What happens with the CO2 when a tree dies?

A forest is a permanent and living carbon sink. Trees release their CO2 even as they decompose, and leave space for new trees to grow naturally and absorb similar or greater amounts of CO2.

The aim of reforestation (among many other positive ones) is to generate an extra carbon sink by improving the cover density of a degraded forest.

When a tree dies, its CO2 is slowly and progressively released into the atmosphere as the tree decays. Some CO2 can be stored for a longer time as biochar, wood, or organic matter. If we oversimplify, taken as an independent element, we could consider the CO2 balance of a single tree as null, since the CO2 absorbed during its lifetime is released. But no tree is an island. If we look at it from the forest perspective, for each tree that dies, a spot in the forest is freed (and a shadow removed) for a new tree to grow and absorb more CO2. To oversimplify again, we could consider a forest a constant carbon sink, that neither intakes nor releases CO2. The reality is a bit different as a forest can keep extending (a tropical forest can grow up to 60% per year) and much of the carbon is permanently sunk into the subsoil.

The idea of a reforestation or afforestation project will be to increase and maximize the carbon storage capacity of the forest. In short, in terms of carbon capture, it doesn’t matter if a tree dies naturally in a forest, providing the whole forest is well managed and not being deforested.