Last week, the U.S. Energy Information Administration (EIA) reported that the country produced more crude oil than it imported for the first time in two decades. * Over the past 5 years, the United States has reduced its dependence on imported oil by nearly 50%, largely through the use of hydraulic fracturing (“hydrofracking”) to tap into oil resources in shale rock in the northern Great Plains. The United States is now also the world leader in shale gas production: 39% of domestic gas supplies are derived from this unconventional resource. † Although this change in the nation's energy portfolio is welcome news, scientists and policy-makers need to be wary of complacency.