The Physics Police

The Physics Police

Friday, December 4, 2015

Agricultural Soil Loss

Yesterday I posted about a demonstrably false claim is currently circulating in the news media.

This started when the University of Sheffield’s Grantham Centre for Sustainable Futures put out a press release saying:
"...nearly 33 per cent of the world’s arable land has been lost to erosion or pollution in the last 40 years ..."
So I contacted Mark Sinclair, the author of the press release asking how they reached this conclusion.

He let me know the intention here was to highlight soil loss, rather than land loss per se as I addressed in my post yesterday. He acknowledged that this distinction has "perhaps been lost in the drafting". I'll say.

He also shared with me the conclusion above comes from a book called Dirt by David Montgomery.
"So far in the agricultural era, nearly a third of the world's potentially farmable land has been lost to erosion, most of it in the past forty years."
As we shall see this is a fantastical exaggeration!

The book cites something call the GLASOD project which in 1991 surveyed 250 scientists across the world and found that about 15% of agricultural land was degraded. This was a map of subjective perceptions, not an objective measure of land degradation. It's now out-of-date and its qualitative judgments have proven inconsistent and hardly reproducible.

Since this was a snapshot in time it can't be used to assess the rate of soil degradation. So how did Montgomery come up with 40 years? In reference to a paper (full text) by Bruce Wilkinson which again reports only the rate of loss.
"...mean soil losses are therefore equal to 885 m/m.y. in the areas under cultivation ..."
That indeed equals about 1.39 inches per 40 years. But that's a rate of erosion today. Not an historical account of the past 40 years.

Even if we ignore this, GLASOD reports 1.96 billion hectares or 15% agricultural land was degraded which is not "nearly a third".

But agricultural land is a small subset of arable land. So only 0.246% of arable land was degraded.

Furthermore, most of the land classified by GLASOD as degraded was only degraded by amounts "light" to "moderate". The book claims land was "lost" as in "could no longer support crops" which corresponds only to the most severe categories "strong" and "extreme".

This brings the total down to 305 million hectares or 0.0381% of worldwide arable land.

That's 866 lower than reported by Montgomery and thereby the Grantham Centre press release!

Soil erosion is a real problem. To address it and make positive change we start with the truth.

Thursday, December 3, 2015

Arable Land Loss

Soil degradation is a serious problem. I care very much about environmental protection and the long-term sustainability of agriculture around the world.

This is why it upsets me that a demonstrably false claim is currently circulating in the news media.
"...nearly 33 per cent of the world's arable land has been lost to erosion or pollution in the last 40 years ..." (,
"... nearly 33% of the world’s adequate or high-quality food-producing land has been lost ..." (theguardian.come,
experts from the University of Sheffield's Grantham Centre for Sustainable Futures revealed that nearly 33 per cent of the world's arable land has been lost to erosion or pollution in the last 40 years

Read more at:
This claim was delivered to the news media by the The University of Sheffield's Grantham Centre for Sustainable Futures which is a political research and advocacy organization. They've circulated a pamphlet and press release which both repeat the "33%" statistic without any indication how the number was calculated.

I suspect they got the number from the FAO website which says:
"... 33 percent of the global arable land used to producing feed for livestock ..."
Or perhaps they misunderstood this description of FAO data:
"Agricultural land covers 33% of the world's land area, with arable land representing less than one-third of agricultural land (9.3% of the world's land area)."
Whatever their mistake, we can use the FAO data to find out for ourselves how world-wide arable land area has changed over time. By multiplying the fraction of arable land by the total land area of each country we get the graph below.

Arable land is not being lost. Click here for the raw data.
But changes in "arable land" over time isn't even useful for measuring soil erosion and degradation. At least, not according to the FAO.
"Data for Arable land are not meant to indicate the amount of land that is potentially cultivable."
The three main causes of soil degradation are overgrazing, deforestation, and mismanagement of arable land. We can do something about all three. Spreading demonstrably false claims about about catastrophic loss of arable land does nothing help. By spreading misinformation, the Grantham Centre for Sustainable Futures only fosters distrust by people who aren't fooled by their doomsday warnings.

If we want people to listen, a good place to start is with the truth. Not demonstrably false claims.

UPDATE: I heard back from a representative of the Grantham Centre, but I still have no idea where the number "33%" comes from.

Power your home with only 150 Indurains!

Today I saw an hilarious news article (more like covert advertisement, but whatever) with the fantastically bullshit headline Pedaling For A Hour Can Power Your Home For Twenty-Four Hours. This may be true if your home has only one dim light bulb. But for modern homes in the USA, it's demonstrably false.

The article advertises a bicycle that's hooked up to generator and battery. You can store charge from exercise and run your home on this power. Well, partially run your home on this power. Don't get me wrong. It's an awesome bike! I want one!

But the average American rural household consumes 93.6 million Btu of electric energy per year.

(93.6 million Btu per year) / (365 days) = 75 kWh per day

The most bad-ass professional cyclists in the world can output at most 0.5 kWh per hour.

So how many Miguel Indurains would you need to invite over to your American rural household each morning to spend an hour peddling in order to supply the average day's power consumption?

(75 kWh) / (0.5 kWh) =  150 Indurains

"We're here to power your home. Don't worry, this will only take an hour. Got any food, by the way...?"

Tuesday, August 25, 2015

Environmental costs are important so stop lying about them

Many people don't read past the headline of a news story. Headline writers have immense and in my opinion unearned power to influence public opinion. Their objective is to capture attention. To this end they often exaggerate or misrepresent to the point of abject falsehood the contents of the article. When the subject is important the results of poor headline writing can be disastrous.

Here's an example.

New UN report finds almost no industry profitable if environmental costs were included

This is a doubly false headline.

First of all, this isn't a "UN report" but a report conducted on behalf of TEEB, a group which aims to draw attention to the global economic benefits of biodiversity. The TEEB is "hosted by" United Nations Environmental Program. This is one of the dirty tricks of headline writers. They fictionalize authority to artificially inflate the headline's credibility.

The big lie is about environmental costs. On page 28 of the report Table 5 shows 62 of the top 100 "greatest impact" region-sectors are still "profitable" when you subtract the natural capital costs from their revenue. That's a majority, even after cherry-picking the most polluting sectors from the NAICS list (page 63) and world regions (page 77).

This report does illustrate that some industries can't afford to pay for their external costs. Many of these industries like water supply and cereal farming are crucial to human survival and we all must share the cost. Nobody is suggesting all industries incorporate all externalities.

Other industries, notably cattle ranching and coal power generation should probably be reduced. Eating less meat and building solar panels will help the environment. Neither of those lessons are news to me. I find this report supports what we already know. If you take the time to read it.

External costs are real and represent a terrible price paid by the environment. Exaggerating them doesn't help protect biodiversity. It only serves to alienate would-be allies.

I would like to see more regulation put in place to factor in external costs. These regulations can force industry to mitigate and repair damage to the environment.

Tuesday, July 14, 2015

Planned Parenthood doesn't sell fetal tissue

First, a warning. This is not a typical lighthearted post exposing innumeracy in the media. This is the debunking of a shock-video about abortions.

A group of citizen journalists who call themselves "The Center for Medical Progress" have put out a video in which they claim Planned Parenthood uses partial-birth abortions to sell baby parts.

The video shows undercover footage of Deborah Nucatola, the Senior Director of Medical Services for Planned Parenthood, discussing how fetal tissue is procured and donated for research. There's nothing unethical or illegal about that.

Mothers give informed consent for this use just as some people donate their bodies to science in the event of death. Some people put organ donor stickers on their driver's license. Some people visit the blood bank regularly.

The video uses out-of-context editing to imply Planned Parenthood is making money from donated fetal tissue. In the full video Deborah Nucatola explains how Planned Parenthood receive compensation for the extra cost of handling and shipping samples. She later explains how this compensation allows them to give patients the option without impacting the bottom line.

The video attempts to confuse illegal "partial-birth abortions" with breech (feet-first) abortion which are in no way illegal. She clearly says the calvarium (head) is evacuated (removed) intact, which is not the case for partial-birth abortions. In the full video she explains how fetal demise is chemically induced before delivery.

The video claims the sale or purchase of human fetal tissue is a federal felony citing 42 U.S.C. 289g-2 which only applies to fetal tissue used "for the purpose of transplantation".

The video claims buying or selling human body parts is a federal felony citing 42 U.S. Code § 274e which also applies only to human organs used "for use in human transplantation".

This blatant misinterpretation of the law shows gross negligence on the part of the filmmakers and suggests intentional deception.

Planned Parenthood respects mothers who make the difficult decision to abort a pregnancy. Once the decision is made, one can only hope some good may come of it. If not for oneself, then for others. For some, knowing that the cell lines derived from their aborted fetal tissue may help cure disease, even if this possibility is remote, provides a small but desperate comfort. They should not be denied this comfort.

Abortions are horrible. This thinly-veiled pro-life slander of Planned Parenthood is even more so for its callous disregard for the suffering of would-be mothers.

Friday, June 12, 2015

Jurassic Park and the Half-Life of DNA

With the release of the Jurassic World I am reminded of the fictional science behind the cloning technique in the original movie.

I see nothing implausible about extracting DNA from blood cells found in a mosquito's gut. Although mammalian red blood cells and platelets both lack nuclei, bird blood cells have nuclear DNA one could theoretically recover.

Mr. DNA comes from non-mammalian blood

Unfortunately, the half-life of DNA is only about 521 years even under ideal conditions. The quantity of any substance with this half-life left over since the extinction of the dinosaurs during the KT extinction event is pretty easy to calculate.

(1/2)^(66 million / 521) = 4.81*10-38135

Though it's hard to make sense of a number this small.

I think we can all agree there were fewer base pairs of dinosaur DNA on the Earth 65 million years ago than there are atoms in the universe. Since there are only about 1080 atoms in the observable universe we can immediately conclude that the expected number of base pairs of dinosaur DNA remaining intact today is zero.

So the the fictional cloning technique in Jurassic Park can't work.

Looks like we're stuck with the dinosaurs we've got.

Wednesday, March 4, 2015

A soda jetpack is physically impossible

Today I saw this funny viral video.

We see a young man appear to lift off the ground propelled by 6 1-liter name brand soda bottles strapped to his feet. We are presumed to believe the carbon dioxide pressure in the bottle produces sufficient thrust to lift an adult human. Most people will intuitively decide the video is fake. After all, he's probably being lifted by a hidden wire.

I'll use some rocket science to show it must be a fake, not just to debunk this silly video, but to provide an example application of physics.

The force to lift a person off the ground must exceed the force of gravity pulling them toward the ground. If we assume the fit young man is 70kg we can calculate this force.

F = m * a = (70kg) * (9.8m/s^2) = 686 newtons

The six 1-liter bottles mass 1 kilogram each for a total of 6 kilograms. You can see on the second attempt they empty in about 3 seconds. Using the ideal thrust equation we can find the minimum exit velocity needed to lift the person.

V = F / ṁ = (686 N) / (6 kg / 3 s) = 343 m/s

That's faster than the speed of sound (340 m/s)!

Since soda bottles don't make sonic booms upon opening, we can conclude this video is fake.

Saturday, February 21, 2015

Himalayan salt is a poor source of magnesium

I've seen claims that you should cook with Himalayan salt because, among many other dubious claims, it's a good dietary source of trace minerals like magnesium. Let's put this claim to the test.

An often-repeated claim by the promoters of Himalayan salt is that it contains 0.16 g/kg magnesium. The dietary recommendation is not to exceed 3750 mg of salt per day. The daily recommended intake of magnesium is 400 mg for adults.

To get your dietary intake of magnesium from Himalayan salt, you'd need to consume 667 times the safe amount of sodium! This is not advised.

Instead, you could eat the following foods. All have a higher concentration of magnesium than Himalayan salt. Even better, you can eat enough of these foods to easily achieve the recommended daily value of magnesium.

Food Magnesium (g/kg) Times more magnesium than Himalayan salt
Almonds 2.821919258 17.63699536
Spinach 0.687842819 4.299017619
Cashews 2.610275313 16.31422071
Peanuts 1.111130708 6.944566924
Soy milk 0.268964179 1.68102612
Black beans 0.529109861 3.30693663
Edamame 0.440924884 2.755780525
Peanut butter 1.731448763 10.82155477
Bread 0.821428571 5.133928571
Avocado 0.194006949 1.212543431
Potato 0.433365953 2.708537208
Rice 0.370376903 2.314855641
Yogurt 0.185188451 1.157427821
Oatmeal 1.285714286 8.035714286
Kidney beans 0.308647419 1.929046368
Banana 0.271186441 1.694915254
Salmon 0.30570756 1.910672251
Raisins 0.202825447 1.267659042
Chicken 0.258675628 1.616722674
Beef 0.235159662 1.469747885

Saturday, January 17, 2015

Red Wine Is Not Exercise

Some online rag called the Elite Daily, which claims to be the premier online news platform for and by millennials, has this article titled A Glass Of Red Wine May Be Equivalent To An Hour At The Gym.
According to a study on the health benefits of resveratrol, a compound found in red wine, your body could receive some of the benefits of hitting the gym without sweat-inducing exercise.
The two-year-old paper they're referencing studied the effects of high doses of resveratrol on rats. They found that rats built more muscle on a 12-weeks progressive treadmill running program when 4 g/kg of resveratrol was added to their diet.

It's important to understand that this study did not compare resveratrol against exercise. It compared resveratrol plus exercise against exercise alone. In other words, says nothing about taking resveratrol instead of sweat-inducing exercise. It should be obvious that resveratrol is no substitute for exercise. Exercise has many benefits. Increasing skeletal muscle is only one of them.

Despite not being comparable to an hour at the gym, just how much red wine would you have to drink to achieve the studied dose of resveratrol?

Red wine can contain as much as 12.59 mg/L resveratrol. Assuming a person eats about 5 lbs of food per day, we can calculate the volume of wine you'd need to drink.

(5 lbs) * (4 g/kg) / (12.59 mg/L) = 720.56 L

That's 4,873 glasses of red wine. Per day.

Drink up!
Of course, no human can drink that much in one day. Since wine contains at least 9% alcohol by volume, all that drinking earns you a daily dose of 50.7 kg alcohol. The LD50 of alcohol is 5 g/kg. Assuming an 80 kg human, we can calculate how many times the lethal dose you'd receive on the Elite Daily's red wine diet.

(50.7 kg / 80 kg) / (5 g/kg) = 126.75

Not doctor recommended.