Let's get this one out of the way first: Farmers have a significant vested interest in sustaining their land. It would cost them more in the long-term to not look after it, so it's worth looking after.
However, it would cost them more, long-term, to not pollute downstream; letting pesticide and effluent run off into our waterways is the cheap thing.
Additionally, there's incentive – taking the above into account – to maximise yields. So, the equilibrium of the system is to farm as much crop/stock as possible, up until the point your own land begins to deteriorate. This would include the point at which downstream effects like pollution begin to 'back up' and affect your land.
It's worth noting that there are two separate (and somewhat conflicting) issues in here:
- What's best for the farm and
- What's best for the surrounding country (and its people.)
Organic farming seems primarily concerned with the second. The only benefit for the farm, long-term, is a lack of dependency on the industrial chemicals that enable high yields – synthesised fertilisers, pesticides, weed-killers, and so on. Sustainability-wise, the only real difference between organic and non-organic would seem to be a bet on whether the products of the industrial complex (particularly the oil-based ones) are going to remain available for the foreseeable future. (My bet would be a "no," but it would still be a bet.)
So, number 2 is the important difference, apparently. How important? Well, Parkinsons might be linked to pesticides. Dairy-farming has had visible and serious consequences in Canterbury, with water supplies depleted and contaminated, and even non-drinking waters and streams seriously polluted. The river at my family's traditional summer camping spot is all but unswimmable due to dairy-farm run-off, these days. It seems it is an important difference.
Questions remain. Is organic farming the right solution? Would it be possible for organic farms (with their lower yields) to produce enough food to feed the planet's population? Should that even be a consideration? Additionally, land which has been industrially farmed takes a long – long – time before it is able to yield any decent volume of organically-farmed produce.
We're in for some tough choices.