I believe the assertion is that in order to maintain the bee population at the level necessary to meet demands on agriculture given the extraordinary rise in the death rate of both individual bees and entire colonies, the beekeeping industry has had to import far more colonies per year.
If you have signed a pollination contract to provide 100 beehives for a commercial orchard and your colonies keep dying then in order to be sure you can perform your contract and not incur damages, you will make sure you have more than 100 beehives in order to allow for colony collapse.
Similarly if you are making honey. If you have the right to make honey over an area that will support 100 beehives but you know that 20 of them are going to die, ten you will put in 120 beehives.
Commercial beekeepers know how to create new colonies by artificially triggering the split/swarming process. Thus, the logical response of commercial beekeepers to the colony collapse disorder is to keep extra colonies around. It makes complete sense.
Unfortunately, I doubt a similar adaptation is happening in the wild. We are losing wild pollinators and that may have all kinds of negative effects on the ecosystem.
Active colonies != total bee population.
If the mortality rate is high, then you need more colonies with reproducing bees in them to maintain the population at a certain level.
Cite the whole context of that quote! They're referring to trends since the 1940s.
The varroa mite literally wiped out the feral honeybee population in the US. There are no more North American feral honeybees! Of course the long-term population trend is downward!