[droningparrot]

One thing that isn't clear is how effective female trees are at removing pollen from the air. Is it possible that even with a much higher population but a more balanced sex ratio, there would still be a lower airborne pollen count?

[floatingatoll]

Yes, that's the core premise made by the author: If we're going to plant male plants, either we plant female plants (which have evolved to take up the maximum amount of pollen possible) or our lungs take up the pollen (which results in biological issues).

There's an inflection point where the amount of pollen left in the air by a sparse male forest equals the amount of pollen left in the air by a dense balanced-ratio forest. The article doesn't say where that inflection point is, though — when you state that inflection point as "a balanced-ratio forest can be XYZ as dense as a male-only forest with same or lower pollen counts", XYZ could be 1.1x, 20x, 5000x. Extrapolating that to urban trees, with pollen measured at human face heights, would be the holy grail of prove-or-disprove the value of this approach.

It is very likely that trees evolved to pollinate no more than is necessary to deliver the correct amount of pollen to the trees near them. I cannot find any estimates of this percentage at all, so as with XYZ above, it could be 1%, 10%, or 99%. More science is definitely required in both forest-shaped configurations and urban-shaped pockets.

[gus_massa]

Pollen is cheap and male trees overproduce it to get an edge over other male trees. Most polen just fall to the floor, a tiny part is lucky and reach the flowers in the female trees.

That's why many plants have nice flowers and use the help of insect to transport the pollen from a plant to another plant. (By the way, the yellow balls in the legs of the bees are pollen that they collect and take to the hive, for food. They "stole" most of the pollen, a small part drops in the other flower.)

Also, the link in the article in the sentence "The pollen grains do not just get to the female trees by accident; rather they are drawn there by this mutual attraction." is not a good justification of that "fact".

[im3w1l]

I wonder how good trees really are at attracting pollen. Intuitively it sounds like the forces should be small and the effect should be pretty marginal.

[floatingatoll]

Trees are 0.3 billion years old, so presumably they are not just good at it, but best at it.

[mrob]

And birds are about 160 million years old, but they can't fly as high or as fast as airplanes. Evolution doesn't plan ahead, so it easily gets stuck in local maxima.

[floatingatoll]

Birds seem to fall out of the sky a lot less often. Could be the same is true for pollen. I don’t know if I agree with the guy, but I think he’s right to encourage more science time and money spent on it.

[jeremysalwen]

What? How could you think this is remotely true. It's international news when a commercial aircraft crashes. Birds, not so much.

[nkrisc]

I don't know about that. A good number of them end up dead below my windows each year.