Why did Americans take an increased interest in the environment during the 1970's?

There are many possible reasons that could be cited for
this development.  Among them are:

• Environmental
  conditions had gotten progressively worse.  For example, the Cuyahoga River in
  Cleveland, Ohio actually caught fire in 1969.  The idea that a river could be so
  polluted as to catch fire was the sort of thing to make people take notice and become
  more interested in environmentalism.


• People were getting
  richer.  When people have more money, they can afford to be more interested in causes. 
  By the '70s, Americans were quite affluent and had the wherewithal to pay attention to
  things beyond their pocket books.


• The influence of the
  '60s.  During the '60s, there were many reform movements going on in the US.  People
  were trying to improve US society in various ways.  This spirit of change lived on into
  the '70s and, as the Vietnam War and the Civil Rights Movement waned, things like
  environmentalism took over.