Understanding animals killed in plant agriculture — and what it means for ethical diets
One of the most persistent arguments raised against vegan and vegetarian diets is that crop agriculture also kills animals — rodents, birds, rabbits, insects, and other small animals caught in harvesting machinery, killed by pesticides, or displaced by land clearing. The implication is that veganism does not actually reduce animal deaths and may not be ethically superior to omnivorous diets.
This argument has been made most prominently by philosopher Steven Davis (2003), who estimated that crop harvesting kills more animals per calorie than pasture-based animal farming. This claim has been extensively examined and largely refuted by subsequent researchers. This page reviews the evidence.
Combine harvesters kill small mammals (field mice, voles, rabbits) and ground-nesting birds during cereal and grain harvest. Estimates vary widely but studies suggest meaningful mortality in harvested fields.
Pesticide use kills insects (often in enormous numbers), soil organisms, and sometimes non-target vertebrates. Rodenticides kill rats and mice that damage stored crops.
Land clearing for agriculture is a major driver of wildlife mortality and displacement. This affects all animal agriculture (which requires far more land than crop agriculture) as well as crop farms.
Irrigation can displace soil animals; field flooding kills many invertebrates and small vertebrates.
Steven Davis's 2003 paper argued that pasture-based animal agriculture kills fewer animals per unit of food than crop agriculture. However, his analysis contained a fundamental error identified by economist Gaverick Matheny in a 2003 response.
Davis compared animals killed per hectare rather than animals killed per unit of food produced. This is the wrong unit of comparison for dietary choices, because:
Matheny recalculated using correct per-calorie and per-protein comparisons and found that a plant-based diet causes fewer animal deaths than an omnivorous one, even accounting for crop deaths.
A crucial point often overlooked in crop-death arguments: most farmed animals eat enormous quantities of crops. Approximately 70–80% of global agricultural land (and a large fraction of global crop production) goes to feeding livestock.
| Animal Product | Approx. Feed Conversion Ratio | Land per kg protein (relative) |
|---|---|---|
| Beef (feedlot) | ~8 kg grain per kg beef | ~20x wheat |
| Pork | ~4 kg grain per kg pork | ~7x wheat |
| Chicken | ~2.5 kg grain per kg chicken | ~4x wheat |
| Dairy | ~5 kg grain per kg protein equivalent | ~10x wheat |
| Eggs | ~3 kg grain per kg eggs | ~5x wheat |
| Wheat / Legumes | 1 (direct) | 1x (baseline) |
Every crop death associated with plant agriculture is also incurred (and multiplied) by feeding animals those same crops. A vegan diet avoids both the direct consumption of animals and the indirect crop deaths associated with feeding those animals.
Even if crop agriculture did kill comparable numbers of animals to animal agriculture (which the evidence does not support), there is a meaningful moral distinction between:
Most ethical frameworks — utilitarian, deontological, and virtue-based — treat intentional killing as more morally significant than unintentional side-effects. We generally hold people responsible for what they choose to do, not just for all downstream harms they cannot fully control.
Acknowledging that crop agriculture does kill some animals, there are meaningful ways to reduce this harm:
The evidence on crop deaths and animal welfare strongly supports the following conclusions:
Crop Deaths Vegan Ethics Plant Agriculture Land Use Feed Conversion Field Mice Davis Argument Animal Deaths