Coffee has been hit by a crisis. Global warming, deforestation and pests are the main causes, and scientists warn that one of the world's most popular drinks could be history if conservation measures are not taken.

A study published in Science Advances said that at least 60 percent of coffee varieties are threatened with extinction, 45 percent are not in any germplasm collection, and 28 percent are unknown to exist in any protected area. The existing conservation measures for coffee are not sufficient.

Also, a new study published in the journal PLOS One simulates how the growth conditions of three popular foods (coffee, cashews and avocados) will change over the next 30 years.

Of the three crops, coffee is being hit hardest by global warming: the study predicts that the number of areas where coffee can be grown will decline across the board by 2050. The main reason for the decline is higher annual temperatures in coffee-producing countries such as Brazil, Vietnam, Indonesia and Colombia.

Arabica coffee is one of the two main plants used to harvest coffee beans. This plant evolved in the high-altitude tropics of Ethiopia and is very sensitive to climate change.

However, how can coffee bean production be maintained under global warming? In a recent review published in Nature Plants, scientists from the Royal Botanic Gardens argue that Liberian coffee, once rated the second most traded coffee crop variety, could re-emerge to help sustain coffee production in a warming climate.

The authors argue that there are three ways to help coffee cultivation adapt to a changing climate: move coffee production to more suitable areas. Adapt coffee growing methods. Developing coffee crops that are better adapted to future climate conditions. They suggest that changing crop types is likely to be the least disruptive and most cost-effective approach. The Liberian species of coffee was once widely grown in the second half of the 19th century because it was productive, resistant to pests and diseases, and could grow in warmer ground to which Arabica coffee did not adapt. However, in the early 20th century, interest in this coffee was lost because of its inconsistent quality and profitability, among other issues.

The authors state that the initially introduced Liberian coffee fruit and seeds were difficult to process and therefore unpopular with coffee traders. In contrast, there has been a recent expansion of excelsa coffee (a Liberian species of coffee) in Africa. This coffee bean and fruit is similar to Arabica and produces a mild and smooth coffee with low acidity and bitterness, but contains equal amounts of caffeine.

Researchers believe that in a changing climate, in a warmer climate and at a lower altitude than that in which Arabica is grown, the Liberian species offers the potential to grow a commercially viable and perhaps even more valuable coffee.

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