... article linked to, part of the support for local agriculture has been the previous history of driving people into the cities, which in many countries creates both a supply of land to be worked with new methods, as well as turning all subsistence crops into cash crops.

Its not universal ... again as partly recounted in the article. Some nations, like Mali, are so densely populated that substantial increases in agricultural productivity will still leave them in a near-Malthusian state.

And roving bands of soldiers financed by alluvial diamonds, as in the Democratic Republic of Congo, are worse than plagues of locusts for agricultural development. And no story about an "agricultural revolution" in Africa can ever be a complete success story unless the breadbasket of Central Africa is one of the success stories.

I'd say the core anchors for political stability in sub-Saharan Africa are South Africa, the DRC, and Nigeria. One way to understand the strong "project" focus among economics working in economic development in the continent in the 80's and 90's is in terms of the elephant in the room ... given that all three anchors were instead spreading instability, the only solace was to try to get some project up and running and providing some marginal benefit as things fell apart.

So until the DRC gets on track with agricultural development, all of the good news is provisional.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.