Expert reaction to new study on bees and crop pollination
The extent of the contribution of #bees to #crop pollination and factors which affect their health and survival are active areas of research. Publishing in the journal Nature Communications, researchers have reported that the significant contribution of bees to aiding human crop production is limited to a subset of all species, and suggest that conservation and management projects should be more targeted.
“This is an important and extremely carefully conducted and exhaustive study, involving a high proportion of all the relevant #pollination scientists including the very best of them, and covering many crops across many regions, so it gives a reliably data-rich message.
“The key point is that wild bees, mostly the solitary bees, matter greatly for crop pollination, just as many other studies just looking at one crop at a time have already shown. But crucially the commonest wild bees are the most important, which gives us the ‘win-win’ situation where relatively cheap and easy conservation measures can support these and give maximum benefit for the crops. For example planting wild flowers with wider grassy margins around crops, as well as less intensive or more organic farming, all enhance abundance of the key crop-visiting bees.
“The study also shows that bee biodiversity in itself is less crucial, since it is the common species that matter most. There may be very good reasons for trying to conserve bee diversity in the longer run of course, and this requires more complex and expensive approaches; but it should be helpful to farmers to know that the simple and cheap measures can give them what they need for pollination and crop productivity purposes.”
“It shows that the value of wild insects to crop pollination is roughly equivalent to the value of managed #honey bees. Twenty-five wild bee species each contribute more than $100/ha on average to the production of insect-pollinated crops. Wow.
“The study shows that most of the crop pollination service is delivered by a few very common species – generally the same bees you find in gardens, or anywhere with flowers providing nectar and pollen. This means the argument that we should conserve the diversity of pollinators because of their value to people in pollinating crops is flawed. 80% of crop pollination is provided by just 2% of all bee species, according to the paper.
“Some wild pollinator species have quite specific habitat or food needs – like the small black and red mining bee Andrena hattorfiana that only feeds on the pollen of scabious flowers. Specialised species like this are more likely to be declining, so should be a focus of conservation action, and these actions need to be specific to each species or similar group of species, and carefully targeted.
“The paper shows that relatively ‘easy’ pollinator conservation actions, such as planting flowers and keeping patches of rough grassland in intensively farmed areas, more than triple the abundance of the common crop-pollinating bee species (abundance increased by a factor of 3.2 across all studies).
It is important to say that, while these actions may not always help threatened species, they sometimes do, in areas where source populations are near enough. Just over 9% of Europe’s bees are threatened with extinction in Europe, according to a new Red List.
“One piece of research conspicuously not cited in this new study showed that generic agri-environment options planted for pollinators in six sites across central and Eastern England attracted three less common or declining bumblebee species – Bombus ruderatus, Bombus ruderarius and B. muscorum (Carvell et al. 2007). The last of these – the beautiful moss carder bee B. muscorum – is one of the 9%, classed as Vulnerable in the new Red List. So let’s not write off agri-environment schemes on intensive farmland as no good for supporting a wide diversity of pollinator species.”
Carvell, C., W. R. Meek, R. F. Pywell, D. Goulson, and M. Nowakowski. 2007. Comparing the efficacy of agri-environment schemes to enhance bumble bee abundance and diversity on arable field margins. Journal of Applied Ecology 44:29-40.
‘Delivery of crop pollination services is an insufficient argument for wild pollinator conservation’ by David Kleijn et al. published in Nature Communications on Tuesday 16 June 2015.