Another Life: The true cost of our year-round supermarket appetites

Michael Viney: Imported bumblebees are needed to pollinate but can spread disease to our native species

Wobbling down to the polytunnel to plant a few early tomatoes, I found it flooded with flowers.

In runaway growth through the winter, blossoming yellow nasturtiums now sprawl across a room-sized patch of soil. A thicket of herbal sage has trebled in growth, massing spires of purple blossom.

An old corner of wallflowers is now a bank of golden blooms, pressing around my old canvas chair. I eased into it, drugged by their scent and fussed over by visiting bumblebees.

The flowers had been planted for bees, years ago, attracting them to pollinate tomatoes, beans and peas. They had arrived in summer as lone voyagers, individually welcomed. Now they were here in busy dozens, perhaps scores. I sat delighted, as brightly striped Bombus terrestris fumbled at velvety wallflowers a nodding stem away.

These were wild bumblebees, free to come and go. But a vast international army of purpose-bred bumblebees spend short, slavish lives locked in polytunnels and greenhouses to pollinate supermarket crops. After eight weeks of duty, fruit swelling on the vines, their busy lives are ended and a new colony booked.

In commercial “domestication”, more than a million colonies of artificially bred bumblebees are exported around the world in a trade worth more than €55 million. Some 2,000 are imported into Ireland as more and more growers of tomatoes and strawberries buy colonies from the Netherlands.

Fruit orchards

The domestication of wild honey bees is ancient and their hives are used to pollinate fruit orchards and other crops. They are seekers after nectar, but tomato flowers offer only pollen. Bumblebees want pollen and buzz at different frequencies to release it from particular flowers, notably tomatoes. To pollinate the plants by hand would cost €10,000 an acre.

For crops such as strawberries, bumblebees pollinate the flowers more than twice as efficiently as honey bees. While the early import of colonies to Ireland was mainly to serve greenhouse tomatoes, almost two-thirds now pollinate polytunnel strawberries. The plants need up to five bumblebee visits for full pollination, but they boost the strawberry crop substantially and cut misshapen berries by half.

Two kinds of parasite have already been found in imported colonies in Ireland and the UK

A native bumblebee colony has up to 200 workers. At the end of the summer the workers and old queen die off and a new fertilised queen spends the winter in hibernation to start a fresh colony the following spring.

A commercial colony, with one queen and 50 to 70 workers (enough to pollinate 5,000 polytunnel strawberry plants) is locked in its box at the season’s end and left to die, with a recommended final spell in a freezer to ensure that they are all dead.

Artificial breeding

In Europe, where major private companies export from the Netherlands and Belgium, the bumblebee species chosen for artificial breeding is Bombus terrestris, the buff-tailed bumblebee, common throughout Europe and North Africa but with important native subspecies.

This is the bee whose big Irish queens are first abroad in spring. But the breeding stock for the colonies was not gathered from Irish buff-tailed queens and nor do its workers always settle for captivity. Escaping through gaps in glasshouses and at polytunnel doors, they can roam up to 10km, competing with native bumblebees and bringing new risks of disease.

In the 30 years of captive breeding, scientific concern has grown along with the industry. Studies in Canada and Japan have shown that imported bumblebees spread both disease and parasites to native bumblebees. Two kinds of parasite have already been found in imported colonies in Ireland and the UK.

In America, where commercial colonies of Bombus impatiens have been used to pollinate wild blueberries, scientists last year urged tighter federal controls. In Ireland, in 2009, a study for the Department of Agriculture warned that “unregulated importation [of commercial bumblebees] could pose a serious risk to our native species”.

This is also the concern of ecologists who run the All-Ireland Pollinator Plan. They have written extensive guidelines for users of commercial colonies, published by the National Biodiversity Data Centre.

Wild Irish species

Uncertainty about the origin of imported Bombus terrestris has made them fear for the genes of the wild Irish species, long adapted to this island’s flora, crops, landscape and climate. They acknowledge that Dutch companies have begun to produce colonies of a subspecies native to Britain and Ireland called Bombus terrestris audax. But so far, with a limited market, no national Irish producer has yet emerged to breed them.

So we work our way through the rest of the natural world, bending its useful species to our year-round supermarket appetites. Meanwhile, seated in my unintended bower of wallflowers, I shall enjoy wild Mayo bumblebees that come and go all on their own.