I'm afraid I only recall the closing paragraphs of this story. I'm hoping they are distinctive enough that the story can be identified.
The story closes with the Earth now having been abandoned far in the future. I think this conclusion takes places many centuries after the bulk of the story. As in "this is where events led to in the distant future."
Anyway, what I remember most is a passage about the seas lapping against the shores of an empty eastern U.S. seaboard. The seas are crimson with a bacteria that flourishes in what I believe is an climate/ecosphere dramatically different from present day Earth. There is a line about there being no 4th of July celebrations in what was America, and another about no May Day parades in the Soviet Union's Red Square. I distinctly remember a phrase along the lines of "bacteria just don't care."
The story closes with a line or two about where Man is living now. (The story is upbeat, despite what the preceding paragraph might suggest). I think some people are living in other star systems, but I am not sure about that. I'm more certain that there is a line about the only people still living in our system is an orbiting L5-type colony.
If I had to guess, I'd say 1970s for time-frame. That would coincide with both the mention of the Soviet Union, and with the L5 Society being "a thing" in popular culture. I'm reasonably certain I read this in a sci-fi magazine of some sort. I've done a bit of Googling under L5 and O'Neill, but I haven't turned anything up as of yet.