Organic farming is probably the most sustainable form of agricultural practice that is available... but probably can't produce the amounts of food needed to sustain the current population.

Like everything else, it depends ...

Modern agriculture farms dollars. It produces billions of livestock and wastes a large percentage of production in processing. We have to support our livestock, our processing, our unbelieveably lovely and incredibly desirable motor vehicles ... as well as the current populations.

That's a lot to sustain. Cuts will be necessary. People will eat less meat. This means a reduction in the numbers of livestock requiring sustainence. The auto population will shrink. The war between people and cars for 'food' will end with the annihilation of the car (hopefully). Processing will be simplified. More food equivalent in dollars (or other currencies) will be freed from 'sugarization' and packaging to feed.

And, of course, there will be better land and water management ... organic farming in place of subdivisions.

The greatest question I have with this presentation is that it considers the ecosystem as fixed, when it is not. Whatever state the biosphere is in at any given time ... it is in equilibrium.

I am not an expert, so I will keep my remarks brief. I have been in areas in the Andean highlands in Ecuador and Peru that have been cultivated with row crops by indigenous citizens of these lands for thousands of years. The terrain is steep and unforgiving with large rainfall amounts during the wet season. The inhabitants practice traditional agriculture as machinery is impossible to use. There is no reason that these areas cannot be productive for as long as people are willing to work the soils.