Hugh Pickens continues: "Arabica is one of only two species of bean used to make coffee and is by far the most popular, accounting for 70 per cent of the global market, including almost all fresh coffee sold in high street chains and supermarkets in the US and most of Europe. A different bean known as Robusta is used in freeze-dried coffee and is commonly drunk in Greece and Turkey, but Robusta's high caffeine content makes it much less pleasant to most palates. In some areas, such as the Boma Plateau in South Sudan, the demise could come as early as 2020, based on the low flowering rate and poor health of current crops. The researchers used field study and 'museum' data (including herbarium specimens) to run bioclimatic models for wild Arabica coffee, in order to deduce the actual (recorded) and predicted geographical distribution for the species. 'Arabica can only exist in a very specific pace with a very specific number of other variables,' says Aaron Davis, head of coffee research at the Royal Botanic Gardens. 'It is mainly temperature but also the relationship between temperature and seasonality – the average temperature during the wet season for example.'"