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What happens with the CO2 when a tree dies?

A forest is a permanent and living carbon sink. A dead tree releases its CO2 as it decays but also leaves space for new trees to naturally grow and absorb similar or higher quantities of CO2.

When a tree dies, its captured CO2 will be progressively released as the tree decays. However, the fallen tree will also leave space for new trees to naturally grow, these trees will absorb similar or higher quantities of CO2, essentially making the forest a permanent and living carbon sink. 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. 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.