A quantitative approach to social-ecological systems: mapping nature’s contributions to people and human health dynamics in the Kilimanjaro region
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Philipps-Universität Marburg
Abstract
Social-ecological systems (SES) describe the dynamic interconnections between human societies and their environments, where changes in one domain reverberate through the other. Historically, however, ecological and social science researchers have treated nature and society as separate spheres, obscuring their critical interdependencies. To overcome this divide, integrated frameworks have emerged, most notably the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) conceptual framework, which explicitly links scientific understanding to policy decisions. Drawing on the SES theory and the ecosystem-services tradition, the IPBES framework consists of six interlinked components: nature; Nature’s Contributions to People (NCP); anthropogenic assets; institutions and governance; direct and indirect drivers of change; and good quality of life.
However, a significant gap persists between the IPBES framework's conceptual ambition and its practical application. Empirical research often remains fragmented, focusing on isolated components rather than integrated analyses that capture the crucial feedback loops between ecological processes, human well-being and drivers of change. This fragmentation is largely fueled by the persistent challenge of creating harmonized, interoperable datasets that can bridge scales and disciplines, particularly in complex SES like Kilimanjaro in Tanzania.
To address this critical implementation gap, this thesis demonstrates how an IPBES-inspired, cross-scale SES framework can be successfully operationalized to guide transformative environmental governance. Focusing on the southern slopes of Mount Kilimanjaro, in this thesis, I develop and apply a novel, multi-method approach grounded in two collaborative and mulit-disciplinary platforms (Kili-SES and Ripa2Tan). I show that the barriers to operationalization can be overcome by first tackling the foundational data challenge. Recognizing that persistent cloud cover and geometric misalignments render raw satellite data unusable in the Kilimanjaro region, I created a novel, high-resolution analysis-ready dataset. This foundational work, which also revealed that two decades of deforestation have caused local warming surpassing background climate change, provides the robust, spatially explicit basis for the work described in the following paragraphs.
The central aim of my thesis is to advance the understanding of the Kilimanjaro SES by applying this foundational data to investigate two core components of the IPBES framework: Nature’s Contributions to People (NCP) and Good Quality of Life. In the first application, I conduct a comprehensive spatial assessment of 25 context-specific NCP. This analysis involved synthesizing an extensive 13-year dataset and spatially modeling 57 individual indicators to produce NCP potential supply maps, which were then hierarchically aggregated into three groups: regulating, material and non-material NCP and ultimately a final map of total NCP supply. This mapping reveals critical NCP hotspots, particularly in biodiverse and multifunctional mid-elevation areas of the mountain, and coldspots in high and low elevations (foothills) of the mountain. The analysis further establishes that climate is the dominant driver shaping synergies and trade-offs among these NCP, as their interrelationships weaken markedly once climate's influence is statistically removed. This underscores the necessity of assessing other drivers to effectively manage the Kilimanjaro SES. Crucially, while these data-driven maps provide an essential objective baseline, a comparison with different the perception of different social actors of Kilimanjaro revealed a significant mismatch for certain non-material NCP, highlighting the critical need to integrate the potential supply data with the diverse values of local communities, particularly as they report a decline in these NCP.
Building on this environmental analysis, I then investigate the health dimensions of the ‘Good Quality of Life’ component. I conduct a detailed retrospective epidemiological study showing how the Kilimanjaro region is grappling with a complex double burden of diseases. The shift from a landscape once dominated by communicable diseases to one where non-communicable diseases are also emerging is not a uniform process, but a complex tapestry woven from social and ecological threads, revealing divergent, place-based drivers of disease. In the urban district, while chronic respiratory cases were linked to PM2.5 pollution, communicable diseases remained persistently high despite better infrastructure. Conversely, rural health patterns were shaped by natural systems: higher greenness was associated with a lower prevalence of diabetes, while rainfall variability was a key driver of infectious disease spikes.
Finally, this thesis presents an overview of two additional contributions that enhance the understanding of the NCP and Good Quality of Life components. The first study forwards the analysis of NCP by using simulation modeling in Kilimanjaro to provide a scalable framework for assessing governance trade-offs related to land-use and resource access. Building on the public health theme, the second study validates the power of citizen science for fine-scale disease surveillance by mapping tick-attachment risk in Switzerland with advanced spatial modeling.
In sum, this thesis advances social-ecological research by moving beyond disciplinary silos, providing quantitative insights for targeted environmental and public-health interventions that can foster more sustainable futures in coupled human-environment systems.