Does growing crops kill more animals than raising cows on pasture?

Question

In 2003, Steven L. Davis published an analysis in the Journal of Agricultural and Environmental Ethics which speculates:

Is it possible that some other agricultural production alternatives may result in least harm to animals? An examination of thisquestion shows that the LHP [least harm principle] may actually be better served using food production systems that include both plant-based agriculture and a forage-ruminant-based agriculture as compared to a strict plant-based (vegan) system. Perhaps we are morally obligated to consume a diet containing both plants and ruminant (particularly cattle) animal products.

This is based on the premise that animals are inadvertently killed in crop agriculture.

Animals living in and around agricultural fields are killed during field activities and the greater the number of field activities, the greater the number of field animals that die.

Davis presents a back-of-the-napkin calculation that is quite alarming.

There are 120 million ha of cropland harvested in the USA (USDA, 1997) each year. If all of that land was used to produce crops to support a vegan diet, and if 15 animals of the field are killed per ha per year, then 15 × 120 million = 1800 million or 1.8 billion animals would be killed annually to produce a vegan diet for the USA.

What can be said in response to this?

Answer 1

Assuming that the study estimating the 15 animals killed per ha of harvested crop is this one, it must be noted that the study was widely criticized for these and other mistakes and I would not in any case take it at face value.

To address the numbers mentioned in the question:

Davis estimates that 15 wild animals per hectare per year are killed as a result of harvesting annual crops, and guesses that maybe half that, or 7.5 animals per hectare per year, are killed on grazed land with managed perennial forage.

Now, in the same paragraph, the methodology for this calculation is mentioned:

He does this by averaging a mortality rate from the English mouse study (including animals killed by predators in the week following harvest), and a mortality rate from a study of a number of rats killed in sugarcane harvesting.

The article further admits possibility of inaccuracy of these estimates but argues that untill we have actual data they should be fine.

They actually do not seem to be, though. Apparently, out of 33 English mice living in fields fitted with radio collar, only 3 of these were killed by a combain. More than a half of them were killed by predators - these were argued to be more likely to catch them because of the lack of cover. A lot of the other deaths were attributed to stubble burning, a practice that is no longer in widespread use and restricted by governemnts.

Even if the above-mentioned numbers were absolutely correct though, there are still arguments that make veganism an absolute no-brainer when it comes to adhering to LHP (Least Harm Principle).

There is a huge difference (I believe) in accidental death or suffering and the focused, cold-hearted and intentional enslavement, violence and mass killing of agricultural animals.

The former is a by-product of actions that can be further reduced by conscious efforts and improved practices (see restrictions on stub burning above). It does not target specific species and does not make it impossible for these animals (as a group) to escape or adapt.

The latter is a targeted effort of our species which sees billions of animals imprisoned, inseminated, held in terrible conditions, being treated as things with no other real value besides the dollar that they are later exchanged for. It means that these animals are forcibly bred (often selectively, making animals unable to support their own weights because of the maximization of muscle as a result of that) and forced to watch their offspring going through the exact same thing. Well, they usually never really see their offspring because it is taken from them as soon as possible so yeah, there is that. There is no escape for these animals and even if there was, they have been so deformed by humanity's farming practices that their chances for survival without humans are.. slim. By definition, there is nothing that can be done to reduce most of the things I mention above. There can be improvements in taking care of these animals but they are often not economically viable and the invisible hand of the market stubs them out in their beginnings.

I think it is upon every one of us to decide what the least harm is in this situation. It may depend on your definition of harm or on your willingness to ackowledge things (on both sides of debate, please call me out on anything I might have omitted). For me though, the answer is quite clear.

Answer 2

Growing crops for humans kills significantly fewer animals than growing crops for meat. The specific number of animal deaths by crop area doesn't actually matter; even taking the most liberal estimate possible (which, if you include insects, could be thousands or more), this is still true. The reason for this is simple: meat animals eat more calories than they produce.

Growing crops to feed animals, then killing those animals for food, is a very inefficient food-producing system. Specific numbers vary by livestock type; the most efficient meat-producers, chickens, consume at least twice their weight in feed. Cows consume as much as 40 times their weight. So even if everyone decided to eat only chicken from now on, we would have to grow 2n pounds of crops to produce n pounds of chicken meat.

It's easy to see why this results in a lot more dead animals than eating the crops ourselves. If the whole world went vegan, we could feed about half again as many people. So along with a dramatically increased food supply, whatever the actual number of field-animal-deaths-per-hectare is, we'd be killing just as many of them as we are now-- but completely subtracting out the livestock.