Once a month, retired accountant Sarah Hudson picks a path through historic Bunhill Fields cemetery to count bumblebees, noting the number, species and whereabouts of every one she sees. She is part of an army of people at the forefront of conservation efforts to save one of Britain’s best-loved creatures - bumblebees. There are 270 different species of bee in Britain, 250 of them solitary bees. Beekeepers manage honeybees who live in hives of 50,000 or more individuals. But bumblebees, who live in nests of 100 or so workers, do not roam far to forage for food and two species have gone extinct in the UK in the past century. Between March and October each year, BeeWalk volunteers walk a designated route and count how many bees they see. Sadly, due to habitat loss and the changing climate, more than half of British species are getting scarcer, and wildflower hedges and verges are disappearing from the countryside. Urban gardeners, however, can play an important role in protecting bumblebees.