Leideners find more than 2,000 species in urban biodiversity inventory
Biodiversity image: Minke Holleman
Around 1,300 Leideners found 2,265 species during the Expeditie Stadsnutuur urban biodiversity inventory. ‘It’s been a huge success’, says scientific coordinator Frederic Lens.
It wasn’t certain Expeditie Stadsnatuur would succeed. ‘I didn’t expect to achieve the ambitious goal of 2,025 species in just five weeks’, says Lens. Participants could record animals, plants and fungi with ObsIdentify, an app that automatically identifies species from photos taken with your smartphone. ‘But many species look alike or have internal species-specific characteristics that a camera can’t record.’
Observations only counted if the app could determine the species with more than 90 per cent certainty or if experts could validate the species name. ‘It’s been such a success because so many people wanted to join in. We’re really grateful.’
Rare species
In total, 1,305 participants made 22,148 observations of 2,265 species. These included 25 very rare species, such as the common midwife toad, the thread bug, Medusa moss, Cryptachaea blattea and a pale orchid known as the bird’s nest orchid. Of the species found, 155 had never been observed in Leiden through the app. All the details about the observations can be found on Waarneming.nl.
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Common midwife toad. Source: Laurent Lebois - Flickr -
Thread bug. Found by: Aglaia Bouma -
Medusa moss. Found by: Corrie
Long-term monitoring
The inventory was a success, but what will happen with all the data? This year is the start of a series of observations. ‘If we repeat this over several years, we will be able to see how the biodiversity changes through time and what areas in Leiden require extra attention, such as the built-up city centre.’
This timeline is also of interest to the Municipality of Leiden. ‘We’ll be able to help the municipality take structural measures to boost biodiversity in the city.’ The data could also help the municipality determine when and how often to cut grass, thus informing its grass-cutting policy.
Next edition
Lens and his co-organisers are already working on the 2026 edition. ‘We would love to expand to the surrounding municipalities next year. The data would help create “green corridors” that make it easier to bring diversity from the outskirts into the city. But we still need to brainstrom within the Leiden Biodiversity Network to find the best strategy.’
The initiators also want to contribute to the ‘second green ring’, which is set to be realised between 2035 and 40. This green belt will connect canal banks, parks, allotments and areas for nature and recreation around the outskirts of Leiden, following on from the Singel Park, the city’s ‘first green ring’.
Citizen science
In addition to building a dataset, the project also connects Leiden residents with local biodiversity. ‘By making observations, people gain a better understanding of what biodiversity really means.’ This form of citizen science helps involve the public in ecological research. ‘That’s something we really value.’
An evaluation found that participants’ main motivations were learning about local biodiversity and recording species. And a good sign for next year: 94 per cent enjoyed taking part and 96 per cent would do so again next year.
About the project
Expeditie Stadsnatuur Leiden is the initiative of Leiden Biodiversity Network in collaboration with Leiden University, Naturalis Biodiversity Center, University of Applied Sciences Leiden, Leiden City of Knowledge, MBO Rijnland and the Municipality of Leiden. For general information about this project, please contact Frederic Lens. For questions about the city expeditions, please contact Jordy Janssen (Citizen Science Lab).