Delicate as a coffee tree
The coffee plant is an extremely sensitive plant. Arabica (Coffea arabica) grows and bears fruit well when grown at altitudes of 600 to 1200 m above sea level, on slopes and preferably on volcanic soil. The best yields occur when the air temperature is between 18 and 22 degrees Celsius and when large trees grow between the coffee plants, protecting the delicate Arabica from the sun.
Robusta (Coffea canephora) plantations should be located at an altitude of 400-600 m above sea level, on plains and low hills. Harvests are successful when the temperature is between 22 and 28 degrees Celsius. The amount of rainfall is also important for coffee cultivation. Arabica grows well and bears many fruits when the average annual rainfall is 1,400-2,000 mm, and Robusta – 2,000-2,500 mm.
Around 75 coffee tree species out of the 124 that grow in the wild are at risk of extinction
Harvests have been failing for 40 years, but farmers describe the past few years as tragic. Scientists from the CSIRO Oceans & Atmosphere Institute in Australia analyzed climate conditions from 1980 to 2020 in twelve regions around the world where most coffee is grown. They took into account temperature, rainfall and humidity. They found that average temperatures have risen in all of these regions over the past decade. The results of the research were published last year in the scientific journal PLOS Climate. “In every region we studied, it is getting too hot to make coffee production profitable,” said Dr. Doug Richardson, the study’s lead author. There is also less and less rainfall and longer dry periods.
The southeastern part of Brazil and the southwestern part of Ethiopia seem to be the least exposed to the consequences of global warming, but this is not much consolation. Because these two regions will not meet the demand for coffee, of which more than 2.2 billion cups are consumed every day worldwide. The world loves coffee. It is a delight for the senses – from the smell of freshly ground beans to the last sip. But coffee is not just about taste and smell. For years, it was believed that it increased the risk of many diseases. Today we know that not only is it harmless, but it even protects against, among others: type 2 diabetes, Alzheimer’s and some types of cancer. It contains polyphenolic compounds that protect the endothelium of blood vessels and have a beneficial effect on the cardiovascular system. It does not always raise blood pressure. People who drink it regularly will not feel this. Your body gets used to coffee and does not react by increasing blood pressure. Only coffee drunk occasionally causes sudden spikes. In 2016, a cup of coffee was included in the new food pyramid.
With climate change, coffee plants are increasingly threatened by pests and diseases. For example, a fungal infection known as coffee leaf rust has been devastating plantations in Central and South America for several years.
Climate change is not just about warming, but also about extreme events that are happening more frequently and are increasingly intense and surprising. For example, in 2021, unusually severe frosts and snowstorms decimated the Arabica harvest in Brazil, its largest producer.
If climate change continues at its current rate, the area under coffee cultivation will decrease by 50 percent by 2050, scientists at Humboldt University in Berlin predict. Half of the areas where coffee plantations are currently located will no longer be suitable for growing the crop. They will have to be moved to higher ground. For example, in Nicaragua, coffee plants currently grow at an altitude of 1,200 meters above sea level. Within a quarter of a century, they will only be able to be grown at an altitude of 1,600 meters above sea level, and there will no longer be as much space for them as there is now.
Robusta instead of Arabica
Climate change and increasingly unpredictable weather are particularly threatening Arabica crops. Estimates show that its production will decrease by around 80% by 2050. Roman Gruter from the Institute of Natural Resource Sciences at the Zurich University of Applied Sciences argued in the scientific journal PLOS One that it should be replaced by Robusta, which is generally considered to be worse than Arabica, but is more resistant to climate change and produces higher yields faster. Robusta contains almost twice as much caffeine as Arabica. It generally produces higher yields and at the same time is less demanding to grow – it requires less fertilizer and water.
Felipe Ferrão of the University of Florida, who with a group of colleagues conducted five years of research in Brazil on both varieties of coffee grown in the country’s mountainous regions, found that Robusta can be successfully grown at altitudes previously considered suitable only for Arabica. And importantly, the Robusta flavor will be preserved. He published the results of the research in the journal Crop Science.
“Robusta, however, is not a panacea for climate change,” says Jennifer Vern Long, CEO of World Coffee Research, an organization created by the global coffee industry in 2012 to support innovation. “Although it is more resistant to heat and some diseases and pests than Arabica, its cultivation has certain limitations. When temperatures rise, robusta will not meet consumer needs. And these changes are already evident.”
In Vietnam, the world’s largest producer of Robusta, yields are falling every year. Some years there is not enough water to irrigate crops, and other years there is too much rain. Increasingly difficult growing conditions make Robusta production increasingly uncertain. Some Vietnamese farmers are ripping up trees to plant more profitable black pepper and durian, a spicy fruit popular across Southeast Asia and among Chinese consumers. “Coffee is more sensitive to temperature changes than many other crops,” Michael Hoffmann, professor emeritus at Cornell University’s College of Agriculture and Life Sciences, told CNN.
A forgotten species
The most promising solution is to find new, more resilient species that can not only tolerate higher temperatures and less predictable rainfall, but also meet consumer expectations in terms of taste and smell. Scientists have counted 124 species of wild coffee plants. They are not currently of economic importance, but researchers hope that at least some of these species will not only survive extremely hot days, but that their beans will also be able to produce coffee that is as good as it is today.
Scientists at the Royal Botanic Gardens in Kew, near London, have studied these coffee plants. They have shown that there are some species among them that could be cultivated on a large scale – they would produce a lot of fruit in a relatively short time and could replace Arabica and Robusta. Some wild coffee plants appear to be resistant to diseases, especially leaf rust, and to deteriorating weather conditions – high temperatures and long periods of drought followed by heavy rains.
The greatest hopes were raised by the species Coffea stenophylla, which has a unique combination of resistance to climate change, including high temperatures, and excellent flavor. The plant was found in Sierra Leone and was first described in 1834. It was cultivated in humid regions of West Africa until the early 20th century, when it was replaced by the newly discovered and more fertile Robusta. The coffee industry forgot about it. It grew wild in the humid forests of Guinea, Sierra Leone and Ivory Coast, but progressive deforestation of these areas has meant that the species is now considered endangered.
Champagne instead of vinegar
Dr. Davis and his team organized an expedition to find wild Coffea stenophylla. They went to Sierra Leone, where the plant was last seen in 1954. In the 1980s, coffee trees probably also grew in Ivory Coast, but they considered this information less certain. “We didn’t know exactly where to look. After many weeks, we accidentally found a plant, but we needed healthier trees to see under what conditions Coffea stenophylla can grow,” Dr. Davis recalled in an interview with “The National”.
The expedition of British experts became famous in Sierra Leone. The researchers were joined by a local farmer who claimed to have seen a small plantation of trees similar to those growing in the area where he lived. “We went looking for these trees and after many hours of walking we came across a group of very healthy plants,” says Dr. Davis. In 2020, the team collected seeds for testing.
Botanists traveling through Africa in the 19th century described not only the exceptional resistance of Coffea stenophylla to leaf rust and drought, but also the excellent taste of coffee. However, tastes change. “Before our first tasting in the summer of 2020, our expectations for coffee flavor were low. That all changed when I tried my first cup with five other coffee experts. The first sips were revelatory. We expected vinegar, but got champagne,” says Dr. Davis.
The next tasting was conducted by experts from France. They found that the taste of stenophylla coffee is very similar to that of Arabica. It has notes of peach, blackcurrant, tangerine, honey, light black tea, jasmine, chocolate, caramel and elderberry syrup. In a word: it’s delicious.
Scientists didn’t expect Stenophylla to taste like Arabica. The two species are not closely related. They come from opposite sides of the African continent, and the climates in which they grow are very different. They also don’t look alike. Stenophylla has black fruits and more complex flowers than Arabica, which has red fruits. It can be grown at lower altitudes than Arabica and Robusta, and in warmer climates. It grows at an average annual temperature of 24.9 degrees C, which is 1.9 degrees C higher than Robusta and up to 6.8 degrees C higher than Arabica.
Dr. Davisa’s team is currently working on propagating Coffea stenophylla and planting trees in different locations to determine the ideal growing conditions. For example, they are interested in whether the crops can be moved to higher elevations than they are currently in. The scientists are also trying to cross Stenophylla with Arabica or Robusta to create a variety that is more resilient to climate change, and perhaps even improves its flavor and aroma.
