TMC Earth Day 5K at Biosphere 2

2025: Registration is now open for the April 19, 2025 TMC Earth Day 5k! 

Looking for a way to celebrate Earth Day? Join us at Biosphere 2 for a 5k run and walk, entirely on the grounds of the famed facility. 

Whether you're a seasoned athlete or just looking for a fun way to get some exercise, you're sure to enjoy yourself at the world-famous Biosphere 2.  

Clear your schedule and join us at the April 19th TMC Earth Day 5k, where you can walk or run the hidden Biosphere 2 backroads, nestled at the base of the majestic Catalina Mountains, north of Tucson. The rolling 3.1 mile course is perfect for racing and walking, with gorgeous desert and mountain views and a start and finish on the beautiful Great Lawn.  

After the 5k, you can relax, listen to live music, snag some food, and enjoy other fun activities, so make sure to stick around to socialize and have some fun. All registrants receive free entry to the Biosphere 2 informative tour of the renowned research facility, with an exclusive peek into the inner workings of the Biosphere 2, a wild world of wetlands, rainforests, grasslands, fog deserts, and the big blue ocean. It's like a backstage pass to nature's superstar habitats!

The TMC Earth Day 5k is raising funds for the Ocean Reef research project, learning how to grow ocean reefs in a changing climate.  See details and donate here. 

We've raised the limit, so now capped at 800 registrants

• Souvenir shirt to first 800 registrants

• Timed 5k with finisher's video

• Age group and overall awards courtesy of The Running Shop

• Free entry to the world-famous Biosphere 2

• Snacks and drinks

• Food trucks with yummy post-race food for purchase

• Children's activities

• COX Conserves special festivities planned

Nice words from 2024 runner Dale: It’s important to me to thank the people who help make Tucson the awesome community it is! Saturday’s Earth Day was fabulous! I’ve been fortunate to attend all the races you’ve had out there! Just the view and space is incredible and what a gift to be able to “struggle” up the hills while taking it all in!   Thank you so much for all you and your staff/team do. 

Nice words from 2024 runner Louise: Wow!! Are you guys efficient or what?  Thanks so much for the quick turnaround with results and, again, for organizing and running a great event.  The water stop was especially appreciated on a hot day. (And even if we were running short of time, the announcer was funny and added an enjoyable element to announcing the winners.)

Don't miss this chance to visit the earth's entire ecosystem under one roof while celebrating Earth Day.

Bring the Kids! Strollers are allowed at this child-friendly event, with a free Kid's Dash & Kid's Zone.  Special $5 price for children 14-and-under: includes race number, timing, and entry to Biosphere 2, but no t-shirt.

Do Good! This inaugural event raises funds for the world-renowned Biosphere 2's Ocean Reef Lab. 

Terrain: mostly pavement, with a brief dirt section

Difficulty: hilly in sections

Weather: 50's - 70's

Differently Abled: Yes, be mindful of hills and dirt road

Pets Allowed: No

Want Training Advice? Contact RRCA-certified running coach Tia Accetta at tia@runtucson.net. 

Planned 2025 Schedule:

7:15-8:15 am Race day registration and packet pick up
8:30 Start time for TMC Earth Day 5k Run/Walk
9:30 Free Kids Dash
9:45 or so: Awards
Ongoing: All registrants can visit Biosphere 2 on their own -- no need for a formal tour!

All non-running guests can purchase Biosphere 2 admission for the discounted rate of $10 (before 8:30 am) and all children under 12 are free.

This event is a partnership between Run Tucson & the Biosphere 2, the University of Arizona

Questions? Contact Race Director Randy Accetta at randy@runtucson.net.