Five thousand years of sustainability? : a case study on Gedeo land use (Southern Ethiopia)

Key words : Ethiopia, Gedeo, ensete , pacemaker , spacemaker , placemaker, agroforest, agro-ecosystem, sustainability, biodiversity.The present volume is a study of an ancient way of land use, over five thousand years old, by the Gedeo in Ethiopia. The densely populated Gedeo country (500 persons per km 2) covers highlands (range 1200 to 3000m asl) between 5 oand 7 oNorth and 38 oand 40 oEast, in the escarpment of the Rift Valley facing Lake Abaya. Based on perennial cropping, emphasis on trees in particular lends the "agroforests" a forest-like appearance. Ensete ( Ensete ventricosum (Welw.) Cheesman Musaceae) and Yirga-Chaffee, one of the world's renowned cultivars of Coffea arabica L. Rubiaceae, is grown under these trees. Largely due to their unique cropping system, the Gedeo are immune to soil erosion and famines, ravaging the Ethiopian highlands at intervals. The central theme of the present ecological study is to understand theoretical and practical aspects of the holistic Gedeo land use better, and to contribute to the design capability of the farmers. Theoretically, farm design is examined from the perspective of forest ecology. The concepts of eco-unit and agro/silvatic mosaic , at the lowest and highest levels, respectively, provide more insight in agroforests as blocks of forests, with humans assuming the roles performed by some natural forces in forests. Therefore, these agroforests remain multivalent resources. Empirically, the design is examined as farmers' day-to-day management of these resources. The study provides a strong theoretical basis in favor of Gedeo land use with its complex mix of elements to represent a multiple purpose land use from which modern day agriculture and forestry emerged as overspecialized offshoots. Gedeo land use harmonises aspects of production and protection. Agroforest components are divided into core and subsidiary components. The first type has a pacemaker role (regulation of agro-ecosystem rhythm), a spacemaker role (provision of biotope space for other crops) and/or a placemaker role (provision of living space, or niches for other organisms). Ensete and various multipurpose tree species fulfil the latter function. Annual crops, the coffee or farm animals are regarded as "fillers". Ensete , with its anatomical water-stocking and storage mechanisms and with its fibrous root system forming a mat-like structure 30 to 60 cm deep which on decomposition yields organic matter for soil maintenance, is more than a mere crop. The higher carrying capacity of Gedeo "agroforests" is traced back to the high productivity of ensete (over 5.6 tons ha -1year -1) and judicious use of accompanying crops. It has been found that six mature ensete plants ( gantticho type) feed an adult during a year. A farm household of seven persons then needs an area of no more than 0.2 hectare for a sustainable yearly supply of 42 ensete plants, gantticho type. Management is based on either single or multiple rotations. The latter is explained, using ensete as an example. Analyses revealed that the soils are clay-loam, their pH (H 2 O) ranging between 5 and 6. The limiting factor is available phosphorus (range 1.0 to 4.0 ppm). Organic matter (%) ranged between 4 and 5, total nitrogen (%) between 0.3 to 0.5, and cation exchange capacity (meq/100g soil) from 21.0 to 25.0. Gedeo soil management is organic, using as inputs crop by-products, leaf litter from multipurpose trees and "weeds", domestic wastes, rotation of dwelling sites and farmyard manure. In achieving sustained products and services from "agroforest" components, farmers' effort is mainly directed at optimisation of the interrelationships among diverse components. Number and/or mass of "agroforest" components to be harvested and planted are balanced. This fully corresponds to the Central-European concept of sustained yield forestry. No organism is intrinsically harmful to the farmers. The weedy flora, for instance, is used to protect future yield, first by providing physical cover to the soil, second by conserving soil nutrients in its biomass, later to be released to "crop" plants by mulching the weedy biomass.Gedeo land use contains elements of shifting cultivation, the basis of farmers' management at the level of an agro/silvatic-mosaic . Like in shifting cultivation, vegetation is used to regenerate exhausted land. However, unlike in shifting cultivation, this enables production and regeneration, simultaneously. Whereas shifting cultivators burn and convert mature forest plots, the Gedeo synchronize harvest and replanting. In this way, continuous use of the same plot of land is ensured indefinitely. It is concluded that this way of land use is best suited to the mountainous terrain of the Gedeo country. It is argued that through the judicious use of high-yielding and environment-friendly ensete , subsistence agriculture can stave off the recurring famine and drought-ridden image of Ethiopia. The level of employment provided by Gedeo "agroforests" is declining as a result of growing population. Therefore, there is an urgent need for assistance. The present productivity of these systems can be enhanced by carefully redesigning existing composting processes. Finding better marketing channels for the produce of the "agroforests" is a priority in the short term. Thus, organically grown arabica coffee from the Gedeo "agroforests" should be certified and processed in situ . Unused biotopes for integrating components in the system still exist or can be opened up in Gedeo "agroforests", e.g., for a multipurpose tree species such as Morinaga sp. (locally called shiferaw ), a leguminous timber tree, the leaves of which are eaten as a vegetable. Diverse species of wild mushrooms can be domesticated. Generally, ways and means should be found for cultivation of miniature crops of high value in the soil and the canopy, particularly tiny organisms such as nitrogen-processing bacteria, mycorrhizal and edible fungi (diverse mushrooms) or medicinal lichens. The Rift Valley and its inhabitants were a source of civilized human development for millennia. The present study demonstrates that principles of sustainability were successfully woven in at least some of their societies. This book therefore advocates building on this basis by studying and teaching these principles as a base for new, sustainable land use design in the Twenty First Century.