The main environmental issue at the first Earth Day was pollution. Climate change was then theoretical and not at the forefront. Air and water pollution were terrible in most major cities of US and Europe. They made good progress by the end of the century.
From my faint memory as a ~12 year old in 1980, Acid Rain killing off woodlands and lakes, caused by European and UK heavy industries, was a massive concern back in the early 80's at its peak, fortunately mostly rectified in Europe now. Shortly afterwards the media latched onto the hole in the ozone layer which lead onto the climate crisis. Hard to believe these things were 30+ years ago (when I became aware), but we seem to be no further forward.
