Scientists predict that we are now entering into a period of great extinctions. Extinction rates are estimated to be between 40-400 times greater now than in the past. By the year 2000, at least 2/3 of the tropical rainforests may be gone, up to on million species may have become extinct.
Other estimates: P. Raven estimates 1-2 species per day are becoming extinct, and in next 20-30 years will approach 2000 species per year.
For U.S., about 10% of the flora is endangered and rare. 90 species became extinct between 1800-1950. 475 taxa will become extinct between 1950-1998. 5 times the number of extinctions in 1/3 the time.