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The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.

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Abstract• Context This review paper provides an overview of approaches to which we may resort for handling the complex decision problems involving uncertainty and risk that climate change implies for forest managers. Modelling approaches that could support adaptive management strategies seem to be called for, not only as climate change denotes increased economic uncertainty but also because new and more reliable information becomes available as time passes and climate changes.• Aims The paper (1) provides a broad overview of state-ofthe-art methods for optimal decision making under risk and uncertainty in forestry and (2) elaborates on the possible use of these methods in adaptive forest management under climate change.

empirically based typology of private forest owners in Denmark: improving communication between authorities and owtwrs. Scand. J. For. Res. 19(Suppl. 4): 45-55, 2004.For policy instruments to be effective, they should motivate forest owners to adjust behaviour in agreement with forest policy objectives. It may therefore be beneficial to know the motivations of private forest owners. Often, forest owners are assumed to constitute an entity, although statistics and structural changes indicate increasing heterogeneity. Instead, forest owners can be divided into types, i.e. groups that include forest owners with similar attitudes, and where attitudes of each group differ from those of other groups. Based on a survey among private forest owners in Denmark, three types of owners were identified: (1) the classic forest owner to whom the forest has economic importance; (2) the hobby owner who enjoys work and recreation in the forest; and (3) the indifferent farmer to whom the different values provided by the forest are equally (un)important. Implications of this typology for forest poliey formulation and implementation are discussed.