November 1, 2020

Plastic nets in the canal

We discovered a year ago that plastic nets to make grass mats stronger end up in large numbers in the water. We asked the municipality, cleaned the nets up as much as possible and are still monitoring their distribution. So please, share your observations!

During the redevelopment of the Lammermarkt in Leiden, millions of plastic nets were incorporated into the grass. These nets serve as reinforcement, making the grass more resistant to pressure during events. In addition, the grass should be more resistant to heavy traffic. In practice it resulted in tens of thousands of nets appearing at the surface. They are then blown by the wind to the adjoining canals and we find them everywhere in the canals. We organised clean-up campaigns, had discussions with the municipality of Leiden and are still mapping the distribution of the nets.

Response from the municipality
The municipality of Leiden admitted that mistakes were made in this project as no maintenance contract was signed. Also, in future projects by the municipality only a plastic-free and sustainable alternative will be used. In the meantime, the grass at the Lammermarkt is being maintained better, but there are still many nets at the surface and in the canals, and millions of nets hidden in the ground for many hundreds of years to come. We call on the municipality that this plastic should be removed from the soil as quickly as possible.

Share your observations of floating nets!
By displaying all observations on a map, we hope to get a better picture of the extent of the problem. Are they heading towards the sea or are they stranded in the vegetation? What quantities are we talking about? Monitoring can provide insight in this. Spotted floating net(s)? Send an e-mail with the location!

On 28 December 2019, with volunteers from Jutters Katwijk, Jutters Noordwijk, Vrienden van het Singelpark and Partij voor de Dieren department Leiden and others, we picked up 20,000 tidy people from the Lammermarkt in one session. Keep in mind that we limited ourselves to the tidy ones that were lying loose, the rest is still with millions in the grass and could come loose bit by bit in the years to come. There are still tens of thousands of nets visible between the grass, in bare spots and along the water's edge.

16 volunteers collected 20.000 nets during 90 minutes.

Nets used elsewhere in the Netherlands and Belgium
It appears that the reinforcement nets have also been put into the ground in other projects. More precisely, they are polypropylene nets and have been used in these projects, among others:

– Polderpark Cronesteyn waterspeelplaats, Leiden
– Manifestatieterrein Westergasfabriek, Amsterdam
– Evenemententerrein Park Transwijk, Utrecht
– Natuurgebied de Kattevennen, Genk (B)
– Parkeerterrein vliegbasis Soesterberg
– Middenberm Ookmeerweg en Plasmanlaan, Amsterdam
– Wegbermen Hoogland en Vathorst. Amersfoort
– Glazenwaslocatie Pré Wonen, Velserbroek

In the news:
– Leidsch Dagblad 3 juni 2020: Tot in Katwijk en Wassenaar ligt het plastic van de Lammermarkt
– Sleutelstad 13 mei 2020: Gemeente verzuimde onderhoudscontract gras Lammermarkt af te sluiten
– Sleutelstad 31 maart 2020: Partij voor de Dieren wil einde aan kunststof netjes in bodem Lammermarkt
– Trouw 31 januari 2020: Leidse matjes, bedoeld voor stevig gras, drijven weg als plastic soep
– De Partij voor de Dieren Leiden stelt schriftelijke vragen over het gebruik van wapeningsnetjes in Leiden (inclusief antwoorden)
– De Partij voor de Dieren Amsterdam stelt schriftelijke vragen over het gebruik van wapeningsnetjes in Amsterdam
– Leidsch Dagblad 27 december 2020: “Leidse grachten vol met duizenden plastic grasnetjes van Lammerenmarkt
– Leidsch Dagblad 18 januari 2020: In Leiden wordt nergens meer ’gefundeerd gras’ gezaaid
– Sleutelstad: “Ruim 10.000 kunststof netjes in anderhalf uur
– Unity: “10.000 plastic netjes van Lammermarkt gehaald
– Omroep West: “Duizenden kunststof netjes geraapt in Leiden
– Hortipoint: “Plastic netjes van versterkt grasveld vervuilen Leiden
– Een natuurlijk alternatief voor plastic netjes