Land use legacy effects on woody vegetation in agricultural landscapes of south-western Ethiopia

Abstract

Aim: Past land use legacy effects-extinction debts and immigration credits-might be particularly pronounced in regions characterized by complex and dynamic landscape change. The aim of this study was to evaluate how current woody plant species distribution, composition and richness related to historical and present land uses.Location: A smallholder farming landscape in south-western Ethiopia. Methods:We surveyed woody plants in 72 randomly selected 1-ha sites in farmland and grouped them into forest specialist, generalist and pioneer species. First, we investigated woody plant composition and distribution using non-metric multidimensional scaling. Second, we modelled species richness in response to historical and current distance from the forest edge. Third, we examined diameter class distributions of trees in recently converted vs. permanent farmland.Results: Historical distance was a primary driver of woody plant composition and distribution. Generalist and pioneer species richness increased with historical distance. Forest specialists, however, did not respond to historical distance. Only few old individuals of forest specialist species remained in both recently converted and permanent farmlands.Main conclusions: Our findings suggest that any possible extinction debt for forest specialist species in farmland at the landscape scale was rapidly paid off, possibly because farmers cleared large remnant trees. In contrast, we found substantial evidence of immigration credits in farmland for generalist and pioneer species. This suggests that long-established farmland may have unrecognized conservation values, although apparently not for forest specialist species. We suggest that conservation policies in south-western Ethiopia should recognize not only forests, but also the complementary value of the agricultural mosaic-similar to the case of European cultural landscapes. A possible future priority could be to better reintegrate forest species in the farmland mosaic.

Land‐use history determines ecosystem services and conservation value in tropical agroforestry

“…However, the differences between agroforests of contrasting land‐use history might diminish over time. Oftentimes, forest‐derived agroforests lose tree cover due to logging of existing trees, natural mortality and limited recruitment (De Beenhouwer et al., 2016; Shumi et al., 2018; Valencia et al., 2016), typically resulting in a reduction of biodiversity (Philpott et al., 2008; Tscharntke et al., 2011). Contrastingly, open‐land‐derived agroforests gain tree cover over time and could thereby enter into a positive biodiversity trajectory (Perfecto et al., 1996).…”

Woody plant species diversity as a predictor of ecosystem services in a social–ecological system of southwestern Ethiopia

“…In line with this, the empirical findings by Jiren et al (2017) in our study area showed that many local people favoured multifunctionality-oriented land management. Such integrated land management may be rooted in historical land use, as indicated by a higher woody plant species richness in long-established compared to more recently converted farmland (Shumi et al 2018).…”

“…In the region, while the landscape harbours a high diversity of woody plant species that provide key services for local people (e.g. Jara et al 2017;Shumi et al 2018Shumi et al , 2019b, current agricultural policies favour agricultural intensification (e.g. Kassa et al 2016) and thus negatively impact woody plant species diversity and associated ES.…”

Woody plant use and management in relation to property rights: a social-ecological case study from southwestern Ethiopia

“…The study was conducted in subsistence-dominated rural landscapes of six kebeles (the lowest administrative unit) located in the Gera, Gumay and Setema districts of Jimma Zone, Oromia Regional State, southwest Ethiopia ( Figure 1). The kebeles were selected to span a gradient in forest cover, ranging from 11% to 84% within a kebele ( Figure 1(c,d)) (for specific details see Shumi et al 2018). The region is characterised by a mosaic of forest, farmland (arable land, grazing land and homegardens) and settlements.…”