Former Shell president John Hofmeister's prediction that gasoline prices could hit $5 per gallon in 2012 represents both an enormous challenge and an important opportunity for environmentalists working to stop global warming, protect our coasts, and to stop the destructive expansion of Canadian tar sands and other dirty fuels. We should seize this moment to launch a major campaign to end our dependence on oil by investing in new technologies and building the clean transportation alternatives that will protect our environment and middle class families from our dependence on oil. With America at a crossroads, we should recognize this challenge …