What are the Pros and Cons?
The “Pros and Cons” that surround the controversy over old-growth and young-growth forests is based on the fact that different scientists express different opinions about what they believe to be the best way to lower the overall global atmospheric carbon. The reason for this has to do with carbon sequration rates vs carbon storage.
There have been essentially 3 methods implemented as attempts to use forest sequestration as carbon offsets: Reforestation, Afforestation, and Forest Preservation, all of which have called into question, old-gowth or young-growth? These methods all have positive and negative aspects because they are not constant in their applications. In other words, each project is different and therefore provides inconsistent results, making it unclear as to which method works best in the long run to prevent the rising carbon dioxide in the atmosphere.
Old-Growth Forests vs. Young-Growth Forests
Old-growth forest store large amounts of carbon in their biomass and surrounding soil, however they capture new carbon at a very slow rate, if at all. Reforestation projects typically consist of old-growth forests being cut down, because they are no longer sequestering carbon, and replaced with new, fast-growing forests. Therefore, it is common for these young-growth forests (aka fast-growth), to be planted over land that recently contained carbon storing forests. With these new forests, the rate of carbon capture, provided it is a fast-growing species, will be high. There is much controversy in the scientific community over whether or not this is a logical thing to do. When you cut down the old forest, you release carbon into the atmosphere, but we do not know exactly how much. It is also uncertain how much carbon is stored in the soil after a tree is cut down, and therefore the carbon capture may depend on what was previously occupying the space.
Afforestation is another common method used, and typically involves tree plantations (one species used for the entire or a portion of a forest). These forests are planted with fast-growing trees over areas that have not contained forests for at least 50 years (UNFCCC 2001). This has its advantages because it is planted a new forest to sequester carbon, and is not releasing carbon in the atmosphere by cutting down any trees. However planting same species forests will affect the ecosystem and may not provide the needed shelter to local wildlife.
Forest Preservation is more or less the management of standing forests. Projects put into motion by carbon offset companies are implemented to keep forests healthy as a method of offsetting carbon emission. Since trees hold carbon in their biomass, it is important to keep them healthy. However, some preservation projects restore degraded land and replant in that area. Once again, fast-growing trees capture, or sequester more carbon then Old-growth do, but is it better to release the carbon already held in the ground, or to plant to young-growth forests in hopes that it will capture carbon at a super fast rate and take your chances that the soil will hold some of that carbon from the old forest left behind.
These are just some of the points made for and against old, slow growing forests vs. fast, young-growth forests in respects to carbon offset projects.