West Has Oil That Equals 'World's Proven Reserves' But GAO official warns Congress about environmental impact By Neal Colgrass, Newser Staff Posted May 13, 2012 3:43 PM CDT 107 comments Comments This July 2011 image provided by the Wyoming Game and Fish Department shows cattle grazing on the Fish Creek Ranch near Big Piney, Wyo. (AP Photo/Wyoming Game and Fish Department) (Newser) – Maybe President Bush should have invaded the Rocky Mountain region instead of Iraq: Turns out that a mostly vacant area of land across Colorado, Utah, and Wyoming has about as much recoverable oil as the world's reserves combined, according to a US official. A government agency "estimates that the Green River Formation contains about 3 trillion barrels of oil, and about half of this may be recoverable, depending on available technology and economic conditions,” GAO auditor Anu K. Mittal told Congress this week. Washington is in "a unique position to influence the development of oil shale," said Mittal, because about 75% of it is on federal land, CNN reports. She acknowledged that developing the shale would create jobs and "go a long way to help to meet our future demands for oil," but she warned about damaging the region's air, water, topsoil, vegetation, and wildlife. A boom-and-bust influx of workers could also be tough for officials to handle, she said.