The first full assessment of risks to the world's coffee plants shows that 60 per cent of 124 known species are on the edge of extinction.
More than 100 types of coffee tree grow naturally in forests, including two used for the coffee we drink.
Scientists say the figure is "worrying", as wild coffee is critical for sustaining the global coffee crop, reports BBC.
About one in five of the world's plants is threatened with extinction, and the 60 per cent figure is an "extremely high" one.
"If it wasn't for wild species we wouldn't have as much coffee to drink in the world today," said Dr Aaron Davis of the Royal Botanic Gardens, Kew.
"Because if you look at the history of coffee cultivation, we have used wild species to make the coffee crop sustainable."
Research published in the journal, Science Advances, found conservation measures were "inadequate" for wild coffees, including those considered "critical" for long-term global coffee production.
The study found that 75 wild coffee species are considered threatened with extinction, 35 are not threatened and too little is known about the remaining 14 to make any judgement.
Furthermore, it was found that 28 per cent of wild coffee species grow outside protected areas and only about half are preserved in seed banks.
A second study, in Global Change Biology, found that wild Arabica coffee can be classed as threatened under official (IUCN Red List) rankings, when climate change projections are taken into account.
Its natural population is likely to shrink by up to 50 per cent or more by 2088 because of climate change alone, according to the research.
Wild Arabica is used to supply seeds for coffee farming and also as a harvested crop in its own right.
Ethiopia is the home of Arabica coffee, where it grows naturally in upland rainforests.
"Given the importance of Arabica coffee to Ethiopia, and to the world, we need to do our utmost to understand the risks facing its survival in the wild," said Dr Tadesse Woldemariam Gole, of the Environment and Coffee Forest Forum in Addis Ababa.