France, Feb. 2 -- Fertile soilsare key to meeting the world's exploding demand for food. With Africa set to become the most populous continent by the end of the century, repairing its eroded soils is ever urgent, says US Special Envoy for Food Security Cary Fowler.

RFI: A year ago, the US launched the Vision for Suitable Crops and Soils (Vacs) programme, which promotes a return to traditional crops. What is it about?

Cary Fowler: It aims to do work in the two most fundamental aspects of food security: crops and soils. If you want to have food security and you want to have it be sustainable, you have to ensure you've got good, fertile soils and you have crops that are adapted to climate change.

That's not what we have today in Africa, w...