Challenge Complete: City Nature Challenge London Results| Citizen Science

Over the last weekend of April, London competed with over 150 cities worldwide in the City Nature Challenge. People across the globe banded together and spent four days finding as much wildlife and nature as possible in their respective cities. London was one of the top five cities in Europe, with 5470 observations of 1115 different species recorded by 258 people in total.

Read on for a recap of how the weekend went and a video report:

A worldwide competition

Originally a BioBlitz competition between two rival cities, the City Nature Challenge has grown to 159 participating cities worldwide. The Challenge aims to engage people in documenting the nature around them and raising awareness of the importance of urban biodiversity. Cities compete to see who can make the most observations, find the most species, and get the most people involved.

Residents and visitors have four days to find as much nature as possible in their respective cities and record them using an app called iNaturalist. This app is a hassle-free and easy-to-use platform that can relatively accurately identify observations with only a photo (or even sound if you use their website). These identifications can be checked and verified by other naturalists in the community.

In this year’s challenge, 963,773 observations were made, over 31,000 species were documented, and 35,126 people participated. These observations are important for scientific research and environmental monitoring and are shared with scientists across the globe.

Finds from the Hyde Park BioBlitz

The Citizen Science team at the Natural History Museum held a BioBlitz in Hyde Park on the Saturday of the Challenge. We had a series of activities – including guided walks, pond dipping, worm surveys, and self-guided activities – for families and individuals to pop in and join. Despite Storm Hannah, we had almost 100 people join us on the day. Afterwards, our team worked hard on verifying all observations made that weekend. Here are some of our favourite finds:

Brimstone Moth

Photo: iNaturalist user Paigemj

We found this brimstone moth in our moth trap early morning at the bioblitz. The moth trap was set up the night before to see what sort of nocturnal wildlife lived in the area. Brimstone moths are widespread across the UK and can usually only be seen just before dusk. They are easily identifiable by their distinctive brown-and-white spots on its angular forewings.

Rose-Ringed Parakeet

Photo: Victoria Shennan

Although not native to the UK, Parakeets are unusually common in London. It’s a mystery why their UK population is so big when they are mostly found across South Asia and Central Africa. The likely theory is that they escaped from the cages of bird keepers and collectors, and have adapted to the British climate. Despite the windy weather – this one joined us on our bird walk!

Green Cellar Slug

Photo: Rachel Ng

We found this green cellar slug under some logs at the LookOut. It almost managed to climb out of its collecting tray! Originally from Ukraine, the species found its way to the UK in the 1970s. It’s usually mistaken for its yellow competitor – the yellow cellar slug. Unfortunately, yellow cellar slug numbers have declined dramatically in recent years and may be on the verge of extinction. The Cellar Slug Hunt has been launched to locate more of these species.

A big thank you

Thank you to all the volunteers who helped run events for City Nature Challenge – we couldn’t have done so well without your efforts! And congratulations to Cape Town and San Francisco for coming first in this year’s event. We’ll be competing again next year so watch out for us then.

If you want to take part in next year’s event, make sure you follow the Citizen Science team on twitter @NHM_CitSci for news and updates. In the meantime, download the iNaturalist app and start spotting! If you are a member of a naturalist organisation and would like to be involved in either helping to organise next year’s City Nature Challenge, running an event of your own or attending to record species, email us at

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