One of the problems has been that it’s tricky to pinpoint exactly what is harming bees. But understanding how bees operate gives us clues to what’s going wrong.
The life of a bee is an industrious one. It takes a huge amount of energy, and brain power, to collect pollen and nectar. Bees need to navigate huge distances, remembering sources of food and how to get back home again. Bees’ brains might be tiny but they can interpret different kinds of landscapes, flower species, shapes and patterns. Bees have been shown to be able to work out the shortest distances between objects, display both long- and short-term memory, communicate symbolically and demonstrate spatial awareness. Anything that interferes with these cognitive abilities has a devastating impact on bees. If a bee can’t forage properly, find its way home or taste properly, it’ll die. Equally, if its digestion is impaired or immunity compromised, a bee becomes more susceptible to illness. And this is the issue. A number of things we do, in the modern world, are interfering with bees’ ability to function properly. No single thing is killing them off – it’s more that a range of what are called sub-lethal stressors are weakening bees and affecting their behaviour.
Here are just a few of the things bees have to contend with:
HABITAT LOSS
Just like us, bees need a varied diet to thrive. No single pollen source contains all the vitamins, proteins and other goodies necessary for nutrition. Intensive monoculture agriculture, where one type of crop is grown on a large scale, reduces plant diversity. This, combined with a loss in natural habitat from increasing urbanisation, places nutritional stress on bees, who have to cope with a decrease in the quality and quantity of nectar and pollen available. Starvation leads to bee losses and poor colony health. The loss of uncultivated, natural habitat also creates issues for wild bees, who need places to nest and reproduce.
PESTICIDES/HERBICIDES
A number of widely used chemicals are making life difficult for bees. Neonicotinoids (which are sprayed onto crops such as wheat and barley to kill pests such as aphids) have been shown to cause a wide range of problems for bees, impacting their ability to navigate and reproduce. The European Union recently banned neonicotinoids for outdoor use in agriculture. Meanwhile, in the United States, the EPA banned 12 neonicotinoid pesticides in 2019, although some neonicotinoids still remain on the market. Nutritional stress has been shown to exacerbate the negative effect of neonicotinoids in bees. Similarly, a common weedkiller – glyphosate – in high doses seems to disrupt bees’ digestive systems, making them more vulnerable to infection. It’s a complicated issue – farmers are being asked to produce greater quantities of food, at ever cheaper prices, and scientific studies about which chemicals cause harm frequently contradict each other or bring up new evidence, with farmers often playing catch-up. Take chlorothalonil, for example, a fungicide that has been widely used since the mid-1960s. Farmers have been using this on barley, wheat and other crops for years, but it was only in 2017 that research finally discovered a link between chlorothalonil and bumblebee declines. The EU recently voted to ban it but it makes one wonder how many other pesticides and agricultural chemicals are unwittingly harming bees.
LIGHT POLLUTION
Street lights can throw the behaviour of nocturnal creatures into disarray. Some insects fly at night, dawn or dusk and studies have shown that artificial lighting interferes with their pollinating habits. If street lights drive away the night-time pollinators, it means less fruit and fewer plants overall, a change that then has a knock-on effect on daytime foraging bees. (There are also several species of mainly tropical bees – like the Central American sweat bee or the Indian carpenter bee – that have evolved to fly at night. These species may also be affected by night-time light pollution.)
CLIMATE CHANGE
A recent UN report revealed the potential effects of climate change on bees and other pollinators. It highlighted two specific problems: the first is that habitats where bees forage will change as the climate gets hotter – the balance of plants may alter with no guarantee that bees will be able to adapt; the second is the changing seasonal behaviour of different species. Thanks to warmer weather, and seasons arriving earlier, many wild bee species are emerging too soon. And while some flowering plants will also start to blossom earlier, there is a lag between the two. In other words, bees are waking up before any of their food sources are available to eat.
PESTS AND PATHOGENS
Bees, like any other animal, can get sick. Honey bees, because they live in colonies, are particularly susceptible to the rapid spread of infectious diseases; the honey bee hive is a crowded, warm environment, the perfect setting for pests and pathogens to exploit. Thankfully, honey bees are brilliant at keeping diseases at bay – over millions of years they have evolved various strategies and defence mechanisms to cope with potential attacks, from scrupulous hygiene and antibiotic propolis to undertaker bees to clear out the sick and dying. We are only just beginning to understand how sophisticated these methods are. Unfortunately, some parasitic diseases have hit hives hard in the past decades, undermining colonies already weakened by exposure to pesticides, lack of nutrition or a changeable climate. These parasites include:
•nosema, a parasitic fungus that causes dysentery
•tracheal mite, a parasite that shortens the lifespan of bees
•varroa, a mite that deforms wings and weakens the colony
•bacteria that cause a fatal disease known as foul brood.
BAD BEEKEEPING
Following on from pests and pathogens, some of the issues facing honey bee hives are made worse or spread through poor management of colonies. Diseases can be spread through contaminated combs or hive equipment, for example, or by ignoring simple hygiene practices. Beekeeping associations recommend that beekeepers can reduce the impact of pests and diseases using apiary hygiene, regular brood comb changes, the right treatments, and ensuring that colonies are strong, fit and well-nourished to begin with.
DISEASE TRANSFER
Diseased honey bees can also affect wild populations, usually when they feed on the same flowers. One disease in the UK, for example, called deformed wing virus, is thought to have transferred from honey bees to wild bumblebees this way. The University of Cambridge’s Zoology Department compared the transfer of these illnesses to ‘germs passing between humans through a shared coffee cup’. Simply keeping more honey bees, therefore, is not the answer to declining bee populations. In fact, ‘bad beekeeping’ may be making things worse, not only by spreading pathogens but also by encouraging farmed bees to compete for pollen and nectar in an ever-diminishing natural world.
DIESEL EXHAUST FUMES
Traffic fumes, which contain toxic nitrogen oxide, are not only harmful to human health; exposure to diesel exhaust emissions has been shown to affect bees’ ability to recognise different flower scents. Studies of polluted environments revealed that diesel fumes chemically alter almost half of the most common flower scents that bees use to find their food, confusing their sense of smell and making it difficult for them to forage.
FEAR OF BEES
Many people are scared of bees. One issue is that we lump all bees, wasps and other insects with similar colouration into the same category. And while a few species can be aggressive, most bees will only sting if seriously provoked and male bees have no sting at all. Bumblebees are not naturally aggressive. Solitary bees rarely sting, and in most cases the sting is not particularly painful. And honey bees may sting but usually only if they’re defending something – that is, their hive, which is why beekeepers wear suits. The most ‘terrifying’ of all bee spectacles – a honey bee swarm – is ironically a time when they are at their most docile and least likely to sting. And if we find a wild nest, we tend to panic and call in the exterminators.
Part of the issue may be a greater public awareness of extreme allergic reactions to bee stings. And while it’s important not to dismiss the 2–5 per cent of people who develop severe allergies to bee stings, it’s also important to note how rare deaths from bee stings are. Between 2008 and 2015, for example, in the US the number of deaths caused collectively by hornets, wasps and bees was 1.4 annual deaths per 10 million people. Pet dogs caused almost as many fatalities, at 0.8 deaths per 10 million people, and yet we have a completely different relationship with them. It’s also interesting that, in the search for a cure for severe venom allergies, bee stings might provide the answer – experiments are showing that high doses of bee venom early in the year seem to block further reactions later in the season.