They found 75 species (60%) were considered to be threatened with extinction, with 13 species in the most at-risk category of critically endangered, while 40 are endangered and 22 vulnerable to extinction.
But with deforestation and a changing climate, which brings unpredictable rain, pests and fungal diseases, coffee farmers will be hit hard.
"As a coffee drinker you don't need to worry in the short term", said Davis.
"Many protected areas fail to conserve the diversity encompassed within their borders, and workable management plans would be required to ensure that target species are effectively conserved", the authors write.
The analysis was based on the scientists' examination of the 124 known coffee species, and an assessment was produced for the International Union for Conservation of Nature, which publishes the global Red List of threatened species. As the researchers note, "Protection of wild populations of Arabica coffee is therefore viewed as a key part of the long‐term sustainability strategy for Ethiopian coffee production and the global coffee sector".
Global coffee chain Starbucks, which uses all Arabica beans, failed to respond to a request for comment. "Our niche in the coffee research world is that we do have a deep understanding of the wild relatives, and particularly of where they grow and their climactic tolerances - what we call the climate envelope".
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 over the years, the experts said. A morning cup of domesticated Arabica (Coffea arabica, the species that dominates commercial cultivation) might have been produced with the help of disease-resistance genes from the once-wild robusta (C. canephora), for example.
Australian Open: John Millman loses thriller to Roberto Bautista Agut
Once Bautista Agut broke in the fifth, Murray's resolve finally crumbled and the Spaniard took it 6-2. I can't walk properly at all just now. "Tonight I gave everything I had, it wasn't enough tonight".
They found that almost a third of all wild Arabica species were grown outside conservation areas.
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. Now, in what is perhaps his most disheartening research, Davis has found that wild coffee, the dozens of varieties that once occurred under forest canopies on at least three continents, is at risk of vanishing forever.
Most wild coffee beans don't contain that much sugar - or caffeine either, for that matter.
What are crop wild relatives?
This is because seed bank storage freezers, even at -20 degrees Celsius, don't cut it when it comes to preserving coffee beans.
Coffee trees, like many tropical plants, have seeds that do not survive the freeze-drying process used in conventional seed banks - 45% of coffee species have not been "backed up" outside the wild.
By Somini Sengupta New York Times News Service Aaron Davis, a British botanist, has spent 30 years trekking across forests and farms to chronicle the fate of one plant: coffee.