Carbon and credits
Permanence
Permanence is how long removed carbon stays removed. A forest holds carbon while it stands and releases it if it burns, is cut or dies. Carbon locked into a stable form resists that. Buyers price the difference, because a reversal undoes the purchase.
The question underneath it is simple: can this be undone, and by what. Fire, felling, drought and a change of landowner are the risks that apply to standing biomass.
A long lease is one answer, because it puts the same party in charge of the land for the period the claim covers. Chemical stability is another, which is why char based removal prices differently to forestry.