1. The effect of field size on the
number of bumble bees
Anna-Reeta Aalto
2. Introduction
• Bumble bees have always been
important pollinators both in
agricultural and natural
ecosystems. Due to
homogenization of fields and
changes in land-use during last
decades the number of bumble
bees is however decreased.
3. Introduction
• In this research the aim was to study the
effect of field size on the number of bumble
bees in Estonia
• Compared to previous studies in Central and
Western Europe, Estonian fields are very
heterogenous and smaller surrounded with
semi-natural habitats
4. Methods
• Data was collected from 66 farms in Southern-
Western- and Mid-Estonia in summer 2007
• Bumble bees were counted three times from
400 x 2 m wide transects
• Monitoring was done only in dry weather with
more than +16 °C and wind speed under 6 m/s
5. Results
• The results show that there is a negative
correlation between the number of bumble
bees and the field size: the bigger field is, less
bumble bees are shown
• This result is similar to the previous studies
done in 2005 and later in 2009
6.
7. Discussion
• Homogenous fields
– The abundance of bumble bees is usually
dependent to the amount of food resources
(crops and wild flowers) which they need through
whole foraging season
– Not enough nesting and hypernating places
> More undisturbed perennial vegetation along
fields
8. Discussion
• Large fields
– Bumble bees have a limited foraging range (some
species only 450 m)
> Smaller field sizes
