2021 City Nature Challenge

Started in 2016 as a competition between San Francisco and Los Angeles, the City Nature Challenge has grown into an international event, motivating people around the world to find and document wildlife in their cities.
City Nature Challenge
Started in 2016 for the first-ever Citizen Science Day, the citizen science teams at Natural History Museum of Los Angeles County and California Academy of Sciences dreamed up the City Nature Challenge as a fun way to capitalize on their home cities’ friendly rivalry and hold a citizen science event around urban biodiversity. 

From April 30 through May 3, Colorado residents are encouraged to go outside in their neighborhood to photograph and identify plants and animals using the free iNaturalist app as part of a global initiative called the City Nature Challenge.  

City Nature Challenge 2021 is an international effort to find and document plants and wildlife across the globe. Cities are encouraging their citizens to get outside in whatever way is safe for each region and document the plants and animals in their surroundings. The City Nature Challenge is organized by the California Academy of Sciences and the Natural History Museum of Los Angeles County.

Taking Part is Easy

Download the app from the AppStore or Google Play

Find Wildlife

It can be any plant, animal, or any other evidence of life found in your city.


Take a Picture

Take a picture of what you find. Be sure to note the location of the critter or plant.


Share your observations through iNaturalist or your city’s chosen platform.

upload icon

The City Nature Challenge and COVID-19

In light of the COVID-19 pandemic, the City Nature Challenge has made some modifications to the annual event to help keep organizers and participants safe. Although it has been promoted as a friendly competition in previous years, this year it’s about embracing the healing power of nature. Participants should safely document biodiversity in whatever way they can, even from the safety of their own homes if necessary. Participants are urged to carefully follow public health guidelines provided by your local governments, as they are changing in real-time. Individual safety and public health is of utmost priority. 

Citizen Science and the iNaturalist app

To participate in this collaborative effort, go to www.iNaturalist.org or download the iNaturalist mobile app, create an account, and log in. Then get outside and start taking pictures of nature around you. By participating, you will be embracing the healing power of nature while also contributing crucial data about Colorado’s unique biodiversity. Scientists can then use this information to make important decisions about how to protect and improve Colorado’s nature.

The iNaturalist app that people use to identify species during the City Nature Challenge has been part of Colorado Parks and Wildlife’s efforts to engage citizen scientists over the past few years.

In just under six years, the app has documented more than 32,600 observations of nature in Colorado’s 42 state parks. The new technology is helping CPW biologists track the wildlife resources, and in some cases, even contributing toward furthering important research.

Two Part Challenge

iNaturalist Screenshot

The City Nature Challenge takes place in two parts. The first four days, April 30 – May 3, are the days that iNaturalist observations will be collected (aka the Bioblitz), and the last six days, May 4 – May 9, are when those observations will be identified and verified. Only those observations identified down to the species level will contribute to the final tally. Participants can also continue to upload observations during this six-day period, as long as the sightings took place during April 30 – May 3.

Colorado nonprofits and government agencies like Colorado Parks and Wildlife, The Nature Conservancy, the WILD Foundation, MetroDNA, Denver Botanical Gardens, Denver Audubon, and Colorado Springs Parks, Recreation and Cultural Services all see the value in this effort to connect people to their environment and reap the benefits of crowd-sourced citizen science.

“We have so much amazing nature in and around Denver. We encourage people to explore their backyards and neighborhoods to discover incredible wildlife,” said Chris Hawkins, urban conservation program manager for The Nature Conservancy in Colorado. “Not only will participants be having fun outside, but they will also be making valuable scientific contributions that will help The Nature Conservancy and partners as we work to create a thriving region for people and nature.”

“As a mom of two young children, I am so excited about the opportunity to engage them in a community science project that gets us outdoors in our own neighborhood,” said Kate Hogan of Denver Audubon. “The iNaturalist.org app is easy to use, and even my 5-year-old knows how to take pictures with my cell phone, so each one of us can be involved!”

“At its core, it’s a citizen science project that is trying to engage as many people as possible to record the diversity of life wherever they happen to be,” said CPW Forest Management Coordinator Matt Schulz. “Anyone can participate with this challenge, just by observing what is outside their door, whether it’s the tree that lines your street or the bird stopping over to find a bit of food.”

Locations Near You

Video: How to Take Better Photos for iNaturalist

Colorado state parks are a great place to be outdoors, as well as a great place to participate in the City Nature Challenge. But please remember to only visit your neighborhood state parks consistent with public health recommendations. 

There are two areas in Colorado that will be participating in this year’s CNC: the Denver-Boulder Metro Area (Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson Counties) and the Colorado Springs Area (El Paso County and Pikes Peak). Within those areas, you can make iNaturalist observations anywhere wild nature exists, but we encourage you to visit a state park to participate! Colorado state parks within this year’s boundaries include: Barr Lake, Castlewood Canyon, Chatfield, Cherry Creek, Cheyenne Mountain, Eldorado Canyon, Golden Gate Canyon, Roxborough, and Staunton.


2020 City Nature Challenge Stats

Denver-Boulder Metro Area 2020

  • Total observations: 6,374
  • Total observers: 433
  • Species identified: 955

Colorado Springs Area

  • Total observations: 3,443
  • Total observers: 97
  • Species identified: 717


Total observations: 815,000+
Total observers: 41,000+
Species identified: 32,600+

Travis Duncan is a public information officer for Colorado Parks and Wildlife in Denver. Travis has lived in Colorado nearly 20 years and loves the outdoors. If you have a question, please email him at travis.duncan@state.co.us.

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