I'd like to see a citation for that. That may be true if we don't use any GMO crops, but GMO doesn't necessarily have to be incompatible with organic practices for fertilizer, pesticides, etc. IANAF, but my understanding is that organic practices are often more labor intensive rather than more land intensive.
Reduced yields per acre due to not using fertilizer, pesticides etc. are the main reason for the increased land usage for the same amount of food produced.
Whether it could be balanced out by a huge reduction in growing corn for HFS, feed and ethanol is a whole 'nother topic.
Organic farming doesn't mean not using any fertilizer or pesticides—it just means using certain types that are considered safer. For instance, natural fertilizers (such as compost) are used instead of petroleum-based products. Same for pesticides and herbicides.
