> Given the damage that agriculture has done to the environment

Has it? I thought that the worst thing for the environment was subsistence farming.

I guess people mostly downvote you because your statement is not popular, but it's not quite correct either. 'Subsistence farming' isn't one well defined thing. There are form of subsistence farming that are very bad; for example, I'm doing work on agriculture in Madagascar now where people (due to a lack of knowledge and systemic thinking) do agriculture by slashing down rainforest to get access to the very fertile soil underneath. That soil inevitably washes out fast (because the trees and more in particular the roots that hold the soil are removed), so a few seasons later they move on to the next patch of rain forest and so on. This is one of the major environmental threats on the island.

That said, 'subsistence farming' in temperate climates as it was practiced say in the 18th and 19th century in Europe is quite different. It revolved around permanent settlements (so people couldn't move on quite as easily) and used crop rotation and animal manure for keeping productivity if not high then at least at sufficient levels. We couldn't live from a system like that today, and it was bad for the environment in the sense that it made people put essentially all land into cultivation, but it wasn't as immediately destructive as other forms of subsistence farming are.

> as it was practiced say in the 18th and 19th century in Europe is quite different

With minor variations it's still practiced in parts of Europe, to this day :)

Why? Pesticides kill non-pests, irrigation dries up entire rivers, destroying ecosystems, waterways get poisoned, nutrients run off land, deforestation causes erosion, mono-crop farms starve bees, etc., etc. Humans, through our large-scale agriculture, have an unprecedented negative effect on our environment. Subsistence farming has had these effects to a much smaller extent (due in part to it only being viable with smaller populations).

But, people need to eat, and so here we are. Alternatives to traditional agriculture would be great, but must make economic sense to actually take hold.

Besides, subsistence farming is agriculture.

Near 60% of the world's total crop yield is the direct result of artificial fertilizer, which uses methane/natural gas as a base reagent + large amounts of power. If it wasn't for the artificial fertilizer it wouldn't be that bad for pollution, but at the same time we would be looking at near 3x or more the amount of farmland to grow the same amount of crops.

>Has it? I thought that the worst thing for the environment was subsistence farming.

Who says that subsistence farming is bad?

I've always heard that large-scale industrial agriculture is bad because it destroys the soil. Or that it breaks the soil up so it then blows or washes away.

If that were true modern industrial agriculture would self-destruct within 5 years.

IMHO modern industrial agriculture isn't using the soil ( in the strict definition of soil) anymore. It is basically just using the ground as a growing medium and then providing the nutrients that the soil would provide through applications of nitrogen/phosphorous/potassium.

Every year I watch the sand from the farm next door runoff in spring rains into the ditch, which ends up in the creek across the road, which then runs down into Lake Ontario. There's no soil left. On almost all the farms here. But they can still grow things through 'artificial' means.