Two solutions to save your cup of coffee from climate change.

Imagine that you are struggling to find water during the dry season, from October to April. Imagine that every year, the dry season is longer and drier because of climate change. Now, imagine that you cannot move to get water because you are a coffee plant.

A coffee tree does not have many options to get water. It can grow longer roots or lose its leaves to collect or save water. The plant can also regulate its water loss by adjusting the opening of its stomata which are very small holes on its leaves invisible to the naked eye.

In these ways, a coffee tree could have survived a drought 200 years ago; however, there is another, more recent, problem: climate change. The large amount of greenhouse gases like carbon dioxide and methane which were released into the atmosphere in the last 200 years have disturbed our climate. The average temperature around the world is higher, this is global warming.

A hotter world means longer and drier drought with less water for the coffee tree to grow and produce fruits. For us, this is disastrous. No coffee fruits mean no coffee to drink in the morning. For farmers it is even worse because they need coffee beans to earn money to buy food and send their kids to school.

Can we find solutions for a coffee tree to better support drought and help farmers to maintain their income?

Coffee originally grew up under the shade of the Ethiopian forest: a more lush area, with a more friendly environment for coffee trees. Here in Vietnam, it’s a little different. Coffee trees are grown all alone on the field — and, as climate change makes the environment drier, coffee struggles to survive and produce fruits. How can it grow up in a place where irrigation technology is hard to get, water reserves can be exhausted, and coffee often competes with its partner trees for the shallow water on top rather than sticking its own roots deeper down?

The first solution is to look for better coffee hybrids and varieties. In Ethiopia, certain wild varieties can be selected and crossed with commercial varieties to create improved hybrids. Such crossings can also happen naturally: in the early 20th century, for example, a Robusta coffee naturally crossed with an Arabica coffee tree creating a new hybrid resistant to the leaf-rust coffee disease.

Contrary to past breeding programs which focused on increasing coffee yield under full sun conditions, scientists have now been selecting hybrids which resist extreme drought — and produce lots of high-quality beans under shade. The second part is especially important. During a drought, if a coffee tree is in the shade, shade trees compete with it for water which is already scarce in the soil. Still, the right shade tree can keep air humidity under its canopy and pump up water from deep soil layers to irrigate the coffee tree.

These varieties have been tested in Nicaragua, Cameroon, and Costa Rica, but not yet in Vietnam. In 2018, my team planted three of these improved hybrids in Vietnam. From the growth measures we took this year, I can say that the new hybrids are larger and higher than the commercial variety usually grown in Vietnam. After we measure the yield and bean quality, we will know whether these hybrids can really produce more and better coffee beans here like they do in Latin America and Africa.

From past studies in other countries, we are already very confident that the yield and bean quality will be higher than the Catimor — which is the Arabica coffee commonly cultivated in Vietnam. What we don’t know is why these new hybrids produce more beans of higher quality. We also don’t know why they resist drought better.

How do these varieties behave in dry conditions?

We can look at the physiology of the different coffee hybrids, at their stomata, their transpiration, and their eating habits.

All hybrids do not behave the same way. Some of the hybrids open their stomata even in dry conditions, losing a lot of water while others close them. Some open their stomata when it is hot and dry to capture CO₂ and make sugar through photosynthesis, while others take a nap and stop to capture CO₂ in the hot hours of the day. It is this difference in eating habits or time of activity that makes the new hybrids better than commercial varieties.

In addition, each hybrid behaves differently to small changes of the environment like soil humidity, air humidity, temperature and light. This also influences the productivity and drought resistance of the different hybrids.

Once we will know more about specific hybrid behaviour, we will look at their genetic differences. Do hybrids express different genes compared to commercial varieties when they lack water? In past studies, scientists have observed differences in coffee gene expression during a stress. However, nobody knows which genes are involved in drought resistance in the coffee tree.

The only thing we know is that drought resistance is regulated by many different genes and a cascade of complex chemical reactions. Even though we have identified specific genes and molecules influencing drought resistance, we still have not put the pieces of the puzzle together.

Identifying genes, molecules and traits which make a coffee hybrid more resistant to drought is crucial to inform the next breeding programs to create coffee plants adapted to extreme drought and heat caused by climate change.

Instead of changing the coffee tree itself, we can change the environment around the coffee tree and better manage the coffee plantation.

Climate change increases global average temperature and shifts all areas suitable for coffee plantations to higher altitudes. In a close future, it will be risky and even impossible to establish plantations in lowlands, that’s why coffee plantations should be planted in higher lands. On average, temperature decreases of 0.6 °C for every 100m increase in altitude; consequently, a fresh environment suitable for Arabica coffee will only be available at high altitude.

An easy trick to make the environment around the coffee tree less dry is to irrigate. Watering a plant sounds an easy business but on the field it is not. Very poor farmers do not have access to water or irrigation technologies. Farmers who can afford irrigation systems often over-irrigate and waste water. Underground water reserves can quickly be exhausted when all farmers of the region open the tap for too long. The challenge here is to give farmers a good irrigation system and tell them how to sustainably use underground water reserves.

The direct environment of the coffee tree can be altered with one last tool: agroforestry. Agroforestry is about planting coffee along with shade trees, for example fruit or timber trees. These trees intercropped with coffee allow farmers to make an extra income by selling fruits or timber. In addition, those trees create shade and protect coffee trees against extreme temperature and wind. Temperature in a plantation under agroforestry can be 4 to 5 °C lower than in a plantation fully exposed to the sun. Air humidity is maintained by the shade trees as well.

A potential problem of agroforestry is when the tree intercropped with coffee competes for water instead of bringing up water from soil deep layers, but this can be solved by carefully selecting the right shade tree species. Farmers should also learn how to plant, prune and fertilize shade trees, otherwise they may create too much shade and not produce much fruit.

Originally growing under the shade of the Ethiopian forest, coffee trees thrive under low levels of shade, for example 30% of the sunlight is optimum for coffee trees to produce beans of high quality without reducing the overall yield.

Agroforestry is a shelter for insects and animals and can also store carbon thereby reducing the impact of agriculture on biodiversity loss and climate change. With the current rate of deforestation, there will soon be more trees outside forest than inside forests, making agroforestry the last refuge for trees. We really need trees to store carbon and avoid worsening climate change, if they cannot be in forests, let’s plant them in agricultural fields.

We have talked about how coffee trees can be improved to thrive under a hotter and drier climate. We have also seen that a better management of the coffee plantation can reduce the effect of climate change on coffee production. These two solutions are not possible without you. You are the one who decides the kind of coffee you drink. You can drink sustainable, organic, or bird-friendly coffee. You can be more mindful of your consumption and look for a coffee with less impact on the environment, or a fair coffee where farmers receive a larger part of the price you pay.

Climate change is creating more extreme conditions for coffee to grow. Scientists look for better varieties, governments and NGO train farmers to better irrigation or manage shade trees. You too can contribute to maintaining coffee production under climate change. You can better buy coffee today so you will still have coffee tomorrow.