I recently had to do a case study on bees in general, their decline, reasons for and possible solutions. As gardeners, we all appreciate the severity of the problem and results of a declining bee population. Also, being such a critical and important part of the garden I thought I’d share the basic case study with you. Initially I wasn’t aware of what the factors were that are causing the ongoing problem or just how long the problem has been going on for. Hopefully the study is useful to anyone interested in why but struggling due to the few number of articles that actually sum up the whole thing.
Bees are flying insects closely related to wasps and ants. They are well known for their important role in pollination and also for producing honey and beeswax. There are nearly 20,000 known species of bees in 7 to 9 recognised families, though many are undescribed and the actual number is thought to be higher. Bees are found on every continent except Antarctica, in every habitat on the planet that contains insect-pollinated plants.
The smallest bee known to man is Trigona minima, which is a stingless species whose workers are only around 2.1mm long. The largest bee in Megachile pluto, a leafcutter bee whose females can be as long as 39mm.
The most common type of bee in the northern hemisphere are members of the Halictidae family, also known as sweat bees. They are often mistaken for wasps or flies. Although not the most common, the best-known species is the ‘European Honey Bee’. This bee produces honey (as do only a few other types) and are used in beekeeping or apiculture.
Decline in worldwide bee population and possible causes:
The worldwide bee population is declining at an alarming rate, the consequences of which will affect food production around the globe. One in three mouthfuls of what we eat is dependent on bee pollination and some fruits such as apples, pears and plums are up to 90% dependent on bees for pollination.
The economic value of crops grown commercially in the UK that benefit from bee pollination is around £120m-£200m per year. The value of honey production in the UK can be between £10-£30m per year on average. US bees are experiencing similar mysterious shortages. Without bees to pollinate their crops, the US could potentially lose $15 billion worth of produce.
It became clear that the problem was getting worse after 2008; the worst honey crop on record.
One theory is that the blood sucking mite Varroa, which arrived in bee colonies in the early 1990’s in the UK, is responsible. Originally the infestation of mites devastated wild honey bee colonies, but beekeepers were able to treat the mite in managed hives. It is possible that the mites have now become resistant to the treatments and that the fungus Nosema ceranae has added to the problem.
A potentially bigger threat is the condition called ‘Colony Collapse Disorder’ (CCD). No one really knows the cause for sure but it is thought to be a combination of viruses, stress from working hard over a long season, possible pesticide accumulation, bad weather and disease. The disorder has cause huge losses of colonies in the USA and has been found in parts of Europe but it is still uncertain whether the disease has reached the UK yet. Bees from beehive colonies abruptly disappear. Such disappearances have occurred throughout history and have been given different names. It was renamed colony collapse disorder in 2006 in conjunction with a drastic rise in the disappearance of honeybee colonies in North America. The same symptoms were later reported throughout Europe.
A newer theory is that commonly used pesticides are damaging honey bee brains. This is now thought to be a key factor in the cause of CCD. Scientists have found that two types of chemicals called Neonicotinoids and Coumaphos are interfering with the insects ability to learn and remember. This would explain the strange disappearance in colonies, and why the majority of bees fail to return; that they cannot remember. Companies that make the substances have argued that laboratory-based studies did not always apply to bees in the wild and another report from Defra’s Food and Environment Research Agency, concluded that there was no link between bee health and exposure to neonicotinoids.
Neonicotinoids are used more commonly in Europe, while Coumaphos are more often used in the US. Experiments carried out in Scotland revealed that if the pesticides were applied directly to the brains of the pollinators, they caused a loss of brain activity.
Experiments in Newcastle also proved that bees exposed to pesticides were unable to learn and then remember floral smells associated with nectar.
With such clear evidence that pesticides are having a negative impact on the population of honeybee’s the European Commission recently called for a temporary moratorium on the use of neonicotinoids after a report by the European Food Safety Authority concluded that they pose a high acute risk to pollinators. Out of the 27 EU nations, 14 opposed the ban including Germany and the UK. Critics say that studies are not conclusive enough, and that the experiments do not necessarily have the same results on bees outside of the laboratory.
More recent research into the disappearance and causes of both CCD and the overall decline that bees have experienced in the last 25 years have led scientists to attaching tiny antenna’s to the thorax of bees. Scientists are using harmonic radar technology. The radar transmitter emits a signal which is received by a tiny antenna glued on a honey bee’s back, also known as thorax. A small diode in the centre of the antenna converts it into a different wavelength that can be detected and followed.
Each antenna is stuck to the honey bees by hand and test bees are prepared by gluing a small plastic disc with an identification number. The technology was initially used to try and track the tsetse fly in Africa which spreads the sleeping sickness. The antenna was too big to tag the flies but works well with bees because of their larger size.
In Australia another way in which scientists hope to stop the decline in bees is the search for honey bees immune to the mite Varroa. Australia has the only significant bee population in the world that is till free of the deadly mite. The mite is so dangerous because it drops into the brood cells, attaches itself to the developing bee and lays its eggs. When the baby bee leaves the brood cell to join the adult colony, the parasite and its offspring follow, infecting the entire hive.
Between 1988 and 1993, the Varroa mite wiped out half of the hived colonies in the US. Australia has the only significant bee population in the world still free of the mite. Even New Zealand’s bees were affected in 2000.
For millions of years the Varroa co-existed with another species of honeybee found in Asia. As western civilization made its way across Asia, swarms of European honeybees, lacking their Asian cousins’ evolutionary armour, followed. Supposedly the european bees were unrecognisable to the mite. By sheer accident a single Varroa mite from around the North Korea-China border jumped from an Asian to a European honeybee.
To protect the Australian bee population the government have been investing in border protection. Strategically placed “bait hives” dot the coastline and surround Australian wharves and airports, and are checked regularly by beekeepers for any sign of the dreaded parasite.
The head of the whole project, Dr Denis Anderson, criticizes industry funding saying that the money is directed towards existing problems in bees whereas it should be given to future proofing the bee industry against parasites such as Varroa.
A further new plan to try and slow down the decrease in bee population is homeowners being allowed to keep bees on their roofs in urban areas. Los Angeles residents could soon be able to keep bees on their roofs as part of new plans in the city. The city council is to vote on whether to allow residents to keep beehives in built up areas. The vote has been the aim of many bee lovers in the city and is to allow cities to do their bit against the threat of CCD threatening the US’ bee population.