Out of the approximately 11,154 known bird species, 159 (1.4%) have become extinct, 226 (2%) are critically endangered, 461 (4.1%) are endangered, 800 (7.2%) are vulnerable and 1018 (9.1%) are near threatened. There is a general consensus among scientists who study these trends that if human impact on the environment continues as it has one-third of all bird species and an even greater proportion of bird populations will be gone by the end of this century.