Asked by: Adam Young, London
You might think it would just be a question of learning to live without honey, but bees play an incredibly important role in agriculture as pollinators. Cereal crops are wind-pollinated but virtually all fruit and many vegetables are insect-pollinated, overwhelmingly by bees. Without bees, crop yields would fall off dramatically. It's estimated that one-third of all the food we eat relies on bees for its production. That includes virtually every fruit you might make into jam, but finding something to put on your toast would be the least of your worries.
Over evolutionary timescales, other insects would probably take over the empty ecological niche but in the short term you could expect the apple, orange, coffee, chocolate and rapeseed oil industries to collapse. This wouldn't be an extinction-level event for humans, but it would cause widespread economic hardship and possibly famine until alternative cultivation systems and crops could be developed.