That obviously depends with what happens with the trees that could not have been preserved. If you burn a tree you set almost it's entire absorbed CO2 free. On

That obviously depends with what happens with the trees that could not have been preserved. If you burn a tree you set almost it's entire absorbed CO2 free. On the other hand, a recently planted tree has absorbed almost nothing - it will take decades if not longer to grow to a big one - reaching the level of absorbed CO2 of the other tree before it has been burned. Nevertheless, a tree at the place of an older one can help binding CO2 when the old tree is used such that the CO2 is not released to the atmopshere, such as for a well-crafted table (which could be used for decades, too). But don't forget that it usually is not just removing one tree - usually big areas are cut out, which includes the huge ecosystems around trees in untouched nature. Though, always keep in mind, this is not a choice. The goal should be to preserve as much as possible (especially untouched ecosystems) as well as planting as much as possible.