A few years ago, the weeds and rushes were growing out of control on one of my pastures, so I mowed it with the tractor. Chickens range widely over short grass, and mowing the grass helps keep it green. (Chickens can’t digest tough, brown, woody plants, but they can deal with succulent green plants.)
As I mowed, crows appeared. Mowing uncovers field mice and other rodents that live in the grass, exposing them to predators. The mower also kills some creatures outright.
“It’s a good thing I’m not a vegetarian,” I though. “If I’m killing this many animals just by mowing, imagine what would happen if I plowed this field every year to plant corn and soybeans!”
If you think through the process, you’ll see just how hard farming is on the local wildlife. You start by cutting down all the trees that make up the normal ground cover on your land (at least, that’s what grows naturally in my part of the world.) This displaces all the birds and animals that used to live there. Because all ecological niches are already full, displacing creatures has the same effect as killing them. The only real difference is that the cause of death — starvation, exposure, and disease — is more lingering.
Then, each year, you plow the land, killing burrowing animals outright and preventing the land from being colonized by ground- and tree-dwelling creatures. By growing only one or two crops, which become edible only for a brief period before harvest, you create a wasteland with little food value 11 months out of the year. No creature can survive by eating for one month and starving for eleven, so farming greatly reduces the amount of wildlife the land can support.
So a piece of cropland is an open scar on the landscape that kills and starves birds and animals every year. And vegetarians pat themselves on the back and feel smug, because they didn’t actually eat any of the dead creatures themselves. They died anonymously, out of sight. To a lot of people, that’s the same thing as not dying at all. It makes me angry. We’re all in the same boat: animals are being killed so that we can eat. Being a vegetarian doesn’t change this. We’re all benefiting equally from the deaths of our fellow creatures.
If you’re interested in treading lightly on the earth, the best lifestyle is probably that of a hunter. In this case, you are basically displacing your weight in predators. That is, a 150-pound hunter eats about as much meat as two 75-pound wolves. The impact on the prey species is the same either way.
Nomadic herding is also low-impact. In this case, you’re displacing your weight in predators again. The total biomass of ruminants will end up the same, with your domestic animals displacing their weight in native animals.
You don’t start cutting a serious swath through the ecology until you start farming. That’s when all hell breaks loose. Farming lets us achieve a human population that is much larger than we could with hunter/gathering or herding, but it’s not all that easy on the planet, even when you do it right. (Also, I suspect that native peoples with a more nomadic lifestyle have more fun than we do, since they’re living the lifestyle with the longest track record. It suits us.)
Ethically, of course, it doesn’t matter whether you kill an animal outright and eat it yourself, or whether it dies because you displaced it so you could grow soybeans. You killed it for your own purposes either way.
I think people are approaching the whole issue from the wrong end. The real issue is that everyone has a yearning to be connected to nature and the land. It’s a basic human need. Almost by definition, people with a lifelong disconnection from the land don’t know how to connect to it appropriately. Their yearning will attach itself almost at random to one of the half-measures or palliatives offered by the people around them — who are also lifelong city dwellers. After all, the people who have achieved a true connection don’t live in the city anymore! Their good example is not very visible to their former neighbors.