At least 60pc of wild coffees are threatened with extinction, including the species behind one of the world's most popular beverages, scientists warn.
Researchers at the Royal Botanic Gardens at Kew, near London, have found that 75 of the world's 124 wild coffee species are under threat from the loss of forests, climate change and the worsening problem of fungal disease and pests.
They include wild Arabica, a species from Ethiopia that has been cultivated to provide 60pc of the multibillion-euro global trade in coffee, but which is assessed as endangered largely as a result of climate change.
Wild coffees are threatened by destruction or damage to the forests where they grow, for agriculture and other human activities, and by rising temperatures which alter the specific climatic conditions they need to thrive in.
The threats facing wild coffee are significant for the future of one of the world's most widely drunk brews because wild varieties have been used to breed and improve the cultivated stock, the experts said. Coffee farmers, who grow either Arabica or Robusta coffee, have already begun to report their crops being affected by changing weather patterns, rising temperatures and new pests and diseases.
The variety of traits found in wild species are likely to be even more important in the future to develop plants that can cope with threats such as longer dry seasons caused by climate change or the spread of pests.
Kew's head of coffee research, Dr Aaron Davis, warned: "If you start to lose these species, the options for developing resilient coffee for the future diminishes very rapidly."
Less than half of the wild coffee species are held in seed banks or living plant collections and 28pc are not known to occur in any protected areas, the scientists also warn.
They called for increased conservation in the natural environment as well as in seed banks and plant collections.
Dr Davis, lead author of the study, said: "What we're saying is 60pc is just really high, that's a real wake-up call. For a major global commodity, that starts ringing alarm bells. It's a tragedy losing any wild species, whether it's a...plant or animal, that's bad enough.
"But when you've got a crop that supports the livelihoods of 100 million people just in production in coffee farming, then you look at value of high street coffee chains and supermarket coffee, it's enormous," he said.