Picture by José Felipe (Alpiarça)
In April 2025, the REWET project proudly took part in the City Nature Challenge (CNC) 2025, a global citizen science initiative aimed at documenting urban biodiversity.
Alongside more than 650 cities in 62 countries, REWET’s Open Labs in Portugal, Italy, and Austria actively contributed to this inspiring environmental effort.
What is the City Nature Challenge?
Organized annually by the California Academy of Sciences and the Natural History Museum of Los Angeles County (NHM), the City Nature Challenge is a four-day global bioblitz held at the end of April. It invites individuals and communities to observe and record local wildlife using the iNaturalist app, helping raise awareness about biodiversity and the importance of preserving urban ecosystems.
From April 25 to 28, 2025, thousands of citizens worldwide stepped outside to photograph wild plants, animals, fungi, and other organisms in their local areas, creating a shared, crowd-sourced snapshot of the planet’s biodiversity.
City Nature Challenge 2025: Global Highlights
This year’s challenge saw record-breaking participation:
- 3.310.131 observations submitted
- 102.945 observers joined in
- 73.765+ species documented, including over 3.338 rare, endangered, or threatened species
- 669 cities across 62 countries took part
- Most observed species: Common Dandelion (Taraxacum officinale) with 8.617 observations
REWET’s Open Labs Contributions
Marchegg, Austria – REWET Open Lab #2
Located in the WWF Nature Reserve in Marchegg, Lower Austria, REWET OL#2 joined the CNC for the first time. Despite some unfavourable weather conditions, the BOKU team, REWET partners (who were there for the periodical meeting), and the WWF mobilized a strong community response.
Marchegg 2025 Results:
- 301 observations
- 192 species identified
- 26 observers participated
This participation was a key opportunity to engage local citizens, promote awareness of regional biodiversity, and connect scientific research with community involvement, a cornerstone of the REWET mission.
🔗 Explore the Marchegg results on iNaturalist 🦋
Alpiarça, Portugal – REWET Open Lab #7
In Alpiarça, REWET OL#7 brought together the Câmara Municipal, University of Évora, and the Associação dos Amigos da Natureza for a full schedule of biodiversity-focused activities. Events included butterfly watching, bird ringing, flora and dragonfly walks, nature drawing sessions, and local food picnics, making it a lively, multi-generational experience.
Alpiarça 2025 Results:
- 555 observations
- 282 species identified
- 22 observers participated
This event helped deepen public understanding of wetland ecosystems, while celebrating the local culture and natural beauty of Alpiarça.
🔗 Explore the Alpiarça results on iNaturalist
Gussola, Italy – REWET Open Lab #6
In Gussola, Italy, REWET OL#6 invited citizens to explore the Gussola oxbow lake, part of the UNESCO Biosphere Reserve ‘Po Grande’. Led by the University of Parma, the event emphasized the ecological importance of restored wetlands.
Gussola 2025 Results:
- 69 observations
- 38 species identified
- 11 observers participated
This unique wetland, shaped by seasonal flooding and ecological restoration, acts as a living lab where biodiversity and carbon fluxes (CO₂, CH₄, N₂O) can be monitored. The CNC encouraged citizens to engage with this vital river habitat and reflect on the impacts of climate change on freshwater ecosystems.
🔗 Explore the Gussola results on iNaturalist
Why citizen science matters
The participation of REWET’s Open Labs in the City Nature Challenge 2025 marks an important step toward inclusive environmental monitoring. Engaging the public in biodiversity documentation helps build a sense of community ownership, supports climate change research, and fosters environmental stewardship across generations. Whether through taking a photo of a wildflower or spotting a rare bird, every contribution helps build a global biodiversity database and enhances our understanding of how nature thrives, even in urban spaces.
Thank you to everyone who participated and supported REWET’s mission to protect and restore European wetlands through community-driven science.