Seven years ago, when I started free soloing long, hard routes in Yosemite - climbing without a rope, gear or a partner - I did it because it seemed like the purest, most elegant way to scale big walls. Climbing, especially soloing, felt like a grand adventure, but I never dreamed it could be a profession.

There's a constant tension in climbing, and really all exploration, between pushing yourself into the unknown but trying not to push too far. The best any of us can do is to tread that line carefully.

Yosemite has the most impressive and accessible granite big walls in the world. The rock is amazing. And because of that, it's been the mecca for climbing in the U.S. - and the world to a large degree - for all of climbing history. It's the place to test yourself against the historic routes of the past.

I've tried to approach environmentalism the same way I do my climbing: by setting small, concrete goals that build on each other.