A Delta farming island crucial to sandhill cranes is so mismanaged that the levees may break, a lawsuit alleges. Ironically, the allegedly bad manager is The Nature Conservancy. A suit by the Wetlands Preservation Foundation seeks to stop TNC’s allegedly bad, even dangerous, farming practices to avert a potential catastrophe on Staten Island in San Joaquin County. “TNC has failed to live up to its proud environmental tradition,” says the suit, filed in San Joaquin County Superior Court. The Nature Conservancy counters that the suit is baseless. The nonprofit is proud of its work on Staten, which is helping cranes rebound, a spokesman said.