City Nature Challenge 2021: April 30th - May 9th

May 1, 2021

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 bio blitz 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. 

In light of the COVID-19 pandemic, the 2021 City Nature Challenge will not be focused on competition; instead, it will embrace the healing power of nature and celebrate tens of thousands of people all around the world, searching for and documenting their local biodiversity, together in this event.

The 2021 City Nature Challenge takes place in two parts:

  • Taking pictures of wild plants and animals: April 30 - May 3
  • Identifying what was found: May 4 - May 9

Results will be announced on Monday, May 10th.

Last year Denver Metro Area competed against 244 cities throughout the globe and came up with some impressive numbers: 

  • 5,847 total observations
  • 838 plant and wildlife species identified
  • 443 observers
  • 373 identifiers

🌱 Why participate in the City Nature Challenge?

There is nature all around us, even in our cities! Knowing what species are in our city and where they are helps us study and protect them, but the ONLY way to do that is by all of us – scientists, land managers, and the community – working together to find and document the nature in our area. By participating in the City Nature Challenge, not only do you learn more about your local nature, but you can also make your city a better place – for you and other species!

🌱 How to Participate

Help show the world how biodiverse our region is by documenting observations of wild plants and animals from April 30 – May 3, 2021! Document nature in your home, backyard, neighborhood, or nearby parks or trails during off-hours, and upload your observations to iNaturalist, an online platform for citizen scientists. Any observations of plants, animals, and fungus found throughout our boundary will count. Check out the Denver-Boulder City Nature Challenge Guide here.

  • Visit
  • Download the app from the AppStore or Google Play
  • Sign In
  • Start sharing your observations
  • Get feedback from actual scientists, experts, and other naturalists

Find out more about the Denver-Boulder Bioblitz here.