Many farmed and domesticated plants and animals have lost genetic diversity through the extinction of races and varieties. By 2016, 559 of the 6190 domesticated breeds of mammal were recorded as extinct (including 182 breeds of cattle, 160 of sheep and 108 of pig), as well as 84 of the 2632 domesticated breeds of bird (including 62 chicken breeds and 15 breeds of duck) (FAO Unedited draft chapters 31 May 2019 66 2016b). A further 1500 breeds (999 mammals and 501 birds) are currently threatened with extinction (FAO 2016b). These numbers are sure to be underestimates as the conservation status of 58% of breeds remains unknown (FAO 2016b). Modernization of agriculture has sharply reduced both the numbers of crop species and numbers of varieties of those species that are cultivated (Esquinas-Alcazar 2005).
Knowledge gaps: Global synthesis of patterns and trends in genetic composition is still at an early stage, with analyses so far having limited taxonomic or geographic coverage.