What is pollination?
Pollination is defined as the transfer of pollen (male gamete) from the male to the female part of a plant, allowing fertilization and later the production of seeds and fruit.
Pollinators are animals that visit flowers to primarily drink nectar or feed on pollen, but also carry pollen grains as they move from place to place in the plant (Image 1). Vertebrates such as bats, birds, monkeys, possums, rodents and some lizards also pollinate plants. But in this article, we will only talk about insect pollinators.
Image 1. Pollen-covered bumblebee. (Credit: P7r7 / Creative Commons 3.0)
Common pollinating insects, not just honeybees:
Although honeybees (Apis mellifera) are the world's most important pollinator, other insect pollinators are generally overlooked but are just as important as honeybees, providing 25-50% of visits to crop flowers [1].
These other insect pollinators include beetles, flies (including bee flies, hoverflies, blowflies, and mosquitoes), ants, moths, butterflies, bumblebees, solitary bees, and wasps (image 2).
Why are insect pollinators important to our economy?
About 80% of all flowering plant species require pollination by animals, primarily insects. Insect pollinators improve or stabilize the yield of three-quarters of all crop types worldwide, accounting for about 35% of global crop production by volume [2,3].
Although it is difficult to translate the importance of insects into economic terms, some studies have estimated the importance of pollinators to national and global economies. Lautenbach et al. (2012) estimated the economic benefits of global pollination services to be 190-467 billion euros in 2009. This study also estimated that 9.4% of the global agricultural gross domestic product depends on pollinators [4,5].
In the United States, for example, insect pollinators are estimated to contribute $29 billion to agricultural income each year [6]. In France, plant production for human consumption attributable to the action of pollinating insects is worth between 2.3 and 5.3 billion euros (2010), or between 5.2% and 12% of the total value of production [7]. Among the crops for which pollinators are most important in France are melons, watermelons, cucurbits, apples, cherries, cucumbers and gherkins.
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Image 2: Hawk hummingbird consuming nectar from a pink zinniaf
What are the main factors of its decline?
Recent studies have estimated a 45% global decline in insect populations over the past four decades [8]. Many factors are involved in this decline, but most scientists attribute it to the widespread use of pesticides, the increase in (self-pollinating) monocultures such as corn and soybeans, and habitat destruction associated with urbanization [2].
Of particular concern is the widespread use of pesticides and their impact on non-target species. A particular class of pesticides called neonicotinoids, used for many years in Europe until a partial ban in 2013, is the prime suspect for insect losses. Indeed, this type of pesticide induces abnormal behaviours and reduces the pollination performance of honey bees [9].
What is probably more worrying is that until now, only the decline of honey bee populations has received widespread public attention, while the rest of the insect world has been largely ignored. The situation may well be worse than we think.
What can we do to help?
Today, citizens play a valuable and growing role in monitoring programs, primarily by reporting sightings of pollinator species. This practice, also known as citizen science, involves a large, volunteer workforce that can collect far more data than any other method. Many initiatives in North America and Europe involve citizens in monitoring various pollinators such as honeybees, butterflies and bumblebees. For a list of some of the organizations, see the EU Science for Environment Policy website (page 53, box 14) [5].
If you have some space in your garden or on your property, plant wildflowers and install well-designed insect hotels to provide food and habitat for all kinds of pollinators, including bees, beetles, and butterflies (image 3) [10]. A shift in perspective is needed to assess the biodiversity of crop pollinators and the economic value of pollination, without focusing solely on the honeybee. Researchers, policymakers, and the general public should consider the value and services provided by other insects, such as flies, wasps, beetles, and moths-important pollinators that are currently overlooked.
Finally, remember that honeybees are just one species of bee and also just one species of insect pollinator.
Image 3. Les prairies de fleurs sauvages fournissent un habitat et de la nourriture à de nombreuses espèces de pollinisateurs.
References
1. Rader R et al. 2016. Insects other than bees make important contributions to global crop pollination. PNAS 113 (1): 146-151. DOI: 10.1073/pnas.1517092112
2. Schwägerl C. 2016. What's causing the sharp decline in insects, and why it matters. Yale Environment 360. Available at: https://e360.yale.edu/features/insect_numbers_declining_why_it_matters
3. Food and Agriculture Organization of the United Nations (FAO). 2021. FAO global action on pollination services for sustainable agriculture. Available at: https://www.fao.org/pollination/background/en/
4. Lautenbach S, Seppelt R, Liebscher J & CF Dormann. 2012. Spatial and temporal trends in global pollination benefit. Plos ONE 7(4): e35954. DOI: 10.1371/journal.pone.0035954
5. Science for environmental policy. 2020. Pollinators: importance for nature and human well-being, drivers of decline and need for monitoring. Future brief produced for DG Environment of the European Commission. Bristol: Science Communication Unit, UWE Bristol.
6. Ramanujan K. 2012. Insect pollinators contribute $29 billion to U.S. farm income. Cornell Chronicle. Available at: https://news.cornell.edu/stories/2012/05/insect-pollinators-contribute-29b-us-farm-income
7. The French Assessment of Ecosystems and Ecosystem Services (EFESE). 2016. The pollination service. Ministère de l'Environnment, de l'Énergie et de la Mer. Available at: https://www.ecologie.gouv.fr/sites/default/files/Th%C3%A9ma%20-%20Efese%20-%20Le%20service%20de%20pollinisation%20-%20Analyse.pdf
8. Rodolfo Dirzo et al. 2014. Defaunation in the Anthropocene. Science 345 (6195): 401-406. DOI: 10.1126/science.1251817
9. Colin T, Meikle WG, Wu X and AB Barron. 2019. Trace amounts of a neonicotinoid induce early foraging and reduce foraging performance in honey bees. Environmental Science & Technology 53 (14): 8252-8261. DOI: 10.1021/acs.est.9b02452
10.Turner A. 2021. Bees are voracious: is it time to put the brakes on the beekeeping boom? The Guardian: Environment. Available at: https://www.theguardian.com/environment/2021/jul/24/this-only-saves-honeybees-the-trouble-with-britains-beekeeping-boom-aoe