Monday 26 September 2016

Heat turning up on bumbles

Published 19/07/2015 | 02:30

bumble bee
bumble bee

The life of that happy gardener, the poor old bumble bee (bombus hortorum), continues its fitful journey from parasites, pesticides and habitat loss to global warming.

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Last week, a scientific study reported that climate change was squeezing the insect's range across northern Europe and North America. But, instead of moving to more temperate climes, the bumbles appear to be stubbornly hanging on in increasingly difficult conditions in their old territories.

The bees are being killed off by increasing heat compressing them to a parched existence but, unlike butterflies and other insects, they are not moving with the shifting sands of change. It all appears to be a mystery so far. Science has not come up any answers.

A report says researchers are surprised and even shocked by the stalling bees.

They have every reason to be worried because of the vital work of these insects as plant and crop pollinators and their position as a keystone species in agriculture.

Bumble bees evolved under a cool climate, unlike butterflies which have tropical ancestors. And they are relatively intolerant of heat - extreme temperatures of 43°C will kill them outright while prolonged heat can dry up food sources. The study, in the journal Science, examined records going back more than a century and included 400,000 observations of 67 European and North American species.

Old gardens are the real countryside for bees and, in walking through, they may be observed going about their busy lives. Just what would we do without bees? They are close to all our hearts, says the naturalist Roger Deakin. And much more.

When the sun is out they are pollen-gathering endlessly, honey workers from wild nests and, here and there, a humble bumble trundles about.

Kitted out like an exotic footballer in, usually, bands of black, yellow and white, the regal lady can dive into a bell of foxgloves or burrow beneath the silken fold of rose petals. Earlier you may have seen her searching for nest sites to begin a new colony. When a brood of workers emerges she will feed them until they start to find food for her.

She is a rare creature and struggles on in the face of adversity. Eighteen species have disappeared because of disease and pesticides, habitat damage and food scarcity such as the reduction of forage crops like red clover. This huge decline in numbers may be traced to the harvest switch from hay meadows and their clover base to silage making more than 40 years ago.

Bumble bees do not store food and only mated queens survive the winter. They lead reclusive lives and are difficult to monitor but it is estimated that about 20 species remain in Ireland though many have moved westwards because of development.

Because of their vital role in horticulture, colonies are regularly imported, usually from Holland, by greenhouse businesses. But the poor bees seem to have had prophets of doom popping up in history. Darwin blamed mice for their setbacks about 200 years ago. He said if bees were lost so would red clover and, ergo, the cattle trade would go! His contemporary, T E Huxley, advocated fewer marriages in that unmarried maidens were fond of cats (that hunted mice) so more spinsters were needed to save the bees! Meanwhile, the bees are still suffering.

Sunday Independent

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