National Public Radio: Young people have been the life blood of the environmental movement for decades. There could be trouble on the horizon though, and it all comes down to semantics. To explain, it's helpful to use the example of Lisa Curtis, a 26-year-old from Oakland, California. Curtis comes from a long line of environmentally-conscious Americans. Her grandmother, Sis Curtis was an avid hiker and at 84 remains a Sierra Club and World Wildlife Fund member. Lisa's 55-year-old mother, Barb Curtis drives a hybrid car,...