Savanna Woody Encroachment Simulator

Savanna is not simply what grows by default given local rainfall — it's an actively maintained state that depends on recurring fire and grazing to keep tree and shrub seedlings from ever establishing. This simulator runs a grid of cells forward through simulated decades under user-set fire-frequency and grazing-pressure sliders, tracking which seedlings survive to become fire-tolerant mature trees, how tree canopy shades out the grass fuel beneath it, and how that thinning fuel load feeds back into weaker future fires — the self-reinforcing woody-encroachment loop that can flip an open savanna into closed woodland once disturbance drops below a threshold.