U.S. mayors are adding their voices to those raising concerns about energy produced from Alberta's vast oilsands. The U.S. Conference of Mayors, meeting in Miami this week, has approved a resolution calling on its members to ban the use of energy from unconventional sources because of its impact on the environment. "We don't want to spend taxpayer dollars on fuels that make global warming worse," said Eugene, Ore., Mayor Kitty Piercy, who submitted the resolution.