A key assumption in many homegarden studies is that homegardens are ecologically and socio-economically sustainable due to their species diversity. The precise relation between diversity and sustainability is still heavily debated, however. A basic question is how diversity in homegardens can best be characterized in view of the various dimensions of species diversity and their variation in time and space. This paper assesses different types of species diversity in the homegardens of Sidama region of southern Ethiopia. In a survey of crop species in 144 homegardens a total of 78 cultivated crop species (excluding trees) belonging to 10 functional groups were recorded; there were on average 16 crop species and 8 functional groups per farm. Within homegardens, plots differ in species composition and crop diversity. Four types of homegarden systems are distinguished differing in both type and area-share of dominant species, relative orientation at subsistence or cash production and overall crop diversity. The gradual replacement of enset by maize and of coffee by more financially attractive cash crops khat and pineapple causes a decrease in overall crop diversity. Our data demonstrate that it is incorrect to consider homegardens as generic systems with a uniform distribution of species diversity: important within and between homegarden variation exists. Ecological and socio-economic sustainability is not just related to species diversity per se, but rather to more specific features such as presence of keystone species and diversity in functional species groups. Socioeconomic sustainability in terms of adjustment to socio-economic change implies dynamics in species diversity.

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Homegardens in Kerala have long been important multi-purpose agroforestry systems that combine ecological and socioeconomical sustainability. However, traditional homegardens are subject to different conversion processes linked to socioeconomic changes. These dynamics were studied in a survey of 30 homegardens. On the basis of a cluster analysis of tree/shrub species density and subsequent further grouping using homegarden size as additional characteristic, six homegarden types were differentiated. These were assessed regarding structural, functional, management and dynamics characteristics. Four development stages of homegardens were found along a gradient from traditional to modern homegardens. Fifty percent of the homegardens still displayed traditional features, whereas 33% incorporated modern practices. The process of modernisation includes a decrease of the tree/shrub diversity, a gradual concentration on a limited number of cash-crop species, an increase of ornamental plants, a gradual homogenization of homegarden structure and an increased use of external inputs. One homegarden was characterised as an adapted traditional homegarden combining multispecies composition and intensive management practices using internal inputs with commercial production. In comparison to modern homegardens, this homegarden type offers an example of an alternative development path in adapting homegardens to changing socioeconomic conditions. The study of structural and functional dynamics of homegardens offers the opportunity to understand the trends in socio-economic sustainability and how these relate to ecological sustainability.

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