Restoring degraded land follows ecological succession: bare soil is colonized first by shrubs and pioneer saplings, then by a closing young-forest canopy, and finally by a mature, structurally complex forest. Each sapling has a survival probability set by soil quality and how well its species is suited to the site; canopy closure follows a logistic growth curve once enough trees establish.
P(survive) = soil_quality × species_suitability
canopy(t) = 100 / (1 + e^(-k(t - t_mid))) [logistic closure]
years_to_maturity ≈ 25 / (density_factor × soil_quality)
- Planting density — more saplings per plot raises early canopy cover but increases competition for light and water.
- Soil quality — degraded, compacted or nutrient-poor soil lowers every sapling's survival probability.
- Species mix — native species survive better long-term and build resilient mature forest; fast-growing pioneers close canopy quickly but with lower long-run survival.
- Time speed — fast-forwards the simulated years so succession stages become visible within a short session.
Forest-restoration NGOs use exactly this kind of planning model to choose planting density and species mix before committing seedlings and budget to a degraded site.