November 5: Grand Canyon Trail Half Marathon and 5k Run/Walk, in the Kaibab Forest near the South Rim  – Register Here

Earth Day 5k at Biosphere 2

TMC Earth Day 5k at the Biosphere 2, April 23, 2023

2023 Race Registration Now Open

2022: Click here for the Run Tucson Race Report

Click here for overall results from our friends at Roadrunner Race Timing.

Click here for age group results

Click here for the Damion Alexander photos

Click here for the video Damion put together.

Click here to see the KGUN Morning Blend pre-race interview about the event.

Run the Desert . . . then roam through a rain forest, view an ocean reef, and wander through savanna grass lands . . . all in one day!

Join us at the inaugural TMC Earth Day 5k, where you can walk or run the hidden backroads of the world-famous Biosphere 2, nestled at the base of the majestic Catalina Mountains, north of Tucson.

The rolling 3.1 mile course offers gorgeous desert and mountain views, with start and finish on the Biosphere 2 Lawn.  Don’t miss this chance to visit the earth’s entire ecosystem under one roof while celebrating Earth Day.

2022 Schedule — 2023 TBD Friday, April 22 at The Running Shop, 3055 North Campbell, Tucson
3:00 – 6:00 pm Packet pickup and in-person registration.
Medals to the first 400 registered. Race numbers will be marked.
T-shirts to the first 500 registered, with sizing given away on a first-come, first-served basis at packet pickup. 
Saturday, April 23rd at Biosphere 2, 32540 S Biosphere Rd, Oracle, AZ 85739
6:30- 7:15 am Race day registration and packet pick up in the parking lot by the front entrance at the Biosphere 2.
Medals to the first 400 registered. Race numbers will be marked.
T-shirts to the first 500 registered, with sizing given away on a first-come, first-served basis at packet pickup. 
7:30 am Start time for TMC Earth Day 5k Run/Walk
8:45 am Free Kids Dash on the Great Lawn
9:15 am Awards, courtesy of the Running Shop. Remaining medals and shirts given to late participants
10:00 Event wrap-up
Ongoing: All registrants can visit Biosphere2 on their own — no need for a formal tour!
All non-running guests can purchase Biosphere 2 admission for the discounted rate of $11 (before 8:30 am) and all children under 12 are free.
SOUVENIR REMINDER: as of April 6th, we reached the 400-person cap for a guaranteed race medal. If you are among the first 400 registrants who registered before April 7th, you will be able to pick up your medal and shirt at packet pick-up before the race and on race morning. After the race, remaining medals will be available to all registrants, including those who registered after April 6th.
All remaining shirts and medals will be brought to the Running Shop and available for remainder pickup between April 26 – May 15.

Bring the Kids! Strollers are allowed at this child-friendly event, with a free Kid’s Dash & Kid’s Zone

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

Runner Quote: Amazing course.  Long upgrades.  Very challenging.  Great setting and wonderful cause.  Thanks again.

Weather: 50’s – 70’s

Chair Athletes: Chair athletes may find this a doable but challenging course, with a couple of steep hills and the dirt road.

Pets Allowed: No, pets are not allowed on the Biosphere 2 grounds.

Want Training Advice? Contact RRCA-certified running coach Tia Accetta at  

Terrain: the race starts and ends on grass, but it’s mostly pavement, with a brief dirt section … and, well, it’s hilly in some sections…
The Start: The event starts on the grass of the Great Lawn, crosses some gravel, then drops down a steep hill before heading south on a gentle downhill to the turnaround at about the 3/4 mile mark (see the “X” below). There are a few speedbumps on this opening out-and-back, so please keep an eye out for varied terrain.
Mile Two: The second mile is a bit twisty, as you climb past the stables and swing past the historic ranch house built in 1890. You’ll head north on a flat dirt road for a bit, with views of the Catalina Mountains off to your right. Then you’ll drop down a hill before hitting the 2-mile mark
Mile Three to the Finish: You’ll begin the third mile by climbing up again to the edge of the Biosphere 2 property and turning back towards the Biosphere 2 — watch out for free-ranging cows. As you can see in the elevation chart below, the final three-quarters of a mile includes a lengthy downhill past the housing units and past the main structures, before the final quarter mile up to the finish line in the middle of the Great Lawn.
Chair Athletes: Chair athletes may find this a doable but challenging course, with a couple of steep hills and the dirt road.
Strollers: Strollers are allowed in the race, but please be mindful of the hills and ensure that you are tied to the stroller you’re pushing. Please remember sun protection.
Headphones: We request that you do not wear headphones while participating in the event. Enjoy the camaraderies of your fellow athletes, enjoy the scenery, and keep an ear open for rattlesnakes, javelinas, and other participants.
Wildlife: This event takes place in a rural environment adjacent to wilderness, so you may encounter any number of wildlife, including but not limited to rattlesnakes and other snakes, javelina, cattle, deer, wild turkeys, bobcats, and more. Please do not try to touch the wildlife. Please do not wear headphones.
Heat and Altitude: The race starts at approximately 3820 feet, so be mindful that you’re at a bit of elevation. It looks like race morning may be about 50 degrees at the start, climbing to the mid-70’s. Stay hydrated, wear sunscreen and a hat.
Measurements: The route is garmin- and map-my-run correct but not a USATF certified course. The mapmyrun online map is here.


Click here for the Run Tucson race report.

Click here for the race results from our good friends at Roadrunner Race Timing.