What the Environment magazine have to say.

"3.85 billion years ago: earth life may have begun. Now it is being damaged by air pollutants, global warming, the greenhouse effect, and other dangers to the planet.
10,000 years ago: More than 15 billion acres of land are covered with forest. 1750–1850. 1960s: Dangers to the ozone layer from jet planes are investigated.1970: The Environmental Protection Agency (EPA) is formed by the U.S. government to enforce laws that protect the environment.1970 (April 22):
Earth has its first official birthday celebration in the U.S. More than 20 million people march in parades, sing songs, and attend teach-ins on the environment. 1973: The Endangered Species Act is passed to protect wildlife. Every year the names of 35 to 60 insects, plants, and animals are added to the list of species threatened with extinction. By 1998, there were about 1,200 threatened and endangered plants and animals on the list.The Safe Drinking Water Act outlaws pollutants (substances in water that make people sick) to ensure that people drink safe water.
1982:
A hole is discovered in the ozone layer over the Antarctic by a British scientist, Joe Farman.
1982:
The EPA creates a superfund, setting large amounts of money aside to clean up harmful waste sites across the U.S.
1988:
Scientists discover a second hole in the ozone layer, this time over the Arctic.
1990 (April 22):
Earth Day 2 is celebrated. This time 100 million people around the globe participate. The tradition of celebrating Earth Day every year on or around April 22 is begun.
1990s:
“The Decade of the Environment.” Congress passes stricter environmental laws; people are increasingly committed to protecting the environment; mandatory recycling begins in many cities and towns; cars must pass annual emissions tests to protect the air quality; people are more careful about how they use energy at home"said the Environment magazine.