Case study: The Honey Bee

Bees are an integral component of both agricultural and wild species pollination, widely acknowledged as being economically indispensable. It has been estimated (vanEngelsdorp et al. 2008) that up to a third of the food we consume is pollinated by bees.

Increasingly, however, honeybee populations have been declining, leading to a pollination crisis, in which reductions in pollinators results in the loss of plant species (Ghazoul 2005), Klein et al. 2007).

Honey bees require a diverse community of flowering plants that bloom throughout the spring and summer. Climate change induced shifts in floral density and distribution can lead to alterations in species interactions. In particular, dry regions are predicted to become drier, which will deprive honeybees of necessary moisture, rendering them unable to cope. Yields of pollinator dependent crops have declined, perhaps due to expansion and simplification of agricultural areas on such a scale that numbers of bees simply cannot meet the demand placed upon them. Despite these negative anthropogenic effects, new research suggests that the introduction of new plant species, whose pollen is rich in protein, can be beneficial to bees.

Honeybee mortalities cannot be attributed purely to common diseases and pests, such as the mite Varroa destructor (Sammataro et al. 2000). A recent paper points out that Apis mellifera, the Western honeybee, is under increasing threat from anthropogenically induced habitat fragmentation. In addition to this, the introduction of non-native species, such as the Italian Bee Apis mellifera carnica, and the aggressive African honeybee Apis mellifera scutellata, has resulted in reductions in A. mellifera populations (Ghazoul 2005).

CCD, Colony Collapse Disorder, has been blamed for widespread reductions in honeybee numbers. The disorder is characterised by fewer adult bees within hives, accompanied often by disease pathogens (Olroyd 2007). This phenomenon is not yet fully understood, but it is thought to be multifactoral, a combination of attack from viruses and fungi, depleted immunity, and the narrow genetic base of colonies (Ghazoul 2005). Colony loss is so severe that in the USA, colony numbers have fallen from 5.9 million in 1947 to 2.44 million in 2008.

Colony Collapse Disorder is explained in this clip:

For beekeepers, colony loss is upsetting. But from a large-scale environmental perspective, the repercussions of permanently losing these industrious creatures could be devastating. Indeed the reproductive decline of wild plants has been attributed to pollination failure (Ghazoul 2005).

Le Conte (2008) notes that although A. mellifera has shown remarkable resilience to past changes in climate, there is doubt as to whether it will be able to adapt to the level of environmental change that Earth is currently undergoing.


References

Ghazoul J. (2005) ‘Buzziness as usual? Questioning the global pollination crisis’, Trends in Ecology and Evolution, 20, 7, 367-373.

Klein A.-M., Vassiere B.E., Cane J.H., Steffan-Dewenter I., Cunningham S.A., Kremen C. and Tscharntke T. (2007) ‘Importance of pollinators in changing landscapes for world crops’, Proceedings of The Royal Society Biological Science, 274, 303-313.

Le Conte Y. and Navajas M. (2008) ‘Climate change: impact on honey bee populations and diseases’, Revue Scientifique et Technique Office, 27, 2, 499-510.

Levy S. (2011) ‘The Pollinator Crisis: What’s best for bees’, Nature, 479, 164-165.

Olroyd B. (2007) ‘What’s killing American Honey Bees’, Public Library of Science Biology, 5, 6, 1195-1199.

Ratnieks F.L.W. and Carreck N.L. (2010) ‘Clarity on honey bee collapse’, Science, 327, 152-153.

Sammataro D., Gerson U. and Needham G. (2000) ‘Parasitic Mites of Honey Bees: Life, History, Implications, and Impact’, Annual Review of Entomology, 45, 519-548.

Soland-Reckeweg G.S., Heckel G, Neumann P, Fluri P and Excoffier L. (2009) ‘Gene flow in admixed populations and implications for the conservation of the Western honeybee, Apis mellifera’, Journal of Insect Conservation, 13, 317-328.

vanEngelsdorp D., Hayes J., Underwood R.M. and Pettis J. (2008) ‘A survey of honey bee colony losses in the US, Fall 2007 to Spring 2008’, Public Library of Science, 3, 12, 1-6.