Eat the Dog? Using Fake Data to Sell a Bad Book

Over at The Daily Signline, Clark Williams-Derry smashes the nonsense put out by a New Zealand couple that has promulgated a lie in order to sell their crappy book.

Promulgated a lie?

Yes a lie.

You are a liar when you know the truth, and run away from that.

A lie is not a mistake, a mis-statement, or a bit of clumsy sentence construction. A lie is served up calculated and cold, and in this case, it was designed to sell books.

And what was the lie? Simple: that owning a dog is as environmentally destructive as owning a Sports Utility Vehicle.

So what does Clark Williams-Derry say about this lie? Nothing but the truth. He writes:

You may have seen the meme circulating around the internet: some researchers from New Zealand are claiming that owning a dog has as much impact on the planet as owning an SUV. I'll let New Scientist summarize their case:

"[A] medium-sized dog...consume[s] 90 grams of meat and 156 grams of cereals daily in its recommended 300-gram portion of dried dog food...So that gives him a footprint of 0.84 hectares...

"Meanwhile, an SUV...driven a modest 10,000 kilometres a year, uses 55.1 gigajoules, which includes the energy required both to fuel and to build it. One hectare of land can produce approximately 135 gigajoules of energy per year, so the Land Cruiser's eco-footprint is about 0.41 hectares - less than half that of a medium-sized dog."

It's just the sort of counter-intuitive claim that gets lots of attention on the brave new internet era. So interesting! So science-y! So Twitter-able!

And yet, so false! Once you sniff around the numbers, it quickly becomes apparent that those researchers are barking up the wrong tree.

Let's get one thing out of the way: I'm not a dog owner. Much to my kids' dismay, I don't even want a pet. Nor do I own an SUV. So, in theory, I...er...don't have a dog in this fight. Still, this claim struck me as so wrong that it made the hair on my neck stand up. And I'd hate to have someone catch scent of this meme and conclude that buying an SUV is no big deal -- "It's not like I'm buying a dog or anything" -- if the real numbers don't support that conclusion. (That's the risk of bad information: it can lead us to make choices that are in stark conflict with our values.)

So let's paws for a moment, and see if this sleeping dog is actually a lie.

First, let's look at that SUV. The calculations behind the internet meme say that it's driven about 6,200 miles per year (10,000 km). And yet, according to the US Department of Energy, a real SUV in the US is driven an average of 13,700 miles annually. Already, the internet meme is off by a factor of roughly 2.2. I haven't checked whether the 10,000 km figure is reasonable for Australia New Zealand -- but it for the US, their mileage assumptions certainly skews the numbers in favor of SUVs, and against dogs.

And then there's the total energy estimates. The pet-pessimists estimate that an SUV (in their calculations, a 4.6 liter Toyota Land Cruiser driven about 6,200 miles) consumes 55.1 gigajoules of energy in both fuel and amortized manufacturing energy every year. That, too, is low. A Land Cruiser gets about 15.25 mpg in combined city/highway driving -- meaning that if it's driven 10,000 km, it consumes about 407 gallons of gas, or 53.6 gigajoules worth of energy. But once I add in the energy used to produce that gas, along with what's likely a low-ball estimate of the "embodied" energy from vehicle manufacturing, I get get about 74.9 gigajoules -- 44 percent more than the authors estimate. Yet again, they've low-balled the impacts of the SUV in a way that makes dogs look worse by comparison. (Here, I'm drawing from the data collection and calculations I did for our CO2-by-transportation-mode charts. And I'm looking only at energy, not at the additional climate and pollution impacts of emissions from tailpipes and smokestacks.)

So even before you start to look at dogs, the authors have underestimated the environmental impacts of SUVs by a factor of at least 3. And that's not including the indirect impacts of SUVs -- the parking spaces we build for them; the roads and bridges they drive on; the impacts of insurance and licensing operations; etc., etc., ad nauseum.

Then there's flip side: the authors' claims about the impact of feeding pets. The anti-doggists estimate it takes .84 hectares -- or about 2.1 acres of cropland -- to meet a a pooch's food needs for a year. There are a little over 70 million dogs in the US (the Humane Society says 74.8 million, the veterinarians say 72.1 million, and the pet food industry says 66.3 million, for an average of 71.1 dogs). So by the authors' estimates it must take about 150 million acres of US farmland to feed our dogs. In all, there are 440 million acres of cropland in the US -- suggesting that the equivalent of one-third of all US cropland is devoted to producing dog food.

We use the equivalent of a third of all US cropland to feed dogs? That's barking mad!

To see why it's wrong, you can look from the bottom up, at the foods that dogs eat. Or you can look from the top down, at the aggregate sales of dog food vs. the entire agricultural economy. I'll do both.

First from the bottom up: what, exactly, do dogs eat? The anti-pet-ites seem do a good job of calculating dogs' calorie requirements. Canines wolf down a lot of food: a mid-sized dog consumes roughly 30 calories per pound of body weight per day. (Smaller dogs eat as many as 40 calories per pound of body weight, while larger dogs eat as few as 20 calories per pound. Call it the yapping-to-napping spread.) I couldn't find the average weight of dogs in the US, but the median dog breed listed here has an adult weight of 47 pounds. If that's representative of US dogs, then the average dog will eat 1,410 calories today, give or take -- which, as I read it, is roughly what the authors' figures imply.

So the real problem with the authors' calculations isn't with their estimates of how much each pet eats. It's with this statement:
[A] medium-sized dog...consume[s] 90 grams of meat and 156 grams of cereals daily

Strike that: most dogs DO NOT eat meat and cereals. With a few exceptions, they eat "meat" and "cereals." The "meat," in particular, tends to be byproducts -- things that people in the US simply won't eat, even in hot dogs. Here's one description of the ingredients in pet food:

The protein used in pet food comes from a variety of sources. When cattle, swine, chickens, lambs, or other animals are slaughtered, the choice cuts such as lean muscle tissue are trimmed away from the carcass for human consumption. However, about 50% of every food-producing animal does not get used in human foods. Whatever remains of the carcass -- bones, blood, intestines, lungs, ligaments, and almost all the other parts not generally consumed by humans -- is used in pet food, animal feed, and other products. These "other parts" are known as "by-products," "meat-and-bone-meal," or similar names on pet food labels.

Even the cereals dogs eat are often deemed unfit for human consumption. I'm not trying to gross you out here, or encourage you to feed choice cuts to your pooch. Instead, I think it's probably a good thing that dogs eat things that humans won't -- since otherwise they really would be eating people food, which really would increase their environmental impact. But since most dogs get their calories and protein from the waste products of people food, the idea that the environmental impact of dog food is additional to the impact of human food is simply wrong.

Read the whole thing here, but let it be said that I said it first (albeit without quite as much specificity)!

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