Planting forests can rebuild soil life and carbon—but the trajectory depends on what came before
WHAT THE EVIDENCE SAYS
A Nature Ecology & Evolution synthesis compared 1,158 paired afforestation or reforestation sites with reference conditions across six continents. Afforestation was associated with greater soil microbial biomass and topsoil carbon across stand development, while reforestation showed substantial early recovery of soil carbon and microbial biomass toward original-forest conditions during roughly the first three decades. The magnitude and persistence of gains varied with prior land condition, stand age and restoration pathway.
WHY IT MATTERS / OUR READ
The useful signal is that forest recovery is not just a canopy process: belowground biological condition can improve alongside carbon storage. But the starting state and restoration pathway matter, so the same planting effort can produce different soil trajectories. For project design, degraded-land recovery and long-term monitoring of soil function deserve explicit treatment rather than assuming tree cover is a sufficient proxy.
CAVEATS / UNCERTAINTY
This global synthesis combines heterogeneous chronosequences and paired-site studies rather than one standardized experiment. Older reforestation stands did not show a uniformly continuing increase in every soil metric, and the result should not be converted into a universal prescription to plant trees in naturally open ecosystems where afforestation can harm native biodiversity, fire regimes or water balance.
SOURCE
Nature Ecology & Evolution
View original evidence ↗
A global synthesis of 1,158 paired sites finds afforestation and reforestation generally increase soil microbial biomass and topsoil carbon, with especially strong gains on degraded land and different time courses after forest recovery.
Read the Wild Lands assessment →