http://www.kqed.org/.stream/anon/radio/quest/2010/11/2010-11-01-quest.mp3
Air pollution may seem like an urban problem, but it's becoming an increasing concern in California's national parks. Pollution from cars and trucks blows into the Sierra Nevada mountains, where it can have a dramatic impact on the ecosystem. In Yosemite National Park, researchers are trying to gauge that impact and they're using an unexpected tool: a fungus called lichen. Lauren Sommer has the story.