Bees are just one of many pollinators that provide an important role in influencing genetic variation in plant communities and ecosystem health. In agriculture, honeybees contribute to the pollination of crops, from nuts to vegetables including apples, sunflowers and alfalfa to name a few. Pollination by honeybees produces three quarters of the world's leading food crops. The extent of pollination determines the maximum number of fruits which means that many fruit and nut crops rely heavily on pollination. Since the 19th century bee colonies have declined but today the collapse of bee colonies has become a global crisis. With the decrease of wild bees used for crop pollination, a pollination market emerged for farmers to hire honeybees to pollinate their fields. The growth and demand of this market has placed considerable strain on the health and population of bees.
While supporting inputs post-pollination such as pesticides, water or fertilisers are designed to lead to better quality crops, a 2011 U.N. Report claims that common pesticides may be interfering with the bees homing instincts. The report considers pesticides as one of the biggest drivers for the decline of bee populations around the world alongside habitat deterioration, air pollution, disease and parasites. Reduced bee pollination has serious implications for ensuring the diversity of thousands of flowering plant species and is a risk for food security.
Though the pesticides don't directly kill the bees they have other disastrous impacts. The ability for bees to pollinate are affected in two ways. The first is the loss of homing and foraging instincts, as well as an impairment for communication, flight ability and a healthy immune system by blocking specific neural pathways of the central nervous system. After the death of one third of French honeybees researchers Henry et al. (2012) found that neonicotinoid pesticides impaired the honeybee’s neural capacity, even at very low doses, and the exposed foraging bees were unable to find their way back to their hives. The second is a reduction of queens per colony in pesticide affected colonies. Research by Whitehorn et al. (2012) recorded a loss of 85% queens from neonicotinoid pesticide affected colonies compared to non-pesticide affected colonies. Responsible for the sole reproduction of a colony, and thus its survival, the queen bee is the most important member of the colony. Without the queen the colony collapses.
Imidacloprid is a neonicotinoid that is one of the world's best selling pesticide, and is one of the causes identified affecting honeybees. It is now one of three neonicotinoid pesticides, the others are clothianidin and thiamethoxam, that will face a 2 year suspension ban across the European Union from July 1, 2013. The decision was made following a publication by the European Food and Safety Authority determining the risks to bees by the three neonicotinoid pesticides. Despite the level of uncertainty of the evaluations due to data gaps, the European Commission has decided to apply the precautionary principle by not continuing its use on crops attractive to bees, including sunflower, rapeseed, corn and cotton without further information.
The studies on the effects of neonicotinoid pesticides on bee colonies show a clear link in the field with large-scale bee declines. This makes bee conservation critical. One of the best options includes changing the mix of pesticides applied to pollinated crops or trying to find non-chemical alternatives. The timing of chemical use can be changed to be applied in the late evening when bees are inactive so that the chemical has a chance to degrade. Another strategy is to protect existing wild habitats and remnants or creating new ones intermingled with agricultural land, leaving these as well as roadside verges and woodland edges unsprayed and undisturbed. The 2 year ban in the E.U with provide an opportunity for researchers to study the affects that the removal of the three neonicotinoids will have on bee colonies.
References:
1. Whitehorn. P.R, O'Connor. S, Wackers. F.L and Goulson. D. Neonicotinoid Pesticide Reduces Bumble Bee Colony Growth and Queen Production. Science 20 April 2012: 336 (6079), 351-352.Published online 29 March 2012 [DOI:10.1126/science.1215025]
2. Henry. M, Béguin. M, Requier. F, Rollin. O, Odoux. J, Aupinel. P, Aptel. J, Tchamitchian. S and Decourtye. A. A Common Pesticide Decreases Foraging Success and Survival in Honey Bees. Science 20 April 2012: 336 (6079), 348-350. Published online 29 March 2012 [DOI:10.1126/science.1215039]
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