5 August 2019

Foraging behaviour of bumblebees and its implications for biodiversity and food security

Up to 90% of all wild plants and about a third of the world’s most important food crops are insect-pollinated. But what happens when pollinators like bumblebees don’t have their favourite flowers nearby, like in areas dominated by intensive agriculture? This is one of the questions that Janna Einöder is investigating through her MSc research on bumblebee foraging behaviour.

Wild plants and pollinators such as bumblebees share a mutualistic relationship. Bumblebees find their food in form of nectar and pollen on a plant. At the same time, the plant’s pollen gets stuck in the bumblebee’s fluffy fur and thereby transferred to another plant, securing the plant’s reproduction. A win-win situation!

Photo: Janna Einöder

Insect pollination vital

This win-win situation is highly important for nature, and also for us humans. Up to 90% of all wild plants and about a third of the world’s most important food crops are insect-pollinated. Bumblebees, honeybees, hoverflies or butterflies are all efficient and valuable pollinators. There are worries about what will happen to these insects and the flowers they pollinate as their surroundings are changing due to human influence.

Monocultures may lead to bumblebees switching flower species

Utrecht University MSc student Janna Einöder is investigating how different bumblebee species search for food and how the type of landscape or the quality of flowers affect this behaviour.

Photo: Janna Einöder

Janna is specifically focusing on flower consistency in bumblebees - when bumblebees prefer to visit only one species of flower at a time. The hypothesis is that in simple landscapes such as monocultures, or at low-quality sites with few flowers, bees have on average fewer resources and higher competition. In these areas, bumblebees might be more willing to switch between multiple flower species than in a more complex landscape like flower-rich grasslands.

To test this hypothesis, Janna sampled at 16 different landscapes in southern Sweden and recorded around 900 bumblebees using event recorder software on a tablet.

Flower inconsistency behaviour would be bad news for some wild plants and insect-pollinated crops

Flower inconsistency might lead to less or no pollination

Flower inconsistency behaviour like this would be bad news for some wild plants and insect-pollinated crops. These plants rely on the correct deposit of their own pollen on the female parts of another plant. Pollen from another plant might clog the pollen tube and lead to less or no pollination.

Major implications from a loss of biodiversity

With changing landscapes due to human influence, bumblebee species with a specialised and narrow diet might not find flowers to feed on. Both wild plants and certain pollinator species might become extremely rare or even disappear forever. This loss of biodiversity might eventually have major implications for future food security through its impact on insect-pollinated crops.

Understanding the consequences of a changing environment

Janna and her colleagues are currently analysing the field data and will soon understand more about the different bumblebee species and how they find their food. This knowledge will contribute to our understanding of what will happen to these insects and the flowers they pollinate as their surroundings are changing due to human influence.

Janna Einöder is supervised by Dr. Pita Verweij (Copernicus Institute of Sustainable Development) and Johanna Yourstone and Ola Olsson (Lund University)