Bark Beetle Outbreak: Reaction-Diffusion Wave Model

This 2D companion to the 3D bark-beetle forest simulator swaps the discrete tree-by-tree stochastic mass-attack model for a continuous Fisher-KPP reaction-diffusion PDE, solved on a real finite-difference grid every frame. The same three real mechanisms — a logistic cold-hardening winter-survival curve, a summer-temperature voltinism switch, and tree-defense/predation-modulated growth and dispersal — combine into a single local growth rate r and diffusion coefficient D, and the Fisher-KPP equation has a textbook closed-form invasion-front speed, c = 2·√(D·r). Watch the outbreak's real front speed, measured directly from the growing infestation field each year, track that analytic prediction live as you change the climate and forest-resistance sliders — a genuine mathematical cross-check that the 3D model's spreading behavior isn't just tuned dressing.