One of the great global challenges of the next half a century will be feeding a human population set to rise beyond nine billion. Farmers worldwide face an enormous productivity challenge. Mike Mack is the CEO of Syngenta – one of the world’s biggest agribusinesses. He sees farming's future driven by bioscience and genetic manipulation. But why does he face so much mistrust and suspicion?(Photo: Mike Mack, CEO of Syngenta)