Look at these sites for a quote you may want to use.

http://www.quotegarden.com/earth-day.html

http://www.stresslesscountry.com/earth-day-quotes/

http://www.takepart.com/blog/2008/04/21/top-ten-quotes-for-earth-day-2008/

http://www.epa.gov/Region2/library/quotes.htm

http://www.altiusdirectory.com/Society/earth-day-2009.html

http://www.greenlivingonline.com/article/earth-day-quotes

http://www.imdb.com/title/tt0043456/quotes

http://www.theholidayspot.com/earth_day/earth_day_quotes.htm