Death of Trees Correlated With Human Cardiovascular & Respiratory Disease

eldavojohn writes "PBS's NewsHour interviewed Geoffrey Donovan on his recent research published in the American Journal of Preventative Medicine that noted a correlation between trees (at least the 22 North American ash varieties) and human health: 'Well my basic hypothesis was that trees improve people's health. And if that's true, then killing 100 million of them in 10 years should have an effect. So if we take away these 100 million trees, does the health of humans suffer? We found that it does.' The basis of this research is Agrilus planipennis, the emerald ash borer, has systematically destroyed 100 million trees in the eastern half of the United States since 2002. After accounting for all variables, the research found that an additional 15,000 people died from cardiovascular disease and 6,000 more from lower respiratory disease in the 15 states infected with the bug, compared with uninfected areas of the country. While the exact cause and effect remains unknown, this research appears to be reinforcing data for people who regularly enjoy forest bathing as well as providing evidence that the natural environment provides major public health benefits."

Comments

Before assuming "they didn't control for"

[pepty]

and posting your indignant observation, please check and see if they did.

Re:Before assuming "they didn't control for"

[nadabu]

Sorry but the very phrase "After accounting for all variables" when doing statistical analysis on any complex real-life scenario is laughable. We don't even know all the variables, much less have rigorous data for them all.

I think their theory is probably right. It makes a lot of sense and the data we do have does fit. But this is statistics, not science; correlation, not proof of causation. It is far from being without value, but it is also far from being conclusive or thorough. It is merely as thorough as it could be given available data.

Re:Before assuming "they didn't control for"

[gstoddart]

There's things you think you know that are obvious, and then there's actual science.

Sometimes, you need the proper study just to verify your hunch isn't entirely wrong -- everything else is an anecdote or a guess.

Re:Before assuming "they didn't control for"

[sjames]

By that criterion, no study of anything ever has been good enough because we NEVER know for a fact that we have covered all variables.

'good enough' is only knowable in retrospect since at the time, we (by definition) didn't know about the unknown variables..

Re:Before assuming "they didn't control for"

[pspahn]

Speaking of poking out eyes, I have long known that EAB (Emerald Ash Borer) has been affecting human health, and you would too if you watch much baseball.

The death of ash due to EAB has caused a significant uptick in the amount of bats made from maple instead of ash. Maple doesn't have the same kind of durability that ash does, and what you end up with are bats that are easier to break. On any given night, you can see highlights of some pitcher nearly losing his face because a large chunk of maple is flying at him. You almost never saw this when bats where made exclusively from ash, as maple is simply more brittle and not as elastic.

Save a pitcher, plant an ash!

Re:Before assuming "they didn't control for"

[thedonger]

My study found a similar correlation between cardiovascular and respiratory disease and radio stations whose names begin with "W" compared to those beginning with "K."

Re:Before assuming "they didn't control for"

[Jane Q. Public]

"Want to bet that this will be exhibited soon as a poster child of spurious significance and poor statistical analysis?"

As Darrell Huff, author of the 1954 classic How To Lie With Statistics pointed out, the salaries of Protestant ministers at the time was very strongly correlated with the price of Jamaican rum.

The point being: so what? A correlation is all well and good, but the chances are overwhelming that it means exactly shit.

Bad science

[girlintraining]

Take a good look guys. This guy just committed a basic mistake in method. He made a leap unsupported by the facts. The presence and quantity of trees may be correlated with healthier people, but that in no way means there's a connection. He hasn't controlled for environmental factors. The most basic would be answering the question -- why are there more trees in a given area? In densely populated urban areas, there will be fewer trees, obviously... and we know cities have more pollution than a prestine wilderness. But that doesn't mean the trees are what's making people healthy... it could just be that the absence of pollution is.

This is an incomplete analysis and an attempt by an amateur scientist to start with a conclusion and work his way back to find supporting facts, while ignoring the fact that in science, you do things the other way around. And if you don't, you get crap like this.

I'm not about to go throw myself in a lake and start tree bathing because I think it'll improve my health... at best it'll be a placebo reaction. At worst, it'll kill me due to my allergies. What I'd do instead is try to find populations where trees are present at various threshold concentrations and match the environments as closely as possible so the only control would be the number of trees in a given area, and see if the correlation still holds.

Oh, and something to be aware of... richer neighborhoods have more trees than poorer neighborhoods, to the point that if you take satellite photography of a large metropolitan area, that alone can predict to a high degree of accuracy where the rich people live. Is this because they can afford to keep their environment cleaner as well?

You have to control for human behavior in this, or your analysis is broken.

Re:Bad science

[Anonymous Coward]

> Take a good look guys.

Too bad you didn't.

> -- why are there more trees in a given area

Isn't what this work studied. They correlated a specific insect cause of tree death with human welfare. The methodology was specifically constructed to remove confounding factors— things like air pollution killing both the trees and the humans.

That isn't to say the research is flawless but it was deeper and more carefully constructed that your slashdot arm-chair-expert off the hip comment gives it credit for.

Re: Bad science

[stranger_to_himself]

There's no claim that health was correlated with the presence of trees. The claim is that health is correlated with the presence of something that kills the trees, effectively at random (or at least in a way which is uncorrelated with anything that also directly affects human health) making this quite a neat natural experiment. Your arguments about other confounding factors don't hold in this case. look up natural experiments or instrumental variables if you want to know more about the method.

Re:Bad science

[Baloroth]

Seriously, did you even read the damned summary before you post? They controlled for demographic variables over time. The exact quote from the abstract is "Two fixed-effects regression models were used to estimate the relationship between emerald ash borer presence and county-level mortality from 1990 to 2007 in 15 U.S. states, while controlling for a wide range of demographic covariates." But yeah, I'm sure you identified the major problem with the whole study in 10 seconds. A study that was done over several years analyzing 17 years of collected data. But it's wrong, because there is absolutely no way they thought to correct for human behavior, no matter what the summary says.

Oh, hey, whats that, they controlled for income? Even spelled out that the effect of the ash borer was greater in wealthier regions thanks to the greater amounts of tree cover? Well, what do you know, scientists can sometimes actually know what they're talking about! Shocking, I know.

Next time, you could even try reading the full paper before you comment and call them "amateur scientists." Especially when they, you know, have already thought of everything you've pointed out.

Re:Bad science

[pspahn]

Not only that, but ash are a tree that does this better than others. There is a reason ash are commonly used as a 'street tree', and that is because they are effective cleaners of the particulates in the air while remaining healthy themselves.

I think an interesting extension of the study would be to look at any similar effects found in the West as a result of MPB (Mountain Pine Beetle). I'm not sure how different the loss of biomass is between MPB and EAB, but I can say I've never seen ash forests tens of thousands of acres in size be completely devastated where tree mortality is clearly over 90%.

With MPB, you have a much larger (and concentrated) loss of biomass while at the same time it is occurring in less densely populated (human-wise) geographies.

Re:Bad science

[gr8_phk]

The data they collected is by county. There are 3143 counties in the US. The Ash borer problem only affected about 15 states over a known period of time. This has the potential to have very good data (I have not seen the actual study but did follow the link to summary). The time period they were looking at included the time Vioxx was on the market, so there's one interesting thing they must have seen - but that didn't correlate with which state had ash trees dying. No doubt there were other things present in the data, but that didn't correlate with the bug-affected areas. Remember, you can pull some bullshit thing out of your ass and say "not accounted for" but unless your bullshit correlates with the areas affected by the bugs and trees then it probably HAS been accounted for by the correlation statistics.

Science is increasingly being used like a religion - even on slashdot. Use it to support the things you like and complain about it when it suggests something you disagree with, and either way don't bother to RTFA.

For all you M. Night Shamylon haters

[GodfatherofSoul]

Suck it!

Re:Haha

[wbr1]

Pardon me while I pull something out a my ass.

So I get my gerbil back?

Re:Classic

[Impy the Impiuos Imp]

Reread the OP, and the linked article.

The linked article states so in the abstract itself, using weasel words of "provides stronger evidence of causality".

The OP also strongly suggests it by mentioning asinine "forest bathing".

I will gladly go out on a limb (so to speak) and predict the ultimate validation of my use of "asinine".

Is there anything else you'd like me to do for you?

Re: After accounting for all variables *they know

[DarrenBaker]

That would be the *media's* fault for cherry-picking the language and the studies. If you ever really drill down into a study, you'll find a metric shit-tonne of ambiguous language the media turns into certainties.

Re:Deforestation != Causation

[Will.Woodhull]

Deforestation != Causation

Hmm. I first read that as "Deforestation does not equal Caucasian, which seemed strangely racist. Then I thought maybe it was "Defenestration does not equal Caucasian", which kind of made more sense, since being tossed out a window is pretty much an equal opportunity experience. But that seemed to be stating the obvious.

I got it right on the third read.

That course in speed reading may not have helped my reading comprehension, but it has made my world a more interesting place.