Pine beetle killed trees may not be a significant factor in upsurge in western US forest fires — says University of Colorado study

© 2015 Peter Free

Citation — to study

Sarah J. Harta, Tania Schoennagel, Thomas T. Veblen, and Teresa B. Chapman, Area burned in the western United States is unaffected by recent mountain pine beetle outbreaks, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1424037112 (online before print, 23 March 2015)

Citation — to press release

Jim Scott, Study: Western forests decimated by pine beetles not more likely to burn, University of Colorado at Boulder (23 March 2015)

The gist

From the press release:

Western U.S. forests killed by the mountain pine beetle epidemic are no more at risk to burn than healthy Western forests, according to new findings by the University of Colorado Boulder that fly in the face of both public perception and policy.

The CU-Boulder study authors looked at the three peak years of Western wildfires since 2002, using maps produced by federal land management agencies. The researchers superimposed maps of areas burned in the West in 2006, 2007 and 2012 on maps of areas identified as infested by mountain pine beetles.

The area of forests burned during those three years combined were responsible for 46 percent of the total area burned in the West from 2002 to 2013.

“The bottom line is that forests infested by the mountain pine beetle are not more likely to burn at a regional scale,” said CU-Boulder postdoctoral researcher Sarah Hart, lead study author. “We found that alterations in the forest infested by the mountain pine beetle are not as important in fires as overriding drivers like climate and topography.”

© 2015 Jim Scott, Study: Western forests decimated by pine beetles not more likely to burn, University of Colorado at Boulder (23 March 2015)

Surprising? — Maybe not

It seems to me that beetle-killed trees would only increase the probability of forest fire, if they noticeably increased:

(i) overall forest trees dryness — (the whole forest cumulatively becomes drier),

(ii) microclimate dryness — (less evaporation from a significant dead forest fraction reduces atmospheric humidity),

or

(iii) the dead trees significantly increase the risk of several of them simultaneously catching fire, which then creates a hot spot expansive enough to spread to the rest forest.

None of these factors (however) work in just one direction:

For example, dead trees would take up no water, leaving more for the rest. Presumably, this fraction would now be wetter than they might otherwise be, thereby reducing their chance of going up in flames.

Relatedly, dead trees would evaporate no water, but their now wetter companions might evaporate more, balancing out the micro-atmospheric difference.

Third, at a macro spatial level, the influence of drought and topography might always have been so massive as to cancel out the significance of other factors.

Caveats

Obviously, the study is not conclusive, given its narrow time span.

One also has to accept that the 54 percent non-overlap (between beetle kill and non-beetle kill areas) proves the team’s conclusion. Mathematically, I am a bit skeptical that essentially a half and half distribution (presumably chance) necessarily proved the reported conclusion:

Although MPB [mountain pine beetle] infestation and fire activity both independently increased in conjunction with recent warming, our results demonstrate that the annual area burned in the western United States has not increased in direct response to bark beetle activity. Therefore, policy discussions should focus on societal adaptation to the effects of recent increases in wildfire activity related to increased drought severity.

© 2015 Sarah J. Harta, Tania Schoennagel, Thomas T. Veblen, and Teresa B. Chapman, Area burned in the western United States is unaffected by recent mountain pine beetle outbreaks, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1424037112 (online before print, 23 March 2015) (at Abstract) (paragraph split)

What would the fire distribution have been like, if noticeably fewer trees had been beetle-killed or killed in different patterns of density?

I do not see how the team could so narrowly have pinned down the possible combinations of drought and varying terrain, so as to eliminate the possibility that beetle kill does increase the chance of fire by some percentage in some locales.

Without having access to the whole article, I do not know whether these considerations were statistically eliminated.

The moral? — Our assumptions about cause and effect are often just weak hypotheses

Hence the value of the scientific method.

A reportedly dramatic statistical error in setting the minimum level of vitamin D supplementation — is the current Institute of Medicine recommendation 10 or more times too low? — two studies say so

© 2015 Peter Free

Citations — to studies

Robert Heaney, Cedric Garland, Carole Baggerly, Christine French, and Edward Gorham, Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472–4475; doi:10.3390/nu6104472, Nutrients 7(3): 1688-1690; DOI:10.3390/nu7031688 (10 March 2015)

Paul J. Veugelers and John Paul Ekwaru, A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D, Nutrients 6(10), 4472-4475, DOI:10.3390/nu6104472 (20 October 2014)

The 2014 assertion of error — with regard to the Institute of Medicine’s 600 IU vitamin D supplementation recommendation

From Veugelers and Ekwaru:

The correct interpretation of the lower prediction limit is that 97.5% of study averages are predicted to have values exceeding this limit.

This is essentially different from the IOM’s [Institute of Medicine] conclusion that 97.5% of individuals will have values exceeding the lower prediction limit.

To illustrate the difference between the former and latter interpretation, we estimated how much vitamin D is needed to achieve that 97.5% of individuals achieve serum 25(OH)D values of 50 nmol/L or more.

For this purpose we reviewed each of the 10 studies used by the IOM.

Eight studies reported both the average and standard deviation. These eight studies had examined a total of 23 supplementation doses. For each of these 23 study averages we calculated the 2.5th percentile by subtracting 2 standard deviations from the average.

Next, we regressed these 23 values against vitamin D intake to yield the lower prediction limit. This regression line revealed that 600 IU of vitamin D per day achieves that 97.5% of individuals will have serum 25(OH)D values above 26.8 nmol/L rather than above 50 nmol/L which is currently assumed.

It also estimated that 8895 IU of vitamin D per day may be needed to accomplish that 97.5% of individuals achieve serum 25(OH)D values of 50 nmol/L or more. As this dose is far beyond the range of studied doses, caution is warranted when interpreting this estimate.

© 2014 Paul J. Veugelers and John Paul Ekwaru, A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D, Nutrients 6(10), 4472-4475, DOI:10.3390/nu6104472 (20 October 2014) (at 2nd paragraph) (paragraph split, underlines added)

A second study has now confirmed the first’s finding

From Heaney et al.:

In this communication, we present data from a different cohort entirely, including many individuals with vitamin D intakes spanning a range from zero to above 10,000 IU per day.

While the 3875 IU intake value [that we found is] needed to achieve at least 20 ng/mL (50 nmol/L) in 97.5% of the population is lower than the estimate of Veugelers and Ekwaru, it should be noted first that, as Veugelers and Ekwaru had stated, both estimates are roughly an order of magnitude higher than the published IOM value.

Also, it must be stressed that this input is explicitly supplemental, i.e., it presumes a daily, basal input from food and sun of some non-zero magnitude.

Since an RDA, by definition, relates to intake from all sources, it is clear that total intake required to achieve 20 ng/mL in 97.5% of the cohort must be close to 7000 IU per day, not substantially different from that calculated by Veugelers and Ekwaru.

Thus, we confirm the findings of these investigators with regard to the published RDA for vitamin and we call for the IOM and all public health authorities concerned with transmitting accurate nutritional information to the public to designate, as the RDA, a value of approximately 7000 IU per day from all sources.

We note that this conclusion applies specifically to the IOM’s designation of 20 ng/mL as the lower bound of adequacy, and that higher values, such as that of the Endocrine Society and GRH, would mandate the higher RDA values cited above.

© 2015 Robert Heaney, Cedric Garland, Carole Baggerly, Christine French, and Edward Gorham, Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472–4475; doi:10.3390/nu6104472, Nutrients 7(3): 1688-1690; DOI:10.3390/nu7031688 (10 March 2015) (at 4th paragraph) (paragraph split, underlines added)

The moral? — Thinking through the appropriate application of statistical methods to data is important

If these studies’ reasoning is correct, we see how such an understandable conceptual error may have huge consequences.

It will be interesting to see how the Institute of Medicine and the clinical medical community respond.

Conjecture is not even remotely fact or likelihood — arguably exaggerated press release reporting about Ganymede’s supposed salt water ocean

© 2015 Peter Free

Citation — to study

Joachim Saur, Stefan Duling, Lorenz Roth, Xianzhe Jia, Darrell F. Strobel, Paul D. Feldman, Ulrich R. Christensen, Kurt D. Retherford, Melissa A. McGrath, Fabrizio Musacchio, Alexandre Wennmacher, Fritz M. Neubauer, Sven Simon, and Oliver Hartkorn, The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals, Journal of Geophysical Research: Space Physics, DOI: 10.1002/2014JA020778 (early view before print, 12 March 2015)

Citation — to press release

Ann Jenkins, Ray Villard, and Felicia Chou, NASA’s Hubble Observations Suggest Underground Ocean on Jupiter’s Largest Moon, HubbleSite.org (12 March 2015)

The implied press release claim

From the press release:

NASA’s Hubble Space Telescope has the best evidence yet for an underground saltwater ocean on Ganymede, Jupiter’s largest moon. The subterranean ocean is thought to have more water than all the water on Earth’s surface.

© 2015 Ann Jenkins, Ray Villard, and Felicia Chou, NASA’s Hubble Observations Suggest Underground Ocean on Jupiter’s Largest Moon, HubbleSite.org (12 March 2015)

Evidence for the claim

From the abstract:

We present a new approach to search for a subsurface ocean within Ganymede through observations and modeling of the dynamics of its auroral ovals [see explanation here].

The locations of the auroral ovals oscillate due to Jupiter’s time-varying magnetospheric field seen in the rest frame of Ganymede.

If an electrically conductive ocean is present, the external time-varying magnetic field is reduced due to induction within the ocean and the oscillation amplitude of the ovals decreases.

Hubble Space Telescope (HST) observations show that the locations of the ovals oscillate on average by 2.0° ±1.3°.

Our model calculations predict a significantly stronger oscillation by 5.8° ± 1.3° without ocean compared to 2.2°±1.3° if an ocean is present.

Because the ocean and the no-ocean hypotheses cannot be separated by simple visual inspection of individual HST images, we apply a statistical analysis including a Monte Carlo test to also address the uncertainty caused by the patchiness of observed emissions.

The observations require a minimum electrical conductivity of 0.09 S/m for an ocean assumed to be located between 150 km and 250 km depth or alternatively a maximum depth of the top of the ocean at 330 km.

Our analysis implies that Ganymede’s dynamo possesses an outstandingly low quadrupole-to-dipole moment ratio. The new technique applied here is suited to probe the interior of other planetary bodies by monitoring their auroral response to time-varying magnetic fields.

© 2015 Joachim Saur, Stefan Duling, Lorenz Roth, Xianzhe Jia, Darrell F. Strobel, Paul D. Feldman, Ulrich R. Christensen, Kurt D. Retherford, Melissa A. McGrath, Fabrizio Musacchio, Alexandre Wennmacher, Fritz M. Neubauer, Sven Simon, and Oliver Hartkorn, The search for a subsurface ocean in Ganymede with Hubble Space Telescope observations of its auroral ovals, Journal of Geophysical Research: Space Physics, DOI: 10.1002/2014JA020778 (early view before print, 12 March 2015) (paragraph split)

Let’s get real

This technique evidently assumes that:

(i) patchy observations

(ii) of magnetosphere activity,

(iii) as reflected in fluctuations of Ganymede’s aurora —

(iv) a phenomenon whose mechanics we do not fully understand even on Earth, much less Ganymede —

(iv) can explicate the general chemical composition of subsurface liquid bodies,

(v) as well as their areal size and volume —

by

(vi) modeling those subsurface bodies’ presumable fluid and chemical dipole magnetosphere signature(s)

(vii) accurately enough to distinguish their presumable water and salt content, as opposed to some other blend of ions and apparent fluids.

Best evidence?

Sure — for demonstrating a (maybe wild) conjecture built on a foundation of other stampeding guesses.

The moral? — Good scientific work, but an exaggerated (implied) press release claim

The HubbleSite press folks would have been better off abandoning their “best evidence” and “thought to have more water” semantics for a less provocative way of explaining the clever (and necessary) ways in which science has to (ambiguously) approach things that it cannot sample or directly see.

Milky Way’s fastest yet observed star — is traveling at a galaxy-escaping 1200 kilometers per second

© 2015 Peter Free

Citation — to study

Geier, F. Fürst, E. Ziegerer, T. Kupfer, U. Heber, A. Irrgang, B. Wang, Z. Liu, Z. Han, B. Sesar, D. Levitan, R. Kotak, E. Magnier, K. Smith, W. S. Burgett, K. Chambers, H. Flewelling, N. Kaiser, R. Wainscoat, and C. Waters, The fastest unbound star in our Galaxy ejected by a thermonuclear supernova, Science 347 (6226): 1126-1128, DOI: 10.1126/science.1259063 (06 March 2015)

Citation — to press release

Andrew Kennedy, Queen’s astronomers discover fastest ever unbound star in our galaxy, Queen’s University – Belfast (11 March 2015)

On its way out of the Milky Way

From the abstract:

Hypervelocity stars (HVSs) travel with velocities so high that they exceed the escape velocity of the Galaxy. Several acceleration mechanisms have been discussed. Only one HVS (US 708, HVS 2) is a compact helium star.

Here we present a spectroscopic and kinematic analysis of US 708. Traveling with a velocity of ~1200 kilometers per second, it is the fastest unbound star in our Galaxy.

In reconstructing its trajectory, the Galactic center becomes very unlikely as an origin, which is hardly consistent with the most favored ejection mechanism for the other HVSs.

Furthermore, we detected that US 708 is a fast rotator. According to our binary evolution model, it was spun-up by tidal interaction in a close binary and is likely to be the ejected donor remnant of a thermonuclear supernova.

© 2015 S. Geier, F. Fürst, E. Ziegerer, T. Kupfer, U. Heber, A. Irrgang, B. Wang, Z. Liu, Z. Han, B. Sesar, D. Levitan, R. Kotak, E. Magnier, K. Smith, W. S. Burgett, K. Chambers, H. Flewelling, N. Kaiser, R. Wainscoat, and C. Waters, The fastest unbound star in our Galaxy ejected by a thermonuclear supernova, Science 347 (6226): 1126-1128, DOI: 10.1126/science.1259063 (06 March 2015) (at Abstract) (paragraph split)

Method

From the press release:

Dr Rubina Kotak and Ken Smith, from the Astrophysics Centre at Queen’s University, were part of a team of scientists from countries across the world who made the ground-breaking discovery using data gathered by the Pan-STARRS1 telescope [see here] on Mount Haleakala on the Hawaiian island of Maui.

Using a range of data gathered over the last 59 years the team were able to determine the full 3-D motion of the star and measure how quickly it is moving across the plane of the sky.

US708 is believed to have once been part of a double-star solar system, which also included a massive white dwarf star. The white dwarf is thought to have turned into a ‘thermonuclear supernovae’ and exploded, kicking US708 and sending it hurtling across space.

© 2015 Andrew Kennedy, Queen’s astronomers discover fastest ever unbound star in our galaxy, Queen’s University – Belfast (11 March 2015) (resequenced extracts)

The moral? — The ejection hypothesis sounds reasonable

U708 seems to be looking at an eventually “lonely” future, once it is outside its galaxy of birth.