2017 Volume 16 Issue 2 Pages 61-76
Biodiversity offsets are a mechanism that compensates for the residual negative effects of project development after avoidance, minimization, and restoration of environmental impacts have been implemented. Offset policies have been developed in a growing number of countries as biodiversity conservation and restoration strategies, and are also expected to be an effective approach in Japan toward achieving Aichi Targets. Achieving no net-loss, which means that biodiversity gains from targeted conservation activities match the losses of biodiversity due to the impacts of a specific development project, is a principle of biodiversity offsets. However, the no net-loss concept of biodiversity offsets leaves various unsolved ecological problems pertaining to theory, technology, and practice. This review summarizes the key components of no net loss of biodiversity from ecological perspectives, focusing particularly on 1) explicit measures of biodiversity and ecological equivalence, 2) additional conservation benefits, 3) uncertainty and the risk of failure, and 4) limits to what can be offset and the mandatory mitigation hierarchy. We also discussed challenges to introducing the biodiversity-offset concept in Japan, which is characterized by species-rich secondary ecosystems. We particularly considered a number of specific issues concerning the regional framework in selecting offset-site locations and restoring degraded Satoyama ecosystems as potential impact- and offset-sites in Japan.
