Nature's Carbon Machines

Trees are biological carbon capture machines. Through photosynthesis, they pull CO₂ from air, split it using sunlight, release O₂, and lock carbon in wood, roots, and soil. A single mature tree absorbs ~20 kg CO₂/year. Scale that to millions of hectares—afforestation (planting new forests) and reforestation (restoring degraded ones)—and you approach gigatonne-scale removal.

Afforestation vs. reforestation: subtle but important difference. Afforestation = establishing forests on land that hasn't been forested for decades or centuries (grasslands, degraded pasture). Reforestation = replanting areas recently deforested or burned. Both sequester carbon, but afforestation often faces more ecological scrutiny—converting native grassland can harm biodiversity and water cycles. Best targets: degraded agricultural land, abandoned mines, urban wastelands.

Carbon sequestration timelines vary by species and climate. Fast-growing tropical species (eucalyptus, acacia) can sequester 5-10 tCO₂/ha/year but reach maturity in 20-30 years. Temperate hardwoods (oak, beech) grow slower—2-4 tCO₂/ha/year—but live 200+ years, accumulating 200-400 tCO₂/ha over time. Boreal conifers are slowest (~1-2 tCO₂/ha/year) but store carbon in cold, stable soils with minimal decomposition.

Forests provide co-benefits beyond carbon. They regulate water cycles (prevent floods, recharge aquifers), prevent soil erosion, support biodiversity (habitat for thousands of species), provide livelihoods (timber, fruits, tourism), and improve air quality. Unlike engineered CDR, forests also cool locally through evapotranspiration—important for climate adaptation.