The first full assessment of risks to the world's coffee plants shows that 60 percent 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 the BBC.
About one in five of the world's plants is threatened with extinction, and the 60 percent 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.
Many coffee drinkers are unaware that we only use the coffee beans from two species – Coffea Arabica and Coffea robusta – in the thousands of different blends of coffee on sale.
Many of these wild coffees are undrinkable, but may contain genes that can be harnessed to help coffee plants survive in the future, amid climate change and emerging diseases that attack coffee trees.