Telegraph: Professor Stephen Hopper, director of the Royal Botanical Gardens at Kew, in London, argues that the world is currently too reliant on just a handful of key species of edible plants for food. He warned the combined threat of disease, climate change and lack of diversity in commercial crops has left the dozen staple species that provide the bulk of the global food supply – such as wheat, maize and barley – increasingly vulnerable. He said farmers and consumers in Britain needed …