Forest naturalness assessment as a component of biodiversity monitoring and conservation management.

A primary prerequisite for the preservation of global diversity is often assumed to be a high level of naturalness. This paper reports a synthesis of naturalness definitions, distinctions between the concepts of naturalness and of hemeroby and an analysis of different naturalness assessment approaches. Naturalness may be commonly defined as ‘the similarity of a current ecosystem state to its natural state’. Hemeroby, a concept related to human impacts, is often associated with naturalness but, in principle, the two concepts are not inversely related. The hemeroby concept defines narrow assessment classes for greater hemeroby, whereas the naturalness concept defines narrow assessment classes for great naturalness. The rapidly increasing number of forest naturalness papers relies on the following main indicators in decreasing order of use: tree species, forest structure, fauna, ground vegetation and deadwood. A review of the literature on forest naturalness suggests four main reasons for the lack of a widely accepted approach for assessing naturalness: (1) the lack of a commonly accepted reference concept, (2) an incomplete list of essential naturalness traits, (3) unknown linkages between some naturalness traits and biodiversity and (4) the lack of an assessment approach that can be adapted for use at both regional and large scales. Following review of the literature on forest naturalness, a seven-level framework is presented to guide development of naturalness assessment approaches as a component of forest biodiversity monitoring and conservation management. [ABSTRACT FROM AUTHOR]