COS 22-3 - An integrated understanding of coffee alternate bearing and feedbacks with farmer decision-making.

Abstract: Coffee, like numerous perennial crops, exhibits alternate bearing, a pattern of reproduction in which a high-yielding year is followed by a low-yielding one. From our previous work, we know that coffee alternate bearing can synchronize even at a regional scale. Moreover, intrinsic resource tradeoffs are a driver of coffee alternate bearing at a plant level. Patterns of synchrony across a farm, however, remain underexplored and little is known about how farmer management decisions might mitigate, or exacerbate, alternate bearing. Conventional practice suggests that chemical fertilizers allow for consistently high yields. Yet the resource budget model, an ecological theory of reproductive variability in perennial plants, predicts that increased fertilizer would exacerbate rather than alleviate alternate bearing. It also predicts that factors that limit plant-level investment in fruit load (e.g., shade cultivation and higher farm elevation) would allow for more consistent yields, though empirical evidence is scarce. In collaboration with 30 coffee farmers in Santa María de Dota, Costa Rica, we characterized patterns of alternate bearing at the farm scale and explored their relation to farm management practices and elevation. Data comprised 10 years of farm-level production, 2 years of plant-level fruiting effort, and farmer interviews. We found evidence of synchronous alternate bearing at a farm scale, resulting in fluctuations in on-farm income, but the degree of synchrony was unrelated to variability in fertilizer or shade management. Higher elevation farms, however, exhibited significantly less alternate bearing (i.e., more stability at the farm scale). Farmers possessed detailed knowledge of alternate bearing, including intrinsic and extrinsic drivers operating at different scales, and alternate bearing played an important role in their management decision-making. Most, however, expected that higher fertilizer rates would mitigate alternate bearing, contrary to what we observed. Further, to cover the fertilizer cost following a low-yielding year, farmers reported taking out loans, limiting household expenses, and supplementing with off-farm income, citing fears that failure to do so would result in a downward spiral of farm health. Together, the results indicate that farmer capacity to mitigate alternate bearing via management is limited and that predominant coping strategies may be maladaptive in the long-term; opportunities to support more adaptive responses to low-yielding years include expanding income diversification and securing farm health with less reliance on agrochemical inputs.