Denver-Boulder Metro City Nature Challenge

City Nature Challenge

April 28 – May 7

Get to know your neighbors – plants, animals and people. The 2023 City Nature Challenge (CNC) is a friendly global competition among cities to see who can document the most wildlife. Join the CNC and contribute to community science.

Make your observations between Friday, April 28 and Monday, May 1. Between May 2-7 help us identify as many observations as possible within the project. Observations must be uploaded by May 7 to count towards our total observations for the CNC. Results announced on May 8.


Here’s how you can get involved in the Denver-Boulder Metro area:

Training Workshops

Denver Audubon

Denver-Boulder City Nature Challenge Training Workshop
Date & Time: Saturday, April 1, 1:30-3:30 p.m.
Location: Audubon Nature Center at Chatfield


Join a Hike

City of Aurora  |  Parks, Recreation and Open Space

BioBlitz Events:

Date & Time: Friday, April 28, 9-11 a.m.
Location: Delany Farm with the Aurora History Museum

Date & Time: Saturday, April 29, 9-11 a.m.  
Location: Star K Ranch, 16002 E Smith Rd, Aurora, CO 80011 

Date & Time: Sunday, April 30, 9-11 a.m.
Location: Plains Conservation Center, 21901 E. Hampden Avenue, Aurora, CO 80013

Register for these BioBlitz events 


Sand Creek Regional Greenway Partnership
City Nature Challenge Field Trip

Date & Time: Friday, April 28, 4-5:30 p.m.
Location: Smith Road Trailhead, 9450 E. Smith Rd. Denver, CO 80239 (use Google Maps)
Register for this field trip
All ages welcome. 


Denver Audubon 

City Nature Challenge Field Trip
Date & Time: Sunday April 30, 10 a.m. – noon
Location: Audubon Nature Center at Chatfield, 11280 Waterton Road, Littleton, CO 80125 (NOT at Chatfield Farms or Chatfield Reservoir)
Register for the City Nature Challenge Field Trip

Jefferson County Open Space
Date & Time: Monday, May 1, 1-3 p.m.
Location: Crown Hill Park, 9357 West 26th Avenue, Wheat Ridge, CO 80033
Register (under the Education Programs tab)

High Line Canal Conservancy BioBlitz
Date & Time: Saturday, April 29, 9-11:30 a.m.
Location: High Line Canal Conservancy Headquarters
Parking: 4010 E Orchard Road, Centennial, CO 80121 
Register for this BioBlitz 

Lead a Hike

Hike leaders will guide a group trek sometime between Friday, April 28 and Monday, May 1. They will help others document the natural world with iNaturalist. Anyone can be a hike leader – a parent with their kids, a friend with their neighbors or a professional naturalist with a team of community scientists. Locations could be alleyways or mountain vistas, as long as they fall within the Denver-Boulder boundaries.

Email us to connect to a training session and to sign up.

Fly Solo

All you need is a smartphone and the iNaturalist app. Any observations you take between Friday, April 28 and Monday, May 1 will count towards the project. You have up until Sunday, May 7 to identify as many observations as you can.

What is the City Nature Challenge? 

The City Nature Challenge (CNC) is an international effort to document biodiversity by finding and documenting plants and wildlife across the globe. Cities are encouraging their citizens to get outside and document the plants and animals in their region. The CNC is organized by the California Academy of Sciences and the Natural History Museum of Los Angeles County. 

Further questions? Please email us.

Why should you participate?

There is nature all around us, even in our cities! Knowing what species are here and where they are helps us study and protect them, but the ONLY way to effectively do that is by working together (scientists, land managers, community members, you name it) to find and document nature in our area. By participating in the CNC, not only do you learn more about local nature, but you can also make our urban areas a better place – for you and other species!



Denver Audubon logo
Denver Museum of Nature and Science logo
High Line Canal Conservancy logo
City Nature Challenge organized by logo
2022 The Nature Conservancy logo

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