The environmental movement By Isaiah Dooley Period: 1804 to 1927 1 Billion reached Period: 1927 to 1959 2 billion reached Period: 1960 to 1973 3 billion reached Period: 1974 to 1986 4 billion reached Period: 1987 to 1998 5 billion reached Period: 2011 to 2022 7 billion reached Period: 2023 to 2025 8 billion reached