Anyway, sitting at the IFAOM Booth at the COP15 (H-017F) I have been approached by many people who want to hear about yields and argue about the merits of a high input conventional system for the necessary yield increase for a growing world population.
My response, thus far, has been to report the fact that the world is already producing more than enough food to feed everyone - the problem is giving access to that food to the people who need it. Another argument has been to point out that the yield potentials of high input systems is based on the additions of resource inefficient and biologically hazardous chemicals. The pesticides and herbicides remove the potential for the farmer to harvest nutritionally important non-crop food sources. This is a big problem in a world where 1 in 3 people is a farmer and most of these farmers are marginalized people on degraded land and a tradition of gathering food in nature as well as from cropping systems.
After a short chat with Australian Water Lilly farmer and IFOAM World

Have a look:
Andre Leu 'Organic Can Feed the World'
Science Daily 'Organic Farming Can Feed The World'
Christos Vasilikiotis, Ph.D. University of California, Berkeley 'Can Organic Farming "Feed the World"?'
Catherine Badgley, University of Michigan 'Scientists Find Organic Agriculture Can Feed the World & More '