It would be quite difficult to follow a bee on foot for more than a few metres. Up, down, a quick buzz into the hedgerow, out the other side – hmm, same bee? It's hard to be sure. A quick wriggle down inside a flower to suck a bit of nectar, then it's off again across the farmland.
Unsurprisingly, this was not the method used when researchers at the University of Northampton tried to understand how bees find their way around the countryside in search of nectar-rich flowering plants. Some species of bumblebee can travel up to 3km a day, and, although larger insects can be fitted with tracking devices, these only work in open fields.
"We know that bees and other pollinating insects use hedgerows as places to feed," says Dr Jeff Ollerton, who heads Northampton University's Landscape and Biodiversity Research Group. "But we're also interested in the way these pollinators move around the landscape. We wanted to understand the relationship between bee and butterfly movements and the hedgerows we often see them near to."
The concerns prompting this research, recently published in the ecological journal Oikos, have serious economic and social consequences. About a third of crop plants worldwide are pollinated by insects. When it comes to UK flowering plants, around 80% are reliant on animal pollination. Flowering plants might sound less important than crops, but they aren't.
Ollerton explains that some scientists and campaigners now suggest that the environment should be seen through the prism of "ecosystem services" – a way of looking at nature in terms of its economic and social value. "Without flowering plants we're in a very difficult position," he warns. "If we didn't have wild flowering plants in rivers, for instance, they'd become faster flowing, flooding would occur more frequently and water quality would decrease."
Insect pollinators not only shape our physical environment by transporting DNA in pollen between plants, enabling them to cross-fertilise, they also save us an awful lot of money.
In 2010, Natural England estimated that crop pollination alone was worth £430m a year to the UK economy. That's apples, pears, strawberries, plums and tomatoes, among scores of other foodstuffs that wouldn't exist in such quantities were it not for the efforts of insect pollinators.
"What that figure doesn't take into account is what it would cost to pay someone to do this by hand if the insects didn't do it," observes Ollerton.
This isn't as absurd an idea as it might seem. "In China, that's what they do in some apple orchards, because they've lost their pollinating insects due to habitat decline," he says.
So, fewer bees and butterflies equals less pollination equals a heap of trouble and expense for humans. With 23 bee species out of 260 having become extinct in the UK since 1800, and serious declines in other bee species in the postwar period, finding out how to keep the remaining ones healthy should be a rural policy priority, says Ollerton.
But with more than 90% of the country's flowering meadows gone because of intensive agriculture, what's left is just fragments of land offering the occasional oasis of nectar. Getting bees, and the pollen they carry, from one fragment to the next – which may be hundreds of metres away – is a problem. And this is where hedgerows come in.
It's well known that hedgerows are used as corridors by birds and mammals. What Ollerton, his colleague Dr Duncan McCollin, and their PhD student Louise Cranmer discovered by close observation of their subjects' flying patterns was that the nearer bees and butterflies got to hedgerows, the straighter they flew alongside them.
"The technique is to find your hedgerow, take a line out at 90 degrees and set up observation stations every 10 metres," explains Ollerton. "What we saw was that as they get closer, their flight behaviour becomes increasingly more parallel. It's not foraging flight, darting from one flower to another, but flight that follows the line of the hedge."
Ollerton and Cranmer also found that plants did better at reproducing when they were located at a point where several hedgerows converge. "This is because greater numbers of bumblebees are being channelled towards these patches of plants," explains Ollerton.
Just in case it was something other than the hedgerow that caused their insects to fly more directly between food sources, the researchers set up a control experiment of imitation hedgerows made from black fabric draped over wooden poles. This created an artificial physical connection between one patch of nectar-rich plants and another.
Far more bees still opted to use this artificial guide to find their way to their next meal than the nearby alternative; an empty space between two other patches of equally delicious bee-food.
Having proved that hedgerows do indeed lead bees and butterflies directly from one nectar-rich area to another, Ollerton says their findings could guide the way the UK's highly managed landscapes are planned in the future.
"We've only got small fragments of flower-rich land and, realistically, it's not going to be restored to the way it was, so bigger expanses of this habitat aren't going to happen," he explains. "But what you can do is make the decision to manage land in a way that connects these fragments up. Strategic planting of hedgerows could be one approach."