City Nature Challenge 2026

DB+

Join the international City Nature Challenge (CNC) event and become community scientists in Colorado! This annual event motivates people around the world to take observations of the natural world using the iNaturalist app. Last year, more than 100,000 people participated and made 3.3 million biodiversity observations worldwide.

The City Nature Challenge consists of two phases – the Observation Phase – where community scientists use the iNaturalist smartphone app to record observations of nature in their community, and the Identification Phase where nature enthusiasts and experts work to link species identifications to the observations.

Key Dates for the 2026 CNC

April 24-27 | Observation Phase
April 28-May 10 | Identification Phase
May 13 | Results Announced

Why you should participate

Every observation and identification can contribute to biodiversity research. Data on iNaturalist is available to anyone and is also shared with scientific data repositories such as the Global Biodiversity Information Facility. Data is also often used on a local scale and can help inform management decisions that help protect our environment. By participating, you are not only contributing to urban biodiversity science but also learning about your local environment!

Several organizations in the Front Range have come together this year to host events related to CNC! But you don’t have to attend an event to participate; observations can be made at your local park, in your backyard, or along your streets’ greenway! Or if you’re interested in identifying species, you can do that in the comfort of your own home after the observations have been made by others.

Our Goal for 2026

Within the Front Range, we hope to make 10,000 observations of animal, plant, and fungi life. We aim to have 1,000 observers take part in the observation phase, and 800 identifiers in the identification phase. By the end of the event, we hope to identify at least 1,000 research grade species and that 75% of all our observations are considered research grade. Help us make our goal a reality by joining an event or participating on your own!

Join an Event

Colorado Open Lands
April 22-25 | Anytime
Statewide

Beginning on Earth Day, get a new daily challenge delivered to your inbox with a fresh idea to help deepen your connection to our state’s nature. You’ll also have an opportunity to participate in the City Nature Challenge with a step-by-step guide provided by us! The challenges each take less than 10 minutes and can be adapted to any age or ability level. Try the challenges on your own or share the experience with loved ones! Explore, learn, reflect, and reconnect with nature.
Sign up here!

Denver Parks and Recreation and High Line Canal Conservancy

Saturday, April 25 | 11:00 a.m. – 1:00 p.m.
Hentzell Park in Denver

Let’s see what can be accomplished when we all work toward a common goal! You can help Denver by participating in this challenge alongside Denver Parks and Recreation and the Highline Canal Conservancy staff on April 25 at Hentzell Park.
Learn more here!

The Nature Conservancy Colorado
Monday, April 27 | 10:00 a.m. – 12:00 p.m.
Aiken Canyon Preserve in Colorado Springs

Join The Nature Conservancy’s 13ers young professionals in a mini-bioblitz at the beautiful Aiken Canyon preserve outside of Colorado Springs! We will build the park’s species list by using iNaturalist to document plants and animals that live there and contribute to citizen science. This event is sponsored by the 13ers but open to all ages.
Learn more here!

Participate on your own

All you need is a smartphone and the iNaturalist app. Any observations (can be a photo or sound recording) you take between April 24 and 27 will count towards the project. You have up until May 13 to upload your observations and identify as many observations as you can. Any observations made within the majority of the Front Range on the dates above will automatically be added to our community’s project.

Don’t live in the Front Range? You can still participate by joining other “cities” such as the CO West Slope Project or the Global Project.