Environmental and socio-economic changes are causing increased levels of land abandonment worldwide, leading to noticeable changes in landscape cover. Throughout the European backcountry, forests and shrublands are spreading due to the decline of agricultural practices, pastoralism, etc. Importantly, when source populations are small or sparse, a positive relationship between population size and individual fitness (the so-called ‘Allee effect’) can severely restrict plant colonization process. This phenomenon is expected to be particularly crucial for plants dispersed by animal guts (endozoochores) because such seed dispersers are becoming progressively deficient. To simulate the complex process old-field colonization by endozoochores requires the combination of plant demography with rule-based and spatially-explicit modelling and animal movement. In this project we aim to comprehensively simulate the colonization process of old fields by animal-dispersed plants in humanized landscapes. Specifically, we aim to: 1) develop spatially-explicit, individual-based models that simulate the distribution and dynamics of both endozochores at the old field, as determined by the movement of their dispersers and seed retention times, the resulting seed rain, and the transition probabilities for key plant ontogenic stages, 2) To optimise the models by systematically comparing our simulation results versus the observed patterns of adult plants and seed rains and, thus, to indirectly identify potential missing processes or parameters in the models, and (3) Using extensive simulation experiments, to investigate the spatial and demographic consequences of contrasting realistic scenarios and to propose a general model for the colonization of old fields by animal-dispersed plants that accounts for potential Allee effects and the movements of dispersers.