Complex sentence: The degradation of the natural quality of the Everglades became an issue in the United States in the early 1970s after a jetport was proposed to be constructed in the Big Cypress Swamp that studies indicated would have destroyed the ecosystem in South Florida and Everglades National Park.
Split into simpler sentences: The degradation of the Everglades became an issue in the United States in the early 1970s after a proposal to construct a jetport in the Big Cypress Swamp. Studies indicated the jetport would have destroyed the ecosystem in South Florida and Everglades National Park.