Million-dollar subsidy for the control of exotic aquatic plants in Overijssel

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The exotic species takes over the waters of De Wieden and Weerribben

NOS News

In the De Wieden and Weerribben nature reserves in Overijssel, exotic aquatic plants do not belong there at all. They displace the original aquatic plants, says forester Melvin de Jong. “That could have disastrous consequences for biodiversity.” Europe is giving a multi-million subsidy to tackle the plants.

The Wieden and Weerribben are Natura 2000 areas, protected nature reserves for the preservation and restoration of biodiversity. The exotic water plants are a huge pest there, writes regional broadcaster Oost. This is an uneven-leaved featherwort: a stringy plant that originally comes from the United States.

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The only way to control the exotic aquatic plants is to rigorously obtain the entire soil. “We prefer not to do that, because you also remove native plants,” says De Jong. “But doing nothing is simply not an option. And then there will be room for the native plants to develop.”

Melvin de Jong of Natuurmonumenten with a bunch of the uneven-leaved featherwort

Clearing the soil is expensive and labor-intensive and has therefore only been done on a small scale so far. Now a European grant of 4.3 million euros has been awarded, allowing it to happen on a larger scale.

The grant is intended to influence and control exotic aquatic plants for the recommended five years, with special equipment. Two ‘raking rounds’ are carried out every year, during which unnecessary plants are removed from the water. This is supplemented with manual removal of the plants.

Aquariums

In the Netherlands, the uneven-leaved featherwort is used as an oxygen plant in aquariums. So it can simply be purchased at the garden center. Yet the plants are no longer just in fish bowls, De Jong sighs. “People probably empty their aquarium into the ditch behind the house. They don’t see a problem, but this is how the exotic species ends up in protected waters. These plants can spread very quickly.”

They have no natural enemy and substantial balance in Dutch waters. Plants are displaced and animals that depend on them are affected by the war. “Normally you will find crabs here,” says De Jong, pointing to the water in De Wieden. “The green glazier, a special kind of libel, then lays its eggs. But that libel is not going to grow here now.”