Abstract :
An unprecedented database concerning the apparent condition of forest trees has been created over the last decade. In particular, millions of data concern crown transparency and discoloration have been collected. Unfortunately, the subjectivity and poor specificity of the international data complicate their comparability and interpretation. A suite of other indices with species-specific relevance were also been used in various surveys. However, the development of suitable indices is incomplete and there is an urgent need for the improvement of definitions, training, data collection and reporting.
