Tobias Rohmer and Ben Chen’s careful work in Hayward’s Cogswell Marsh represents one small moment in the massive, nearly 20-year-old Invasive Spartina Project. Treatment of the southern section of Cogswell marsh was halted in 2011, however, due to concerns about Ridgway’s rails who’d made homes in the invader. “Complete eradication has been and still is our goal,” says Marilyn Latta…