A general model for the economics of land–use change and pathogen dynamics
The extremely poor generally rely on their immediate natural environment for subsistence and suffer high rates of morbidity and mortality due to infectious diseases. We present a general framework for modeling the ecology of poverty, focusing on the exemplar drivers: land use change and infectious diseases. Interactions between these drivers and poverty create reinforcing feedbacks associated with persistent poverty, which can be characterized as a stable, low level, equilibrium in ecological-economic space. We use simple coupled land use change-infectious disease-economic development models to demonstrate nonlinear relationships that give rise to multiple stable equilibria, such that initial conditions (or threshold levels) determine whether populations can experience vicious versus virtuous cycles and the associated transitions or “tipping points”. The inherent complexity of these relationships, combined with the spatial and temporal scales at which they occur in the real world, create empirical challenges for estimating parameters and validating the models. We accordingly present a series of sensitivity analyses to explore the range of uncertainty and variability around the multidimensional parameter space.
We find out that the disease transmission and recovery parameters and the investment rate in human capital are consistently more significant in introducing uncertainty and variability in specific outputs of interest, such as per capita income, disease prevalence, agricultural land and the region of multistability. The results of our analysis also indicate that vicious cycles of infection and subsistence are inevitable when the number of pathogens in the system is sufficiently large. We then provide specific suggestions for future theoretical and empirical work that can bring these coupled models to life.