|Introduction to bee declines|
For the past few years reports of massive numbers of bees dying unusual deaths have been flooding in from across the globe. Most reports are related to the deaths of honey bees, including the phenomenon that has come to be known as Colony Collapse Disorder (CCD). The first reports of large scale bee deaths that were attributed to CCD started to arrive from the US in 2006, and have continued since with an estimated 30% of managed colonies being lost each year - considerably higher than the usual losses over winter.
Sudden, unexplained losses of managed bee colonies has been reported in other regions: losses of 25-30% in Europe, in Japan 25% beekeepers report the same phenomenon and similar reports have emerged from China and Egypt.
It is not just honey bees that are in decline. Many native wild bee species, such as bumblebees and leafcutter bees, are suffering severe population losses across the world, with some species facing extinction. These wild bees are important pollinators for food and medicinal crops we grow and for plant species we want to conserve. Other pollinating insects, such as butterflies and moths, are also under threat.
Several factors are thought to be behind these declines: changes in farming practices which affect bees’ food sources; increased levels of parasites and diseases; and contamination by pesticides and other pollutants.
Bees have been in decline for several decades now but little attention was paid until the CCD story hit the news. As US researchers expressed in their article ‘The Plight of the Bees’: “Bees are reaching their tipping point because they are expected to perform in an increasingly inhospitable world”.
Importance of bees
Honeybees pollinate 40% of leading food crops. Honeybee pollination increases the edible yield of 46 of the world's leading 115 food crop species - including apples, citrus, tomatoes, sunflowers, rapeseed and soya - while a further 10 crops gain following pollination by other species of bee and insect. Less than 25% of the world's leading food crop species are wind pollinated and do not benefit from honeybees.
Honeybees play a key role in the successful production of over 80 million tonnes of EU food produce each year - which equates to 160 kilos of food per EU citizen. The economic value of insects and other animals pollinating crops is estimated at US$216.5 billion.
Pollinators are not only essential for producing much of our food, they also contribute to the sustainable livelihoods of many farmers and beekeepers world-wide. Their declining numbers are affecting rural communities in developing countries. India’s huge decline in bee and other pollinator species is resulting in reductions in the yield of date palms, lemon, papaya and mangoes. Wild honey collection in the Kutch region fell from the usual 300 tonnes to just 50 tons in 2010, because of the fall in the number of honey bees. In Kenya, reports of low pollinator abundance and diversity have recently appeared, with crops such as passion fruit showing deficiency of pollination.
Colony Collapse Disorder (CCD)
Colony collapse disorder (CCD) is a phenomenon in which worker honey bees from a hive or bee colony abruptly disappear. While bee kills and sudden hive losses have occurred throughout the history of apiculture, the term colony collapse disorder was first applied to a drastic rise in the number of disappearances of honey bee colonies in North America in late 2006. It is natural for sick bees to leave a colony to die but the symptoms of CCD are very different: affected colonies rapidly and unexpectedly lost their workers, leaving the queen, food stores and bee brood abandoned, but with no dead bees observed in the area. CCD incidents have been reported every winter since 2006 in the US.
The causes of CCD syndrome are not understood. Some authorities attribute the problem to pests and diseases infesting the hives, such as parasitic Varroa mites, the diseases caused by Nosema fungi and Israel acute paralysis virus. Other proposed causes include environmental change-related stresses, reduced and poor quality sources of pollen and nectar, pesticide contamination of food sources and migratory beekeeping. More speculative possibilities have included both cell phone radiation and genetically modified (GM) crops with pest control characteristics. No ‘smoking gun’ has been found yet in the research underway in different countries. It is likely that several factors play a role, as well as interactions between them.
Mass bee kills and hive health problems linked to pesticides do not necessarily display the same symptoms as CCD. In 1994 French beekeepers first noticed problems in bees foraging on sunflower in spring, with groups of bees found disoriented in front of the hive and some dead individuals. The widespread bee deaths in Germany in 2008 were due to problems with the seed coating process for the insecticide clothianidin used on maize seed, accidentally releasing it into the air when bees were active.
Role of pesticides in declines
There are many factors that could be contributing to the loss of bees and to date it has been impossible to single any one out as being of particular concern. However, what is not in doubt is the fact that all over the world pesticides that are harmful to bees and other pollinators are being used in ever increasing amounts. In May 2008 the UK Pesticide Safety Directorate, now the Chemicals Regulation Directorate, analysed 286 pesticides used in the EU and identified 40 as being toxic to bees. Even the companies that make such pesticides do not deny their direct toxicity to bees, if sprayed or released into fields when bees are foraging or if high levels contaminate hive food sources.
What is less clear and therefore contested is the role of low level exposure to pesticides, especially those used in seed treatments. The film Vanishing of the Bees contains a lot of information about bee deaths from the point of view of US beekeepers who are unanimous in stating that pesticides are a big part of the problem. Many European beekeeping organisations hold similar views, as do many environmental NGOs, including PAN UK. The issue is controversial among governments and public research institutes, with different national agencies and individual academics taking different views. We explore these issues on this website in the sections under Pesticides.