This is serious: climate change could put your caffeine supply at risk. Coffee is notorious for being picky about its climate conditions, with the most popular varieties only growing at specific altitudes in the tropics. That alone makes coffee susceptible to climate change, but the plants are also fussy about their pollinators, which will also be affected by the changing climate.

A new analysis suggests that climate change on its own could cause coffee producing areas in the Americas to drop production by roughly 80 percent. But the remaining productivity might drop even further unless we ensure the crops have access to pollinators.

Coffee and climate

Only two varieties of coffee are cultivated. One is called "robusta;" as its name implies, it's more tolerant of heat and holds up better to insect pests, so it can be grown across a lot of the tropics. Unfortunately, robusta is uniformly acknowledged to not taste that great. Complicating matters further, its caffeine content is high enough to set off heart palpitations at nearly double the levels found in the other major coffee variety.

That variety is "arabica," which provides the rich, complicated flavor most of us associate with coffee. But arabica is extremely fussy about its conditions. At the equator, it only grows at altitudes above a kilometer, and it can tolerate a variety of rainfall patterns. Farther from the equator, it grows at altitudes between 500 meters and a kilometer, and it relies on specific rainfall patterns.

A few robusta-arabica hybrid strains have been developed, but plants take roughly four years to start producing beans, so improving the crop through breeding is a long-term endeavor.

Obviously, for a crop this sensitive to climate variations, climate change poses a challenge. In most of the existing growing regions, rising temperatures would push the crop uphill. Obviously, there's less land as you go up a mountain, so this means less land available for the crop. That problem would be partly offset by areas farther from the equator that warm up enough to allow the arabica to grow there. But, overall, global analyses have suggested the area where arabica could be cultivated would be cut in half by the middle of the century.

High resolution + bees

The new analysis extends the earlier work by focusing on the Americas and massively increasing the resolution. The team used two different emissions scenarios (RCP 4.5 and 8.5 from the Intergovernmental Panel on Climate Change). The future climate, averaged between the years 2040 and 2060, was analyzed using a total of 36 different climate models. Nineteen different climate variables—things like temperature and precipitation—that influence coffee production were extracted from the models. And, critically, the analysis was performed at a very high spatial resolution, with the landscape broken up into squares one kilometer on a side.

This higher resolution makes a big difference. Rougher estimates suggested that the amount of coffee-producing land would drop by about 30 percent. But the new work suggests that the numbers are much higher, with suitable land going down by more than 70 percent and perhaps as much as 88 percent at higher levels of warming.

Coffee is also dependent upon pollinators. While domesticated bees are important contributors to coffee pollination, past studies have shown that having access to more pollinator species increases the yield. Many of the local bee species are sensitive to climate change, so the researchers included them in the analysis.

Here, the news was a bit better. Across South America, the species diversity of bees goes down considerably due to the changing climate. Only about five percent of the continent sees an increase in species diversity; it drops in 65 percent of the terrain. But coffee-growing regions happen to start with very high diversity, with an average of 13 different species. While climate change causes that number to drop slightly, crops will still have plenty of pollination options; even the worst-hit regions will still have at least five bee species that like the climate.

What the authors suggest is that pollinators could become critical in areas that haven't previously supported coffee production. As farmers expand into these areas, they could engage in practices that create good habitats for wild bees.

Aside from the obvious worries about the global coffee supply, the analysis indicates that there may be some specific national issues. Countries like Honduras and Nicaragua, for example, already grow coffee on the highest parts of their terrain. As the planet warms and optimal growing areas move uphill, there will be almost no place for them to go here. And as coffee is a major source of income for small farmers in these countries, it'll be important to adjust policy well in advance of crop failures.

PNAS, 2017. DOI: 10.1073/pnas.1617940114 (About DOIs).