Tree Planting

This calculator uses 22 kg a year for a mature mixed-forest tree, 30 kg for mangroves, 26 kg for hardwoods such as oak, and 16 kg for conifers such as pine. Real rates vary with climate, soil, and age, so treat them as planning averages rather than measurements.

At 22 kg per mature tree per year, you would need about 46 trees to absorb one metric ton in a year. Switch the species to mangroves and the number drops to about 34. Young trees absorb less, so the real number is higher in the early years.

The calculator assumes about 10 years. Absorption starts at 10 percent of the maximum in year one and rises in even steps to 100 percent in year ten. That is why 100 trees over 10 years absorb far less than 100 trees would at full maturity for ten years.

Not every planted tree lives. The tool uses an 80 percent survival rate by default, so planting 100 trees counts 80 growing ones. Lower the rate to model a project with poor aftercare, or raise it for watered and protected planting. Dropping from 80 to 50 percent cuts the result by more than a third.

The tool divides the total CO2 absorbed by 4.6 tons, a typical passenger car's emissions in one year, and by 1.0 ton, about one transatlantic flight. For 100 mixed-forest trees over 10 years at 80 percent survival, that is about 9.7 tons, or roughly 2 cars for a year and 9 flights.

It is an estimate. Real absorption depends on species, rainfall, soil, fires, and how well the trees are looked after, and it can differ widely from these averages. Use it to compare planting plans, and do not count on it to cancel a large footprint without also cutting emissions.