Paradise lost? A case for (re)-introducing trees in the enset farming systems of the Ethiopian rift

Abstract

Global food insecurity is on the rise, having worsened since 2015 primarily due to conflicts and climate-related extremes, and jeopardizing the UN Sustainable Development Goal of zero hunger by 2030. Especially in sub-Saharan Africa, where the population is estimated to double by 2050, food demand is expected to increase by 3.9 percent annually. It is essential to increase agricultural production sustainably, without undermining the ecosystems’ capacity to sustain human well-being. In this context, neglected/orphan crops are gaining attention as an avenue to alleviate food insecurity. These crops are often produced under subsistence farming and have gained less attention from the scientific communities. Enset (Ensete ventricosum), a multipurpose, perennial, herbaceous-like plant domesticated only in Ethiopia, is a prime example of an underexploited crop. Although a model enset-based homegarden agroforestry exists, it is mainly produced as a monocrop in most Ethiopian regions, which exposes the crop to stressors such as climate extremes, soil fertility imbalance, and diseases. In certain regions, scattered agroforestry tree species exist inside enset farms, while information on the tree species' potential benefits and ensets’ response to tree canopy shade is not well documented.   Our study examined how scattered trees in enset farms affect the microclimate and soil properties and evaluated the phenotypic responses of ensets.  The trees significantly reduced the daily air, soil surface, and soil temperatures, ranging from -0.5 to -1.9 °C, -0.4 to -2.1 °C, and +0.4 to -1.0 °C, respectively, and maintained the minimum soil moisture by +0.8% to +5.7% compared to open areas. On the other hand, although the tree species had high-quality leaf litter, their effect on the soil fertility indicators was minimal. However, our on-field observation suggests that the old big trees improved total carbon, C/N ratio, cations (Ca²⁺), and CEC, suggesting the importance of conserving the already existing trees besides planting the new ones. Moreover, our observations on enset phenotypic response to the changing microenvironment by tree canopy covers revealed that enset can adapt to a new environment through plastic responses. Overall, our findings suggest that introducing woody trees into the enset farming system can enhance enset productivity by preventing extreme heat and frost and enhancing soil quality. Besides, they can help to reduce landslide risks commonly affecting farmers in the region.

Key words: Enset, Trees, Microclimate, Soil fertility, Phenotypic plasticity