CALEXICO, Calif. — Legislation passed by Congress mandating the fencing of 700 miles of the U.S. border with Mexico has sparked opposition from an array of land managers, businesspeople, law enforcement officials, environmentalists and U.S. Border Patrol agents as a one-size-fits-all policy response to the nettlesome task of securing the nation’s borders. Critics said the fence does not take into account the extraordinarily varied geography of the 2,000-mile-long border, which cuts through Mexican and American cities separated by a sidewalk, vast scrubland and deserts, rivers, irrigation canals and miles of mountainous terrain. It also seems, they say, to ignore advances in border security that don’t involve construction of a 15-foot-high double fence and to play down what are expected to be significant costs to maintain the new barrier. And, they say, the estimated $2 billion price tag and the mandate that it be completed by 2008 overlook 10 years of legal and logistical difficulties the federal government has faced to finish a comparatively tiny fence of 14 miles dividing San Diego and Tijuana. ‘This is the feel-good approach to immigration control,’ said Wayne Cornelius, an expert on immigration issues at the University of California at San Diego. […]