REDD is receiving considerable attention as an effective mechanism for offering incentives to developing countries to slow the rate of deforestation and forest degradation. We show that the trading ratio of credits that is consistent with the social optimum, is not one to one because of uncertainty, and can be more or less than unity, depending on the type of uncertainty. Moreover, we show that the trading ratio will always be less than unity. Furthermore, we present a condition where a country that had a higher level of forest management in the past is assigned a higher trading ratio. Finally, we demonstrate that if the level of forest management is controllable for each country, then REDD does not achieve the social optimum in general.