A continent finds it is getting too hot for coffee

Like most of the small landowners in Colombia’s lush mountainous Cauca region, Luis Garzón, 80, and his family have thrived for decades by supplying shade-grown, rain forest-friendly arabica coffee for top foreign brands like Nespresso and Green Mountain. A sign in the center of the nearby town proclaims, ‘‘The Coffee of Cauca is No.1!’’

But over the past few years, coffee yields have plummeted here, as in many of Latin America’s other premier coffee regions, as a result of rising temperatures and more-intense and unpredictable rains, phenomena that many scientists link partly to global warming.

Coffee plants require the right mix of temperature, rainfall and spells of dryness for beans to ripen properly. Coffee pests thrive in the warmer, wetter weather.

Bean production at the Garzóns’ farm is down 70 percent from the level of five years ago, leaving the family short of money to buy clothing for toddlers and ‘‘thinking twice’’ about sending older children to college, said Mr. Garzón’s 44-year-old son, Albiero, interviewed in a yellow stucco house decorated with coffee posters and Madonnas.

In 2006, Colombia produced more than 12 million bags of coffee and set a target of 17 million for 2014. Last year the yield was 9 million bags.

The shortage of high-end arabica coffee beans is also being felt in New York supermarkets and Paris cafes, as customers blink at sky-high prices. Purveyors fret that bean taste will deteriorate and that the arabica coffee supply will never rebound — that the world has, in effect, hit ‘‘peak coffee.’’

Lower-end brands have increased the retail prices of many grinds by 25 percent or more since the middle of last year in light of short supply and higher wholesale prices. Profits of high-end coffee chains like Starbucks and Green Mountain have been eroded.

Coffee futures of arabica, the high-end bean that comes predominantly from Latin America, have risen 85 percent since June, partly over concerns about the short supply, extreme weather and future quality, said George Kopp, an analyst at International Futures Group in Chicago.

Yet as stockpiles of some of the best coffee beans shrink, global demand is soaring, with the rising middle classes of emerging economies like Brazil, India and China developing the coffee habit.

‘‘Coffee production is under threat from global warming, and the outlook for arabica in particular is not good,’’ said Peter Baker of CABI, a research group in Britain that focuses on agriculture and the environment, noting that climate changes — including both heavy rains and droughts — have harmed crops across much of Central and South America.

A leading coffee scientist, Mr. Baker has rattled trade forums by warning of the possibility of ‘‘peak coffee,’’ meaning that, like oil, supplies of coffee might be headed toward an inexorable decline unless growers make more-concerted efforts to expand production globally.

Announcing its annual meeting this spring, the Specialty Coffee Association of America spoke of ‘‘extreme challenges,’’ warning, ‘‘It is not too far-fetched to begin questioning the very existence of specialty coffee.’’

Two categories of coffee, arabica and robusta, account for virtually all consumption. With its more delicate taste and lower caffeine content, arabica is the more popular and more expensive variety, though generally more finicky in its weather requirements. Robusta production dominates in Asia and Africa.

Here in the Colombian highlands, where some of the most prized arabica in the world grows at elevations of almost two kilometers, or more than a mile, residents say that climate-related threats seem to be coming from all directions.

The Colombian Coffee Growers’ Federation says that high fertilizer prices have also led to reduced yields. But it agrees with a report released by the International Coffee Organization in 2009 that concluded, ‘‘Climatic variability is the main factor responsible for changes in coffee yields all over the world.’’

Average temperatures in Colombia’s coffee-growing regions have risen about half a degree Celsius (0.9 degree Fahrenheit) in the past 30 years, and in some mountain areas the increase has been 1.5 degrees, according to Cenicafé, Colombia’s national coffee research center. Precipitation in this area was more than 25 percent above average in the past few years.

At the new, higher temperatures, the plants’ buds abort or their fruit ripens too quickly for optimum quality. Heat also brings pests like coffee rust, a devastating fungus that could not survive the previously cool mountain weather. The heavy rains damage the fragile arabica blossoms, and the two-week dry spells that prompt the plant to flower seldom occur.

‘‘Half a degree can make a big difference for coffee — it is adapted to a very specific zone,’’ said Néstor M. Riaño, a specialist in agroclimatology for Cenicafé. ‘‘If temperature rises even a bit, the growth is affected, and the plagues and diseases rise.’’

While climate scientists agree that the increase in temperature is a clear signal of global warming and that high ocean temperatures are generally associated with more frequent storms, scientists are uncertain whether the peculiar weather patterns in the area are directly related to warming, said Stephen E. Zebiak, director general of the International Research Institute for Climate and Society at Columbia University in New York.

‘‘It is hard to know whether this severe weather represents natural fluctuations or is a climate-change signal, Dr. Zebiak said. ‘‘Though from a risk-management sense, there is good reason to consider how to cope with these extreme events.’’

In the hope of restoring coffee output, researchers at Cenicafé’s labs in Chinchiná, Colombia, are toiling on a mission that seems as pressing a priority for the country as finding a cure for cancer is for medical researchers.

Agronomists are teaching the farmers how to control the pests that arrived with the change in the weather. Climatologists are working to provide better local weather predictions. Geneticists are breeding plants that are more resistant to diseases or that can withstand torrential rains or a hotter environment.

The coffee growers’ federation has advised farmers like Mr. Garzón to switch to a newer, hardier strain of arabica that has been developed by plant breeders at Cenicafé over the past two decades.

While the coffee growers’ federation says the strain tastes the same as traditional variants, many farmers believe the switch will affect flavor. They have also resisted because they can ill afford to forgo the income of a yearly crop as they wait for new coffee plants to mature.

Taste, quality and supply are delicate issues for an industry whose aficionados are notoriously picky. Coffee companies are ‘‘working with farmers across the region to address the impact of changing weather patterns that are a direct result of climate change,’’ said Lisa Magnino, a spokeswoman for Starbucks.

Starbucks has already bought enough coffee to last until 2012, she added.

Luis Samper, a spokesman for the Colombian coffee growers’ federation, said the beans that do make it to breakfast tables will yield coffee that is as good as ever. The problem is for Colombian farmers, who are producing far fewer beans over all and ‘‘more defective beans’’ that do not meet export standards.

For decades, said Luis Garzón, who started working at the family business in Timbío at age 7, it was dry from June 1 to Sept. 8. Then, several years ago, the perplexing weather arrived.

‘‘It can start raining at 6 a.m. and go on for 24 hours,’’ he said.

First, yields declined. Then last year, the coffee rust fungus arrived at the Garzón farm, killing entire fields. ‘‘We learned our lesson,’’ he said, stroking the mottled yellowed leaves of some damaged plants.

Now, the family is planting the new, hardier arabica variant, called castillo. The coffee federation hopes that such innovation will allow growers to meet the demand for expensive arabica coffee.

In the meantime, it is creating a ‘‘product origin’’ certification program for Colombian coffees, like those from Cauca, similar to the one that protects Parmesan cheese in Italy.

That way, it hopes, importers will not be tempted to substitute Colombian beans with for ones from Brazil or Indonesia.