Friends of the Inyo is among the organizations with opportunities to volunteer.
Check their site for a full calendar of events.
https://friendsoftheinyo.org/

Immediate examples:

Trail Work Thursday — Whitney Portal
July 19 from 9:00 am - 12:30 pm

Join us for the summer’s southernmost Trail Work Thursday in the shadow of Mount Whitney on July 19. Meet at 9AM at the Whitney Portal Store to tackle crucial trail work on some of the Eastern Sierra’s most iconic trails.
The Whitney Portal Store is generously donating French fries to reward all volunteers!

All ages welcome. Bring water and sunscreen and wear long pants and closed-toed shoes. We will provide work gloves and tools.

Inyo National Forest Wilderness Project
July 25 - July 29
Inyo National Forest Wilderness Project

Five lucky volunteers will get to spend five glorious days in the Inyo National Forest's wilderness, stewarding trails and swimming in creeks! Stay tuned for details... Space is limited—RSVP now to hold your spot!

Dale B. Dalrymple