A growing body of evidence highlights the importance of biodiversity for ecosystem stability and the maintenance of optimal ecosystem functionality. Conservation measures are thus essential to safeguard the ecosystem services that biodiversity provides and human society needs. Current anthropogenic threats may lead to detrimental (and perhaps irreversible) ecosystem degradation, providing strong motivation to evaluate the response of ecological communities to various anthropogenic pressures. In particular, ecosystem functions that sustain key ecosystem services should be identified and prioritized for conservation action. Traditional diversity measures (e.g. 'species richness') may not adequately capture the aspects of biodiversity most relevant to ecosystem stability and functionality, but several new concepts may be more appropriate. These include 'response diversity', describing the variation of responses to environmental change among species of a particular community. Response diversity may also be a key determinant of ecosystem resilience in the face of anthropogenic pressures and environmental uncertainty. However, current understanding of response diversity is poor, and we see an urgent need to disentangle the conceptual strands that pervade studies of the relationship between biodiversity and ecosystem functioning. Our review clarifies the links between response diversity and the maintenance of ecosystem functionality by focusing on the insurance hypothesis of biodiversity and the concept of functional redundancy. We provide a conceptual model to describe how loss of response diversity may cause ecosystem degradation through decreased ecosystem resilience. We explicitly explain how response diversity contributes to functional compensation and to spatio-temporal complementarity among species, leading to long-term maintenance of ecosystem multifunctionality. Recent quantitative studies suggest that traditional diversity measures may often be uncoupled from measures (such as response diversity) that may be more effective proxies for ecosystem stability and resilience. Certain conclusions and recommendations of earlier studies using these traditional measures as indicators of ecosystem resilience thus may be suspect. We believe that functional ecology perspectives incorporating the effects and responses of diversity are essential for development of management strategies to safeguard (and restore) optimal ecosystem functionality (especially multifunctionality). Our review highlights these issues and we envision our work generating debate around the relationship between biodiversity and ecosystem functionality, and leading to improved conservation priorities and biodiversity management practices that maximize ecosystem resilience in the face of uncertain environmental change.

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While many tropical countries are experiencing rapid deforestation, some have experienced forest transition (FT) from net deforestation to net reforestation. Numerous studies have identified causative factors of FT, among which forest scarcity has been considered as a prerequisite for FT. In fact, in SE Asia, the Philippines, Thailand and Viet Nam, which experienced FT since 1990, exhibited a lower remaining forest area (30±8%) than the other five countries (68±6%, Cambodia, Indonesia, Laos, Malaysia, and Myanmar) where forest loss continues. In this study, we examined 1) the factors associated with forest scarcity, 2) the proximate and/or underlying factors that have driven forest area change, and 3) whether causative factors changed across FT phases (from deforestation to net forest gain) during 1980–2010 in the eight SE Asian countries. We used production of wood, food, and export-oriented food commodities as proximate causes and demographic, social, economic and environmental factors, as well as land-use efficiency, and wood and food trade as underlying causes that affect forest area change. Remaining forest area in 1990 was negatively correlated with population density and potential land area of lowland forests, while positively correlated with per capita wood production. This implies that countries rich in accessible and productive forests, and higher population pressures are the ones that have experienced forest scarcity, and eventually FT. Food production and agricultural input were negatively and positively correlated, respectively, with forest area change during 1980–2009. This indicates that more food production drives deforestation, but higher efficiency of agriculture is correlated with forest gain. We also found a U-shaped response of forest area change to social openness, suggesting that forest gain can be achieved in both open and closed countries, but deforestation might be accelerated in countries undergoing societal transition. These results indicate the importance of environmental, agricultural and social variables on forest area dynamics, and have important implications for predicting future tropical forest change.

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Global wood trade Gross forest cover loss Growing stock density Industrial roundwood Wood fuel a b s t r a c t Forest cover loss is a major cause of both the decline in global biodiversity and the increase in carbon emissions into the atmosphere. Focusing on the effects of logging, this study introduces an index of wood production, the forest harvest index (FHI), which calculates the expected gross forest cover loss (GFCL) reflecting the demand for timber and wood products at the global scale. We examined the accuracy and precision of the index by investigating the relationship between the FHI and actual GFCL measured through remote sensing. The index incorporates wood-and climate-specific biomass expansion factors and countryspecific growing stock densities to convert wood production volume to expected GFCL. We quantitatively examined the effect of data uncertainty in the growing stock density values obtain from FRA 2010 on the predicted relationship between the FHI and actual GFCL. We quantified the FHI for both industrial roundwood and wood fuel during a 5-year period (FY2000-FY2004) in each of the 139 nations considered. Results demonstrated that the FHI of industrial roundwood (18.6 million ha yr −1 ) corresponds well to actual GFCL (19.3 million ha yr −1 ) during the same period. The data uncertainty analysis suggested that increasing the frequency of forest monitoring at the national level can improve the precision and accuracy of the FHI, but discrepancies between the FHI and actual GFCL were also identified. Furthermore, to demonstrate the utility of our index as a metric of virtual GFCL of wood products, we disaggregated the FHI into export, import and domestic based on global wood trade data and compared the strength of the relationship with actual GFCL. Export FHI had a strong positive relationship with GFCL, which effect far exceeded the compensating effect of import FHI, indicating that wood trade overall increased GFCL at the global scale.