Nearly 4 million people visited Yosemite National park last year and most of them stayed- as we did- within the 7 square miles that is the valley floor. Granted it’s full of unreal sites: several thousand-foot waterfalls, massive sheer granite faces and thousand-year-old trees, but such a small area quickly becomes packed with tourists and after a few hours in the valley, we left feeling like theme park refugees.

Even such a quick trip launched us on a quest to learn more. In this video, we take a spin around the valley floor’s tourist loop and talk a bit of what we discovered about its changing ecosystem: how climate change may be helping shrink the number of huge trees and about one theory of how the killing of cougars here in the 1920s may have resulted in trophic cascade (less predators for mule deer –> more deer to eat more black oak seedlings –> fewer oaks & more conifers –> more grass & ferns –> less native plants).