Complex sentence: In the 1970s, duck hunters prevented the U.S. Army Corps of Engineers from dredging and straightening the Cache River which led to the establishment of the National Wildlife Refuge in 1986.
Split into simpler sentences: In the 1970s, duck hunters prevented the U.S. Army Corps of Engineers from dredging and straightening the Cache River. The conservation movement led to the establishment of the National Wildlife Refuge in 1986.