If you believe that livestock animals are eating all of our crops, and that this means livestock production kills the slaughtered farm animals plus the animals that died in the production of their grain... you are wrong!
To find out why, read this article and it's supporting sources.
WHAT DOES THE STUDY SAY?
This research was quickly rebuked by the vegan community, and their comments will be the topic of the next post in this series, but, for now, I want to present a solid summary, along with my own criticisms, of Davis’ points:
FORMATING NOTE: Names in all caps attribute authors referenced by Davis.
The concept of least harm depicted by past research
humans, assumes veganism avoids this interference
Least harm principle (LHP) says: "Whenever we find ourselves in a situation
where all the options at hand will produce some harm to those who are
innocent, we must choose that option that will result in the least total sum of
interferes with animals
How many animals of the field would die if a vegan diet was adopted?
(plowing, disking, harrowing, planting, cultivating, chemical applications,
For example, mowing an alfalfa field decreased the gray-tailed vole population
The mortality rate of field mice is estimated to be 52%
Would a pasture/ruminant model kill fewer animals?
From here, Davis inquires about some other LHP alternatives that have been presented and why he feels they’re unsustainable. He also touches on the morality of intent, which I’m going to get into at the end of this series. The conclusions to his research simply state that alternative food-production models kill fewer animals than a vegan diet, making humans morally obligated to consume a diet from plant-based plus pasture-forage-ruminant systems.
However, to tell the truth, Davis’ calculations are a hot mess. He identifies many of the right numbers from pre-existing research, and he does present many insightful ideas, but how he uses those numbers has some major logic gaps.
The best estimate I could find for wildlife population densities was published by Reducing Suffering. The classes of animals listed by this article that would be present in crop fields are mammals, reptiles, and birds. However, their statistics represented world populations of animals—we’re only interested in the populations on crop-producing land, which the FAO estimates to be 11% of the Earth’s land mass, or 13.4 billion ha.
*This is only 32% of Tew and Macdonald’s estimation of 25 mice/ha, and this is an estimate for all mammals. I believe that the reason for this discrepency is that their research identified ideal conditions for mice to infiltrate crop fields. Also, Tew and Macdonald’s research was conducted almost two decades ago, whereas the Tomasik (Reducing Suffering) report was published in 2009 and the FAO report has data as recent as 2015. For these two reasons, I’m going to utilize the calculations in the table, but keep in mind that it could be many more depending on habitat.
HOW MANY OF THOSE ANIMALS ARE KILLED?
So we’ve figured out how many animals live in crop fields and will be affected by crop production… but how many of those actually die?
IT'S MORE THAN JUST HARVESTING
This brings up the issue of field activities. Davis correctly identifies a complete list of all field activities (plowing, disking, harrowing, planting, cultivating, chemical applications, harvesting), but then he references the mortality rate just for harvesting (only one field activity), and uses that mortality rate for his calculations, completely forgetting that the other field activities will contribute to wildlife deaths, as well. This also doesn’t account for the deaths from hunters protecting their crops, or the deaths for aquatic life killed in hypoxic dead zones, discussed in the intro to this series.
HOW MANY DO THE OTHER ACTIVITIES KILL
Harvesting is probably the most extreme instance, causing the highest mortality rate at 60%, discussed in the next paragraph, because it requires both the heavy machinery to remove the crops and other vehicles to be loaded with the harvest. I’m going to assume that the other field activities (plowing, disking, harrowing, planting, cultivating, and chemical applications) cause 5% mortality of all animals present in the crop field. Although few farms will carry out all six of these operations, some will do multiple chemical applications, replacing skipped field activities, and pesticides are one of the most harmful situations to wildlife, so I’m going to use all six in my calculations to balance out the difference. Thus, 5% mortality rate for 6 field activities equals 30%.
ADDING IT ALL TOGETHER
I really appreciate that Davis found two different studies discussing the mortality rate of harvesting then averaged their results (52% found by Tew and Macdonald and 77% found by Nass) to figure 60% mortality rates. Add 30% to this for the other activities, and we find that 90% of all wildlife living in or passing through the area will be killed during one crop season. This may sound extreme, but it actually falls short of the situations Davis referenced: an Oregon farmer observed that all of the small mammals, ground birds, and reptiles were killed when he harvested his crops. So, if 90% of 111 animals (111 pulled from the above table) living in one hectare of cropland is killed, that means that 100 animals will die on one hectare of crops that’s planted, grown, and harvested.
If there are 100 trillion animals in all 6.38 billion ha of ocean, than there are at least 376 billion animals living in the 24.01 ha affected by dead zones (although probably more because marine life is more heavily concentrated at the coasts that receive the fertilizer runoff). Let’s assume a 20% mortality rate, and so we’re estimating that 75.27 billion animals die as a result of hypoxic dead zones caused by crop agriculture every year.
Divide that by the 13.4 billion hectares of cropland that fertilizer is applied to, and you add another 5.6 deaths (this being marine life suffocated in hypoxic dead zones) caused by crop production. For the following calculation, I’m going to round this up to 6 to cover the deaths that result from the hunting of wildlife species to protect crop fields. This is a much smaller in number, but still an important death toll to consider.
111 + 6 = 117 deaths per hectare of cropland.
CORRECTING DAVIS’ PASTURELAND ASSUMPTIONS
Why on Earth is Davis converting crop land to pasture in his model? The 120 million ha he used in his calculations is land that crops are currently being harvested on… why convert that to pastureland when we there’s already pastureland in use? For a livestock and crop model, we’ll still need just as many fruits, vegetables, and grains to be grown requiring all 120 million ha of cropland to continue in production. So let’s re-do some of this math. Both the FAO and Learner agree that about 25% of the earth’s land (about 30.5 billion ha) is pastureland.
I also have a lot of problems with Davis saying that cultivation of forages kills wildlife animals. Forages are not only an appropriate diet for livestock, they also contribute positively to wildlife populations. Having a steady food source prevents diseases and encourages biodiversity, any irrigation or weed control (that uses lower-grade farm machinery and exponentially fewer passes) promotes tree growth which provides wildlife with cover—which would otherwise likely be a limiting factor. It’s not accurate to say that any notable amount of deaths are occurring here, because the field activities that are required are in no way comparable to the very intensive cultivation of crops… if anything, forage maintenance saves wildlife animal lives.
HOW MANY ANIMALS ARE SLAUGHTERED
Okay, so now we have to add in the obvious deaths- the livestock animals killed in slaughter. I’m going to use the American (because America is an example of an intensive agricultural system, it will show an extreme side of slaughter numbers, to be fair) kill count numbers for 2016, which I feel are slightly more accurate (account for more species and more current) than Davis’ statistics:
*Davis’ model factored only these deaths
Sources: USDA Livestock Summary and USDA Poultry Summary
So about 9.3 trillion animals are being slaughtered annually in the US. State Master reported that there are 582.115 million acres (236 million ha) of pastureland that house the livestock in the US. 9.3 billion animals killed in slaughterhouses divided by 236 million ha of pastureland means that 40 animals are slaughtered per ha of pastureland.
To reiterate, 117 animals die per hectare in crop production, while only 40 die per hectare in meat production.
REFRAMING THE DEATH TOLL
Because we’re discussing food, let’s convert this to usable calories, protein, and servings.
So what do these numbers mean in terms of deaths?
In summation, consuming plant products kills 1.03 times more animals per calorie, 5.4 times more animals per gram of protein, and 5.5 times more animals per serving, than consuming animal products.
One more note I want to add in here: Davis’ model was to consume only pasture-raised ruminants. The calculations I have done are representative of our current agricultural system, no changes needed.