Front Range City Nature Challenge

Let’s celebrate Earth Day and our Front Range biodiversity by participating in the City Nature Challenge! This is a yearly event for folks in cities all over the world to observe and document biodiversity in their own backyards. Any living organism is fair game for observation – plants, mammals, birds, insects, fish – they all contribute to the City Nature Challenge. To participate, make observations of any organism on iNaturalist during the observation phase. This is followed by an identification phase—where you can join a community of nerdy naturalists to identify the species observed. Learn more and find local bioblitzes near you.

CITY NATURE CHALLENGE 2026
Observations: April 24 – April 27
Upload and Identification Phase: April 28 – May 10

For 2025’s global challenge, there were 3.3 million observations of almost 74,000 species made by 103,000 people from over 62 countries around the world. This brings the total number of observations made during the past 10 years to almost 13 million! 

Meanwhile, in the Denver-Boulder metro area, more than 9,714 observations were submitted by 764 people of 1,260 species. We nearly doubled our number of observations and observers compared to 2024 and we broke our previous record in 2020 of ~7,000. This year, our most observed species was Chokecherry (Prunus virginiana). Fun species observed included a silver fox, Abert’s squirrel, prairie violet, beaver, black-crowned night heron, little brown bat, American mink, elk, moose, northern harrier and black bear. We even had 145 research-grade observations of 26 species that are listed as rare, endangered or threatened by NatureServe or the U.S. Fish and Wildlife Service (over twice as many as last year). 

It’s easy to participate – your iNaturalist observations will automatically be added to the City Nature Challenge 2026: Colorado Front Range project if they are made during the challenge event and occur in the Front Range (see above link for map of included areas). Additionally, all plant and fungal observations will automatically be added to the Denver EcoFlora Project.