1900,The Galveston Hurricane of 1900 hits Galveston - Texas and reverses the citys previously rapid growth.
1902,George Washington Carver writes How to Build Up Worn Out Soils.
1903,March 14 - US President Theodore Roosevelt creates first National Bird Preserve - (the beginning of the Wildlife Refuge system) - on Pelican Island - Florida.
1905,The term smog is coined by Henry Antoine Des Voeux in a London meeting to express concern over air pollution.
1906,Antiquities Act - passed by US Congress which authorized the president to set aside national monument sites.
1908,Muir Woods National Monument was established on January 9 and now governed by the National Park Service.
1909,US President Theodore Roosevelt convenes the North American Conservation Conference - held in Washington - D.C. and attended by representatives of Canada - Newfoundland - Mexico - and the United States.
1913,US Congress enacts law which destroyed the Hetch Hetchy Valley.
1916,US Congress created the National Park Service.
1918,The Save-the-Redwoods League is founded to the protect the remaining Coast Redwood trees. Over 60% of the redwoods in Californias state redwood parks have been protected by the organization.
1921,Thomas Midgley discovers lead components to be an efficient antiknock agent in gasoline engines. In spite of the well known toxic effects - lead was in ubiquitous use. First banned from use in Japan 1986.[5]
1927,Great Mississippi Flood.
1928,Thomas Midgley develops chlorofluorocarbons (CFCs) as a non-toxic refrigerant. The first warnings of damage to stratospheric ozone were published by Molina and Rowland 1974. They shared the 1995 Nobel Prize for Chemistry for their work. Since 1987 world production is reduced under the Montreal Protocol and banned in most countries.
1929,the Swann Chemical Company develops polychlorinated biphenyls (PCBs) for transformer coolant use. Research in the 1960s revealed PCBs to be potent carcinogens. Banned from production in the US 1976 - probably 1 million tonnes of PCBs were manufactured in total globally.
1930,World human population reached 2 billion[3].
1932 to 1937,Exceptional precipitation absence in northern hemisphere exacerbated by human activities causes the Dust Bowl drought of the US plains and the Soviet famine of 1932-1933 (harsh economic damage in US and widespread death in USSR)
1933,First legislation on Animal rights adopted - Germany[6].
1934,Fish and Wildlife Coordination Act.
1935,Soil Conservation and Domestic Allotment Act.
1939,The insecticidal properties of DDT discovered by Paul Hermann Müller - who was awarded the 1948 Nobel Prize in Physiology and Medicine for his efforts. The first ban on its use came in 1970.
1944,Flood Control Act of 1944 was signed by President Franklin D. Roosevelt on December 22.
1945,Atomic bombings of Hiroshima and Nagasaki. First use of atomic weapons during war.
1947,Federal Insecticide - Fungicide - and Rodenticide Act (FIFRA)
1948,World Conservation Union or International Union for Conservation of Nature and Natural Resources (IUCN) is an international organization dedicated to natural resource conservation. Founded in 1948 - its headquarters is located in Gland - Switzerland.
1949,First known dioxin exposure incident - in a Nitro - West Virginia herbicide production plant. Extensively used during the Vietnam War 1961-1971 as Agent Orange. Production ban in the US on some component from 1970.
1951,The Nature Conservancy is an environmental organization founded in the United States.
1954,The first nuclear power plant to generate electricity for a power grid started operations at Obninsk - Soviet union on 27 June. The first substantial accident happened on 10 October 1957 in Windscale - England.
1956,Minamata disease - a neurological syndrome caused by severe mercury poisoning.
1958,Mauna Loa Observatory initiates monitoring of atmospheric Carbon Dioxide (CO2) levels. The time series eventually became the main reference on global atmospheric change.
1960,World human population reached 3 billion[3].
1961,World Wildlife Fund (WWF) registered as a charitable trust in Morges - Switzerland - an international organization for the conservation - research and restoration of the natural environment.
1962,Rachel Carson publishes Silent Spring.
1964,Norman Borlaug takes position as the director of the International Wheat Improvement Program in Texcoco - Mexico. The program leads to the green revolution.
1965,Hurricane Betsy flooded large areas of New Orleans (USA) drowning around 40 people.
1966,National Wildlife Refuge System Act.
1968,The Apollo 8 picture of earthrise.
1969,National Environmental Policy Act including the first requirements on Environmental impact assessment.
1970,Earth Day  - April 22. - millions of people gather in the United States for the first Earth day organized by Gaylord Nelson - former senator of Wisconsin - and Denis Hayes - Harvard graduate student.
1971,The international environmental organisation Greenpeace founded in Vancouver - Canada. Greenpeace has later developed national and regional offices in 41 countries worldwide.
1972,The Conference on the Human Environment - held in Stockholm - Sweden 5 to 16 June - the first of a series of world environmental conferences.
1973,OPEC announces oil embargo against United States.
1974,Chlorofluorocarbons are first hypothesized to cause ozone thinning.
1975,Energy Policy and Conservation Act.
1976,Dioxin accidental release in Seveso - Italy on 10 July - killing animals and traumatizing the population.
1977,Surface Mining Control and Reclamation Act.
1978,Brominated flame-retardants replaces PCBs as the major chemical flame retardant. Swedish scientists noticed these substances to be accumulating in human breast milk 1998. First ban on use in the EU 2004.
1979,The Convention on Long-Range Transboundary Air Pollution is established to reduce air pollutant emissions and acid rain.
1980,Mount St. Helens erupts explosively in Washington state.
1982,Coastal Barrier Resources Act.
1984,Bhopal disaster in the Indian state of Madhya Pradesh (Methyl isocyanate leakage).
1986,Chernobyl - worlds worst nuclear power accident occurs at a plant in Ukraine.
1987,World human population reached 5 billion[3].
1988,Ocean Dumping Ban Act.
1989,Exxon Valdez creates largest oil spill in US history.
1990,National Environmental Education Act.
1991,The Protocol on Environmental Protection to the Antarctic Treaty was signed 4 October. The agreement provides for the protection of the Antarctic environment through five specific annexes on marine pollution - fauna - and flora - environmental impact assessments - waste management - and protected areas. It prohibits all activities relating to mineral resources except scientific.
1992,The Earth Summit - held in Rio de Janeiro from June 3 to June 14 - was unprecedented for a United Nations conference - in terms of both its size and the scope of its concerns.
1993,The Great Flood of 1993 was one of the most destructive floods in United States history involving the Missouri and Mississippi river valleys.
1994,United Nations Convention to Combat Desertification.
1995,Scotlands Environmental Protection Agency is established.
1996,Western Shield - a wildlife conservation project is started in Western Australia - and through successful work has taken several species off of the state - national - and international (IUCN) Endangered Species Lists..
1997,July - U.S. Senate unanimously passed by a 95–0 vote the Byrd-Hagel Resolution - which stated that the United States should not be a signatory to any protocol that did not include binding targets and timetables for developing as well as industrialized nations.
1999,World human population reached 6 billion[3].
2001,U.S. rejects the Kyoto Protocol.
2002,Earth Summit - held in Johannesburg a United Nations conference.
2003,The worlds largest reservoir - the Three Gorges Dam begins filling 1 June.
2004,Earthquake causes large tsunamis in the Indian Ocean - killing nearly a quarter of a million people.
2005,Hurricanes Katrina - Rita - and Wilma cause widespread destruction and environmental harm to coastal communities in the US Gulf Coast region.
2006,Former U.S. vice president Al Gore releases An Inconvenient Truth - a documentary that describes global warming. The next year - Gore is awarded the Nobel Peace Prize (jointly with the Intergovernmental Panel for Climate Change) for this and related efforts.
2007,The IPCC release the IPCC Fourth Assessment Report.
2009,Power Shift 2009  - The Energy Action Coalition hosted the second national youth climate conference to be held at the Washington Convention Center from February 27 to March 2 - 2009. The conference aims to attract more than 10000 students and young people and will include a Lobby Day.