New research conducted by the Universities of Oxford and Exeter has found that many plant species labeled as ‘pollinator friendly’ in Europe actually bloom too late in spring to effectively support wild bee conservation.

This delay creates a ‘hungry gap’ during the early colony founding stage, which is critical for the survival and success of bee populations.

The study represents the first scientific effort to quantify how the lack of early-season floral resources leads to decreased survival rates and queen production in wild bee colonies.

Senior author Dr Tonya Lander (Department of Biology, University of Oxford) said: ‘The results give us a simple and practical recommendation to help bees: to enhance hedgerows with early blooming species, especially ground ivy, red dead-nettle, maple, cherry, hawthorn, and willow, which improved colony success rate from 35% to 100%. This approach focuses on existing hedgerows in agricultural land and doesn’t reduce farm cropping area, so can appeal to land managers whilst also providing important conservation outcomes for pollinators.’

Researchers focused on two specific European bee species, the buff-tailed bumblebee (Bombus terrestris) and the common carder bee (B. pascuorum), utilising the BEE-STEWARD model. This model integrates various data and simulates outcomes to predict how changes in environmental factors impact bee populations over time.

Investigations centred around determining the periods of highest food demand for bumblebees, understanding the impacts of food scarcity on colony survival, examining the relationship between food needs and seasonal colony dynamics—including the numbers of adults, eggs, larvae, and pupae—and assessing how the presence of early spring-blooming plants influences the survival and reproductive success of bee colonies.

Findings revealed that the demand for bumblebee food, primarily pollen and nectar, peaks between March and June. A shortage of food during this crucial period can have devastating effects on colony survival and the production of daughter queens, increasing the risk of local extinction. The months of March and April are particularly critical; a two-week interruption in forage availability during this time can lead to a dramatic 50-87% reduction in queen production.

Dr Matthias Becher (University of Exeter and Rifcon) said: ‘We were surprised to find that the colony’s demand for nectar and pollen is driven mainly by the number of larvae rather than the number of adult workers. This explains the particularly high colony demand in March and April, before the adult workers are usually seen foraging outside the colony. The larvae need pollen for growth, and most of the energy from nectar is used for thermal regulation of the brood.’ 

Despite numerous pollinator planting and conservation efforts, pollinator populations continue to decline globally. The study highlights that incorporating very early spring flowers into ecosystems could significantly boost bee colony survival and queen production, potentially reversing the troubling trend of pollinator decline.

The research, titled ‘Resource gaps pose the greatest threat for bumblebees during the colony establishment phase,’ has been published in the journal Insect Conservation and Diversity.

This study underscores the importance of enhancing existing hedgerows with early-blooming species as a viable strategy to bridge the hungry gap and support bee conservation more effectively.

 

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