The man who’s in charge of the nation’s Homeland Security says there’s no guarantee terrorists won’t strike again, and he urged Iowans to take steps to guard against attacks on crops and livestock. Homeland Security Secretary Tom Ridge praised Iowa’s Governor for seeking to collaborate with nine other Midwestern states to think about agro-terrorism, which Ridge says would be a “potentially devastating problem.” Ridge says a single, even isolated incident of agro-terrorism would have serious economic and psychological repercussions. Ridge spoke this morning in Johnston, Iowa, to a group of about 100 people he called both “first responders and first preventers.” Ridge said he could offer no guarantee that terrorists won’t strike in Iowa, because all it takes it “one slip, one gap.” Ridge says “all of us, regardless of where we live, have a role and responsibility to take minimal action and preparation to protect against the possibility of a terrorist attack.” Ridge says the American people are better prepared and more secure than they’ve ever been, but “we will never be perfectly immune from an attack.” Ridge singled out 400 soldiers from an Iowa Army National Guard field artillery unit for its recent, 10-month-long active duty assignment. Ridge says the soldiers protected several military installations in the Midwest on a homeland security tour, and he says nothing better illustrates the changing world in which we live.Ridge, a decorated Vietnam veteran and the former Governor of Pennsylvania, was asked by President Bush after 9/11 to be in charge of homeland security.