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Heroes of pollination: Why bees are crucial to crops

May 20, 2019

Bees don’t just make us honey. They deliver a crucial service that supports most of the world’s plant diversity – pollination. Preserving and promoting them and their habitats is good for everyone.

Know your bees? Think again

When you think of bees, you’re probably thinking of honey bees, right? That is, a group of bees, living in a hive, with a queen, drones and workers flying from flower to flower, collecting pollen, making honey, and occasionally delivering an unwelcome sting. However, honey bees are just one small part of the picture. And their peers – wild bees – can be a varied bunch.

  • There are actually more than 20,000 species of bee, more than 85% of which are solitary, and don’t live in hives at all.
  • 80% of wild bee species nest in underground tunnels or other structures made of mud, plant resins, pebbles, and even snail shells. Some even squat in abandoned beetle burrows.
  • Wild bees can be fussy eaters. Over time, they have adapted to different plant types, to varying extents, with some of them specializing to forage on certain plants only.
  • The smallest bee in the world, the Australian Quasihesma bee, is just 2mm long. The largest, the Indonesian leafcutter bee, up to 4cm, which is the size of a walnut!
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The power of pollination

Pollination, the transfer of pollen from the male parts of a plant to the female, is vital for plant reproduction and 90% of flowering plants have help from some kind of pollinating animal species. In agriculture, it is estimated that about a third of total food volume produced benefits from animal pollination.

Lots of animals act as pollinators, from mammals like bats and monkeys, all the way through to hummingbirds, and even some kinds of lizards. But it is insects who are unsurprisingly the dominant group of pollinators, with bees by far the largest of these.

Now, not all bee species are equally important for agricultural pollination. In fact, just 2% of bee species are responsible for 80% of crop pollination. Nor does all food require pollination by insects like bees. But without their help, our diets may become a lot less rich and varied – fruit in particular relies heavily on pollinators. In total, the value of global crops directly relying on animal pollination is estimated to be $236 – $577 billion annually. And bees are a vital part of this equation.

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What is happening to bee populations?

Are bees dying out? For honey bees, the big-picture answer is no. Managed honey bee colonies have actually increased by 65% worldwide since 1961.

For wild bees, the situation is more complicated – different wild bees have vastly different biologies and needs, making it difficult to assess their overall development. However, certain groups of wild bee species, in specific regions, are in fact declining.

And both wild bees and honey bees continue to face a number of challenges:

  • Pests and diseases: The Varroa Mite is the honey bee’s greatest enemy. It latches onto a bee and leeches its hemolymph (the bee equivalent of blood) and its fat body, weakening the bee’s immune system. Varroa mites also transmit viruses between bees, which can then spread throughout the colony. Colonies can also be affected and weakened by other pests and predators, like the Asian Hornet, and diseases caused by bacteria, fungi or viruses. Beekeepers can play a positive role here, making sure their hives are healthy, helping control pests and predators.
  • Genetic factors: Honey bees have been cultivated over the last few decades, selected for desirable qualities like lower aggression and increased rates of honey production. However, this has diminished genetic diversity, making bees more vulnerable to parasites and diseases, and weakening queen bees.
  • Lack of nutrition and habitat: Modern landscapes lack the all-season flowers honey bees need, as well as the specific foraging plants and habitats that wild bees need for nesting.
  • Adverse weather conditions: Unfavorable weather conditions, such as a very cold spring, can interrupt nectar and pollen collection, hurting honey bee colonies and their brood.
  • Agronomic practices: Increasingly intensive farming methods have impacted the habitats of wild bees and their availability to forage. The misuse of pesticides can also affect bees.
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Bringing bees back to the farm

One potential contribution farmers can make to help promote the wellbeing of bees and other wild insects is to support the development of insect-friendly habitats, like flower strips and nesting sites. Bayer’s Bee Care Science Program, in collaboration with the Institute for Agro-Ecology and Biodiversity, and the Institute for Landscape Ecology and Nature Conservation, set out to put this into practice.

Over a 10-year period across sites in Rheinmünster and Dettenheim in Germany’s Upper Rhine Valley, a program has been running to create and sustain a network of wildflower strips and corridors on 10% of farmers’ land. The conservation project is aimed at promoting the diversity and abundance of species like wild bees and butterflies.

The results of the project are very encouraging. Over the period from 2010 to 2017, the number of wild bee species recorded on site increased from eight in each of the trial sites, to respectively 30 and 49 species.

Flower diversity was found to be the key to success. Patches of perennial and winter-hardy flowers are an important early-foraging source for insects. Sowing a diverse mix of flower types was particularly effective at attracting wild bees and butterflies.

For farmers, the insights gained from the project could help them support both conservation and crop production. And bring bees back to the farm.

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