City Nature Challenge

Denver-Boulder Bioblitz: April 24-27, 2020

Which city has the most nature? 

The 2020 City Nature Challenge will help us find out! Last year Denver Metro Area and Boulder County competed against 159 cities throughout the globe and came up with some impressive numbers: 

  • 6,211 total observations
  • 970 plant and wildlife species identified
  • 406 observers
  • 259 identifiers

Of the 159 cities that competed in the 2019 CNC, Denver-Boulder placed 43rd for Total Number of Observations, 47th for Total Number of Species Observed, 33rd for Total Number of Participants, and 2nd for Most People in an Arid Climate. Let’s see what we can do in 2020!

Help us show the world how biodiverse our region is by making as many observations of as many species as possible from April 24-27, 2020! Document nature in your backyard, by your school, in your favorite park or open space area, 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.

The Denver-Boulder City Nature Challenge is organized by

About the City Nature Challenge

The City Nature Challenge (CNC) is an ongoing project to document urban biodiversity and engage city residents in the nature around them. The project is framed as a competition between cities to see which can make the most observations, identify the most species, or have the most participants. The program was started in 2016 by the Natural History Museum of Los Angeles and the California Academy of Sciences as a competition between Los Angeles and San Francisco. This past year in 2019, more than 35,000 participants from 159 cities documented over 963,000 observations of plants and wildlife, and identified over 31,000 species – 1,100+ of those species were threatened/rare/endangered!

The 2020 City Nature Challenge will take place from April 24 – May 3. The first four days, April 24 – 27, are the days that observations will be collected (aka the Bioblitz), and the last six days, April 28 – May 3, are when those observations will be identified and verified. Participants can also continue to upload observations during this six-day period as long as the sightings took place during April 24 – April 27. 


The Denver-Boulder Metropolitan Area City Nature Challenge encompasses Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson Counties.


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! 

Get involved!

There are many ways that you can get involved with various levels of commitment. Some suggestions are listed below. If you are interested in contributing in any way, do not hesitate to contact us!


Spread the word

Whether it’s informing your email lists, posting on your Facebook or Twitter accounts, distributing some of our posters and flyers, or just telling your friends, it all helps. The more promotion CNC has the more successful it will be!

Offer extra credit to students

We realize the 2019 CNC takes place right before finals week for many universities in the area. Offer extra credit to your students by encouraging them to take a study break to get out into nature and contribute to the Denver-Boulder CNC.

Host an event

A mini bioblitz, big bioblitz, guided nature hike, lunch break scavenger hunt, friendly competitions, CNC presentations or events… the possibilities are endless!

Make it a class project

If you’re an educator, you could create a weekend assignment to get your students outside and teach them the value of citizen science. They don’t even have to put their phones down!

Make observations

Whenever you’re outside between April 26-29, whether you’re on a hike, walking the dog, or taking the trash out, pause a moment to observe the nature around you. You might discover something you’ve never noticed before!

Sponsor the Denver-Boulder CNC

Make a donation or sponsor a prize for iNaturalist participants. We’re looking for items like binoculars, a variety of outdoor gear, nature guide books, outdoor attire, gift cards, and more.

Make species identifications

We can only count observations toward our project if they are identified down to the species level by midnight on May 5. We will need lots of help assigning those IDs as the observations roll in! You could do this in your PJs from your couch, or you could make it a social event by planning an ID party.

Event & Outreach Partners

Americas for Conservation

Bird Conservancy of the Rockies

Bluff Lake Nature Center

Boulder County Parks & Open Space

Butterfly Pavilion

City of Aurora Open Space & Natural Resources

City of Boulder Open Space & Mountain Parks

Finkel & Garf Brewing Co.

Majestic View Nature Center

Regis University

Rocky Mountain Wild

University of Colorado Boulder

How to contribute observations


*While any observation will count, we encourage you to only upload wild and non-captive observations.  Please, no photos of people, pets, or potted-plants.*


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