iNaturalistUK
City Nature Challenge
City Nature Challenge
Started in 2016 as a competition between San Francisco and Los Angeles, the City Nature Challenge (CNC) has grown into an international event, motivating people around the world to find and document wildlife in their cities. Run by the Community Science teams at the California Academy of Sciences and the Natural History Museum of Los Angeles County, the CNC is an annual four-day global bioblitz at the end of April, where cities are in a collaboration-meets-friendly-competition to see not only what can be accomplished when we all work toward a common goal, but also which city can gather the most observations of nature, find the most species, and engage the most people in the event.
The majority of sightings are recorded using iNaturalist available as a free app or via the website. Visit iNaturalistUK or read more about how we use iNaturalist in the UK.
In the UK, we have been taking part since 2018 with Bristol leading the way. The term ‘city’ has also evolved over this period and includes wide urban areas eg Birmingham and the Black Country; the North East as well as City of Nottingham and Gloucester. The Natural History Consortium are leading on co-ordinating the UK’s involvement. Take a look at their CNC pages and wider website for information and resources.
Do you want to take part in 2026?
Next year’s City Nature Challenge will take place April 24 – 27 2026 – put it on your calendar!
Would you like to find out more about becoming a City Nature Challenge Organiser for your city in 2026? Complete the sign up form which can be found on the City Nature Challenge participate page to register your interest. Please email the Natural History Consortium team at info@bnhc.org.uk to let them know you are signing up. They may be able to link you up with other people or groups who want to take part in your local area. They can also offer help and advice on what’s involved.
What happened in 2025?
The City Nature Challenge took place between Friday 25 April – Monday 28 April 2025. There were 669 cities in 62 countries on all 6 continents participating!
Take a look at the FAQ page for much more information about the event.
See what happened across the UK in previous years.
View pdf of the above graphic.
The City Nature Challenge (CNC) results have arrived! Around 103,000 people across 669 cities in 62 countries in 6 continents documented more than 3.3 million wildlife observations for the 10th annual community science initiative. More than 73,765 species including more than 3,338 rare/endangered/threatened species were observed, with the Common Dandelion as the most popular around the world.
In the UK, 26 urban areas took on the challenge. You can see the cities that took part on the City Nature Challenge UK Leaderboard.
Observations that are included are those made between Friday 25 and Monday 28 April 2025. When collating the results the figures were taken as at 11:59 pm, Sunday, May 4 in each respective country. The week following the event was to allow time for observations to be added to iNaturalist and the community to identify observations to the highest level possible at that time.
The UK tally for the UK cities registered for the City Nature Challenge is as follows:
Total Observations: 153,189
Total Species Recorded: 5,143
Number of Observers: 3,666
Worldwide, the most commonly recorded species was Common Dandelion, Mallard, Western Honey Bee, Garlic Mustard and Rock Pigeon. The Common Dandelion came 5th in the UK. Common Hawthorn topped the UK list.
To view the results in depth and see the current, up to date numbers, the UK City Nature Challenge species list is available on iNaturalistUK.