Effects of rainfall and temperature variabilities on coffee (Coffea arabica L.) productivity in eastern Ethiopia

Coffee is more than a morning ritual for millions; in Ethiopia, it is the heartbeat of the economy and a deep-rooted cultural tradition. The country is the birthplace of the Arabica coffee plant, a crop that thrives only within a very narrow band of weather conditions. For this plant to flourish, it needs a specific rhythm of rain and a temperature that stays comfortably cool. When the rains arrive too late, stop too soon, or when the air grows too hot, the coffee beans struggle to develop, and the harvest shrinks. This sensitivity makes Ethiopian farmers uniquely vulnerable to the shifting climate, where even small changes in the weather patterns can ripple through the entire national economy, affecting livelihoods and the global supply of this beloved beverage.

A team of researchers from Haramaya University has turned its attention to the eastern regions of Ethiopia, specifically the districts of Melka Balo, Bedeno, and Shenen Dugo, to understand exactly how these weather shifts are impacting coffee production. They looked back at eighteen years of daily records, from 2007 to 2024, tracking the amount of rain that fell, the number of days it rained, and the average temperatures during the two main rainy seasons known as the Belg and the Kiremt. By comparing this historical weather data with the actual amount of coffee harvested each year, they built a clear picture of what the plants need to succeed. Their analysis revealed a straightforward but critical relationship: reliable rainfall is the engine of productivity, while rising temperatures are the brake. The data showed that when the rainy season starts late or when the average temperature climbs, the coffee yield drops significantly. Conversely, having more days with rain, particularly during the early season, directly supports a better harvest.

The researchers then used advanced computer models to project what the next thirty years might hold for these districts, looking ahead to 2055 under a moderate climate scenario. The simulations painted a sobering future. They predict that the total amount of rain falling during the early season will decline sharply, while the main rainy season will see a slight but variable decrease. More concerning is the timing; the rain is expected to arrive later and stop earlier, effectively shortening the window of time the coffee plants have to grow. At the same time, the average temperature during both rainy seasons is set to rise steadily. When the researchers fed these projected changes into their models, the result was a steady decline in coffee production. They estimate that yields could drop by nearly one-tenth of a quintal per hectare every single year, a loss that compounds over time.

The study highlights that the threat is not just a lack of water, but a fundamental change in the climate's rhythm. The delay in the start of the rains disrupts the coffee's flowering cycle, and the earlier end to the rainy season leaves the beans to mature under stress. The rising heat accelerates the plant's development too quickly, shortening the growing period and reducing the quality and quantity of the beans. While the models show some year-to-year fluctuations, the long-term trend points toward a climate that is increasingly hostile to the delicate Arabica plant in these lowland areas. The researchers emphasize that without intervention, the livelihoods of the farmers and the country's export potential are at serious risk.

To counter these looming changes, the paper suggests a set of practical steps that could help sustain the industry. These include moving coffee cultivation to higher, cooler altitudes where the air remains suitable, and planting shade trees to buffer the plants against the heat. The authors also advocate for introducing new coffee varieties that are bred to withstand drought and higher temperatures, as well as improving soil and water conservation techniques. They argue that simply relying on traditional methods will no longer be enough. By combining these adaptation strategies with stronger support for farmers, Ethiopia may be able to protect its coffee heritage against a warming world, ensuring that the harvest continues despite the changing skies.