Ecological and socio-economic effects of industrial oil palm plantations in Southwest Cameroon
von Denis Kupsch
Datum der mündl. Prüfung:2019-09-30
Betreuer:Prof. Dr. Matthias Waltert
Gutachter:Prof. Dr. Matthias Waltert
Gutachter:Prof. Dr. Gerhard Gerold
EnglischRural agroforestry landscapes in West and Central Africa face a number of threats. Since decades, the ever escalating bushmeat crisis is pushing populations of threatened wildlife closer to extinction in many parts of West and Central Africa. In addition, population growth and economic needs are driving a slow but steady landscape transformation with protected areas being more and more isolated and surrounded by a mix of agricultural land, forestry and secondary forest patches. However, a recently emerged new wave of oil palm development might have the potential to outweigh experienced miseries. Since there is the risk that hundreds of thousands hectares of Afrotropical forest and agroforestry might be converted to homogeneous agro-industrial cultivations within only a few years. Since West and Central African forested landscapes are characterized by social and economic complexities, site-specific, multi-faceted research approaches are needed to derive evidence-based conservation recommendations in the context of land use change. This doctoral thesis aimed to address some of the apparent knowledge gaps on land use and its effects on biodiversity and rural livelihood in an Afrotropical forest biodiversity hotspot, in Southwest Cameroon. Our first study aimed to assess the status of large mammals and identify predictors of their distribution to inform conservation management in Southwest Cameroon. Based on line transect data from different sites and years as well as modelling of various predictor variables, we found that threatened wildlife in most abundant in protected areas but mainly due to their remoteness and high habitat quality, and less due to direct management interventions, such as patrolling. In addition, we estimated severe population declines between 29% and 94% from 2007 to 2014 of two conservation flagship species, the forest elephant and the chimpanzee. Contrastingly, the second part of our research highlighted the high value of rural agroforestry systems also outside protected areas for native bird communities. Applying multivariate adaptive regression splines on bird count data from oil palm plantation and agroforestry in and outside Korup National Park as well as Landsat imagery, we identified high critical habitat thresholds at above 70% of forest cover for habitat and foraging specialists. In addition, generalists and wide-spread species mainly dominate in areas with low forest cover, such as oil palm plantations. Moreover, we modelled extinction thresholds for ant-following birds at 52% of forest cover for the most sensitive species. As result, we more than the half of resident ant-followers were absent from our data in oil palm plantations. On the other hand, based on direct observations during transect walks and a distance sampling approach, we yielded higher density estimates of Congo Grey Parrots in oil palm plantations compared to Korup National Park. Whereas this is probably solely attributed to the abundant palm nut supply all year round, the agroforestry matrix provided a significantly higher variety of trees utilized and supported estimated densities thrice as high compared to the plantation. However, comparing our findings with previous density data from the same region suggests that parrots in the Korup region experienced severe population declines during the last decade. The third part of our research focused on income and expenditure structures of households in the Korup region. Based on quantitative household interviews in settlements in Korup National Park, its surrounding agroforestry landscape and the adjacent oil palm plantation, we found little differences in income between plantation, park and non-park settlements, though plantation household member had to work more for the same income and spent much more money on food items, mainly due to limited food farming. At the same time plantation households supported less members than park and non-park households. From a socio-economic point, villagers that mainly depend on forest product seem to be better off than plantation workers depending on wage labour. In a final study we analyzed the short-dated effects of motorbike road access on income activity choice in Korup National Park using a difference-in-difference approach. We found that road access led to a rise in total household income by 38% due to higher household participation in self-employment and wage labor, however, we did not study direct ecological effects of road construction. Any road construction should be carefully considered and accompanied by strict law-enforcement measures. This thesis highlights the importance of using multi-taxa approaches. Whereas we may conclude from our research on large mammals that only protected areas seem to have the potential to halt population declines, the threshold analysis on bird assemblages also revealed high biodiversity values in agroforestry landscapes outside the park. Moreover, endangered Grey Parrots were often encountered feeding in the oil palm plantation adjacent to Korup National Park. These complex response patterns call for careful planning of task-specific conservation measures. Nevertheless, our results highlight that Afrotropical agroforestry can assure sustainable livelihoods for local inhabitants, while securing forest biodiversity if substantial proportions of forests are maintained.
Keywords: African bird diversity; African mammal populations; Deforestation; Extinction thresholds; Rural livelihood analysis; Korup National Park Cameroon; Wildlife conservation management; Land use management