Coffee under threat of extinction: is this the bitter end?

Are we about to run out of coffee? Nearly all the 10 million tonnes of coffee beans consumed worldwide come from two plant species: arabica and robusta. Both are critically threatened by climate change. Scientists at the Royal Botanic Gardens, Kew, in London have been looking into the viability of using a new bean to save our morning cuppas. Guest: Dr Aaron Davis, Senior Research Leader of Plant Resources at the Royal Botanic Gardens, Kew