Shepherdstown, W.Va. The American conservationist may be an endangered species, both in numbers and public influence. That's the bleak news suggested by some attendees at the National Conservation Learning Summit, held this weekend at the sprawling woodland campus of the National Conservation Training Center in West Virginia. Some estimates indicate that as many as 60 percent of the most senior federal employees are eligible to retire in 2007. Many of those are in conservation and natural resource fields. Over one-half of the senior executives at the Department of the Interior, USDA Forest Service and Environmental Protection Agency will retire by...