Let's look at the numbers:
http://www.washingtonpost.com/wp-srv/onpolitics/elections/2000/results/whitehouse/
In Florida, Ralph Nader actually did poorer than he did nationwide. Nationally, Nader garnered 2.68% of the vote, while in Florida, Nader earned only about half that many, 1.63%.
That hardly looks like a massive shift of environmental votes from Gore to Nader.
How about the second question, did Florida environmental voters stay home on election day?
Again, the answer is no. Voter turnout in Florida in 2000 was 70%, higher even than 67% recorded in the 1996 election (see http://election.dos.state.fl.us/online/voterpercent.shtml).
Furthermore, in 2000, 400 thousand more votes were cast for Al Gore than were cast for Bill Clinton's during his "Landslide" four years ealier (2,912,253 vs. 2,546,870).
Nope, environmentally minded voters did not stay home on election day 2000, and they did not cast their votes for Ralph Nader. The Everglades airport is a non-issue.