Colony collapse disorder

Colony collapse disorder (CCD) is an abnormal phenomenon that occurs when the majority of worker bees in a honey bee colony disappear, leaving behind a queen, plenty of food, and a few nurse bees to care for the remaining immature bees.^[1] While such disappearances have occurred sporadically throughout the history of apiculture, and have been known by various names (including disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease),^[2] the syndrome was renamed colony collapse disorder in early 2007^[3] in conjunction with a drastic rise in reports of disappearances of western honey bee (Apis mellifera) colonies in North America.^[4] Beekeepers in most European countries had observed a similar phenomenon since 1998, especially in Southern and Western Europe;^[5][6] the Northern Ireland Assembly received reports of a decline greater than 50%.^[7] The phenomenon became more global when it affected some Asian and African countries as well.^[8][9] From 1990 to 2021, the United Nation's FAO calculated that the worldwide number of honeybee colonies increased 47%, reaching 102 million.^[10]

Colony collapse disorder could cause significant economic losses because many agricultural crops worldwide depend on pollination by western honey bees. According to FAO, the total value of global crops pollinated by honey bees was estimated at nearly US$200 billion in 2005.^[11] In the United States, shortages of bees have increased the cost to farmers renting them for pollination services by up to 20%.^[12] Declining numbers of bees predate CCD by several decades, however: the US managed hive industry has been shrinking at a steady pace since 1961.^[13]

In contrast, the bee population worldwide has been increasing steadily since 1975, based on honey production, with China responsible for most of the growth.^[14] The period with the lowest growth in worldwide honey production was between 1991 and 1999, due to the economic collapse after the dissolution of communism in the former Soviet sphere of influence.^[13] As of 2020^[update], the production has increased further by 50% compared to 2000, double the rate of growth in previous decades, notwithstanding CCD.^[15] Experts estimate that there are currently more honey bees alive worldwide than at any other point in human history.^[16]

Several possible causes for CCD have been proposed, but no single proposal has gained widespread acceptance among the scientific community. Suggested causes include pesticides,^[17] infections with various pathogens (especially those transmitted by Varroa and Acarapis mites), malnutrition, genetic factors, immunodeficiencies, loss of habitat, or changing beekeeping practices; combinations of these factors have also been cited.^[18][19] A large amount of speculation has surrounded the contributions of the neonicotinoid family of pesticides to CCD, but many collapsing apiaries show no trace of these chemicals.^[19]