 Bumblebee species are declining in Europe , North America , and Asia due to a number of factors , including land @-@ use change that reduces their food plants . In North America , pathogens are possibly having a stronger negative effect especially for the subgenus Bombus . A major impact on bumblebees was caused by the mechanisation of agriculture , accelerated by the urgent need to increase food production during the Second World War . Small farms depended on horses to pull implements and carts . The horses were fed on clover and hay , both of which were permanently grown on a typical farm . Little artificial fertiliser was used . Farms thus provided flowering clover and flower @-@ rich meadows , favouring bumblebees . Mechanisation removed the need for horses and most of the clover ; artificial fertilisers encouraged the growth of taller grasses , outcompeting the meadow flowers . Most of the flowers , and the bumblebees that fed on them , disappeared from Britain by the early 1980s . The last native British short @-@ haired bumblebee was captured near Dungeness in 1988 . This significant increase in pesticide and fertilizer use associated with the industrialization of agriculture has had adverse effects on the Bombus genus.The bees are directly exposed to the chemicals in two ways : by consuming nectar that has been directly treated with pesticide , or through physical contact with treated plants and flowers . The species Bombus hortorum in particular has been found to be impacted by the pesticides ; their brood development has been reduced and their memory has been negatively affected . Additionally , pesticide risk pose consequences colony development and size . 
