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Bridge Guards


Liselotte Rambonnet

Founder // Coordinator

As a child, Liselotte (1991) already freed entangled crabs and fought for the preservation of important nature reserves at the Bird Watch. Now she is pursuing a PhD as a biologist at Leiden University, researching how we learn more about the impact of humans on animals thanks to volunteers: citizen science. For this, she specializes in the amazing work done by animal ambulances and wildlife shelters. With great passion, she talks about this in the (inter)national media and gives talks and guest lectures. She also prepares animals every week in Naturalis' LiveScience room.



Auke-Florian Hiemstra

Founder // Coordinator

Biologist Auke-Florian (1992) researches bird nests, and at Naturalis he is doing his PhD on the use of artificial nesting material. He even discovered bird nests made of anti-bird spikes! The news went around the world and The New York Times even devoted a full page to the story. He also wrote a children's book on urban nature, travels the country with theatre talks, and regularly joins talk shows. He is also active as a photographer - his photos have appeared in The Guardian, National Geographic and Washington Post.


More than 500 volunteers and local heroes

The Grachtwacht exists thanks to more than 500 volunteers and many local heroes! Every week, they collect and examine litter from the Leiden canals. Volunteers Jaap, Pieter, Thalassa, Jos, Edward, Jean-Jacques and Thomas can even be found on the canals almost every day. Not only do the volunteers collect and analyse the finds, they also help organising and write along with the scientific publications. They are heroes!

Entanglements and fish hooks

Thanks to the volunteers who join us during the clean-ups, our collection grows every week with important litter and nature finds. These finds form the basis for our research and the exhibitions we organise. In addition, we receive special finds from urban ecologists from all over the country. Ecologist Peter van Poelgeest, for example, found a goose that died because of fishing line around its legs. But also thanks to animal ambulances and animal rescue centres such as Dierenambulance & Vogelasiel Regio Leiden, we receive objects such as fishing hooks and fishing nets in which birds get entangled. The animals are given a dignified second life thanks to the preparation of Paul Feil and Judith Mellenberg from De Opzetterij.


For the research, we work together with researcher Tim van Emmerik from Wageningen University. Jordy van der Beek is our chief DNA officer and helps us with groundbreaking genetic research. For radiological imaging, we work with Thomas Ruytenberg, who makes X-rays like no other. Through crowdfunding via the platform of LUF Leiden and all the amazing donations, we were able to purchase our clean-up canoes and our research boat was donated, as well as the electric motor. The beautiful berth for our research vessel was made possible thanks to Rederij Rembrandt. For research into terrace waste and the introduction of plastic-free terraces in Leiden, we work together with We are Nature and Stichting Duurzame Horeca Leiden.

Some of our amazing volunteers after a clean-up in the summer of 2020.

The bridge house on the Marebrug

The bridge house on the Marebrug was refurbished in the summer of 2020 thanks to the municipality of Leiden, which repaired the concrete and tiles, among other things. Furniture maker Roos-Marijn Kinkel then made beautiful window sills, showcases, bookcases and light boxes from recycled materials only. The desks are made from a tabletop that we fished out of the canal. Thanks to IT-hero Jaap Bierman we have superfast internet. Light artist Mark Flipse turns anything you give him into a lamp, which suits us fine, because we find the craziest objects. He transformed a kettle from the canal into a lamp and makes beautiful hanging lamps from the fenders of boats floating in the canal. Robbert van Strien's nature-inspired art can also be admired in the bridge house. Our collection cupboard was crafted by Daniël Siepman from reclaimed wood and he also restored the authentic water pump. He also made floating nesting platforms for waterbirds from bottles collected during the clean-ups. One of the platforms can be admired next to the bridge house. The plants in the bridge house have been adopted from the Plantenasiel (plant shelter) in Leiden.

Roos-Marijn Kinkel working on the interior of our bridge house.


For our press photos, we work together with photographer and Zilveren Camera winner Alexander Schippers. The drawings on this website were made by our in-house illustrator Anna van Duijn. Graphic designer Amber Meekel designs like no other and makes our beautiful posters. Roos-Marijn Kinkel developed a unique typeface, based on the letters of the bridge house. Tom van der Heiden makes great animations for us. Aneta Margraf-Duc made our beautiful logo and designed the layout of our website.

Many others

As you can see, we are nowhere without all these great volunteers and creative heroes. And we haven't even been able to name everyone yet. We are very grateful to all these special people. We are also very grateful to all our donors and financial partners, including the municipality of Leiden, Leiden University, Citizen Science Lab, Druckerfonds and WOZfonds. In particular we thank Wouter Wuite and Piet van Vegten of Leiden municipality.


Robbert van Strien

Board member // Secretary

Robbert (1986) is a craft designer. He studied Design Cultures at the VU University Amsterdam and his interest in nature shimmers through in many of his designs. From bronze slugs and porcelain butterfly pupae, to plates in the shape of crabs. He also gives courses on making art, and teaches art to secondary school students!


Mark Flipse

Board member // Treasurer

Mark (1973) works as a light artist. He studied design at the KABK in The Hague and now focuses on WASTE lamps, as his work centres on the reuse of discarded materials. His studio at Haagweg 4 in Leiden is full of unique upcycled lamps. Waste from the canal is also a source of inspiration! With his series 'From the canals', he turns discarded boat fenders into unique design lamps!


Julie de Graaf

Board member // Chair

Julie (1986) is an author and creates great texts. Although she studied public international law and is therefore actually a lawyer, she currently writes children's books! She debuted with 'The Great Grown-Up Book' (Lannoo, 2023). In between writing, she regularly takes a walk around the neighbourhood with her trusty litter grabber.