I do think it’s important to look at whether isoprenes produced from trees should be considered polution.
First, an analogy.
Rainforests have very few nutrients actually in the soil: the large amounts of precipitation wash away any free nutrients. Most nutrients are quickly bound up into local vegetation, however, such that local streams are not full of nutrients.
Are the nutrients in soil or decaying biomass “pollutants”? Of course not: without them, no new vegetation can form.
When logging operations come through, however, there’s a lot of wasted biomass. This biomass does a couple of things:
It rots and erodes into local streams, clogging them; and
It’s often burnt, creating clouds of carbon dioxide.
Are the nutrients in streams “pollutants”? Are the clouds of smoke “pollutants”? Of course they are, in the classic sense of the word.
A pollutant is, first off, waste matter. This is by definition: if someone pours poison into a lake in order to kill the fish in the lake, this isn’t accurately called “polluting” the lake, since the poisoning is the goal, not the byproduct, of the operation. Similarly, a volcano doesn’t produce “pollutants”, since it’s nonsensical to talk about cloud of volcanic ash as waste matter.
Secondly, a pollutant contaminates a system. It must destabilize an ecosystem in a manner that the speaker considers negative. If someone composts their garbage and uses it to fertilize a garden, while they’re destabilizing the nonhuman ecosystem (encouraging the growth of their veggies at the expense of local grasses, for example), they’re not polluting their garden.
Are natural isoprenes pollutants? I’d say no. They are waste products: trees shed them. However, they’re not destabilizing an ecosystem in any reasonable way: on the contrary, they’re necessary to an ecosystem. It is only when other waste materials encounter isoprenes that they destabilise an ecosystem.
This may seem academic to Sam (whom I wish, Svinlesha, you wouldn’t mock with silly names – it only weakens your case IMO). Where I live, however, the “trees cause pollution” argument is brought up almost exclusively to pooh-pooh warnings about pollution in our region. People use this argument to claim incorrectly that the smog and haze we experience in Asheville is the result of nonhuman processes, that it’s foolish to worry about the effects of expanding industry and traffic on our beautiful local ecosystems and on our health.
If you don’t use the argument in that sense – if you are simply suggesting that airborne particles from trees can cause a bluish tinge in the air – then I might agree with you. But I’ve only ever seen the issue brought up in a disingenuously anti-environmental context before. It raises my hackles.
I was away for a week so missed keeping up on this extremely interesting debate. But, yes, Mr. S., I did read your reply about your now no longer so new child. Happy fathering! Allow me to give one small bit of advice which this thread reminds me of:
When he starts the “Why?” phase, shut him up by going for the system overload: “Why is the sky blue? Well son, mostly because natural sunlight consists of various wavelengths which are scattered by the atmosphere to various degrees … (ten minutes later) … and then there is the blue haze in the sky that is cause by naturally occurring terpenes, which may or may not be considered a polluntant …”
He’ll quickly learn to ask Mom next time!
Not being a little kid any more, thanks to all of you for the fascinating debate.
Daniel, xeno, zig, astro, Dseid, Sam, and all other interested parties, please gather round…
Sorry that it’s taken me so long to return to this discussion and polish it off, but mail-orders from the Smokies to the Great White North sometimes take a while. However, as y’all know, good things come to those that wait.
At last, I now have in my possession a slim, specially-ordered volume, entitled PLACE NAMES of the Smokies, published in 1999 and signed by no less a worthy than the author himself, Allen R. Coggins. It makes for very interesting reading, at least to a geek such as myself. The history of place names is not as straightforward as one might assume, especially in and about this particular region of the world. Anyway, regarding the Smokies, Coggins writes (pgs. 68-69):
Now, Coggins cautions that one must be careful when drawing conclusions about the relationship between place names and natural phenomena; these assumed connections can be misleading. Some place names, for example, were used numerous times in this particular stretch of country; the park contained 35 “Mill Creeks” at one time (Coggins, 12). In addition, some places had several names; and place names can be deceptive, or difficult to trace back with any sort of certainty. As an example, Coggins lists “Injun Creek”:
Jay Bird Branch might get its name from the jay birds that are common to the park, or might be derived from the fact that it was a popular location for skinny-dipping, and derive its name from the old expression, “naked as a jay bird.” And so on.
I mention the above with particular reference to the Cherokee names supposedly related to this area. We note that Coggins translates Sha-cona-ga as “blue, like smoke,” rather than “the place of blue smoke.” I submit that the second translation is misleading; there’s nothing particularly unusual about the “smoke” of the Smoky Mountains, nor does it contain an unusual “blue” tint; rather, the smoke is blue-gray, like all smoke. Note as well that the Cherokee also referred to the mountains as white, and called the stretches above and below the park for the White Mountains. In addition, Cherokee names were often related to traditional myths or stories; consider, for instance, the Cherokee name for what we now call Buckeye Gap. The Cherokee called it “Walasiyi,” meaning “Frog Place.” Proof that many frogs once lived in the gap? Hardly. The source is an old Cherokee story about a mystical, giant green frog that lived nearby (ibid., 39). So one must be careful in drawing hasty conclusions about the relation between natural features and place names (unless, of course, you believe there really is a giant green frog chillin’ over at Buckeye Gap).
Nevertheless, Coggins makes it clear that, in relation to the Smokies, the name is derived from all the fog, just as I claimed in my very first response to Sam months ago. I find it incredible that I’ve had to go through all of this trouble just to back up this obvious and simple assertion, but there you are. Given the ease with which Sam admits he’s wrong, I guess I should probably expect him show up presently to admit his mistake, and retract as well the many overgeneralizations he has made along the way. But I won’t hold my breath. Daniel:
Regarding your definition of pollution, I agree with you in principle, but I see potentially serious weaknesses in trying to define pollution on the basis of its context alone. By your definition, for example, any substance, taken to excess, must be considered a pollutant. But zig pointed out that isoprene is isoprene, regardless of source. If trees produce considerably more isoprene that a given industrial process, for example, it seems counter-intuitive to label the industrially-produced isoprene a “pollutant,” while calling the isoprene produced by trees “natural emissions.”
In addition, there are problems with the concept of “destabilizing an ecosystem,” since an ecosystem can arguably understood in terms of a dynamic process, in a state of constant flux, rather than as a “balanced” system. Some species become extinct as part of that natural process, for example, and are replaced with others. Adaptation presupposes that ecosystems are constantly “out of balance,” and that various species, by exploiting their particular evolutionary advantages, impose constant pressures of change/imbalance on the system. Do species that exude poisons as a means of protection, for example, “pollute” the environment they live in?
Mr. Svinlesha: I don’t quite understand. You found one source which claims that it’s moisture and not terpenes. And that closes the matter? After I’ve produced reams of evidence to the contrary, including many from academic and governmental sources?
I don’t know who Allen R. Coggins is. Is he an environmental scientist? Or an historian? If the latter, why would you expect him to be an authority on the chemical composition of the blue haze of the Smoky Mountains?
Last point first: ecosystems tend to be dynamically static systems (it’s too early in the morning to think of the correct word for this phenomenon). They fluctuate, sometimes wildly, around a central point.
They may change from one form to another, viz. hardwood forest succession. Even then, however, there’s the same fluctuation: such a system generally has some traumatic event (e.g., forest fire) which can “reset” the ecosystem. Such traumas are necessary to slowly-changing ecosystems: without them, the organisms that survive in the early stages of the cycle would go extinct once their stage is done.
Events which radically and permanently change a large ecosystem are, absent human actions, very rare. Sure, occasionally a volcano will blow, or a comet will hit, or a glacier will form, or a lake wall will burst, or a significantly new life form will evolve. But such events are definitely the exception, and without them, ecosystems are fairly stable (even as they fluctuate).
Humans are sui generis: we are the only organism capable of making deliberate, radical, permanent alterations to large ecosystems on a regular basis. Because of our capabilities, it makes perfect sense to have words for those changes that humans (and humans alone) are capable of making.
One of the two or three most important ways we make those changes to ecosystems is by making changes we consider negative by disposing of our waste products. When a human waste product makes significant changes to an ecosystem in a way that we consider negative, we call that waste product “pollution.”
So to your first point. I do believe that any substance discarded by humans in sufficient quantities can be considered pollution. If, for some reason, we decided to drag a humongous ice berg into an isolated sound, and if the ice berg melted off enough fresh water that the saltwater creatures in the sound began to die off, I’d consider the iceberg’s freshwater runoff to be pollution, even though it might be almost pure water. Fertile topsoil is a major pollutant in slow-moving rivers.
I’d probably not consider your example of human-created isoprene to be pollution. One of the requirements for my definiton is that the human waste product significantly alters the ecosystem. If humans are creating a tiny amount of isoprene compared to the amount created by trees, it seems unlikely that the human-created isoprene is going to change the ecosystem significantly.
It might, however. Perhaps the ecosystem has very limited tolerance for changes in isoprene levels; perhaps an increase in isoprene gives (for example) red alders a competitive advantage over the pines and maples that currently dominate the ecosystem, and so we start to see the forest’s composition change to favor red alders. If that were the case, as a society, we’d have to look at one more criterion for considering something pollution: is this significant change to the ecosystem one which we consider negative?
If so, then the human-created isoprene is a pollutant. And only if.
Anyway, this debate risks devolving into semantics, and the issue is really between you and Sam, rather than you and me. After all, Sam is the one trying to argue that trees pollute. He’s assiduously avoided getting into a deeper discussion on whether or not it is correct to refer to naturally-produced isoprene/terpene as a “pollutant;” he’s merely stated, categorically, that it is one.
Myself, I’ve gone back and carefully reread zig’s posts, where he addresses this issue, and am beginning to agree with astro’s previous observation regarding semantics. It seems to me that zig has been cautiously noncommittal with regard to this particular question. In his first post, for example, he writes:
There he seems to be saying that isoprene/terpene can rightly be considered a “pollutant,” although he’s rather ambiguous about it. Later, however, he notes:
Here he seems to be indicating that VOCs are not “pollutants” per se; rather, they are precursors to pollutants. But then again, isoprene and terpene are also implicated as possible causes of cancer….
So, zig (or some other specialist out there), let me ask straight out: is Sam’s claim that naturally-produced isoprene and terpenes should rightfully (and unambiguously) be classified as “pollutants” correct? Sam:
I would like to submit these facts, drawn from the discussion above, for your consideration:
Paraphrased from xeno: Spruce-fir forests release more than 1 million gallons of water vapor per square mile, every day.
Taken from zig’s link: in Alabama, during June to July (high season for isoprenes), the 24 hour average mixing ratio of isoprene was measured at 3.8 nanomoles per mole of air (Montzka conducted these measurement in a “rural troposphere”). A nanomole is 10[sup]-9[/sup] of a mole. During July, zig’s model (linked above) predicts a mixing rate of 2 to 5 nmol/mol; during winter, the predicted rate is .001-.01nmol/mol.
By the way, the 3.8 nmol/mol mean was calculated from midday measurements, when isoprene levels are believed to reach their peak. Isoprene has a lifetime of only a few hours, and by mid-afternoon/early evening, the levels are considerably lower.
2-5 nmol/mol, Sam, translates into an incredibly small amount. The standard molar volume of an ideal gas is 22.4 liters; using that as an approximation, there being 1000 liters to the cubic meter, we find that there are about 43 moles of air per m[sup]3[/sup]. Reconverting, then, we find that at peak season, the trees are emitting, at most, 200 nanomoles of isoprene/m[sup]3[/sup] of air per 24-hour period (the vast majority during the mid-morning and early afternoon). At the same time, this same forest is releasing 800 million gallons of water a day.
And you’re telling me that all this water vapor, ubiquitous at all times of the year, has absolutely nothing to do with how the Smokies got their name, and that they are instead named for the production of trace amounts of isoprene, a phenomena scarcely visible even during the height of summer, and generally described vaguely as a “blue hue” seen from a distance on certain days of the year?
I’m not 100% certain that the statement is true, but I certainly cannot think of any other organism that matches my criteria. Trees make radical, permanent alterations to their ecosystems, but they’re not doing it deliberately. Chimpanzees make deliberate alterations to their ecosystems, but they’re neither permanent nor large. When you ask me if the statement is true, do you have a counterexample in mind?
I do think it’s a question of semantics, at least partly. There’s three questions:
Does isoprene emitted from trees cause the air in the Smoky Mountains to sometimes have a bluish tint?
If yes to #1, is this bluish tint responsible for the Smoky Mountain’s name?
If yes to #1, is it appropriate to call these isoprenes “pollution”?
My understanding is that #1 is answered yes; #2 is answered inconclusively (it’s extremely difficult to trace the chemistry of an etymology); and #3 is answered no.
#3 is the semantic argument, but it’s an important one. “Pollution” is by nature a value-laden word; we should be clear on what the values of the word are, and what we’re goint to do with it.
First……you’re absolutely right that I’m being as ambiguous as possible, because this whole question is, at heart, philosophical rather than “factual.”
In the business, we avoid words like “pollutant” and “non-pollutant” or “toxic” vs “non-toxic.” This thread does an excellent job of illustrating why we avoid those words. The magic words are “regulated” and “non-regulated.”
Isoprene is regulated in general. Isoprene from trees is not regulated specifically.
