April 1 — Wangari Maathai, Kenyan Conservationist, Born (1940)
April 2 — Maria Sibylla Merian, German Entomologist, Born (1647)
April 3 — Jane Goodall, Chimpanzee Researcher, Born (1934)
April 4 — “The Good Life” Begins Airing (1975)
April 5 — Civilian Conservation Corps (CCC) Created (1933)
April 6 — American Museum of Natural History Founded (1869)
April 8 — A Tribute to the Endangered Species Act
April 9 — Jim Fowler, “Wild Kingdom” Co-host, Born (1932)
April 10 — Arbor Day First Celebrated (1872)
April 11 — Ian Redmond, Primatologist, Born (1954)
April 12 — Arches National Monument Created (1929)
April 13 — First Elephant Arrives in U.S. (1796)
April 14 — Black Sunday Dust Storm (1935)
April 15 — Nikolaas Tinbergen, Animal Behaviorist, Born (1907)
April 16 — Ling-Ling and Hsing-Hsing Arrive in U.S. (1972)
April 17 — Ford Mustang Introduced (1964)
April 18 — Natural History Museum, London, Opened (1881)
April 19 — E. Lucy Braun, Plant Ecologist, Born (1889)
April 20 — Gro Harlem Brundtland, Godmother of Sustainable Development, Born (1939)
April 21 — John Muir, Father of American Conservation, Born (1838)
April 22 — The First Earth Day (1970)
April 24 — Tomitaro Makino, Father of Japanese Botany, Born (1862)
April 25 — Theodore Roosevelt National Park Established (1947)
April 26 — John James Audubon Born (1785)
April 27 — Soil Conservation Service Created (1935)
April 28 — Mexican Gray Wolf Listed as Endangered (1976)
April 28 — Chernobyl Nuclear Accident Announced (1986)
April 29 — Emmeline Moore, Pioneering Fisheries Scientist, Born (1872)