Most people have no idea how deep. Before there were bees there were very few flowering plants. When bees appeared the number and variety of flowering plants exploded. Today the vast majority of plants are flowering plants and a large percentage of those are primarily pollinated by bees. Apart from grains a huge percentage of plants grown for food depend on bees to pollinate them. There is no substitute.
It is hard to imagine but before there were bees, although the world was filled with plant life, a flower was a very rare thing. Fruit, of the kind that humans like to eat, was non-existent.
. I think this is more than a little alarmist, for there are many other species of bees, and many other insects that could provide pollination if European honey bees completely die out.
In fact, there were no European honey bees in north American before European colonists brought them over in the early days of the colonies.
There were still vast hardwood forests ( flowering trees, all), native fruits and nuts ( think pecans ), and many, many species of native flowering shrubs and flowers of all kinds. All without European honey bees. Pollination still occurred.
Second, even the worst of die-offs do not kill all species. For example, beavers were nearly trapped out, and thought to be nearly nonexistent in much of the land after trappers nearly eliminated them just a short 100 years ago. But, if you visit the inter-mountain west today, you will find them to have expanded way beyond their pre-trapping era extent, proving that the power of regeneration is amazing, even among mammals, which are not nearly as resilant as insects.
Insects are even more quick to adapt to overcome environmental threats, that's why pesticides have to be changed so often: the insects quickly become resistant.
Furthermore, the oft repeated threats of pesticide blow off are not substantiated. Pesticide application is highly regulated, and any die-offs caused by this would have been documented by the professional beekeepers themselves. After-all, if a farmer who had hired your bees, kills them by accidentally over applying pesticide, don't you think that a claim would be filed ? Since there never seem to be any references to these deaths, I think they may be claimed, but not substantiated, like so many claims of environmental disasters.Believe me, if there was some hard evidence, it'd be all over.
The cell phone tower claim, though oft repeated, has never been substantiated by any data, even anecdotal. We just recently got cell phone towers in these parts, yet the fruit industry seems to be fine pollination wise. And my own fruit trees have bees, and lots of other pollinators aplenty. That's not scientific evidence by any means, but it's just as much as the "everything will die if we don't have European honey bees "people have provided.
All the research I've seen with hard data seem to point to a mite, probably imported with some bees that were imported from Russia. Some will die, some will be resistant and survive to provide the population.