This episode's headline: Issue & Debate - '92 - Environment; Agony's Cradle. The guests include CARL POPE, Sierra Club; ROBERT HAHN, Economist; MICHAEL DELAND, Bush Administration; SEN. TIM WIRTH, Clinton Campaign; CORRESPONDENTS: KWAME HOLMAN; MARTIN SEEMUNGAL. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER