Death of Trees Correlated With Human Cardiovascular & Respiratory Disease 152
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."
After accounting for all variables *they know of* (Score:0, Insightful)
Those three words make a huge difference...
Before assuming "they didn't control for" (Score:5, Insightful)
Bad science (Score:3, Insightful)
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:Before assuming "they didn't control for" (Score:4, Insightful)
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" (Score:5, Insightful)
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: Bad science (Score:4, Insightful)
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:Classic (Score:3, Insightful)
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:Ask a silly question, get a silly answer (Score:2, Insightful)
Trees are linked with localized reduce wind, reduce pollutants, increase oxygen, increase biodiversity, and partially regulate local temperature year round. There is just as much to assume that his idea is correct as it isn't. Thus why testing is needed and why his idea is called a hypothesis.
I can't believe you are criticizing someone for doing science by stating that the premise hypothesis is not proven already. Do you always criticize things that are not tautologies?
Re:Before assuming "they didn't control for" (Score:5, Insightful)
"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.