In the 1980 ’ s, after scientists in Germany studied the effects of air pollution and acid rain on the environment, they concluded: ‘ If nothing is done, about the year 2000, people will be left to admire forests only in old photos and in movies. ’
چندین دهه است که طرفداران حفظ محیط‌زیست هشدار می‌دهند که لازم است از اکوسیستم حفاظت شود .‏