So, conventional and organic farming are kinda at odds for they have strategies that harm each other. Conventional farming still has the issue of overkilling ecosystems, though.

expanding organic cropland can lead to increased pesticide use in surrounding non-organic fields, offsetting some environmental benefits.

It's ridiculous to call this a harm of organic farming.

Reduced productivity leading to more land use (hence forest clearing) would be one of the negatives I can see.

Luckily we're probably going to be on the downswing for population soon, but in the meantime, we'll probably lose the Amazon to low productivity farming.