Under the Clean Development Mechanism (CDM) of the Kyoto Protocol, forest projects can receive returns for carbon sequestration via two credit instruments: temporary (tCERs) or long-term certified emission reductions (lCERs). This article develops a theoretical model of optimal harvesting strategies that compares private optimal harvest decision under these two instruments. We find that risk neutral landowners are likely to prefer instituting lCERs over tCERs to maximize surplus. A particular type of early harvest penalty implemented under the lCERs is critical in determining the length of rotation intervals and the carbon credit supply. When this penalty is an increasing function of the difference in biomass before and after harvesting across verification periods, the landowner may choose longer or shorter rotation intervals compared to the Faustmann rotation. The resulting supply curve may have a backward bending region over a range of carbon prices.