Ecosystem restoration projects became common in Japan recently as public works. In this social situation, a method for setting goal of ecosystem restoration is required. The author discussed about two different approaches to set goal of restoration. The first one is setting special or temporal reference. If reference site was available, detailed information which contribute setting model for restoration, can be provided. But in most cases, appropriate reference site is hardly available in neighborhood of given sites. Temporal reference is more difficult to get, because detailed ecological information of the past time is not recorded usually. But in case of its available, it is quite useful for setting model. After all, the role of special and/or temporal reference is indicating rough direction of restoration goal. Estimating environmental potential of ecosystem is another approach. There are four different dimensions of environmental potential, such as abiotic condition of the given site, relationship between source and sink of species, coaction of species and possibility of ecological succession. Among them, coaction of species is most difficult to estimate, but others could be estimated more or less. The role of estimating environmental potential is indicating possibility and limitation of restoration on given site. Combination of two approaches can provide rational direction and possibility for ecological restoration. This combined method for setting restoration goal could be useful in practice.
