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Challenges to bees … and humans

In recent years, bee numbers have declined steeply. Around a third of the bee population was lost in the US in 2007–2008. The number of bees in the UK has halved from the 1960s to 2012. Large losses have been reported in Egypt, China and Japan.

This is alarming because a third of our food comes from crops that rely mainly on bees to pollinate them. A lack of bees not only makes harvests small, unreliable and late, but wildflowers dwindle because there are so few seeds, and there is less honey for bees – and humans – to eat.

The death of the queen bee is associated with one in four colony losses, while 'colony-collapse disorder' in which a whole bee colony goes missing, presumed dead, accounts for about 7 per cent of losses in the US, rather fewer in Europe.

The subject of colony collapse is much debated and theories abound as to the cause. One suggestion is that lead-containing crystals in bees' abdomens sensitize them to the growing number of electromagnetic fields surrounding us, influencing their behaviour and encouraging disease. Another is that infestation with Varroa destructor mites, or infection with viruses, fungi or bacteria, makes bees more vulnerable to disease. Yet another is that vehicle-exhaust fumes react with airborne scent molecules from flowers, making them confusing and unattractive to bees.

But the three most important reasons for the declining number of bees seem to be malnutrition, insecticides and stress. Because these are so important for the future of worldwide honey production, we'll look at each in detail.

Bee malnutrition

A main cause is shrinkage of wildflower habitats reducing the volume and variety of nectars and pollens. In the UK, for example, wildflower populations have fallen by 95 per cent since the destruction of hedgerows accompanying the need for food production after World War 2. Weedkillers and single-crop farming are also to blame. Worryingly, one in five species of wildflower risks extinction.

The other main cause is the poor nutritional quality of food substitutes such as sugar syrup given to bees if honey stores are low or beekeepers have harvested too much. Malnourished bees are more vulnerable to insecticides, infections and parasites.

A colony needs only 9–14kg/20–30lb of honey to survive the average winter, but can store much more given enough space and successful foraging. In an average year, the average colony in a UK Modified National Hive produces a surplus of 10–14kg/22–30lb. In a good season, a strong colony can produce an extra 18–27kg/40–60lb. And some colonies produce an extra 36–45kg /80–100lb or more. One Australian beekeeper took 285kg/629lb per hive when the flow of eucalyptus nectar was particularly good.

Good beekeepers remove only the honey likely to be surplus to the bees' needs. Others take as much as possible and give the bees substitute food. The best substitutes contain protein, carbohydrate, fat, vitamins and minerals. But even these are limited in their range and quality of nutrients and other phytochemicals compared with pollen and honey. The poorest substitute, sugar syrup, provides vastly less nourishment.

However, it must be said that if bees can't make enough honey for their needs, or if honey sets so firmly in the comb that they can't eat it, substitute food given by beekeepers can save their lives.

Exposure of bees to insecticides

At worst, certain insecticides used on farms, gardens, recreational areas, parks, forests, marshes, swamps and hives kill bees outright. Repeated low doses weaken their resistance to infection.

Stress on bees

Bees can become stressed by poorly designed hives, overly frequent inspections and lengthy travel when migratory beekeepers take them to pollinate and produce honey from far-away crops.

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