Coffee crop at risk? An integrated study on biennial bearing, climate change, phenological changes and trends in the territory of the Matas de Minas, Minas Gerais, Brazil
This integrated study reveals that climate change in Brazil's Matas de Minas region has significantly warmed temperatures and reduced water availability, pushing conditions toward the thermal limits of *Coffea arabica* and causing phenological shifts that threaten productivity, thereby necessitating urgent adaptation strategies like heat-tolerant cultivars and improved irrigation.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the highlands of southeastern Brazil, a specific type of coffee plant thrives, producing the beans that fuel much of the world's morning ritual. This plant, known scientifically as Coffea arabica, is a creature of precise comfort. It does not like extremes. It prefers a steady, moderate warmth and a reliable rhythm of rain and dryness to guide its growth from flower to ripe fruit. For decades, farmers in the Matas de Minas region, a mountainous area famous for its coffee, have relied on this predictable climate. However, the world is changing, and the air is getting warmer. When the temperature rises, the delicate balance required for this crop can tip, leading to smaller harvests or beans that lack their signature flavor. Understanding exactly how these shifts affect the coffee plant is no longer just an academic exercise; it is a matter of economic survival for the families who tend these fields and for the global supply of coffee itself.
A team of researchers from the Federal University of Viçosa set out to measure the real-world impact of these changing conditions on the Matas de Minas region. They looked at fifty years of data, from 1975 to 2025, combining records of how much coffee was harvested with detailed daily weather maps. Their goal was to separate the natural ups and downs of coffee farming from the damage caused by a warming climate. Coffee plants have a well-known habit called biennial bearing, where they naturally alternate between a heavy harvest one year and a lighter one the next, simply because they exhaust their energy reserves after a big crop. The researchers needed to account for this natural cycle to see if there were other, more dangerous forces at play. They found that while this natural cycle does cause a swing of about 256 kilograms per hectare between high and low years, something else was hurting the crops. When a negative shock, such as a heatwave or a drought, hits the region, it slashes production by nearly 480 kilograms per hectare. Crucially, this damage happens regardless of whether the plant is in a high-yield year or a low-yield year. The shock is so severe that it overwhelms the plant's natural resilience, hitting it just as hard whether it was already strong or already tired.
The study then turned its attention to the specific weather variables driving these changes. By analyzing decades of temperature and rainfall data, the researchers identified that the hottest part of the day is the most damaging factor. For every single degree Celsius the maximum temperature rises, the harvest drops by nearly 48 kilograms per hectare. This confirms that the scorching heat of the afternoon is the primary enemy of the coffee plant in this region. Interestingly, the study found that warmer nights, represented by higher minimum temperatures, actually had a slight positive effect on production, suggesting that a bit more warmth at night might help the plant's metabolism, provided the daytime heat does not get too extreme. However, the water situation is becoming increasingly precarious. While the total amount of rain falling each year has remained roughly the same, the air is getting hotter, which causes the soil to dry out faster. This has created a growing gap between the water the plants need and the water available, with the region now facing its largest water deficit in fifty years.
Beyond just the amount of coffee produced, the timing of the plant's life cycle is shifting. The researchers tracked when the coffee trees flower and when their fruit reaches maturity. They discovered that these events are happening earlier every year. On average, the flowers are opening and the fruit is ripening about two days sooner for every six years that pass. This shift is happening across all elevations in the region, from the lower valleys to the higher peaks. If the fruit matures too quickly, it may not have enough time to develop the complex sugars and acids that give the coffee its rich taste and high quality. The data shows that the average temperature in the region has risen by one degree Celsius over the last fifty years, bringing the current average of 22.7 degrees Celsius dangerously close to the upper limit of what the coffee plant can tolerate.
The conclusion drawn from this half-century of data is clear: the coffee farms of Matas de Minas are facing a climate that is becoming increasingly hostile. The activity is not yet impossible, but the margin for error is shrinking. The natural rhythm of the coffee plant is being disrupted by heat and water stress that the plants were not evolved to handle. To survive, the region will need to adapt. The researchers suggest that farmers may need to plant new varieties of coffee that can withstand higher heat and less water, or perhaps grow the trees under the shade of taller trees to keep the temperature down. They also point to the need for better water management, such as irrigation during the most critical times of the year. Without these changes, the warming trend threatens to push the region past the point where high-quality Arabica coffee can be grown, altering the landscape and the livelihoods of the people who have cultivated this crop for generations.
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