We know that coffee grows in specific areas of the world. We have intricate maps on the walls at our roastery in Barcelona, charts about altitude, and you’ve never had a coffee grown in Sweden. But have you ever thought about the why behind all of this? In this article, we’re going to take a look at coffee growing and climate, in the process answering a few related questions:
- Why does coffee only grow in certain places? What are those places?
- What is it about those places that make them suitable for coffee?
- Who grows the most coffee? And who consumes the most?
- Can I get a latte with oat milk?
Introduction
The coffee you’re drinking in specialty roasteries and coffee shops (but also all coffee in general) comes from specific growing regions, which are spread out across the world in a region known as the bean belt. The image below shows the bean belt in yellow, with the top 20 coffee-producing countries marked in green.
Just by looking at this image, we can theorise something: it seems like coffee likes to grow in specific places. And that’s true. But why? Some of those places also seem a bit random. What is it that they have in common? Is it just because those people drink a lot of coffee so they plant coffee all around?
In this article, we’re going to discuss coffee growing and the preferred climatic conditions for Coffea arabica, the Latin name for the arabica coffee plant (commonly known simply as Arabica) that is proudly responsible for producing the majority of specialty coffee.
Coffea canephora, or ‘Robusta’, the hardier (‘robust’) and higher-caffeine cousin, can grow in a wider range of climates and is also produced in huge quantities in these same regions. But Robusta is less common in the specialty coffee world due to its association with harsher flavours and a harsher effect due to the higher caffeine content. However, as the changing climate threatens the viability of arabica in many regions, the robustness of robusta is attracting attention. Producing higher-quality robusta is becoming an increasingly feasible path to keep up with demand for specialty coffee. But that’s another story…
Let’s randomly interject with some interesting facts about coffee as an agricultural good:
- Coffee is planted on almost 30 million acres of land, or 1.3 trillion square feet / 121 billion square metres. Those numbers are so big they’re hard to picture realistically, but there’s a lot of land dedicated to coffee production.
- Most of that coffee (~70%) is grown by farmers known as smallholders. This means the majority of coffee comes from many small family farms rather than large industrial operations.
- An estimated 120 million people depend on coffee production for their livelihood (either directly or indirectly). That’s about 1 in every 100 people. Of those, ~25 million are growers, and ~100 million are involved in processing and distribution.
- A rough guess states that 2.25 billion cups of coffee are consumed every day. That’s about one coffee for every 4 people per day, but more realistically it’d be something like 2 or 3 coffees per day, on average, for regular coffee drinkers (who might be ~20% of the population).
- Coffee is often cited as ‘the most-traded commodity after oil’ or other similar phrases. That is not true, but coffee is a major commodity traded worldwide, and is one of the more valuable export products from many developing countries
- The largest coffee producers are Brazil, Vietnam, Indonesia, Colombia, and Ethiopia (in decreasing order). Brazil leads by a long shot, and Vietnam produces more than double the coffee produced in Indonesia.
- Brazil
- The regions of the world that consume the most coffee per capita don’t produce coffee. Northern Europe (Finland, Norway, Iceland, Denmark, Netherlands, Sweden) and Canada were the biggest coffee drinkers as of 2023, led by Finland.
So where does coffee grow, and why does it grow there?
Arabica coffee grows primarily in the bean belt, the region shown above, which lies approximately between the Tropics of Capricorn and Cancer. But this is not because people only plant coffee trees there (if we could grow specialty coffee in Barcelona, someone would be doing it…) Rather, it’s because coffee needs specific conditions in order to thrive. So, the top producing regions may appear to be spread out somewhat randomly across the globe, but they have something in common that makes them an ideal home for happy coffee plants—climate! Of course, in regions where coffee grows well, its production has often been ramped up after it became an important commodity. So there’s also a human factor, in the sense that we plant more coffee and maintain coffee farms in the regions where coffee grows well. But we didn’t decide where it likes to grow, and we can’t force it to grow where it doesn’t want to (or at least it won’t be of high quality).
So the simple version is this:
Local climate determines where coffee can grow, but we influence the extent of its production and the effort put into improving its quality beyond the base level supported by the natural environment.
Climate conditions for optimal coffee production
So, climate determines where coffee can be grown well. The main climatic factors that are necessary for healthy Arabica coffee plants (and thus the production of high-quality coffee beans), are altitude, temperature, water (rainfall and humidity), soil and sunlight, and slope/aspect. Let’s have a look at the specific suitable ranges for each of those factors, and how they influence coffee production. Amidst this discussion, we also speak about environmental factors like biodiversity and how the changing climate (increasing temperatures) are reshaping the areas suited for growing quality coffee.
Figure 1. Geographical and climatic factors affecting coffee growth and quality.
1. Altitude
Arabica grows at high altitudes in general–up in mountains or hilly regions. Altitude refers to the height above sea level, and is usually measured in meters above seal level (masl). The preferred altitude for Arabica depends on the temperature and local climate, which is influenced by latitude - the distance (either north or south) from the equator (the circumferential vertical centerline of the Earth, where it’s really hot). Brief geography lesson over.
At higher latitudes (16–24°)–where climates tend to be subtropical–the ideal growing altitude is between 550–1100 masl (1800–3600 feet). Examples of this type of growing region include Mexico and the more southern regions of Brazil (São Paulo and Minas Gerais). In these regions, there’s usually just one coffee harvesting season (generally around late Autumn).
At lower latitudes (<10°)–closer to the equator–the ideal growing altitude is 1100–1900 masl, or 3600–6300 feet. These tropical regions tend to have high rainfall, which leads to two harvesting seasons, generally at the peaks of the rainy and dry seasons. Examples of this type of growing region include Colombia, Kenya, and Ethiopia.
Why is this the case? Closer to the equator, temperatures are generally higher and its hotter for longer (throughout the year). So to find the temperature sweet spot, coffee grows higher up in the mountains where it’s a bit cooler. Cool. The milder temperatures and high altitudes mean the coffee cherries mature (ripen) more slowly, which appears to increase the complexity of the flavours they develop. Arabica plantations can exist at lower and higher altitudes (from sea level to as high as 3000 m), but these are outside the preferred range and are less common, typically requiring special care for the plants.
2. Temperature
Arabica grows optimally at yearly average temperatures between 18–21 °C (or 64–70 degrees Fahrenheit). As low as 15 °C and as high as 27 °C is generally okay. It’s also important for these temperatures to be somewhat consistent–and that’s most commonly found in higher elevations in equatorial (tropical) countries. So it’s not the case that we could just grow coffee quickly in Barcelona in April–May when winter is ending and the heat hasn’t begun! It gets too hot in summer, and too cold in winter.
Coffee cherries develop more slowly in milder temperatures (higher altitudes), which leads to denser seeds (beans) that are fuller in flavour and aroma compounds, more acidic, and less prone to defects. Along with soil, sunshine, and water (see next sections), temperature is the other major factor directly determining the growth of coffee trees and the quality of the resultant coffee beans. Geographical characteristics–altitude, latitude, rainfall patterns, slope, aspect, and shade–largely influence coffee’s growth via their impacts on these direct factors.
If temperatures get too low (near 0 °C), frost will damage the trees. The upper limit of yearly average temperature is around 24 °C (73 °F). Above that, the coffee fruit grows and ripens faster, which sounds positive but actually lowers the quality of the coffee bean inside. Prolonged temperatures up to 30°C (86°F) can cause severe damage to the plants, including yellowing leaves, stunted growth, and tumours on the stems. Increased temperatures can also increase the prevalence of the coffee borer (H. hampei) as it is able to live at higher and higher elevations, and a fungal infection known as coffee rust.
Increasing temperature is the main factor that becomes problematic for coffee amidst the changing climate. Projections over the next decades predict worrying reductions in the total land area that will be suitable for Arabica production, as the ideal temperatures become restricted to higher and higher elevations and regions with extreme heat increases become inhospitable for coffee. That’s sad news, and is something the coffee industry is working hard to find solutions for–including looking to bring the quality of Robusta up to par with Arabica, since Robusta can tolerate both higher temperatures and lower altitudes. Another strategy is to grow coffee under shaded canopies, which reduces temperatures by blocking sunlight and also provides a habitat for animals that feed on the coffee borer. Nature for the win!
3. Humidity and rainfall
Consistent rainfall, and high annual precipitation averages are generally important for optimal coffee growth. Some areas with lower rainfall can boost growth through irrigation, although this requires a lot of water input, which may be scarce in regions with low rainfall. Tricky. The ideal water/rainfall situation is thought to be between 1500 and 2500 mm of rain per year, mostly concentrated during a wet season (for up to 9 months), followed by a dry season, where coffee will be harvested. This is not a hard and fast rule, it’s just thought to be the optimal conditions. Some areas with more than one dry/wet season cycle will have two harvesting periods for coffee. Since coffee grows on small-ish trees, a lot of trees are needed for a single harvest. So it’s also ideal for the cherries on those trees to ripen at the same time. It’s known that a period of heavy rain after a dry spell promotes homogenous flowering, which in turns helps make the harvesting season clearly defined (as the cherries turn red consistently around the same time).
High humidity is also important–coffee will not grow well in dry climates. Humidity should be above 50% on a consistent basis. Some sources say humidity should be above 70%, or even as high as 80%. This is generally characteristic of rainy tropical and subtropical climates, but any potential dry microclimates in those regions would not be likely to produce high-quality coffee.
4. Soil, shade, and sunlight
Arabica coffee is an evergreen plant that prefers consistent water in the soil, which also explains why it prefers higher rainfall. During wet seasons, the coffee trees grow rapidly. The soil should be fairly deep, but with a structure that makes it well-draining, since drier soil at the surface slows down growth and initiates flowering. Coffee prefers slightly acidic (lower pH) soils, which are often found in rainy and wooded areas, such as rainforests.
As with all plants, sunlight is necessary for photosynthesis, which is how plants get energy. In many coffee growing regions, the wet season corresponds with peak sunlight (i.e., summer), and it’s when coffee trees peak in growth. However, too much sunlight would have detrimental effects, as it causes cherries to ripen quickly, dries out the soil and decreases humidity, and can increase temperatures beyond the comfortable range for coffee. That’s why it’s been suggested that coffee actually grows best under about 35–50% shade cover. Sometimes, coffee trees are pruned (cut to shorter heights and less breadth), which can also reduce the shade on lower parts of the tree.
There’s a debate around the topic of shade in coffee growing. In many areas, government initiatives to promote productivity have led to farmers reducing shade cover to make the coffee trees grow faster and produce more fruit. However, increased yields don’t typically correlate with increased quality. As mentioned above, cherries that ripen more slowly have consistently been favoured in flavour tests, which is why the ‘best’ coffees tend to come from the highest altitudes and areas with some degree of shade cover. Higher shade cover helps maintain high humidity levels and moist soil, keeps temperatures cool, and keeps sunlight levels in check. While this likely means the coffee tree growth and fruit ripening will be slower, this appears to result in better-tasting coffee. And low shade cover often comes as a result of deforestation or clear-cutting for coffee plantations. So there’s a diverging perspective here, with contrasting views between conservationists and specialty coffee aficionados on the pro-shade side (conservation/biodiversity and coffee quality over yield) and those relying on coffee production for their livelihood (prioritising productivity and yield over quality) on the anti-shade side. We won’t get into the economics here, but the possibility for farmers to make the switch from commodity (low-quality/economy of scale) to specialty (high-quality and cost/smaller-scale) production can be limited or difficult, and is not always feasible.
Shade in coffee plantations largely comes from other plant species, and thus also has the benefit of improving environmental sustainability, as it provides habitats for many species, prevents deforestation, and supports biodiversity. Many would argue that this isn’t actually an ‘added benefit,’ but rather an inherent necessity for naturally high quality coffee. Some animals and birds feed on the coffee borer, helping to naturally manage detrimental pests, and others eat coffee cherries and poop them out, helping to propagate the plants and keep the species alive. Coffee is auto-fertilising, but fertilisation by insects can boost the process. Coffee grown nearby other plant species can also ‘pick up’ some of the flavours or characteristics of nearby plants, through their effects on soil composition. This further supports its growth under rainforest canopies and in mixed plantations with other species that also offer some shade. Yet again, we find excellent solutions in nature herself.
5. Slope and aspect
The final factor we discuss here is slope, which refers to the degree of inclination of the land the coffee is growing on. Aspect refers to the orientation of that slope in terms of east/west/north/south. These are relevant because most coffee growing regions are at higher altitudes, in mountainous or hilly regions, and thus coffee is often grown on slopes rather than complete flat lands. Lots of the knowledge about the effect of slope angle and orientation comes from wine production.
While latitude and altitude affect the intensity of sunlight for a region, within that area, hill slope and aspect alter the total duration of this sunlight and the time it begins/peaks/ends, and also affect the degree of shade provided by nearby plants. In the Northern hemisphere, south-facing slopes (southerly aspect) receive more sunlight than slopes with a northerly aspect. In the southern hemisphere, north-facing slopes receive more sunlight. In terms of east-facing vs. west-facing slopes, a slope with an easterly aspect will receive sunlight early in the morning, which tends to make them drier since the early morning sun begins to evaporate dew early in the day. West-facing slopes tend to be warmer due to the hotter sun later in the day, so plantations with a westerly aspect may see their cherries ripen more quickly. The angle of the slope will affect the total duration of sunlight and the angle (and thus amount) of shade coverage provided by neighbouring plants.
It’s not really possible to pinpoint specific effects of specific slopes on the final quality or flavours of a coffee, but we don’t wish to, because that could begin to ruin the magical/unpredictable aspect of the complex natural interactions that govern the nuances in specialty coffee flavours. By making fine-tuned adjustments to more direct factors like sunlight and temperature, slope and aspect are simply additional factors that eventually translate subtly into the unique flavour profile of the coffee bean for that particular region.
References/Sources
https://www.climate.gov/news-features/climate-and/climate-coffee
https://www.coffeeresearch.org/agriculture/environment.htm
https://books.google.es/books?id=T7OxK6U9vu4C&pg=PA4#v=onepage&q&f=false
https://maillardreaction.org/index.php/2019/07/10/shade-slope/