The Doctor wasn't wrong to be worried about bees. Daleks and Cybermen aren't half as scary as the thought of how planet Earth would function without the crop-pollinating insects and the billions they add to worldwide agriculture every year.
But even with everyone's favourite Time Lord on the case, the world's declining bee population is a problem that won't go away. And according to a new study, it could all be down to mankind's penchant for covering almost every inch of farmland with chemicals.
A new study, published online yesterday in the Nature Communications journal, links the long-term decline of bee populations in England with oilseed rape crops that use the neonicotinoid pesticide—a pest-killer applied to seeds prior to planting that gets transported to all tissues of the crop.
While beekeepers have long derided such chemicals and previous studies show links between large-scale pesticide use and bee deaths, the study is the first to find an association between neonicotinoid pesticides on oilseed rape and long-term bee population decline.
Carried out by researchers at the Centre for Ecology and Hydrology (CEH), the study looked at data gathered on 62 different species of bees in England between 1994 and 2011.
It found that on average, population decreases were three times as severe for the bee species that foraged on rapeseed, compared to those that didn't. Some species declined by as much as 30 percent.
Overall, said the researchers, half of the total decline in England's wild bee populations could be associated with the neonicotinoid pesticide.
Study co-author Richard Pywell told New Scientist: "This correlative study has provided the first evidence of negative impacts of neonicotinoid use over the long term and at the national scale for many species of wild bee not previously studied."
Neonicotinoid pesticides were introduced in the UK in 2002 and around 85 percent of the oilseed rape in England now uses them. The European Commission voted to restrict use of the pesticides in 2013 and the European Food Safety Authority is currently carrying out a review of scientific evidence surrounding them, with the new CEH study expected to be included.
Study co-author Nick Isaac told the BBC: "The negative effects that have been reported previously do scale up to long-term, large-scale multi-species impacts that are harmful. Neonicotinoids are harmful, we can be very confident about that and our mean correlation is three times more negative for foragers than for non-foragers."
The CEH researchers also noted, however, that their findings show an association between the use of "neonics" and decline of wild bee populations, not a direct cause and effect link. They added that other factors such as climate change, habitat, and disease should also be noted for their impact on bee populations.
Co-author Ben Woodcock said: "It's not a simple case that pesticides are causing declines. It's likely that there's a whole series of interacting factors and while people like a one-shot solution, it's probably not the case in most situations."
The plight of the bumblebee continues.