## 6 Conclusion  
LCA is product- or process-based and, in terms of forestry most end products (e.g., lumber, paper, or plywood), include forest management as just part of a life cycle. Forest sustainability has a biological foundation with inputs and outputs that can be incorporated into LCA. For example, the biological carbon cycle illustrated in Figure 1 is just one of the many biological systems that make up a forest. Forest sustainability must be part of any LCA that evaluates a forest product and it has the potential to be a very complex portion of an already complex LCA. Even though forest certification systems are single-issue based (quality of forest management), that does not mean they cannot be part of a multiple-issue eco-labeling system. If the eco-labeling system is addressing forest products, then forest certification may be required to be an issue. Thus, forest certification can be part of the eco-labeling process. This usually means a life cycle approach to accomplish the eco-labeling goals; so forest certification systems, that evaluate an extremely important part of the environmental impacts of a forest product, do become crucial additions to an LCA for that forest product. Forest sustainability systems themselves may lend themselves well as complements to LCA, but any forest product undergoing LCA will need to address forest sustainability as a component or adjunct of the analysis. LCA is being expanded beyond environmental and technical aspects of the life cycle. Social LCA addresses many of the issues that impact the social side of forestry (like land ownership, loggers, and property transfer). Social LCA of products can address workers (human rights), the local community (working conditions), society (health and safety), consumers (cultural heritage), and value chain actions (governance and socio-economic repercussions) [72]. LCA does have weaknesses relative to forest sustainability issues. Descriptive data are not readily available to quantify forest ecosystems using the approach. Biological diversity, for example, is a fairly qualitative concept and the social and economic factors associated with forest sustainability can be just as hard to quantify. LCA is especially well-adapted to comparing a renewable resource like forests with nonrenewable resources [73], especially if the accounting system separates fossil from non-fossil carbon. Even though forest certification is a single issue system, the forest is a very complex system itself and can be difficult to quantify as a component of an LCA. Figure 3 shows the complexity of an LCA forest harvesting scheme [74]. Prior to and since the Earth Summit, questions concerning the environmental impact of products have been important. LCA has been used to answer questions about the environmental impact of a product [75]. This resulted in numerous LCA studies such as those comparing paper _versus_ plastic bags [76] and paper _versus_ cloth diapers [77]. While these LCAs provided answers to some generic questions about environmental impacts of a product, they did not address the sustainability of a specific forest that provided the wood for an individual package of diapers or paper bag. Forest certification systems, through their chain of custody programs, can accomplish this. Forest certification systems, when combined with LCA, provide more information about the environmental impact of a product and the sustainability of the forests from which the fiber was produced. The combination of a product LCA and a forest certification label should provide more assurance to the consumer that the product is not harming forest sustainability and its life cycle is more environmentally preferable. LCA's are expensive and are usually performed only for a single product. This generalizes the sources of inputs into the system. It would not account for any specific differences among forests, mines, agricultural fields, rangelands, oil wells, waters, _etc_. Forest certification, through chain-of-custody methods, does account for the differences among forests.