Stochastic modeling of coupled human-water networked communities

Abstract

<p>Water is a resource shared at many spatial and temporal scales, and humans simultaneously influence and are influenced by the availability of water resources to support life and economic activity. The spatial pattern of human settlements is thus affected by landscape heterogeneity and resource availability, with river networks playing a fundamental role in enabling access and mobility. On the one hand, trade and migration routes have been established since ancient times to increase the connectivity among human settlements and therefore allocating resources where they are most needed (or demanded). On the other hand, excessive connectivity can also introduce inter-dependence between population centres, which can ultimately decrease their resilience: their ability to bounce back from an exogenous (e.g., climatic) shock. In this perspective, interactions between spatiotemporal variability in climate and human connectivity (migration and trade) may have not only played a role in the rise and fall of several ancient civilizations, but can still affect the distribution of human settlements across watersheds. Here, we seek to understand the mechanisms through which trade and migration fluxes, and the policies that influence them, may affect the fundamental ability of interconnected communities to cope with climate shocks and sustain a population. To this aim, we developed a stochastic predator-prey model to represent the complex relation between population growth and water resources across multiple predetermined networks of neutral communities. Our model embraces the endogenous nature of human connectivity as an emergent process that arises from numerous independent and self- optimizing agent decisions at individual nodes, and overlays an exogenously determined physical network (e.g., river system). The main novelty of our approach consists in developing a tractable socio-environmental spatially explicit model to capture the critical effect of landscape heterogeneity and (water)resources distribution. The proposed framework can help in developing policies for ensuring availability and sustainable management of water resources under conditions of variability and has potentially applications in a wide variety of settings including natural resources extraction, disease dynamics and climate change policy.</p>