Justin Bieber is all about hiking these days, and he wasn't about to let the smoky air from nearby wildfires stop him on Friday.

The pop star posted the shirtless snapshots above on Instagram and wrote, "Air quality in la, good thing I wore my mask!" He appears to be at Griffith Park, and he even took some time to sign one of the notebooks in the trail register. We wonder what he wrote? Guess we'll have to get up there to find out!

Biebs was joined by a pal, and the previous day he hiked in Temescal Canyon. More shirtless Bieber in nature, please!