[ Recent work has reaffirmed the importance of honey bees to adequate pollination of blueberries in large fields and at the same time emphasizes that small fields adjacent to forests are mainly pollinated by native bees. ]
> We determined the relative importance of wild bees and managed honey bees Apis mellifera L. for crop pollination in the blueberry Vaccinium corymbosum L. system of Michigan, USA, by comparing bee communities in small, isolated blueberry fields with those in large blueberry fields (stocked with managed honey bee hives)
> Wild bees were the dominant pollinators in small fields, comprising 58% of flower-visiting bees, whereas 97% of bees in large fields were honey bees. We estimate that wild bees provide 82% of the pollination in small fields but only 12% of the total pollination services across this system, mostly through their secondary role in large fields.
> Wild bees are the primary pollinators of small blueberry fields, but these insects are at low abundance in large fields, perhaps due to a lack of nesting resources or competition for resources with honey bees. Our findings highlight the dependence of commercial fruit producers on honey bees.
Pollination services provided to small and large highbush blueberry fields by wild and managed bees
Rufus Isaacs and Anna K. Kirk, Department of Entomology, Michigan State University, East Lansing, MI 48824, USA
[ What is interesting about this question is that it provides an opportunity to look at how the domestication of a landscape affects the native pollinator population, and how by destroying habitat, we create the need for domesticated pollinators as well. I am not saying that the preservation of hedgerows and their pollinator communities would offset the cost of bringing pollinators into a mono-cropped environment. However, it might, and there are other considerations as well, such as the protection of the native species. Running smaller field plots enhances their value to agriculture, which is seen as marginal at present. To enhance their usefulness would provide the double benefit of 1) alternatives to honey bees and 2) restoration of the abundance of natives. So far as I know, there is no evidence that natives could ever replace honey bees but they can work in concert with them and offset some of the weaknesses of a honey bee only pollination scheme. ]
> Resource availability is often a critical factor in determining the distribution and abundance of species, and it is recognised that reductions in habitat quality as well as quantity are likely to cause population declines. Many social bumblebee (Bombus Latr.) species have undergone serious declines in recent decades across Europe and North America.
> Several factors have been suggested as possible contributors to these declines, including competition from the honeybee (Apis mellifera), changes in climate and the effects of predators and parasites. However, the principal factor is likely to have been the loss and degradation of habitats and critical food resources due to changes in land-use and agricultural practices.
> An opportunity now exists to use knowledge from this and other studies to inform targeted habitat restoration, to reintroduce important forage plants to the farmed landscape through agri-environment schemes. Sympathetic management of vegetation along hedgerows and woodland edges should also encourage plants such as Ajuga reptans and Lamium album to provide spring forage. [ * Note: this recommendation refers to UK, equivalent plants exist in N. American ecosystems ]
Declines in forage availability for bumblebees at a national scale
Claire Carvella, et al. NERC Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire PE28 2LS, UK
***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html
Guidelines for posting to BEE-L can be found at:
http://honeybeeworld.com/bee-l/guidelines.htm
|
