Model development for the effect of fire in pasture lands and the appearance of desertification trends

This paper presents the structure of a simulation model about the cycle of fire and grazing in pasture lands of Greece with the aim of studying the impacts of the major factors governing this cycle leading to degradation and under certain circumstances to desertification. The model includes submodules about the production of grazing material, the consumption of vegetation through grazing, the condition of the rangeland after grazing and the profit loss or gain for the shepherd. The financial outcome for the shepherd is considered as a main motivation to start a fire to increase short term biomass production in order to make a worthwhile profit. The calculation of the motivation and the amount of yearly rainfall are based on a random algorithm, which gives a dynamic aspect to the model. The user determines the length of the simulation (years). Running the model for several years, he/she can draw conclusions about the grazing pressure on the rangeland, the financial result of the enterprise and the likely role of fire in the way the rangeland will be managed. The model was developed in the Netlogo programming language.