Having worked a farm for a few summers, my understanding is that we're dealing with the following set of tradeoffs. 1. If you allow weeds, you'll need to till

Having worked a farm for a few summers, my understanding is that we're dealing with the following set of tradeoffs. 1. If you allow weeds, you'll need to till the soil to maintain yields 2. If you till the soil you erode it, damaging the the long term health of your farm and water supplies. 3. If you drop yields globally, people starve (and farmers go out of business) Since eroding the soil harms biodiversity in a different set of ways, killing weeds seems like the least bad option. Ideally we wouldn't require harsh chemicals to do that but no one has quite figured it out.