Complex sentence: Before the 1970s, Harkin was viewed as a visionary conservationist and creator of Canada's national park system, but since then many critiques of Harkin have cast him in a darker light.
Split into simpler sentences: Before the 1970s, Harkin was viewed as a visionary conservationist and creator of Canada's national park system. Since then, many critiques of Harkin have cast him in a darker light.