Apparently it has been an assumption for a long time in some circles that early sex by teenagers results in their later delinquency. Two recent papers demonstrate just how muddled this theory is (along with most theories generalizing about human behavior), because they differ in their conclusions based on how the data were analyzed. The first paper's ( Armour, S. and D.L. Haynie, 2007. Adolescent sexual debut and later delinquency. Journal of Youth Adolescence 36:141-152) purpose was to use data to support the theory, which it does. The second paper (Harden, K.P., J. Mendle, J. E. Hill, E. Turkheimer and R.E. Emery, 2008. Rethinking timing of first sex and delinquency. Journal of Youth Adolescence, in press) uses the same dataset to reach the opposite conclusion, that earlier sex reduces future delinquency.

The second group of authors of course claim that their analysis is the better one, and in this case it is true. These papers, in fact, are a good demonstration of one of the major problems of large-dataset human studies, which is that they only control for factors (in this case, survey responses about race, income, parent's education, GPA, drug use, etc.) that the researchers imagine could affect the data, and not all the other hundreds of factors that also could but are ignored out of practicality or researcher bias. The authors' hope is that their use of a giant dataset will obscure the fact that important information is lacking.

(Once again, we will put aside the first major problem of such studies, the use of self-reporting data. Of course since both groups of authors rely on them, neither mentions how unreliable they are, especially, one might assume, with regard to sexual experience. And one might also imagine that the group of people who are most likely to lie about sexual experience is teenagers.)

The reason the second study is the better analysis is because the authors recognize that pooling all the data loses important information. Meaningless averages are calculated by pooling teenagers from all cultures and walks of life. To a repeat a very nice analogy used by the authors of the second paper: if you wish to correlate meat consumption with life expectancy, and you compare two countries, one primarily meat-eating and another not, you find a positive relationship - higher meat-eating correlates with higher life expectancy. But a third ignored variable also correlates positively with meat-eating, and that is level of industrialization. So to truly understand the relationship between meat-eating and life expectancy, you must control for industrialization. When the analysis is rerun within one country, the correlation between meat-eating and life expectancy is negative.

In addition, what is found in both papers is simply correlation, not causation (a trap that first-year undergraduates are taught to avoid, and yet catches so many human-behavior researchers). That is, the only information one has after the meat study is that meat-eating is associated with lower life expectancy. The study has not shown that meat-eating causes lower life-expectancy.

These were the two main problems with the first paper. The authors pool individuals across a wide range of cultural norms, which gives them a spurious result, and then conclude that early teen sex causes delinquency when the two are only correlated. Even though they use a crude control for cultural influence (average reported age of first sex for a given teenager's high school) they ignore any potential unstudied factor that could cause both (just as industrialization causes both higher life expectancy, and more meat-eating), obscuring the results for individuals.

The second paper solves that problem by analyzing only the identical twins in the dataset (which was large enough for them to have data for 289 twin pairs), and therefore controlling for both genetics (which the twins share exactly) and environment (which twins living in the same household largely share). This is an appropriate twin analysis because (for this main point at least) the authors don't care about trying to separate genetics and environment to answer their question. (Twin studies that do confound objective data with subjective assumptions.)

On top of all this, though, is another major flaw in the dataset, which the second group of authors strangely acknowledge despite their analysis. The supposedly "independent" (time of first sex) and "dependent" (delinquency) variables are by definition related from the start, because in much of American society, teen sex itself is considered delinquent behavior. What they are doing is a bit like asking whether or not shoplifting is correlated with delinquency. This certainly confounds the first study.

What does it mean that the second study found that identical twins who have their first sexual experience earlier than their siblings are less likely to engage in delinquent behavior? The authors seem to feel they have no choice but to conclude that there is probably no relationship between these factors at all. Perhaps that is exactly what they would have found statistically if they had used a Bonferroni correction for their dozen or so analyses. Either that, or delinquency is caused by sexual frustration, and the problem of misbehaving teens is now solved.

Labels: behavior, environment, humans, morality, statistics

One common theme of this blog recognizable to regular readers is that medical studies based on giant data sets, especially those including self-reporting data, are quite limited in their implications for how an individual should live his or her life to promote optimum health. A recent article publicized as linking diet soda consumption to greater risk of diabetes and heart disease, and mortality in general, is a good example of this.

The problem with the study (Lutsey, P.L., L.M. Steffen and J. Stevens, 2008. Dietary intake and the development of the metabolic syndrome: The atherosclerosis risk in communities study. Circulation 117:754-761) is not that it is necessarily wrong. It is that it is too hard to tell what importance the findings have in the context of all the other health information with which we are bombarded daily.

Aside from the problems inherent in self-reporting diet data -- which the authors acknowledge in the discussion but which obviously had no effect on likelihood of publication or promotion of the press release -- the authors reveal a troubling bias in their assumptions and use of terminology. They conducted a factor analysis on dietary components in an attempt to see which parts of a diet are more highly correlated with a condition called metabolic syndrome (fat, high blood pressure, high cholesterol, etc.) or "MetSyn". So far so good. But the next problem here is that human beings had to classify the types of food people ate, and these classifications are based on assumptions already about what foods are good and bad for you. For example, "red meat" of course does not take into account what species of mammal was eaten, or the conditions under which it was raised, which surely affect its nutritional and fat content. They use a category "low-fat diary" because they believe there is a reason to distinguish it from non-low-fat dairy.

The use of categories is necessary for their methodology, but it illustrates the problem with nutritional data collection which to this point is always colored by currently held biases about good and bad food. To make matters worse, when their factor analysis revealed two broad dietary patterns (based on their categories) among the people studied, they chose to label these "Western" and "Prudent" dietary patterns. Guess which dietary pattern they have already decided is bad for you, and likely to cause MetSyn?

Although their results showing more people on the "Western" diet to acquire "MetSyn" show a correlation, they are quick to label certain food groups (e.g. dairy) as "protective". But of course this is based on the studies in the past that have shown certain types of food to have negative effects on human health (usually, though, only when consumed in high quantities). Of course then none of the results were too surprising, except for the finding of diet soda, consumption of which in their model increased risk for MetSyn even more than consumption of sweetened drinks. This was the splashy result that got the newspaper headline.

I have no problem with their explanation, it makes perfect sense. They first admit that the data might be confounded, because diabetics are more likely to drink diet soda than nondiabetics, so which came first? But they also cite a rat study which suggested that artificial sweetener screws up our body's ability to determine the caloric content of what we are consuming - our mouth says "caloric" and our body says "not" and thus our body may simply stop trusting our mouth. It's a much more interesting explanation, and makes some intuitive sense, so that makes it easy to ignore the explanation that the data are confounded. The study gets published anyway, and promoters at the journal find the line in the results and discussion that will attract media attention, and bingo.

Those of us who think artificial (= man made) sweetners are potentially nasty unknowns to be avoided if possible, love a result like this. But that still doesn't mean that if you drink a lot of diet soda you are doomed to be fat and get diabetes. Even when we really know very little about what we are studying, even when our methods are poor, and the results questionable (in some cases contradicted by other studies, as the authors cite), and based on broad assumptions, these studies get published, because they get headlines. Bad methods are considered acceptable to medical journals because there are not necessarily feasible methods that are valid. Assumptions may be based in part on established medical knowledge, but they are mostly based on previous, poorly conducted studies such as this one, not to mention constant propaganda from our media and government about what is good for us, and which is so obviously correct that they completely revamp the propaganda every couple of decades or so. We think we are learning more and more and more when we "confirm" these same assumptions, yet in truth we haven't even begun to understand the complexity and variation in the human body. Just ask a scientist researching disease cures, who actually has to get it right for anyone to care about her research. Eating dairy products is "protective"? Check that with someone from a genetic heritage of lactose intolerance.

Never forget that these studies are blunt, blunt instruments, that tell us nothing about what works for an individual. A good rule of thumb for most diets is, simply, variety, and not too much of any one thing. That, not forcing down a gallon of skim milk every day, should be the first step for anyone trying to feel better through a diet better suited to his body.

Labels: health, humans

As suggested in my previous post, it seems unlikely that the clear results of the Science studies will actually affect policy given the hard-to-crack corporate influence on government. Fargione et al. point out that "the recently enacted US Energy Independence and Security Act of 2007 specifies reductions in life-cycle GHG emissions, including land use change, relative to a fossil fuel baseline."

Here are some relevant bits. The first is included under section on grants for biofuels research, amending Energy Policy Act of 2005:

(4) develop cellulosic and other feedstocks that are less resource and land intensive and that promote sustainable use of resources, including soil, water, energy, forests, and land, and ensure protection of air, water, and soil quality.

The second amends the Biomass Research and Development Act of 2000:

(5) the improvement and development of analytical tools to facilitate the analysis of life-cycle energy and greenhouse gas emissions, including emissions related to direct and indirect land use changes, attributable to all potential biofuel feedstocks and production processes; and

(6) the systematic evaluation of the impact of expanded biofuel production on the environment, including forest lands, and on the food supply for humans and animals.

Does the law take into account land use changes beyond those of the United States, in developing countries where the local impacts are much more distructive? There is another growing fear that conversion of food-crop land into biofuels production, which is more profitable due to international demand, could cause even more devastating famines in Africa (for example) than are already occurring on a regular basis. According to the African Biodiversity Network, a car tank of ethanol requires the amount of grain that could feed a child for a year (Bonn, 2008).

But there does not seem to be any specific provision in the law that will call a halt to the madness if the results in biofuels research that companies like ADM wants are not found.

And of course industry is not going to sit there and give any policy ground to actual scientists. From the Times article:

Industry groups, like the Renewable Fuels Association, immediately attacked the new studies as "simplistic," failing "to put the issue into context."

"While it is important to analyze the climate change consequences of differing energy strategies, we must all remember where we are today, how world demand for liquid fuels is growing, and what the realistic alternatives are to meet those growing demands," said Bob Dineen, the group's director, in a statement following the Science reports' release.

The laughable irony here is that it is industry and their governmental cronies who have not put it into context. They are the ones who promote this policy as a "green" solution, when it clearly is not, and has been known not to be for sometime.

But of course they are correct that there is a demand for alternatives to fossil fuels. Are those of us criticizing the ethanol policy just short-sighted and naive? Do we reject the need to find alternatives to Middle-Eastern oil? Not at all. It is the biofuels industry that is being disingenuous by suggesting that they are somehow energy saviors. Unfortunately, it is the silver-bullet approach, rarely effective for any complex problem, that sells in today's America.

The energy pundits and power brokers dismiss wind and solar because they cannot supply all our power needs. The environmentalists dismiss ANWR drilling because it would clearly supply our current needs for only a short time, while doing permanent damage. The pro-nukes camp suggests more nuclear plants in order to reduce CO2 emissions, and yet they have failed to solve the waste problem, which is a (albeit smaller) serious environmental problem in its own right. The laudable attempts to remove environmentally damaging dams do not focus on how hydroelectric power will be replaced in a way that does not damage the environment. What the media and all the energy extremists fail to acknowledge is that a combination of all of the currently known types of energy not only would diversify our energy in a way that would help mitigate problems caused by shortages of any one resource, not to mention eliminate massive region-wide blackouts, and make a wide-ranging terrorist attack on energy sources next to impossible (unlike the current situation we have seen in which one blown power plant blacks out the entire northeast).

The reason this approach has not been advanced by any policy maker is that it doesn't create nice simple soundbites that result in huge amounts of public money flowing into a few giant corporations. Ethanol is a good partial solution to our energy problems. Carried to the extreme it's being carried to is a humanitarian and ecological disaster in the making. Biodiesel in the form of used cooking oil is a great way to recycle and create energy at the same time. But if every car did it, it would be an emissions disaster. We need to have ethanol cars and electric cars and keep working on hydrogen cars. We need it all, and the U.S. could be a technological leader in giving the world it all, which would have the added effect of generating a lot of economy that cannot yet be outsourced, as Tom Friedman has tried to advocate. Oil and natural gas need to have the role of back-up to the other energy solutions. Then we will have them when we really need them.

The problem is, policy makers in the U.S. government don't actually give a damn about energy solutions or preventing terrorist attacks on obvious targets. They care about big, deficit-inflating handouts that enrich certain corporations at the expense of the rest of the world. The outrage is that they use feigned concern about the approaching energy/climate change crisis, and terrorism, to gain unquestioned public support for their objectives. Eventually, it will dawn on the public that years of so-called "energy" and "anti-terrorism" policy has only made their lives worse. But of course it will be too late. Maybe it already is.


References

Bonn, D. 2008. Call for moratorium on agrofuels in Africa. Dispatches, Frontiers in Ecology and the Environment 6:6.

Labels: environment, politics

The announcement of two Science papers (Fargione et al., 2008; Searchinger et al., 2008) calculating higher carbon dioxide emissions through changes in land use is making a lot of noise. But will the public get this travesty enough to force a change in federal policy on ethanol?

It didn't take these studies to wake up scientists and more progressive policy makers to the dangers of overemphasis on ethanol.

Yet a quick check on Technorati of responses to this news shows a lot of people still don't get it. Some bloggers gleefully have blamed environmentalists for going to town on ethanol use, but scientists (the great majority of whom are environmentalists, but not vice versa) have known better for a long time - some smart ones just got a couple of easy Science papers out of the hot political potato that biofuels production is becoming. The papers are highly complementary, and both expose the faulty math that has been done to promote ethanol production as "renewable" energy - which is not so renewable after all when rain forests and grasslands are destroyed to produce it.

Fargione et al. calculated actual carbon release due to land clearing in order to create more land for biofuel production, and Searchinger et al. produced a model which uses estimates of these numbers. Both methods produce the same conclusion: the worldwide ethanol frenzy, ostensibly about reducing greenhouse gas (GHG) emissions, will actually accelerate the production of atmospheric carbon dioxide through the destruction of ecosystems which have much higher carbon storage than the biofuels plants themselves do. This is not a problem of the future, but is currently happening, both directly and indirectly: either new land is cleared for biofuel production, or the conversion of current crop land (or animal-feed land) for biofuel forces creation of new crop land. The fallacy of this is most extreme in Indonesian peatlands, which Fargione et al. point out are huge carbon sinks, and thus liberating this carbon to grow palms for oil leaves us with a carbon debt that may not be repaid for over 800 years.

Searchinger et al.'s model, as all models do, must make numerous assumptions about the numbers that cannot necessarily be confirmed at this time. However, they take great pains to be conservative in their estimates of carbon released due to changing land use, and the logic in their introduction cannot be denied. They point out what is known from previous studies: the carbon cost of growing biofuel feedstocks, refining them into fuel, and then burning them, is no different from the carbon cost of oil. What supposedly swings the balance in favor of biofuels is that while they are growing they take up carbon from the atmosphere, while the burning of fossil fuels liberates previously sequestered carbon. Given that we know that land conversion means a lot less carbon sequestered in plants grown on the same acreage, the model is practically gratuitous.

So why the big push for "renewable" ethanol? It didn't come from environmentalists. It came from agribusiness, the huge corporations such as Archer Daniels Midland, who have the most to gain from this legislation. By declaring the production of ethanol "renewable," (not to mention running their ads on PBS), they have framed themselves as a company who cares about people and the environment. But the consequences of the ethanol rush would have been obvious to anyone formulating the policy. Simply, like most legislation we've seen over the last decade plus, this is all about money - specifically, taxpayer giveaways to huge corporations whose buddies happen to be running the government.

Given that once again we seem to have failed to find our magic energy bullet, then what is the solution? Are scientists who criticize various alternative energy sources on environmental grounds hopelessly naive? Not at all. They simply acknowledge that our range of solutions is quite a bit wider than that proposed by corporate giants who want all the taxpayers eggs in their industry's personal basket.


References

Fargione, J.,Hill, J., Tilman, D., Polasky, S., Hawthorne, P., 2008. Land clearing and the biofuel carbon debt. Science (in press).

Searchinger, T, Heimlich, R., Houghton, R. A. , Dong, F., Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D., Yu, T. 2008. Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land use change. Science (in press).

Labels: biodiversity, ecology, environment, forests, politics

The mountain pine beetle (Dendroctonus ponderosae, Coleoptera: Scolytidae) is native to western North America. A finer resolution of its range, however, reveals that it is historically native to some parts of the West, but not others. Specifically, it has generally had a limited presence in Canada, primarily due to very low winter temperatures. Although the pine beetle's cold tolerance is incredibly high because they have the anti-freeze compound glycerol in their bodies, generally sustained (5 or more days) temperatures below -30F kill most of them off. This has reduced the likelihood of mountain pine beetle outbreaks in Alberta, and thus susceptible trees there have historically been protected, but are now exposed and being attacked (Rice et al., 2007).

In the last 5-10 years, however, conditions in the West, including Alberta, have changed. Rising temperatures have meant that for several winters in a row, the northern Rockies have not reached low enough temperatures to kill off the mountain pine beetles infesting the trees there. Even in the U.S., the historical trend was that every few years most of the beetles are killed due to cold, and thus the outbreaks were knocked back. So the pine beetles, which are a native species, have begun behaving like an invasive one: they are multiplying rapidly without a natural check, and expanding their range, attacking populations of trees that are not adapted to them.

Compounding this problem is the recent history of fire suppression in the West. One of mountain pine beetle's favorite hosts, lodgepole pine (Pinus contorta) is a fire-adapted species; it is common for lodgepole stands left undisturbed to burn once or twice a century, and be replaced by seeds from serotinous cones (cones in which the seeds are sealed unless they reach the high temperatures of a fire). Lodgepole stands are striking in that usually all the trees are the same age and size due to the burn regimen. Mountain pine beetles prefer older, larger trees. The larger the tree, the more food available for the developing beetle larvae, and the larger the increase in population the next year, if there is not a sustained hard freeze. By suppressing natural fires in lodgepole habitat, we may have enhanced the long term outbreak we are seeing now.

But here's the flip side: mountain pine beetle outbreaks make lodgepole pine stands more susceptible to fire down the road (Page and Jenkins, 2007). For instance, the 1988 Yellowstone National Park fires were highly correlated spatially with trees affected by a mountain pine beetle outbreak about fifteen years before (Lynch et al., 2006). What we may be experiencing now is a mega-outbreak, due to warming and fire suppression, which will eventually contribute to massive forest fires throughout the West in the future (also increasing of course from drier weather), which may have the benefit of being a different kind of check on mountain pine beetle populations. But instead of the historical ecology, in which mountain pine beetle outbreaks occurred for maybe 3-4 years, decades apart, a whole new, different ecology driven by constant high beetle populations decimating the forest, which as a result may burn more often, will remake the landscape in ways that we cannot yet imagine.

Of course there are those who believe that we can replicate the ecological benefits of fire, while keeping the timber available for human use. However, thinning trees mechanically is a blunt instrument that does not mimic the effects of fire at all in the case of lodgepole (Sibold et al., 2007). In fact, there is the danger of unintentionally increasing the density of trees (and necessitating, further, constant thinning effort) if enough of the canopy is opened to encourage new seeds to germinate and grow. There are those who believe humans are all powerful and can easily control insect outbreaks and fires through management if only the wicked, meddling environmentalists would let them (never mind that somehow the forests managed themselves just fine for millennia). In fact, many species are adapted to respond to biotic (e.g. herbivory pressure) and abiotic (e.g. weather) influences in ways we don't even understand. Global climate change is now accepted by anyone rational to be at least partly enhanced by the massive release of carbon dioxide into the atmosphere by industrial humans that would not have occurred otherwise. Fire suppression is an active (and expensive) choice that trades short-term convenience for long-term ecological disruption, whose consequences we are barely beginning to understand. Those who blame "environmentalists" for the hundreds of acres of brown pines they see spreading like a cancer in the West, would find that ecologists (pretty much environmentalists by default) only wish they had such god-like power to affect the ecology of our forests, so they could save them from 150 years of disastrous "management."


References

Lynch, H.J., Renkin, R.A., Crabtree, R.L. & Moorcroft, P.R. (2006) The influence of previous mountain pine beetle (Dendroctonus ponderosae) activity on the 1988 Yellowstone fires. Ecosystems, 9:1318-1327.

Ono, H. (2003) Mountain Pine Beetle Symposium: Challenges and Solutions. Kelowna, British Columbia. T.L. Shore, J.E. Brooks, and J.E. Stone (editors). Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Information Report BC-X-399, Victoria, BC. 298 p.

Page, W.G. & Jenkins, M.J. (2007) Mountain pine beetle-induced changes to selected lodgepole pine fuel complexes within the intermountain region. Forest Science, 53:507-518.

Rice, A.V., Thormann, M.N. & Langor, D.W. (2007) Mountain pine beetle associated blue-stain fungi cause lesions on jack pine, lodgepole pine, and lodgepole x jack pine hybrids in Alberta. Canadian Journal of Botany-Revue Canadienne de Botanique, 85:307-315.

Sibold, J.S., Veblen, T.T., Chipko, K., Lawson, L., Mathis, E. & Scott, J. (2007) Influences of secondary disturbances on lodgepole pine stand development in rocky mountain national park. Ecological Applications, 17:1638-1655.


Thanks to T. Etienne for initial information on mountain pine beetle

Labels: ecology, environment, forests, insects, invasive species