Your basic premise is wrong. A forest that is photosynthesizing is not a carbon sink. Once a forest reaches a steady state and births are balanced by deaths t

Your basic premise is wrong. A forest that is photosynthesizing is not a carbon sink. Once a forest reaches a steady state and births are balanced by deaths the forest becomes carbon neutral. For every ton of new tree, an old tree dies, rots(slow)/burns down(fast), and releases it's carbon back into the ecosystem. Otherwise known as the carbon cycle. So sure taking a million acres of trees and cutting them down, burning them, and putting building on them releases significant carbon... once. Similarly taking a million acres of desert and turning it into a forest will consume CO2 for 50 year or however long it takes to reach a steady state.