Pollination is the fertilisation of plants through transfer of pollen. Without pollination, plants would not be able to reproduce, and would quickly die out. It is a crucial process that most living things rely on, wholly or partially. Humans, for example, would be left with very little to farm and eat if all pollination were to cease.
Pollen transfer can be abiotic or biotic. The former refers to non-living mechanisms of transport, such as wind or rain. Biotic pollination is much more common, and occurs when insects, birds, bats (and other mammals like monkeys and squirrels) transfer pollen between plants.
With almost 20,000 known species, bees are perhaps one of the most recognisable and well-known pollinator insects. Studies estimate that one third of commercial crops are either entirely or partially pollinated by (and thus dependent on) bees. These include some of our most loved and economically important produce like broccoli, bell peppers, onions, beans, apples, cherries, peaches, strawberries, coffee, cotton and almonds. This was perfectly illustrated in the activity stand ‘What Happens When Bees Go Extinct?’ as part of the Food for the Future event hosted by the Sheffield British Science Association for the Sheffield Food Festival back in May.
Of the approximate 785 species that pollinate crop plants, the Western honey bee (Apis mellifera) is the single most important one. Its wide dispersion and high populace mean that it pollinates the most crops of all species. Domesticated and kept by humans for around 5,000 years, records of beekeeping exist on the walls of ancient Egyptian monuments. This species is the most common of all seven honey bee species in the genus Apis, and is found on all continents bar Antarctica. This extreme distribution of A. mellifera around the globe is largely due to human activity. For example, migrants from Europe introduced the bee to North America in the 1600s.
The Western honey bee, Apis mellifera
Despite its widespread range, the population of the Western honey bee has dramatically declined in the last decade or so. Research from Pennsylvania State University found that North American populations have been hit hard, as have the populations in several European countries such as Spain, France and Greece. From 2007-2013, it has been estimated that roughly ten million hives were lost. Given the bees’ significance to agriculture and local ecosystems, this is a worrying development for farmers and environmentalists alike. Colony collapse disorder (CCD) is the leading cause of this decline.
CCD has existed throughout history in all regions where honey bees are domesticated, but has recently intensified. The disorder occurs when most or all of the worker bees in a hive disappear leaving only the queen bee, several nurses, and immature bees or larvae behind. Food supplies are usually plentiful. However, with an insufficient workforce, this supply simply cannot be maintained. Causes of CCD are unknown, though there are many factors thought to have some influence. Disease, pesticide use, a lack of genetic diversity, and migratory beekeeping are all potential contributors to CCD and bee death.
The parasitic mite Varroa destructor is perhaps the biggest pest to honeybees. The mite feeds on the blood of adult bees and pupae, and transmits diseases such as deformed wing virus. This virus leads to the exile or death of many bees within a hive. The mites are hard to get rid of and have very high reproductive rates so protecting bees can be quite difficult once mites attach. Fortunately, there are several ongoing studies looking into how to deal with the mites, so there may be hope for affected hives in the future.
Varroa mite on a honey bee
Neonicotinoids (the family of pesticides now the subject of bans heavy regulation and debates) have been shown to negatively affect honey bee hives and contribute to CCD. Queen bees exposed to neonicotinoids had a 60% survival rate compared to 80% of control queens as a recent 2015 study found. Another study concluded that honey bee immune systems are compromised by neonicotinoids making them more susceptible to diseases. In tandem with parasitic mites, this may affect hives even more. It is important to note, however, that there are still knowledge gaps regarding this subject. Research as to how, why and to what extent the pesticides affect A. mellifera is still ongoing.
Luckily, the plight of the honey bee (and other bee species whose populations are falling) has been covered extensively by the media in recent years and many people are trying to help the situation. A veritable fountain of information on how we can help save the bees has sprung up. From the Royal Horticultural Society to the RSPB, there are plenty of articles detailing which plants are best for bees, how to provide shelter and how to revive tired bees. What is also positive is the number of companies invested in helping bees too; from the National Trust to well-known supermarkets. Wildflower seeds (which you can get from Grow Wild UK) are very accessible and can easily be planted for a bee-friendly spot in the garden or window box.
There is hope for the bees yet, but it will take the concern, kindness and help of all of us all if we want the population of these buzzy pollinators to climb again.
About the Author
Helen Alford is an MSc Science Communication and BSc Biological Sciences graduate having studied at the Universities of Sheffield and Birmingham. She has got a particular interest in microbiology, immunology, mycology, and how they often overlap! She is passionate about science communication and is involved with a local radio show focused on science and technology (https://web.sheffieldlive.org/shows/the-live-science-radio-show/)