An international study has shown that wild bees play a vital role in the quality and quantity of crops produced in agriculture worldwide. They are in rapid decline, and it is urgent to protect them.
A study published the 28th of February 2013 in the highly respected Science Magazine (1) challenges the supremacy of our little honeybee in this area.
Lucas Garibaldi from the University of Rio Negro in Argentina, Alexandra Klein from the University of Lüneburg in Germany, and their colleagues around the world have studied the action of pollinators on 41 cropping systems in 600 fields spread on five continents.
The species selected included coffee, cotton, cucumber, almonds, watermelon, buckwheat, strawberry, kiwi, etc., and different kinds of nuts and seeds commonly grown worldwide. And the cultural practices used were going from intensive monoculture to traditional agriculture.
Dans chaque champ, les biologistes ont évalué la diversité des polllinisateurs – abeilles domestiques, abeilles sauvages, coléoptères, mouches et papillons présents sur les sites – et le nombre de fleurs qu’ils butinaient. Ils ont aussi mesuré la quantité de pollen déposé sur chaque fleur, et la fructification – c’est-à-dire, le nombre de fleurs fécondées qui vont réellement donner un fruit par la suite. Enfin, ils ont analysé l’énorme quantité de données ainsi recueillies.
In each field, biologists have assessed the diversity of pollinators – honeybees, wild bees, beetles, flies and butterflies on the sites – and the number of flowers they forage on. They also measured the amount of pollen deposited on each flower and fruit – meaning the number of fertilized flowers that will really give a fruit thereafter. Finally, they analyzed the huge amount of data collected.
The more often a flower is visited by wild pollinators (mainly by wild bees) the more likely it is to produce a fruit and seeds thereafter. And in 100% of cases, regardless of the type of crop studied.
Does it seem obvious to you? Well it is not:
Curiously, this result no longer holds if honeybees are visiting the same flower. With honeybees, increased visits would result in a better fruit only for 14% of the studied systems!
Even stranger: a flower visited by wild bees is two times more likely to give a fruit compared to a flower visited only by honeybees!
The study does not say why. But it shows an extraordinary thing: the maximum fruiting is achieved if the flowers are visited many times, both by honeybees and wild bees! Harmonious nature…
And now, what lessons from these results?
First of all, this study demolishes a myth: the honeybee as principal or even only pollinator of numerous cultures.
This is explained by Lawrence Harder, Biology professor at the University of Calgary, Canada, and co-author of the study:
« We saw that to put more bees in crop areas [that were not sufficiently pollinated] was not sufficient to solve this problem which requires an increase in the number of insects wild pollinators. »
This is not to neglect the contribution of honeybees. The study simply shows that they complement, but don’t replace, the background work lead by wild bees – unlike what farmers and growers often hope when they « lend » their fields and orchards to beekeepers.
Therefore a holistic approach to their problems is needed, and also a protection of both populations, especially from insecticides. (3)
Then it is urgent to act to adapt agricultural practices to the study findings of Garibaldi.
« Our study shows that the production of a large number of fruits and seeds with which we can feed ourselves in many different ways, is limited today because the flowers are not pollinated enough » said Lawrence Harder.
Paradoxically, most of the approaches to increase the efficiency of agriculture – as the cultivation of all available land, the loss of hedgerows, monoculture, and the heavy use of increasingly toxic pesticides – reduces the abundance and variety of pollinating insects that could increase the production of these crops.
These insects tend to live in natural or semi-natural habitats such as forest edges, hedges or grasslands – all habitats, which are becoming scarce, due among other to their conversion into agricultural land.
We therefore need to implement rapidly new approaches to integrate the management of honeybees and wild pollinators into agricultural practices – for example by preserving more their habitat. Global crop yields would be increased in that way, allowing to promote agricultural production in the long term.
To preserve crop yields, we cannot simply reverse the decline of honeybees: we must stop the less publicized but equally real decline of wild pollinators.
For more information:
(1) L. Garibaldi and al., « Science » March 1st.
(2) Read the article of Cécile Klinger « Even wild bees are declining », on the research site: http://www.larecherche.fr/savoirs/environnement/meme-abeilles-sauvages-declinent-01-12-2009-87693
There are 20,000 bee species listed today worldwide. Of these 20,000 species, about 2,500 live in Europe, and around 1,000 in France. The honeybee Apis Mellifera is one of these 1,000 species. Its importance is that it lives in a very large community – up to 40,000 individuals for a hive at the height of summer – and they can be easily transported to pollinate monocultures often turned into biological deserts.
« With beetles, flies and butterflies, these valuable insects are essential to the functioning of the ecosystems: they are involved in pollination – and thus reproduction – about 70% of species of flowering plants, which themselves represent 90% of the vegetation in the world today. Bees, wild and domestic, are far more effective in this role. They feed exclusively on nectar and pollen, which they spend much of their time foraging. » Their body is covered with very suitable hairs – shaped in tree branch forms when observed under a microscope – that hang particularly well the pollen. A bee commonly carries tens of thousands of pollen grains, which it deposits in large amounts on the stigma of other flowers during each trip.
(3) From the article « Insect pollinators are in very bad shape », from Yves Miserey, published in Le Monde March 1st 2013 : «Pollination specialists like Bernard Vaissière (from the INRA from Avignon) are asking for vain since years that the toxicity tests of insecticides be made at least on one wild bee species. The question is vital because for the solitary bees and contrarily to the domesticated bees that live in colonies of 30’000 workers, if the bee dies, it is the whole descendants that disappears. »