Decade	Number of Areas	Total Square Miles
Pre-1900	37	75,056
1900-1909	52	19,867
1910-1919	68	50,728
1920-1929	92	29,723
1930-1939	251	106,324
1940-1949	119	37,493
1950-1959	319	88,426
1960-1969	573	207,692
1970-1979	1,317	783,514
1980-1989	781	412,576

Source: World Resources Institute, 1989.

The table above shows how much land countries throughout the world have set aside each decade.  This part of the environment is protected from development, and allowed to remain in its natural state.

A very clear trend is to be seen over the decades.  People have become more environmentally conscious as time has passed, and governments have been increasingly under pressure to set aside parts of the environment.

The numbers from decade to decade have generally increased.  In the 1940s, when World War II took place, very little land was set aside.

The 1970s were a very important decade for environmental activists.  Earth Day was founded at the start of the decade, and led to a variety of government actions throughout the world.