People who suggest that solving food shortages could be achieved through improving distribution are "living in cloud cuckoo land", a leading authority on sustainable agriculture, Prof Jules Pretty, says.
There were too many competing interests which meant "it's not going to happen".
In an address to the University of Otago Foreign Policy School at the weekend, he said it made more sense to increase people's means of producing food where they lived.
If food production could be increased on the smallest farms in the poorest places, then "other arguments go away", Prof Pretty, who is based at the University of Essex in England, said.
Agricultural sustainability was about making better use of the same land without damaging it.
Sustainability projects did not have to be large to be successful, he said, citing a Kenyan project where women used double-dug beds on the edge of fields, filled with organic matter, which would produce vegetables through the dry season.
Because their children were better fed, their attendance at school was better, and the work also provided employment for village people.
A farmer, seeing its success, also started growing maize in a double-dug bed.
It was important, when innovation was attempted, that people got together to do it.
"When you innovate on your own, you are isolated. If you are with other people, at least you can fail together."
Asked what New Zealand could do, Prof Pretty said it could look at where there was best practice and ways of spreading that elsewhere.
It was a matter of getting alongside farmers and encouraging the positive rather than "bashing people on the head saying `you're doing terribly'. They won't listen."
New Zealand could also invest in science and technology and ensure that people with different interests were all rowing in the same direction.
When it came to biotechnology and genetic modification, there had to be a move away from the notions that it was all awful or all good: "It's more complex than that."
He agreed with a questioner that changing consumption patterns in the West was a big challenge.
"What doesn't work is telling people what to do."
Models which were working were where children from early school age were involved with community gardens and allotments in schools growing their own food.
When they went home from school, they spent more time talking about what they did every day because it was interesting.
Behaviour change could begin through such programmes.
