I looked a a host of different studies about CO2 and plant growth and it is
a bit more complex than it seems from this discussion.

What I have learned is that, generally, increased CO2 leads to increased
plant growth. In some cases nutrients are reduced, but not in all since
temperature plays a significant role. Also, nutrients may not have
decreased in the plant but only in percentage of mass and not by the whole
plant. The plant grows but it is adding structure to support the growth and
not adding additional nutrients. So you can get a decrease in nutrients as
a percentage of the total mass but not of the total plant. You have a
tumbler with one ounce of sugar in 10 ounces of water. Add another ounce of
water and you have less sugar by percentage but the same amount sugar in
the water.

There was a nice study on willows and the larva that fed on the willow
leaves. The larva had to eat more leaves to arrive at maturity with
increased CO2 and constant temperature but did not with the same increase
in CO2 with increased temperature.

So the decrease in protein may be as a percentage of total mass but it is
all still there just diluted. But then we have the well known issue that
all pollen is not created equal. Some are loaded with nutrients and some
are not, So even with a decrease in some plants, does that equate to harm
for the bees?

Probably not for beekeepers like me with a cornucopia of pollen sources all
growing season long. But for some in a less pollen productive area, the
answer is more ambiguous, since it all depends on the plants.

The one thing I carried away from the study on goldenrod pollen is that the
researchers do not know if it effects the bees, but only that it may.
Prudent observation.

Bill Truesdell
Bath, Maine

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