Structure, flow, and inequality : Analysing consumer outcomes in ecological and socio-ecological resource distribution networks with spatially explicit modelling approaches

Davis, Natalie and Jarvis, Andrew and Polhill, J. Gareth and Aitkenhead, M. J. (2021) Structure, flow, and inequality : Analysing consumer outcomes in ecological and socio-ecological resource distribution networks with spatially explicit modelling approaches. PhD thesis, Lancaster University.

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Abstract

The energetic requirements of all physical systems are supplied by resource acquisition, distribution, and end-use (RADE) networks. While the characteristics of these networks vary considerably, they share similar outcomes, namely heterogeneity in natural systems, and inequality in social systems. Despite the criticality of resources for sustaining life, and impacts of their unequal distribution, little work has attempted to explicitly connect RADE network structure, resource flows, and consumer outcomes. The overall aim of this thesis was to develop and use modelling approaches to identify relationships between network structure and consumer heterogeneity in stylised networks. After reviewing the current literature on RADE networks (Chapter 1), we develop a model of RADE networks using an electrical analogue and quantify consumer inequality as networks evolve toward maximum power (Chapter 2). In networks with heterogeneous architecture, such as commonly seen fractal structures, inequality between consumers increases as resource flows increase, even after maximum power has been reached. We then develop a method to extract macropore networks from soil profile images and analyse them with metrics from network science and transport geography (Chapter 3). The networks are used as the environment in an agent-based model (ABM) of foraging soil organisms. The methodology captures known differences between soil types, and shows larger, more heterogenous soil networks support larger, more diverse simulated consumer populations. Finally, we develop an ABM of generic consumers building a network to move between resources in heterogeneous landscapes, attempting to maximise their time-discounted consumption (Chapter 4). The dynamics were similar across the landscapes, with the consumer inequality decreasing during initial network construction, then increasing as the network reached its stable state. The resource distribution in each landscape moderated the specific rates and timings of these dynamics. Overall, the findings here linking known system development trajectories and network architectures to increased inequality provide insight into the emergence and persistence of heterogeneity among consumers in both ecological and socio-ecological systems, and alleviation of inequality in the latter.