
Bee numbers have been declining since the late 1960s, studies show
Credit to: BBC News
By Mark Kinver
Science and environment reporter, BBC News
Gardens are able to sustain a greater number of bumblebee nests than farmed land, a study involving genetic analysis and modeling has suggested.
DNA samples were taken from two species by UK researchers in order to build up a picture of nest density and how land use affects the creatures.
Previous studies have shown that bumblebee numbers are declining in western Europe, Asia and North America.
The findings have been published in the Journal of Applied Ecology.
The team said that the importance of gardens tied in with the findings of earlier studies, which suggested the habitats provided a stronghold for the creatures “in an otherwise impoverished agricultural environment”.
They added: “Our data suggests that the positive influence of gardens on bumblebee populations can spill over at least 1km into surrounding farmland.”

Bee numbers have been declining since the late 1960s, studies show
Lead author Dave Goulson, head of the University of Stirling’s School of Biological and Environmental Science, explained the reason for the study: “If you are a conservation biologist, you want to know how many animals you have got left and whether they are increasing or decreasing.”
“Yet bumblebees are a bit odd because they are social insects, so you could go out into a meadow and count the number of bees you saw.
“But that would not really give you an idea on the population size because it could be that the bees you saw were worker bees, which where sterile, and would never have any offspring of their own.
“So what you need to do is to count nests, because within each nest is basically one single, female breeding bee – the queen. From a population biologist’s perspective, the population size is the number of nests.”
Professor Goulson explained that the nests were very hard to find: “You can walk through a meadow and not see any but you know they must be there.
“As a result, we have ended up with this rather elaborate way of counting the nest by catching the workers and DNA fingerprinting them, allowing you to work out which ones are sisters (all the workers from one nest are deemed sisters, as they are all offspring from the queen).
“Counting the sisterhoods gives you an idea of how many nests you have within the bee-flying range of where you are standing.”
Tongues and toes
The team gathered DNA information on two of the UK’s six most widespread species: the common carder bumblebee (Bombus pascuorum) and the red-tailed bumblebee (Bombus lapidarius).
“Bumblebees and other bees are the main pollinators of lots of wild flowers and quite a lot of our crops”
Quote Professor Dave Goulson University of Stirling
“One of the things that distinguish bumblebees are the length of their tongues and this determines what plants and crops they visit,” Professor Goulson told BBC News.
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