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At present, small pelagic forage fish species (includes anchovies, herring, mackerel, sardines, etc.) represent the largest landed species group in capture fisheries (27.3 million t or 29.7% of total capture fisheries landings in 2006). They also currently constitute the major species group actively fished and targeted for nonfood uses, including reduction into fishmeal and fish oil for use within compound animal feeds, or for direct animal feeding; the aquaculture sector alone consumed the equivalent of about 23.8 million t of fish (live weight equivalent) or 87% in the form of feed inputs in 2006. This article attempts to make a global analysis of the competition for small pelagic forage fish for direct human consumption and nonfood uses, particularly concerning the important and growing role played by small pelagic forage fish in the diet and food security of the poor and needy, especially within the developing countries of Africa and the Sub-Saharan region.
In marine sediments, the major anaerobic mineralization processes are Fe(III) oxide reduction and sulfate reduction. In this article, we propose that the two alternative microbial mineralization pathways in sediments exert decisively different impacts on aquatic ecosystems. In systems where iron reduction dominates in the recently deposited sediment layers, the fraction of Fe(III) oxides that is dissolved to Fe(II) upon reduction will ultimately be transported to the oxic layer, where it will be reoxidized. Phosphorus, which is released from Fe(III) oxides and decomposing organic matter from the sediment, will be largely trapped by this newly formed Fe(III) oxide layer. Consequently, there are low concentrations of phosphorus in near-bottom and productive water layers and primary production tends to be limited by phosphorus (State 1). By contrast, in systems where sulfate reduction dominates, Fe(III) oxides are reduced by sulfides. This chemical reduction leads to the formation and permanent burial of iron as solid iron sulfides that are unable to capture phosphorus. In addition, the cycling of iron is blocked, and phosphorus is released to overlying water. Owing to the enrichment of phosphorus in water, the nitrogen : phosphorus ratio is lowered and nitrogen tends to limit algal growth, giving an advantage to nitrogen-fixing blue-green algae (State 2). A major factor causing a shift from State 1 to State 2 is an increase in the flux of labile organic carbon to the bottom sediments; upon accelerating eutrophication a critical point will be reached when the availability of Fe(III) oxides in sediments will be exhausted and sulfate reduction will become dominant. Because the reserves of Fe(III) oxides are replenished only slowly, reversal to State 1 may markedly exceed the time needed to reduce the flux of organic carbon to the sediment. A key factor affecting the sensitivity of a coastal system to such a regime shift is formed by the hydrodynamic alterations that decrease the transport of O2 to the near-bottom water, e.g., due to variations in salinity and temperature stratification.
Recent research in northern Europe has revised many long-held conceptions of the complexity of forest ecosystems and their natural structure and dynamics. The unveiling of the picture of natural characteristics of forest ecosystem structure and dynamics reveals much more diversity than its traditional complement, highlighting the importance of non–stand-replacing disturbances and the associated heterogeneous and dynamic stand and landscape structures. This increasing detail is a reflection of a fundamental change in the ecological understanding of forests as complex ecosystems. In particular, the generalization that the boreal forest is regulated by fierce stand-replacing disturbances, leading to the dominance of even-aged stand successions, has been disproved. However, this misconception has, until now, been repeated and used to legitimize the dominant practice of clear-cutting as a nature-based way to manage the forest. The practical conclusion of this review paper is that the dominating forest management model in North European boreal forests, which is based on the clear-cut harvesting of timber and growing of even-aged stands, is in contradiction with the variable and complex characteristics of the disturbance-succession cycle observed in naturally dynamic forests with negligible human impact. As a consequence, the structural variation of the boreal forest under management has been grossly truncated compared with its natural range. Because of this, and due to the scarcity of protection areas in many regions of northern Europe, it is not likely that the conservation of native biodiversity and ecological sustainability will be attained, assuming that the model of forest management remains unchanged. Thus, there is a strong incentive for change in the prevailing forest management model toward one that is based on natural ecosystem dynamics and an understanding of forests as complex systems.
The aim of this study was to investigate a combination of satellite images of leaf area index (LAI) with process-based vegetation modeling for the accurate assessment of the carbon balances of Swedish forest ecosystems at the scale of a landscape. Monthly climatologic data were used as inputs in a dynamic vegetation model, the Lund Potsdam Jena-General Ecosystem Simulator. Model estimates of net primary production (NPP) and the fraction of absorbed photosynthetic active radiation were constrained by combining them with satellite-based LAI images using a general light use efficiency (LUE) model and the Beer-Lambert law. LAI estimates were compared with satellite-extrapolated field estimates of LAI, and the results were generally acceptable. NPP estimates directly from the dynamic vegetation model and estimates obtained by combining the model estimates with remote sensing information were, on average, well simulated but too homogeneous among vegetation types when compared with field estimates using forest inventory data.
In recent years, forestry has been strongly promoted by the government of the Socialist Republic of Vietnam through large-scale projects to rehabilitate and reforest millions of hectares of land. One project to reforest 5 million hectares has received hundreds of millions of US dollars for implementation. Yet based on a case study in one area of northern Vietnam, this project appears to have had a number of unforeseen consequences. Large areas of land classified as “bare hills” have been targeted for reforestation, despite the fact that these lands already harbor a number of species that were used by local communities. The bare hills were especially economically important to poor households and to women who collected a variety of nontimber forest products there. Because the reforestation project focused most efforts on establishing new plantations rather than supporting natural regeneration, diverse sources of nontimber forest products were being replaced with monocrop exotic tree plantations. A strong inequity in the allocation of private lands for reforestation has characterized the regreening projects to date, and this may have continuing unwelcome social, environmental, and economic impacts into the future, particularly for the poor.
Zinc deficiency is a problem in developing countries and not least so in Africa. This concerns both agriculture and human food provision. Zinc deficiency in soils may severely decrease yields, whereas insufficient zinc in food intake primarily affects the immune defense, notably in children. The present investigation concerned zinc availability in soils, crops, and food in the Niger inland delta in Mali. Agricultural soils are largely deficient in plant-available zinc, however, soils in close vicinity to habitation show elevated zinc concentrations. The zinc concentrations in crops are low; in rice, they are about half of reference ranges. Zinc intake assessed from a number of sampled meals was about half the recommended requirement. When zinc concentration is higher phytate was also high, which made the zinc less available. In spite of a recorded sufficient intake of iron, anemia is common and is most likely because of the high phytate concentration in the cereal-dominated diet. Increasing zinc and iron availability would be possible through the use of malting, fermentation, and soaking in food preparation. Finally, in the long run, any trace element deficiency, especially that of zinc in agricultural soils needs to be amended by addition of appropriate amounts in commercial fertilizers.
We investigate environmental impacts of off-budget or indirect subsidies, which, unlike on-budget subsidies, are not visible in government budgets. Such subsidies have received little attention in economic and environmental research, even though they may be at least as important from an environmental perspective as on-budget subsidies. We offer a typology of indirect subsidies. Next, we estimate the magnitude of these subsidies and their impact on greenhouse gas (GHG) and acidifying emissions for the agriculture, energy, and transport sectors in The Netherlands. The calculations are based on a model approach that translates a particular subsidy into price and quantity changes using empirical elasticities, followed by environmental effect estimates using pollution-intensity parameters. The various environmental pollution effects are aggregated into environmental indicators. The results show, among others, that GHG emissions caused by off-budget subsidies contribute to more than 30% of the policy targets specified by the Kyoto Protocol for CO2 emissions reduction by The Netherlands. Reforming or removing off-budget subsidies may thus be an important strategy of effective climate policy.