Any other ideas??  After all  we need to save the bees !

Charles, I think we cannot compare bee to human behavior and I'm not sure CO² is linked for this aspect.

Bees will quickly adapt to a new situation. Some believe they will gather more pollen if the protein contain is lower, I don't thing so. You need proteins and amino acids in a certain ratio with fat included. If it's not present the nurses will not be able to produce jelly and the brood surface will decrease accordingly. For exemple during the lavenders bloom period, the queens stop laying because the pollen is not good enough to raise brood, they adapt fast even if bee bread is still there.

Look at this poster, it was presented at Apimondia 2009 but I read it a different way, here is my view below.
https://www.apimondia.com/congresses/2009/Pollination-Flora/Posters/Floral%20origin%20and%20chemical%20characteristics%20of%20the%20honeybee%20pollen%20loads%20in%20western%20central%20france%20-%20MATEESCU%20C.pdf

Note the end April/May period the rich pollen is available, (about 25% protein in canola and fruit trees see green curve) this is our swarming period. Note also the quantity harvested by the bees 50g/day (left graph : récolte en gramme/ruche/jour = collected pollen in g/hive/day). Now in summer time (August), with sunflower 13% and corn 15% protein in their pollen, do you expect they will work harder ? Certainly not, they start to cut the brood down and only collect 10g/day or even less and the colonies are still full of bees at this time. They are not interested in such low protein contain pollen.
In September nurses get fat again with plants having protein above 25%, at this period if nectar is abondant the colony may swarm again, but they collect only 15g/day as the colony is much smaller in Sep compare to May. From September, the colony grow again, they also need fat winter bees. 
The bees adapt to the ressources, and the quality of these available resources. They are not fighting to get more pollen if the protein is low. There is plenty of pollen in the corn fields but they don't exploit or collect this pollen. They are not wasting their energy, this is honeybee economic way.
Hope it helps the exchange.
Georges

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