Bumblebees benefit from broad bean plants. By planting these crops, the declining bumblebee population can be increased again, scientists discovered during a large field study in Germany.
Researchers at the University of Göttingen showed that broad bean plants specifically attract bumblebees and promote their population. Of all pollinators, bumblebees are one of the few that can access the nectar of the broad beanflowers. The plant hides its nectar deep in the flower and only bumblebees have a tongue long enough to gobble up the nectar. Due to the lack of competition, it increases their chances of survival and allows their population to grow. The researchers published their findings in the Journal of applied ecology.
Twice as many bumblebees
The scientists used fields of one square kilometer. Broad bean plants grew in one field, and the other field, five kilometers away, was free of broad beans and other grain legumes. In total, the scientists studied fifteen of these setups, spread across Germany.
For three months, scientists kept track of the population of wild bees and bumblebees on the fields. During two of the three months, they counted twice as many bumblebees on fields with broad bean plants compared to fields without such plants. Other bees were equally common on both fields. The broad bean plants form an ecological niche for bumblebees, researchers concluded.
Pollinators such as bumblebees and wild bees play an important role in nature. For example, eight out of ten edible crops depend on insect pollination. That represents an economic value of 153 billion euros worldwide. But the number of wild pollinators has declined significantly in recent years. The Netherlands is home to 360 species of bees, including bumblebees. More than half of them are in danger of disappearing. This is partly due to a decline in biodiversity. Wildflowers and messy places for bees to nest had to make way for agriculture and cities.
“Some pollinators need specific plant species, as the German scientists discovered for bumblebees.“
Various initiatives are in place to restore the bee population on a national and international level. That is a complex matter, in which nature must be enriched. But planting wildflowers and pollinator nesting sites alone is not enough. Some pollinators need specific plant species, as the German scientists discovered for bumblebees. Now scientists know that broad bean plants stimulate the bumblebee population, the initiatives can incorporate this into their projects and grow broad bean plants at targeted sites.
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Beyer, Nicole, et al. “Functional groups of wild bees respond differently to faba bean (Vicia faba L.) cultivation at landscape scale.” Journal of Applied Ecology.
Press release: “Bumblebees benefit from faba bean cultivation“, Eurekalert (10 september 2020)