Forest ecosystems have high biodiversity and act as important carbon sinks, however human disturbances and impacts on these ecosystems are causing them to rapidly change. Anthropogenic disturbances have a range of impacts on forest ecosystems from the edge to the interior and can result in forest degradation, which has negative impacts on biodiversity and carbon sequestration. In Ethiopia, human presence is widespread, and most forests are surrounded- and used- by local communities for livestock grazing, product extraction and coffee production. Beche et al. (2022) therefore investigated the spatial variations in human disturbances and their impacts on forest structure and biodiversity in the moist Afromontane forest landscapes of southwest Ethiopia.
Since there is little known about the different human disturbances, the depth of their effects into the forest, and how these affect forest structure and biodiversity, the authors designed a study across a district with a large remaining forest area. They assessed the landscape variables, human disturbances, forest structure variables, and species composition across plots in a 750km2 area in southwest Ethiopia and analyzed how forest structure and biodiversity were impacted by human disturbances.
Beche et al. (2022) found that the human disturbances in the form of coffee management and grazing declined with distance to the forest edges, and usually penetrated at least a kilometer into the forest. Most of these human effects were common close to agricultural areas with less forest cover but were limited by steep terrain, and some disturbances were less common at higher elevations. The disturbances near agricultural areas were largely driven by local reliance on forests for provisioning ecosystem services from coffee, spices, honey, and firewood. Grazing was also done in the forest, but the intensity of this reduced towards the interior forest. Of the human impacts, coffee management caused the greatest disturbance in that it affected liana cover and changed the species composition of trees. In general, the authors found that disturbance gradients did not strongly predict forest structure and biodiversity variables.
The authors observed that patterns in disturbance types were often driven by how humans used the landscape, and were also influenced by environmental factors, such as terrain roughness and climate. These factors made it difficult to predict certain human effects in different landscapes. Even though clear edge effects were observed from human disturbances, these did not have a strong effect on variations in forest degradation, which was surprising due to the varied uses of forests for logging, coffee management and cattle grazing.
A complex pattern in the spatial variation of human disturbances with different landscape variables was portrayed by Beche et al. (2022) across the Gera forest landscape. The authors outlined that the intersection of edge effects and forest degradation was highly context-specific and relied on how particular communities and societies use the forests. They argued that strict protection of the forests to prevent further degradation was unlikely and damaging to local livelihoods. Instead, this study suggests that there are high biodiversity values among local communities, which, with local engagement and clear policy outcomes, could result in sustainable use of forest resources and the conservation of the Gera forest landscape in the future.
Read the full paper by Beche et al. (2022) here.