This thesis studies the environmental impact of the invasive crab Percnon gibbesi on Mediterranean sea ecosystems. To quantify this impact, a spatial seaweed herbivore model coupling vegetation growth dynamics with an agent-based framework is developed and calibrated to field data. The ecosystem’s stability is evaluated through the analysis of three variables: the ecosystem’s sensitivity to macroalgae net primary productivity and diffusion rate; the characterization of halo size produced by the grazing of individual crabs; and the ecosystem’s resilience to projected mean temperature increases. Simulations reveal a high sensitivity to macroalgae net primary productivity. Halos are shown to be a result of group dynamics rather than individual grazing. Alarming signs are raised as Percnon gibbesi’s grazing is shown to weaken the ecosystem’s resilience to global warming, driving both flora and fauna to extinction within the coming decades.