Coffee can be a major casualty of a warmer planet. Even if currently declared emission reduction commitments are met, our new research suggests that coffee production will continue to decline rapidly in countries accounting for 75% of the world’s Arabica coffee supply.
Arabica coffee (Coffea arabica) is one of the two main plant species from which we harvest coffee beans. The plant evolved in the high altitude tropics of Ethiopia and is hypersensitive to climatic changes.
Our research shows that there are global warming thresholds beyond which Arabica coffee production drops. It’s not just bad news for coffee lovers – coffee is a multi-billion dollar industry that supports millions of farmers, most of them in developing countries.
If we manage to keep global warming below 2℃ this century, growers responsible for most of the world’s Arabica supply will have more time to adapt. If we don’t, we could see drops in Arabica productivity, supply disruptions and price hikes on our daily cup.
Where does our coffee come from?
Most of our Arabica is grown in the tropics, throughout Latin America, Central and East Africa and parts of Asia. Brazil, Colombia and Ethiopia are the world’s top three producers of Arabica, and the crop is also of crucial social and economic importance elsewhere.
Millions of farmers, mainly in developing countries, depend on productive Arabica for their livelihood. If coffee productivity declines, the economic consequences for farmers, some of whom do not earn a living income as they do, are disastrous.
Arabica coffee is generally most productive in cool high altitude tropical areas with a local annual temperature of 18-23℃.
Higher temperatures and drier conditions invariably lead to yield declines.
Last year, for example, one of the worst droughts in Brazil’s history saw coffee production there plummet by around a third, sending global coffee prices soaring.
What we found
Previous research has focused on how changes in temperature and rainfall affect coffee yields. Although important, temperature and rainfall are not the best indicators of global Arabica coffee productivity. Instead, we’ve found that it’s more efficient to measure how dry and warm the air is, which we can do by using the ‘vapor pressure deficit’.
The vapor pressure deficit tells us how much water a plant is sucking up. Think of when you are walking outside on a hot, dry day and your lips dry and crack – moisture is sucked in because the vapor pressure deficit is high outside. It’s the same with plants.
We have built scientific models based on climate data linked to decades of data on coffee productivity in major Arabica producing countries. We have found that once the vapor pressure deficit reaches a critical point, Arabica coffee yields drop sharply.
This critical point, we have found, is 0.82 kilopascals (a unit of pressure, calculated from temperature and humidity). After this point, Arabica yields begin to drop rapidly – a loss of around 400 kilograms per hectare, or 50% less than the long-term global average.
Vapor pressure deficit thresholds have already been exceeded in Kenya, Mexico and Tanzania.
Continued global warming will endanger the world’s coffee-producing power plants. If global warming temperatures increase by 2℃ to 3℃, then
Peru, Honduras, Venezuela, Ethiopia, Nicaragua, Colombia and Brazil –
together representing 81% of the world’s supply – are much more likely to exceed the vapor pressure deficit threshold.
What can we do about it?
Although there are ways for farmers and the coffee industry to adapt, the viability of their application on a global scale is highly uncertain.
For example, irrigating coffee crops might be an option, but it costs money – money that many coffee farmers in developing countries don’t have. Additionally, it may not always be effective as high vapor pressure deficits can still cause damage, even in well-watered conditions.
Another option could be to switch to other coffee species. But again, it’s heavy. For example, robusta coffee (Coffea canephora) – the other main production coffee species – is also sensitive to temperature increases. Others, such as Coffea stenophylla and Coffea liberica could be tested, but their viability for large-scale production under climate change is unknown.
There’s not much adaptation we can do. Our research provides new momentum, if we needed it, to reduce net global greenhouse gas emissions.
Limiting global warming in accordance with the Paris Agreement is our best option so that we can all continue to enjoy coffee. More importantly, keeping global warming below 2℃ is the best way to ensure that the millions of vulnerable coffee farmers around the world have a livelihood that supports them and their families well into the future.
/ Courtesy of The Conversation. This material from the original organization/authors may be ad hoc in nature, edited for clarity, style and length. The views and opinions expressed are those of the authors.