Another thing Reagan was right about

He said, to much amusement, that trees cause pollution. He was in fact correct in his statement, despite the amusement. and he’s still correct but for a different reason:

City trees, popularly thought to remove pollutants and improve urban life, may also increase the amount of foul air that people breathe, says the UK body which gives independent health guidance to national and local government.

Nature, it’s always been out to kill us……

9 thoughts on “Another thing Reagan was right about”

  1. They left out the turpenes and other volatiles released by leves: “pine freshness”, eucalptus oil, while suppressing the undergrowth are probably not good for mammalian lungs.

  2. Is there a scientific paper behind this, or is it just Nice’s announcement of the month, to be overturned in a few decades’ time when some actual research is undertaken?

  3. Ok, I’ve read the NICE report. Evidence review 1a (pages 50-54, section 4.3.4: Urban greening) summarises three papers: two from Belgium and one from the UK.

    All three studies use computer modelling rather than actual measurements. NICE describes the evidence as “weak”, before concluding:

    The annual effect of trees on PM10 in an urban canyon ranges from increase of around 0.2% to an increase of 2.6%, depending on orientation and type of vegetation.

    It’s a small but tangible effect. I can imagine situations (narrow street canyon, densely-packed broad-leaved trees) where the effect would be even more significant.

    But given that people overwhelmingly like trees, this new evidence doesn’t tilt the balance much.

    On the matter of Reagan’s Terpenes, the Guardian reports that they are only a problem in hot weather, so only about two days a year in the UK. Even then they’re only a tiny component of overall pollution.

  4. The Grauniad article implicitly contradicts the headline – trees act as a sink for pollutants, so reducing the total amount of pollution in the air, but by slowing air currents encourages a concentration *under the trees* – so *not* where people are walking (unless they are *literally* hugging trees). The logic of the argument would lead to treetrunks getting dirty (some Victorians noticed and planted London Planes which regularly shed their dirty bark and grow some clean new bark) and *the ground under the tree* getting dirty – not the air breathed by people walking past.

  5. So Much For Subtlety

    Andrew M – “The annual effect of trees on PM10 in an urban canyon ranges from increase of around 0.2% to an increase of 2.6%, depending on orientation and type of vegetation.”

    Oh. My. God. There are BLTQWERTY trees?

    Not that there’s anything wrong with that. And if you think about it, a lot of trees are a little, well, fruity. You can’t get much more fey than a rowan after all.

  6. Tim (and Andrew M):

    Reagan knew quite well whereof he spoke. His explanation
    was specifically concerned with the notoriously “smoggy” southern California–pointing out that it was the result of a
    particular species (or genus) of conifers common to the coastal area (Linnaean designation begins with “Toxi” or “Toxo” or something closely resembling–just plumb forget, it having occurred quite some years ago.)

    Actually, I remember the event as promoting a wider public respect for Reagan’s intelligence and scientific erudition.

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