Forty years ago, the Arab embargo began a long era of U.S. dependence on foreign oil. And as recently as 2007, experts feared America was running out of natural gas. But the recent fracking boom has made the U.S. the world’s largest energy producer. And in December, North Dakota, Ohio and Pennsylvania together produced 1.5 million barrels of oil a day — more than Iran exported. But as the U.S. moves toward energy independence, environmental advocates warn of dangerous trade-offs on air and water quality, and on climate change. For this month’s Environmental Outlook: Diane and a panel of experts discuss the changing global energy picture.