Photo by J. Scortzman, Flickr
(Click on the following link to listen to an audio version of this blog … Updates on coffee
The small trees or bushy shrubs of the genus Coffea produce “cherries” (red to purple, pulpy fruits) that contain the caffeine and flavor-rich seeds that we call coffee “beans”. These “beans” are then roasted and ground into a fine powder which can be brewed into the wonderful, rich, beverage that so many of us love.
There are 124 species of Coffea and most grow wild in sub-Saharan Africa. Only two of these species, though, are currently extensively cultivated to produce commercially traded coffee. Coffea arabica (“Arabian coffee”) makes up 60 to 70% of the coffee grown and sold around the world, and Coffea robusta makes up the remaining 30 to 40%.
Coffee tree, Photo by T. Brooks, Flickr
Coffea arabica was the first type of coffee to be domesticated. By the early Sixteenth Century it was widely consumed throughout the Middle East. Coffea arabica is native to the southern highlands of Ethiopia and arose, apparently, as a naturally occurring hybrid of two other Coffea species (C. robusta and C. eugeniodes). Most Coffea species have diploid chromosome arrangements, but C. arabica is tetraploid and contains the entire genomes of both C. robusta and C. eugeniodes.
In its natural habitat, C. arabica grows as an understory plant beneath tall, densely packed shade trees. It is capable of self-pollination and relies primarily on wind dispersal of pollen (although wild bees greatly increase its overall pollination efficiency both in wild and domesticated systems). The traditional method of cultivation of C. arabica, which is practiced in more than 70 countries around the world, replicates this controlled, shady, growing environment. In modern parlance this type of coffee growing system generates “shade grown” coffee beans. Coffee plants in shade grown coffee plantations will produce coffee beans for 30 years or more!
Coffee trees. Photo by DirkvdM Wikimedia Commons
In the 1970’s, though, in an attempt to increase the productivity of the coffee trees, sun tolerant varieties of Coffea were developed, and coffee could then be grown in vast, monocultural plantations (systems that generated “sun grown” coffee beans). Sun grown coffee systems do have higher yields per tree, but its trees are only productive for 15 years.
Sun grown coffee was beset with a myriad of other problems, too. Increased levels of fertilizer, pesticides and herbicides were needed to fuel the increased productivity of the coffee trees and to fight the increasing intrusions of pests and weeds. Also, removal of the shading, overstory trees destroyed important habitats of many native birds, mammals and reptiles (many of which were quite active in insect control!). A study published a few years ago counted 204 species of birds living in the shade grown coffee plantations in the Western Ghats of India. Removal of these trees for sun grown coffee production destroyed the foraging and nesting habitats of most of these bird species!
Removal of the protective tree cover also exposed soils to the often violent rain storms of the tropics and led to accelerated rates of soil erosion. Also, the quality of the coffee suffered. The accelerated rate of coffee bean maturation in the sun grown trees led to beans with lower levels of important flavoring chemicals and higher levels of increasingly bitter acids. It was a lose/lose/lose/lose proposition! In Central America alone, over 2.5 million acres have been deforested to make room for sun grown coffee plantations.
Coffee “beans.” Photo by F. Rebelo Wikimedia Commons
Coffea robusta is particularly well adapted to sun grown coffee systems. It’s flavor profiles are not as high in quality as those of C. arabica, but its higher caffeine content makes it a desirable crop. Many sun grown coffee plantations exclusively grow C. robusta trees. Interestingly, C. robusta trees are not self-pollinating. They require the spread of pollen from one tree to the next and are much more dependent on insect pollen transfers than C. arabica. The monocultural nature of these sun grown coffee plantations with their inherent dearth of nectar producing wild plants, though, coupled with the extensive use of pesticides in the sun grown coffee management systems makes these agricultural systems very unconducive to the survival of the insect populations (especially the wild bees) that can accomplish pollen transfers between the coffee trees.
Coffee trees of all types need stable environments to grow and thrive. This has been one of the ongoing arguments in favor of planting coffee trees in shade coffee systems. The micro-environment of shade coffee plantations fluctuate much less than sun grown coffee systems and may even serve as a buffer against some of the temperature and moisture consequences of climate change. This inherent need for consistent growing conditions is also one of the explanations for the superiority of high altitude grown coffee over most low altitude grown coffee. Cooler, less fluctuating temperatures and lower atmospheric oxygen levels slow down the coffee tree’s rate of bean synthesis and maturation and enable the high altitude grown beans to develop their full flavor profiles and potentials.
Map of coffee growing regions. The worldwide “bean belt.” Public Domain.
Back in 2017 I wrote about some very disturbing studies concerning the sustainability of coffee cultivation. A report by the Climate Institute of Australia explored the impact of climate change models on the global distribution of coffee trees. They determined that projected rises in global temperatures would reduce coffee producing land areas by 50% by 2050. Impacts of climate change (which include not only rising average temperatures but also changes in weather patterns and cycles of drought and excessive rainfall) were especially severe at low latitudes and low altitudes. The worldwide, tropical “bean belt” will need to move out of the afflicted tropical zones and up mountainsides in order to find suitable sites to grow coffee. It is estimated that there are 120 million people in these zones whose economic livelihoods depend on coffee.
This impending loss of suitable coffee farming areas has led to an intense exploration of wild coffee species to try to find species that will tolerate the new growing conditions of our climate-changed world. These new coffee species, though, must also produce a good tasting final produce! A study by botanists at the Kew Garden (“Royal Botanical Gardens”) in Great Britain, however, published in 2017 in both Science Advances and Global Climate Change Biology, determined that 60% of these wild Coffea species are at risk of extinction due to climate change and habitat destruction. The potential loss of this diverse and as yet incompletely studied gene pool could leave cultivated coffee without the tools that it needs to survive in our climate changed world!
Roasted liberica coffee beans. Photo by HaztechGuy, Wikimedia Commons
Some good news about coffee, though, has just come out of Uganda. Uganda is a major coffee exporting country and has, for decades, relied primarily on the production of robusta coffee beans. Rising temperatures and drought, however, has led to declines in robusta production and increased diseases and mortalities in the robusta trees. This situation had led to the re-discovery of a heat and drought tolerant coffee species: Coffea liberica (sometimes referred to as liberica-excelsa which is a portmanteau of two different species of Coffea).
Liberica is native to Central Africa but was widely planted around the world especially by colonial nations. Starting in the 1700’s, it was the principle type of coffee grown in the Spanish colonized Philippines. In the late 19th Century, a coffee rust epidemic quickly killed off many of the arabica and robusta trees in coffee farms around the world and eventually even damaged the much more rust-resistant liberica trees. Coffee plantations in Indonesia replaced many of their rust-killed arabica trees with liberica trees, and liberica is still grown extensively in Indonesia. Eventually, though, around the world, arabica and robusta became the two coffee species of choice.
Coffea liberica tree. Photo by DXLNH, Wikimedia Commons
One reason that arabica and robusta coffee trees were preferred over liberica trees is that liberica trees are much taller than either arabica or robusta (libecia grow to about twenty meters (66 feet) in height). This makes harvesting the coffee beans a much more difficult process. Also, libericia trees take longer to mature and produce fruit than either arabica or robusta. The liberica trees, though, grow and produce fruit at higher temperatures and with lower moisture levels than either arabica or robusta. Independent coffee farmers in Uganda are slowly converting their plantations from predominantly robusta trees to liberica.
The Ugandans have been mixing the liberica beans in with the robusta beans for years. They are now, however, selling the liberica on its own. Coffee experts describe the liberica brewed coffee as “smooth and easy drinking.” It is heavy in aroma and lower in caffeine than robusta. It has been described as “a Beaujolais nouveau. It is very soft.”
So ten years from now we all may drinking liberica coffee and will have forgotten all about robusta and arabica beans. Let’s just hope that the Coffea gene pool doesn’t run dry!