digs into river banks.
In total, some 145 unwanted animal and plant species have permanenttly settled in the Netherlands, the paper says.
Experts at Radboud University told the paper that foreign plant and animal life cost Dutch society some €1.3bn in damages a year, and that that is a conservative estimate.