Scientists have discovered that the community composition of bumble bee species and their relative abundances have changed drastically over the last 70 years in Sweden. Over the same period, the average seed yield of red clover has declined and variation in yield has doubled, suggesting that the current dependence on few species for pollination of red clover has been detrimental especially to stability in seed yield.

Source: Pollination services at risk following declines of Swedish bumblebees