The UK has lost two bumblebee species in the past century and six of the 24 remaining species are declining sharply. Agricultural intensification has eliminated the flower-rich habitats that bumblebees require for foraging and nesting.
Declining floral resources cause bumblebee colony starvation, particularly in late summer when nectar gaps occur. Workers that forage in depleted landscapes return with smaller loads, requiring more foraging flights and experiencing greater energy expenditure per unit forage collected. Colony stress from insufficient forage leads to reduced queen production and colony collapse. The welfare of individual bees within failing colonies is impacted by chronic nutritional stress.