The threats facing our pollinators
From pestering you at picnics to providing the honey for your morning porridge we’re all very familiar with bees. What you may not have thought so much about is the importance bees (and other pollinators) have in providing crucial ecosystem services for both agriculture and the wider environment. And it’s not just the honeybee (Apis mellifera) that is important but all bumblebees and solitary bees play crucial roles as pollinators also, as well as hoverflies. It is estimated that the annual value of pollinators for food crops is about €153 billion globally . As well as an economic benefit there’s an obvious ecological benefit as well as pollinators play the crucial role of transferring pollen from one plant to another (of the same species) in order for the plants to reproduce and produce progeny . Many common vegetables and fruits depend on pollinators for reproduction including apples, strawberries, blackberries, raspberries etc .
Unfortunately for us all, populations of bees globally have been decreasing at an unprecedented rate since the 1980s. Here in Ireland 30% of our bee species are considered threatened with extinction from the country, according to the IUCN criteria . Here I will outline some of the major threats facing our buzzing buddies.
1 . Pesticides
Use of pesticides has increased several fold within the last few decades and this has had a noticeable adverse effect on bees and other pollinators. Some of the worst pesticides threatening our bees are neonicotinoids which mess with the nervous system of bees and can interfere with their ability to search for flowers by making them forget the smell of nectar (which they’re attracted to) . More worryingly is that it seems bees are attracted to plants containing neonicotinoids. It is believed that neonicotinoids stimulate a similar part of the brain in bees that nicotine does in humans essentially causing the bees to favour plants sprayed with the pesticide rather than safer alternatives . More research needs to be done (especially in the field) on the effects of pesticides on pollinators before any solid conclusions can be drawn but safer alternatives to pesticides such as biocontrol should be strongly considered.
2. Parasites and disease
Parasites and disease have become a more prevalent threat to our pollinators due to globalisation, with many harmful parasites and diseases being accidentally transported to new areas by human movement . A prime example of this is with the mite Varroa destructor (quite an intimidating binomial). V. destructor is a common parasite of the Asian honeybee, Apis cerana, but has spread to the European honeybee, A. mellifera . Native parasites are important in population regulation, but when a parasite spreads to a new region the ‘locals’ haven’t adapted defences and so are susceptible to huge population declines. This mite is a vector for a few viral pathogens that can affect bees such as deformed wing virus and the combined effect of the parasite with the diseases it can cause has been a major contributor to the declining populations of honeybees in North America and Europe.
3. Habitat Loss
This factor is the same one that threatens most wildlife and primarily consists of humans tearing down natural habitats to build another house/ car park/ McDonalds. Habitat loss rids the bees of two important resources, space & food. Less space pushes the competing colonies and species closer together leading to less food to spread among the populations. A simple solution to help our bees would be to stop ‘tidying’ semi-natural landscape and allow wildflowers to grow on the margins of fields, along hedgerows, and in parks and gardens . However because bee species are highly mobile and used to using patchy resources some bee species can tolerate moderate amounts of disturbance and habitat loss , although it may exasperate some of the other negative factors.
- Climate Change
Global warming is the scourge facing all life on Earth and our bees and pollinators are no different. Whenever warming occurs you would expect the Southern limits of a species range to push northwards, and the Northern limits to expand north (in the Northern hemisphere). However with regards to bumblebees, although a decrease in the Southern ranges has been observed, there is no evidence that the Northern range of bees has been expanding. Range losses of up to 300km have been noted for bumblebees in both North America and Europe  ridding the warmer areas of these continents of their bumblebees. The warming of the planet will also change the seasonal cycles that bees rely on such as the emergence of flowers and important life-cycle events (waking from hibernation, production of offspring etc.).
The problem from these detrimental factors affecting our pollinators is that they work together exacerbating the problem. For example a decrease in the range of bees due to habitat loss and climate change will increase the rate at which parasites and disease spread through the populations of these pollinators. And it is essential for both economic and ecological reasons that we curb the decline observed over the past half century.
For more information on the threats facing our pollinators and what we can do to help combat them I would advise reading the “All-Ireland Pollinator Plan 2015-2020” .
- Stout, J. and Finn, J. (2015). Recognising the value of insects in providing ecosystem services. Ecological Entomology, 40.
- Goulson, D., Nicholls, E., Botias, C. and Rotheray, E. (2015). Bee declines driven by combined stress from parasites, pesticides, and lack of flowers. Science, 347(6229), pp.1255957-1255957.
- Potts, S., Biesmeijer, J., Kremen, C., Neumann, P., Schweiger, O. and Kunin, W. (2010). Global pollinator declines: trends, impacts and drivers. Trends in Ecology and Evolution, 25(6), pp.345-353.
- Kerr, J., Pindar, A., Galpern, P., Packer, L., Potts, S., Roberts, S., Rasmont, P., Schweiger, O., Colla, S., Richardson, L., Wagner, D., Gall, L., Sikes, D. and Pantoja, A. (2015). Climate change impacts on bumblebees converge across continents. Science, 349(6244), pp.177-180.