Evaluating the importance of environmental factors on the spatial distribution of livestock settlements in the Monte desert with a Monte Carlo based model: Settlement Dynamics in Drylands (SeDD)

In the Monte desert, increasing population density, changing land rights and infrastructure may encourage livestock activity, with unknown consequences on ecosystems. Factors that influence livestock settlement distribution may affect ecosystem degradation. We hypothesize that surface and groundwater availability influence livestock settlements distribution. We evaluated this hypothesis with a Monte Carlo based model to simulate Settlement Dynamics in Drylands (SeDD), which calculates probabilities on a gridded region based on six environmental factors: groundwater depth, vegetation type, proximity to rivers, paved roads, old river beds, and existing settlements. A parameter sweep, including millions of simulations, was run with combinations of parameters related to these factors. The sets of parameter values that minimized the residuals between simulations and observations indicated the relative importance of each factors on settlement distribution. Distances to rivers and old river beds were critical to explain the current distribution of settlements, while vegetation, paved roads, and water table depths were not important. Spatial distribution of simulated vegetation, which included degradation around livestock settlements, generally agreed with remotely sensed vegetation classes. The model could be a useful tool to evaluate the effects of land use changes (water provision, river flows), on settlement distribution and vegetation degradation in arid environments.