When the demand of my job and my family life allow, I try to take advantage of the fact that I live in California by maintaining a vegetable garden. One of the less pleasant aspects of vegetable gardening is that, every winter and spring, it requires me to embark on a program of snail and slug eradication -- which is to say, I hunt for snails and slugs in my garden and I kill them.
As it happens, I'm a vegetarian and an ethicist. I'm not sure I'd describe myself as an "ethical vegetarian" -- that suggests that one's primary reason for eating a vegetarian diet is a concern with animal suffering, and while I do care about animal suffering, my diet has as much to do with broader environmental concerns (and not wanting to use more resources than needed to be fed, especially when others are going hungry) and aesthetics (I never liked the taste of meat). Still, given my diet and my profession, one might well ask, how ethical is it for me to be killing the slugs and snails in my garden?
Killing the snails is not something I relish, and not just because of what a slimy job it is. It used to be more slimy, when I was dropping them into a bucket of salt and sucking all the water out of them. Lately, I dispatch them is a solution of cold water and Ivory dish soap (the "Soapy Bucket of Merciful Deliverance"), which seems to drown them, after which I can pour their corpses onto the compost pile.
Although they are molluscs, I'm inclined to think slugs and snails might experience something like pain while the salt is turning them into goo, and I cannot rule out the possibility that they have negative sensory experiences in the "Soapy Bucket of Merciful Deliverance". I suppose it's also likely that they would experience pain while being eaten by a chicken, or while being cooked to be eaten by a human. Would drowning in beer be painless to snails? I don't know. (I do know, however, that the beer method has been less effective for us than pick and destroy -- and that I find it galling to buy beer for gastropod that drink up and then take their party to my lettuce plants.)
Anyway, what I'm doing to the snails probably causes pain. If I knew of a painless (for them) way to destroy them, I'd probably use it. From the point of view of animal welfare, my snail eradication plan is suboptimal.
So what is the interest pulling against minimization of snail pain here?
The short answer is that the current snail population makes it next to impossible for us to successfully raise food crops in our yard. On its face, this looks like a practical consideration rather than an ethical situation. However, our gardening is motivated at least in part by other ethical issues.
Raising food in our back yard is not just a way to feed the family a variety of fresh and nutritious fruits and vegetables (and maybe someday grains). It is also an effort to reduce our toll on the environment by removing a significant proportion of the food we consume from the big agriculture (and even the big organic agriculture) system. The food we are growing has fewer petroleum inputs, since we aren't applying petroleum-derived synthetic fertilizer (we use rabbit poop instead), nor driving tractors or other motorized farming vehicles, nor putting what we grow on trucks to get to the store (and driving to the store to buy it). There is also less packaging generated, since we keep using the same bowls and baskets to carry our crops from the garden into the kitchen.
I suspect we're making more efficient use of water in raising our food crops, too. We use a bucket system to redirect vegetable-washing water, vegetable-boiling water, and the water that comes out of the shower while we're waiting for it to warm up to the garden. In addition, we plant crops close enough to each other that they provide "living mulch" that reduces evaporative loss.
And, I strongly suspect that fewer animals are killed in our garden than are killed in the fields that big ag (even big organic ag) uses to raise crops. Mechanized tilling routinely kills small mammals who may be living under the soil, and pesticides and herbicides kill identified pests while running the risk of killing wildlife (either directly or when they wash into streams and such).
Slug and snail infestation at the commercial growers? I'm willing to bet they're killing those gastropods promptly.
It's probably not the case that everyone with a back yard garden intends it as a means by which to unplug from the big agriculture/supermarket/fast food cycle. However, for us, it is; while we might not be able to unplug completely, we can drastically reduce our participation in the cycle. And this, in turn, is intended to have a positive environmental impact, and thus a positive effect on the prospects of the human community as far as not rendering the earth unlivable.
But we can't have that positive effect without getting a handle on the snail population in our garden.
At this point, you might wonder if we could keep the garden snail population down without killing the critters. I don't see relocating them as much of an option. They're endemic to this region, and seeing as how they were brought here from elsewhere (France, I'm told) and became an invasive species, I would not want to risk doing the same thing to another region.
If I were to buy all our produce at the store, rather than raising it myself in the snail killing fields, that would not necessarily reduce the number of critters that die to make it possible for the peas, the tomatoes, the potatoes, or the carrots to grow to maturity. It would just be the case that I wasn't intimately involved in these killings (whether intended or accidents following upon mechanized tilling or pesticide use), an so would not be directly aware of them.
Plenty of people are happy just to get the food without knowing the details of its provenance. I'd rather shoulder the responsibility of doing my own dirty work here. The karmic costs of my food are not hidden out back in the fields behind the farm stand.
If snails were at all aesthetically appealing to me as a source of food, I'd be eating them instead of just killing them. They aren't, so I don't. I hope that by composting the ones I kill that we're making some use of the nutrients they provide to support the growth of the things we do want to eat.