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Two studies conducted in Guadeloupe (West Indies) and Réunion (Indian Ocean) islands were designed to investigate the benefits of producing sugarcane as an energy crop and to assess the influence of agroclimatic factors on energy efficiency, respectively. In this context, it is essential to know the low heating value of the dry above-ground biomass (LHVd, MJ/kg) and its energy yield (EY, MJ/m2) in order to select the best varieties and set up a payment method for growers. Eighteen Poaceae (sugarcane and Erianthus) cultivars were compared under wet tropical environmental conditions in Guadeloupe. Three sugarcane cultivars were studied in four contrasting environments in Réunion. The partition sampling and biomass measurement procedures were identical at both locations. Low heating value (LHV) predictions were achieved using near-infrared reflectance spectroscopy (NIRS) after specific calibration (Guadeloupe), or arithmetically after lignocellulosic compound prediction (Réunion). In both studies, LHV variability was very low and slightly dependent on the site, cultivar and above-ground biomass components (millable stalks and tops, and green and dead leaves). Considering the overall dry above-ground biomass (DAB, kg/m2), the LHVd was calculated by averaging 159 samples (mean 16.65 MJ/kg) in Guadeloupe and 315 samples (mean 16.45 MJ/kg) for Réunion. An excellent linear relationship between the DAB and its EY, regardless of cultivar, age and environment, was found (n = 474 and R² = 0.99). Sugarcane energy content assessment could thus be simplified by measuring the DAB, while enabling development of a faster method of payment for growers based on the DAB measurement and the correlation between DAB and EY. Finally, the findings of this study should allow growers to rapidly determine the commercial value of their sugarcane crops, and also enable purchasers to assess the amount of recoverable energy. (Résumé d'auteur)

Two studies conducted in Guadeloupe (West Indies) and Réunion (Indian Ocean) islands were designed to investigate the benefits of producing sugarcane as an energy crop and to assess the influence of agroclimatic factors on energy efficiency, respectively. In this context, it is essential to know the low heating value of the dry above-ground biomass (LHVd, MJ/kg) and its energy yield (EY, MJ/m2) in order to select the best varieties and set up a payment method for growers. Eighteen Poaceae (sugarcane and Erianthus) cultivars were compared under wet tropical environmental conditions in Guadeloupe. Three sugarcane cultivars were studied in four contrasting environments in Réunion. The partition sampling and biomass measurement procedures were identical at both locations. Low heating value (LHV) predictions were achieved using near-infrared reflectance spectroscopy (NIRS) after specific calibration (Guadeloupe), or arithmetically after lignocellulosic compound prediction (Réunion). In both studies, LHV variability was very low and slightly dependent on the site, cultivar and above-ground biomass components (millable stalks and tops, and green and dead leaves). Considering the overall dry above-ground biomass (DAB, kg/m2), the LHVd was calculated by averaging 159 samples (mean 16.65 MJ/kg) in Guadeloupe and 315 samples (mean 16.45 MJ/kg) for Réunion. An excellent linear relationship between the DAB and its EY, regardless of cultivar, age and environment, was found (n = 474 and R² = 0.99). Sugarcane energy content assessment could thus be simplified by measuring the DAB, while enabling development of a faster method of payment for growers based on the DAB measurement and the correlation between DAB and EY. Finally, the findings of this study should allow growers to rapidly determine the commercial value of their sugarcane crops, and also enable purchasers to assess the amount of recoverable energy. (Résumé d'auteur)

Rivers are important sources of freshwater and nutrients for the Mediterranean and Black Sea. We present a reconstruction of the spatial and temporal variability of these inputs since the early 1960s, based on a review of available data on water discharge, nutrient concentrations and climatic parameters. Our compilation indicates that Mediterranean rivers suffer from a significant reduction in freshwater discharge, contrary to rivers of the Black Sea, which do not have clear discharge trends. We estimate this reduction to be at least about 20% between 1960 and 2000. It mainly reflects recent climate change, and dam construction may have reduced discharge even further. A similar decrease can also be expected for the fluxes of dissolved silica (Si), strongly controlled by water discharge and potentially reduced by river damming as well. This contrasts with the fluxes of nitrogen (N) and phosphorus (P) in Mediterranean and Black Sea rivers, which were strongly enhanced by anthropogenic sources. Their total inputs to the Mediterranean Sea could have increased by a factor of >5. While N still remained at elevated levels in 2000, P only increased up to the 1980–1990s, and then rapidly dropped down to about the initial values of the 1960s. With respect to the marine primary production that can be supported by the riverine nutrient inputs, Mediterranean and the Black Sea rivers were mostly phosphorus limited during the study period. Their anthropogenic nutrient enrichment could only have had a fertilizing effect before the general decline of the P loads. When also considering Si as a limiting element, which is the case for siliceous primary producers such as diatoms, silica limitation may have become a widespread phenomenon in the Mediterranean rivers since the early 1980s. For the Black Sea rivers, this already started the late 1960s. Gross primary production sustained by rivers (PPR) represents only less than 2% of the gross production (PP) in the Mediterranean, and less than 5% in the Black Sea. Possible ecological impacts of the changing river inputs should therefore be visible only in productive coastal areas, such as the Gulf of Lions, where PPR can reach more than two thirds of PP. Reported ecosystem changes both in the Adriatic Sea and the Black Sea are concomitant with major changes in the reconstructed river inputs. Further work combining modelling and data collection is needed to test whether this may also have been the case for coastal ecosystems at other places in the Mediterranean and Black Sea.

Rivers are important sources of freshwater and nutrients for the Mediterranean and Black Sea. We present a reconstruction of the spatial and temporal variability of these inputs since the early 1960s, based on a review of available data on water discharge, nutrient concentrations and climatic parameters. Our compilation indicates that Mediterranean rivers suffer from a significant reduction in freshwater discharge, contrary to rivers of the Black Sea, which do not have clear discharge trends. We estimate this reduction to be at least about 20% between 1960 and 2000. It mainly reflects recent climate change, and dam construction may have reduced discharge even further. A similar decrease can also be expected for the fluxes of dissolved silica (Si), strongly controlled by water discharge and potentially reduced by river damming as well. This contrasts with the fluxes of nitrogen (N) and phosphorus (P) in Mediterranean and Black Sea rivers, which were strongly enhanced by anthropogenic sources. Their total inputs to the Mediterranean Sea could have increased by a factor of >5. While N still remained at elevated levels in 2000, P only increased up to the 1980–1990s, and then rapidly dropped down to about the initial values of the 1960s. With respect to the marine primary production that can be supported by the riverine nutrient inputs, Mediterranean and the Black Sea rivers were mostly phosphorus limited during the study period. Their anthropogenic nutrient enrichment could only have had a fertilizing effect before the general decline of the P loads. When also considering Si as a limiting element, which is the case for siliceous primary producers such as diatoms, silica limitation may have become a widespread phenomenon in the Mediterranean rivers since the early 1980s. For the Black Sea rivers, this already started the late 1960s. Gross primary production sustained by rivers (PPR) represents only less than 2% of the gross production (PP) in the Mediterranean, and less than 5% in the Black Sea. Possible ecological impacts of the changing river inputs should therefore be visible only in productive coastal areas, such as the Gulf of Lions, where PPR can reach more than two thirds of PP. Reported ecosystem changes both in the Adriatic Sea and the Black Sea are concomitant with major changes in the reconstructed river inputs. Further work combining modelling and data collection is needed to test whether this may also have been the case for coastal ecosystems at other places in the Mediterranean and Black Sea.

The potential for global forest cover The restoration of forested land at a global scale could help capture atmospheric carbon and mitigate climate change. Bastin et al. used direct measurements of forest cover to generate a model of forest restoration potential across the globe (see the Perspective by Chazdon and Brancalion). Their spatially explicit maps show how much additional tree cover could exist outside of existing forests and agricultural and urban land. Ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in forested area, including more than 200 gigatonnes of additional carbon at maturity.Such a change has the potential to store an equivalent of 25% of the current atmospheric carbon pool. Science , this issue p. 76 ; see also p. 24

The potential for global forest cover The restoration of forested land at a global scale could help capture atmospheric carbon and mitigate climate change. Bastin et al. used direct measurements of forest cover to generate a model of forest restoration potential across the globe (see the Perspective by Chazdon and Brancalion). Their spatially explicit maps show how much additional tree cover could exist outside of existing forests and agricultural and urban land. Ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in forested area, including more than 200 gigatonnes of additional carbon at maturity.Such a change has the potential to store an equivalent of 25% of the current atmospheric carbon pool. Science , this issue p. 76 ; see also p. 24

Understanding the causes and consequences of insect declines has become an important goal in ecology, particularly in the tropics, where most terrestrial diversity exists. Over the past 12 years, the ForestGEO Arthropod Initiative has systematically monitored multiple insect groups on Barro Colorado Island (BCI), Panama, providing baseline data for assessing long-term population trends. Here, we estimate the rates of change in abundance among 96 tiger moth species on BCI. Population trends of most species were stable (n= 20) or increasing (n= 62), with few (n= 14) declining species. Our analysis of morphological and climatic sensitivity traits associated with population trends shows that species-specific responses to climate were most strongly linked with trends. Specifically, tiger moth species that are more abundant in warmer and wetter years are more likely to show population increases. Our study contrasts with recent findings indicating insect decline in tropical and temperate regions. These results highlight the significant role of biotic responses to climate in determining long-term population trends and suggest that future climate changes are likely to impact tropical insect communities.