The influence of humic substances on lacustrine planktonic food chains

Humic substances (HS) might influence planktonic food chains in lakes in two ways: 1) by altering the physical or chemical environment and thus modifying autotrophic primary production and the dependent food chains; 2) by acting as a direct carbon/energy source for food chains. HS compete with phytoplankton for available quanta underwater and this effect is seen in the reduced euphotic zone depth in lakes with high concentrations of HS. Thus potential photosynthetic production is lower in the presence of HS. However, this effect can be offset in small lakes in which the depth of mixing is also reduced when HS concentrations are high. Complexation by HS of important nutrients such as iron and phosphorus may also restrict primary production. Evidence is accumulating that photosynthetic primary production is insufficient to support measured metabolic activity in humic lakes, which implies that metabolism of allochthonous HS underpins much of the observed activity. Studies of bacterial abundance and growth in the presence of HS support the view that bacteria are the most significant utilisers of HS. This use is apparently facilitated by photolysis of HS, particularly by short wavelength radiation. Bacteria are grazed by both micro-zooplankton (heterotrophic and mixotrophic flagellates and ciliates) and macrozooplankton. It is within this microbial community that the food chains derived from autotrophic and allotrophic sources interact. These effects of HS on food chains are discussed in relation to possible implications for the response of different lake types to eutrophication.     

Top-predator abundance and chaos in tritrophic food chains

Nonlinear models and laboratory experiments suggest that populations can be chaotic, whereas field data show that a fair proportion of observed populations are not too far from being chaotic. Thus, a natural question arises: do ecosystems enjoy special properties at the edge of chaos? By limiting the analysis to three classes of tritrophic food chains and to the role played by the nutrient available to the bottom of the ecosystem, we show that top-predator mean abundance is maximum at the edge of chaos. The geographical variability of species abundance along nutrient gradients and the dynamic complexity of observed natural populations are consistent with our findings. Effective guidelines for the sustainability of exploited ecosystems are also derived.     

Planktonic food chains of a highly humic lake

The development and metabolism of the plankton of a highly humic lake were followed over the vernal primary production maximum. The study was made in a mesocosm in which large filter feeders, typical of this lake in summer, were absent. During the rising phase of phytoplankton, the community was predominantly autotrophic. The most important constituents in the algal biomass were a dinoflagellate, Gymnodinium sp. (40–50%), and a prasinophycean, Scourfieldia cordiformis (7%). The biomasses of Chlamydomonas spp. and Chrysococcus spp. reached their maxima a few days later and Cryptomonas sp. became most abundant at the end of the experiment. After the phytoplankton maximum, about one week from the beginning ofthe experiment, grazing of algae by phagotrophic protozoans and phosphate depletion led to a rapid decrease of algal biomass and the community became predominantly heterotrophic. In spite of a large variation in algal biomass and primary production, the biomass of bacteria remained of the same order of magnitude as in algae both before and after the algal maximum. Bacteria were mostly responsible for the plankton respiration, which also showed no dependence on primary production. Since exudation by phytoplankton was also low, the nutrition of bacterioplankton was probably mainly based on allochthonous dissolved organic matter rather than or primary production. Thus the production of bacteria was an additional food source for higher trophic levels along with phytoplankton. Because filter feeding zooplankton was absent in the experiment, protozoans were the only grazers utilizing algae and bacteria. Essentially all growth of bacteria was used by bacterivores.     

The relative importance of transport in determining an appropriate sustainability strategy for food sourcing

Background, Aims and Scope Over the last five decades, the nature of food retailing has undergone an enormous transformation. Macro level economic, structural and technological developments have led to a major increase in the level of world trade. These developments have helped retailers to meet modern consumer expectations, but benefits have not been achieved without some drawbacks. This paper seeks to explore the environmental impacts associated with fresh produce supply chains, in order to understand the relative significance of transport as compared to other supply chain activities. Methods Life Cycle Assessment was used to estimate the potential environmental impacts of three fresh produce items sourced from six countries and solid in Marks and Spencer stores: royal gala apples from Brazil, Chile, Italy and the UK; runner beans from Kenya (and extrapolated for Guatemala and the UK); and watercress from the UK and USA (and extrapolated for Portugal). Analysis was also conducted to evaluate the likely impacts of extending the storage period for UK apples thus negating the need to import, against the current strategy of importing fruit from the Southern hemisphere for six months of the year. In addition, the impacts of conventional as compared to organic cultivation were considered for watercress in both the UK and USA. Results and Discussion The results for all three products reveal similar dominating impacts. A clear distinction arises in terms of the activities which contribute most to environmental impact and the magnitude of this impact, depending on the country in which the product is cultivated; i.e. global, regional (European) or local (British) sources of supply. Conclusion Transport (or distance between production and consumption) is therefore an important factor in determining the environmental sustainability of food supply chains (though for long distance haulage, there is a significant distinction between air-freight and shipping). Electricity consumed for storage and packing operations is also significant, and the associated environmental impact is lower in countries where a large proportion of electricity is generated from renewable fuels. However, where this occurs in countries distant from the UK, transport impacts overshadow the environmental savings achieved from the more favourable electricity generation mix. Recommendations and Perspectives The results of this study suggest that when in season it is generally preferential, on environmental grounds, for UK consumers to buy British produce rather than produce imported from overseas. Cultivation overseas is necessary to ensure year-round availability and in these circumstances it is preferable that processing activities also occur overseas if environmental benefits can be derived from local factors (e.g. a favourable electricity generation mix). Overall, the findings should be evaluated in the context of managing wider sustainability interests (including social and economic issues), for which further research is required.     

Opportunities and challenges of sustainable agricultural development in China

This paper introduces the concepts and aims of sustainable agriculture in China. Sustainable agricultural development comprises sustainability of agricultural production, sustainability of the rural economy, ecological and environmental sustainability within agricultural systems and sustainability of rural society. China's prime aim is to ensure current and future food security. Based on projections of China's population, its economy, societal factors and agricultural resources and inputs between 2000 and 2050, total grain supply and demand has been predicted and the state of food security analysed. Total and per capita demand for grain will increase continuously. Total demand will reach 648 Mt in 2020 and 700 Mt in 2050, while total grain yield of cultivated land will reach 470 Mt in 2010, 585 Mt in 2030 and 656 Mt in 2050. The per capita grain production will be around 360kg in the period 2000-2030 and reach 470kg in 2050. When productivities of cultivated land and other agricultural resources are all taken into consideration, China's food self-sufficiency ratio will increase from 94.4% in 2000 to 101.3% in 2030, suggesting that China will meet its future demand for food and need for food security. Despite this positive assessment, the country's sustainable agricultural development has encountered many obstacles. These include: agricultural water-use shortage; cultivated land loss; inappropriate usage of fertilizers and pesticides, and environmental degradation.     

Projections of world population and world food supply

This paper considers projections made about world population levels and world food production from 1945 to 1970, attempting to evaluate them in terms of actual levels of 1975. Most underestimated the population explosion of the past two decades; short-term estimates were more reliable than long-term ones; there was little variation in population estimates at any one time; and U. N. figures were generally the most useful. Projections of world food production were less satisfactory than those of population levels, as both data and measures were debatable. The research suggests some of the problems in evaluating the danger of world famine by examining projections of population and food supply mechanically and in isolation from the complex processes which affect these factors.     

Food waste within food supply chains: quantification and potential for change to 2050

Food waste in the global food supply chain is reviewed in relation to the prospects for feeding a population of nine billion by 2050. Different definitions of food waste with respect to the complexities of food supply chains (FSCs)are discussed. An international literature review found a dearth of data on food waste and estimates varied widely; those for post-harvest losses of grain in developing countries might be overestimated. As much of the post-harvest loss data for developing countries was collected over 30 years ago, current global losses cannot be quantified. A significant gap exists in the understanding of the food waste implications of the rapid development of ‘BRIC’ economies. The limited data suggest that losses are much higher at the immediate post-harvest stages in developing countries and higher for perishable foods across industrialized and developing economies alike. For affluent economies, post-consumer food waste accounts for the greatest overall losses. To supplement the fragmentary picture and to gain a forward view, interviews were conducted with international FSC experts. The analyses highlighted the scale of the problem, the scope for improved system efficiencies and the challenges of affecting behavioural change to reduce post-consumer waste in affluent populations.     

Bioenergy production and sustainable development: science base for policymaking remains limited

The possibility of using bioenergy as a climate change mitigation measure has sparked a discussion of whether and how bioenergy production contributes to sustainable development. We undertook a systematic review of the scientific literature to illuminate this relationship and found a limited scientific basis for policymaking. Our results indicate that knowledge on the sustainable development impacts of bioenergy production is concentrated in a few well‐studied countries, focuses on environmental and economic impacts, and mostly relates to dedicated agricultural biomass plantations. The scope and methodological approaches in studies differ widely and only a small share of the studies sufficiently reports on context and/or baseline conditions, which makes it difficult to get a general understanding of the attribution of impacts. Nevertheless, we identified regional patterns of positive or negative impacts for all categories – environmental, economic, institutional, social and technological. In general, economic and technological impacts were more frequently reported as positive, while social and environmental impacts were more frequently reported as negative (with the exception of impacts on direct substitution of GHG emission from fossil fuel). More focused and transparent research is needed to validate these patterns and develop a strong science underpinning for establishing policies and governance agreements that prevent/mitigate negative and promote positive impacts from bioenergy production.     

Retention versus export food chains: processes controlling sinking loss from marine pelagic systems

The role of export and retention food chains forpelagic-benthic coupling is considered by evaluatingdifferent food chain scenarios and processes such asaggregation, grazing and zooplankton-mediated fluxes.The consequences of grazing of primary production bydifferent zooplankton for the vertical export ofparticulate organic matter from the euphotic zone arediscussed. Reference is made to existing data andalgorithms regarding primary production and verticalexport of carbon from the euphotic zone, both onannual and daily time scales. Examples regarding therole of nutrient addition, removal of pelagiccarnivores and zooplankton grazing for vertical fluxare presented. It is speculated how variable grazingimpact of micro- and mesozooplankton, as well asherbivorous, omnivorous and carnivorous feedingstrategies of mesozooplankton could compete withaggregation during phytoplankton blooms and influenceexport fluxes. It is concluded that the transport ofparticulate organic matter to depth not only dependson bottom-up regulation as determined by physicalforcing, but also on the structure and function of theprevailing planktonic food web. Scenarios arepresented which indicate that top-down regulationplays a pivotal role for the regulation of verticalflux. This conclusion may have crucial consequencesfor future biogeochemical programmes investigatingpelagic-benthic coupling in the ocean. The endeavoursof many research programmes are dominated by lines ofthought where straightforward biogeochemistry andbottom-up regulation is the focus. Phyto- andzooplankton as well as process-oriented researchactivities have to be the focal point of futureresearch if the current comprehension of export fromand retention in the upper layers is going to makedistinct progress. This revised version was published online in July 2006 with corrections to the Cover Date.     

Introducing digital tools for sustainable food supply management: Tackling food loss and waste in industrial canteens

Reducing food waste is essential if we want to create a more sustainable food system, which is why halving per capita food waste by 2030 has been included in the UN Sustainable Development Goals. The main aim of this paper is to demonstrate that by using digital tools to monitor food provisioning and management within canteens, it is possible to achieve a more sustainable food service management within industrial companies and to reduce the overall quantity and environmental impacts of food preparation and consumption thus achieving economic benefits. Longitudinal 2018 and 2019 data collected from the canteen of a major Italian food production company were analyzed. The results showed that the amount of food lost and wasted has decreased over time, reaping important environmental benefits and illustrating specific differences between the food lost in meal preparation and the food left on employees’ plates. It is therefore important to implement education initiatives and to use digital tools to share food-related data collected within companies among both employees and kitchen and catering staff in order to raise awareness of their behavioral strengths and weaknesses. From this perspective, new interventions at both kitchen and customer/worker levels are introduced and discussed.     

Management of fat reserves and food caches in tufted titmice (Parus bicolor) in relation to unpredictable food supply

In the temperate zone, permanent-resident birds and mammalsthat do not hibernate must survive harsh winter conditions oflow ambient temperature, long nights, and reduced food levels.To understand the energy management strategy of food-hoardingbirds, it has been hypothesized that such birds respond to increasedstarvation risk by increasing the number of their hoards ratherthan by increasing their fat reserves and that they cache earlyin the day and retrieve their caches later to achieve fat reservesnecessary to survive the night We tested these hypotheses byobserving the responses in captivity of a caching bird, thetufted titmouse (Parus bicolor), to the combined influencesof reduced predictability of food and naturally occurring ambienttemperature and photoperiod. When the food supply was unpredictable,birds significantly increased both internal fat reserves atdusk and external food caches. Initially leaner birds tendedto increase their fat reserves to a greater extent and initiallyfatter birds tended to cache more food and to fly significantlyless. Half the birds also increased their dawn and mean dailybody mass. All birds tended to forage, gain body mass, and cachefood at significantly lower rates in the morning and at significantlyhigher rates in the evening. Cache retrieval showed the oppositetrend, with birds retrieving most of their caches in the morning.Our results do not support the hypothesis that caching birdsincrease caching rate but not body mass under an unpredictablefood regime. Instead fat reserves and food caches are both importantcomplementary sources of energy in food-hoarding birds. Energymanagement by wintering birds occurs in response to a numberof biotic and abiotic factors acting simultaneously; thus futuremodels must incorporate independent variables in addition tothe state of the food supply and time of day     

Relationships among multiple aspects of agriculture's environmental impact and productivity: a meta‐analysis to guide sustainable agriculture

Given the pressures on land to produce ever more food, doing it ‘sustainably’ is growing in importance. However, ‘sustainable agriculture’ is complex to define, not least because agriculture impacts in many different ways and it is not clear how different aspects of sustainability may be in synergy or trade off against each other. We conducted a meta‐analysis to assess the relationships between multiple measures of sustainability using novel analytical methods, based around defining the efficiency frontier in the relationship between variables, as well as using correlation analysis. We define 20 grouped variables of agriculture's impact (e.g. on soil, greenhouse gas, water, biodiversity) and find evidence of both strong positive and negative correlations between them. Analysis based on the efficiency frontier suggests that trade‐offs can be ‘softened’ by exploiting the natural between‐study variation that arises from a combination of farming best practice and context. Nonetheless, the literature provides strong evidence of the relationship between yields and the negative externalities created by farming across a range of measures.     

Exploitation of endophytes for sustainable agricultural intensification

Intensive agriculture, which depends on unsustainable levels of agrochemical inputs, is environmentally harmful, and the expansion of these practices to meet future needs is not economically feasible. Other options should be considered to meet the global food security challenge. The plant microbiome has been linked to improved plant productivity and, in this microreview, we consider the endosphere – a subdivision of the plant microbiome. We suggest a new definition of microbial endophyte status, the need for synergy between fungal and bacterial endophyte research efforts, as well as potential strategies for endophyte application to agricultural systems.     

The role of birds in sustainable food production

Birds (Class Aves) are already an important source of food in most parts of the world. Only a few species have been successfully domesticated but many others are harvested from the wild. There is potential for greater use of birds as a food source. Existing domesticated species, especially galliforms, need to be better utilized. Certain new species could be brought into domestication. The efficiency and sustainability of harvesting methods for free-living birds might be improved and the harvesting of new species should be considered. These measures could be compatible with improved conservation of wild birds and their habitats, but careful planning and surveillance are essential prerequisites.     

Coral reef mesopredators switch prey,shortening food chains,in response to habitat degradation

Diet specificity is likely to be the key predictor of a predator's vulnerability to changing habitat and prey conditions. Understanding the degree to which predatory coral reef fishes adjust or maintain prey choice, in response to declines in coral cover and changes in prey availability, is critical for predicting how they may respond to reef habitat degradation. Here, we use stable isotope analyses to characterize the trophic structure of predator–prey interactions on coral reefs of the Keppel Island Group on the southern Great Barrier Reef, Australia. These reefs, previously typified by exceptionally high coral cover, have recently lost much of their coral cover due to coral bleaching and frequent inundation by sediment‐laden, freshwater flood plumes associated with increased rainfall patterns. Long‐term monitoring of these reefs demonstrates that, as coral cover declined, there has been a decrease in prey biomass, and a shift in dominant prey species from pelagic plankton‐feeding damselfishes to territorial benthic algal‐feeding damselfishes, resulting in differences in the principal carbon pathways in the food web. Using isotopes, we tested whether this changing prey availability could be detected in the diet of a mesopredator (coral grouper, Plectropomus maculatus). The δ¹³C signature in grouper tissue in the Keppel Islands shifted from a more pelagic to a more benthic signal, demonstrating a change in carbon sources aligning with the change in prey availability due to habitat degradation. Grouper with a more benthic carbon signature were also feeding at a lower trophic level, indicating a shortening in food chains. Further, we found a decline in the coral grouper population accompanying a decrease in total available prey biomass. Thus, while the ability to adapt diets could ameliorate the short‐term impacts of habitat degradation on mesopredators, long‐term effects may negatively impact mesopredator populations and alter the trophic structure of coral reef food webs.     

Cultural values on CSR patterns and evolution: A study from the biplot representation

Based on institutional and stakeholder theory, this study aims to observe the influence the cultural system has on the degree of responsibility of business behaviour and examines how normative isomorphism influences the Corporate Social Responsibility practices at the country level. We use the Hofstede model because its dimension group highlights the cultural similarities and differences between countries, and we measure CSR along five indicators referring to environmental and social dimensions. This study contributes to the literature by adopting a multi-region approach considering a sample of 6600 observations of 600 publicly-listed companies headquartered in 18 countries in Europe, North America, Japan and Australia, during the period 2004–2014. Given the multidimensional character of the data, we use the exploratory statistical techniques X-STATIS and HJ-biplot, since this allows us to approximate a large group of variables in a low-dimensional space, providing us with a useful visualisation of the structure of the data of the sample relative to the variables. Our main conclusion is that cultural dimensions exert important pressures on firms and their commitment, so, companies located in collectivist societies and, even more, in feminist ones, are characterised by the pursuit of the common good and place greater emphasis on social and environmental issues, thereby showing best CSR practices. Overall, the data does point to more activity in Northern than in Southern Europe, and show that companies respond to what is important in their own countries; for example, the Nordic countries give priority to social policies, while Japanese companies are more committed to the environment. Finally, our results evidence that companies worldwide adopt similar patterns of CSR practices, but their degree of development is strongly determined by the normative institutional characteristics.     

Effects of habitat disturbance and food supply on population densities of three primate species in the Kakamega Forest, Kenya

While habitat disturbance and food availability are major factors thought to determine the abundance of primates, evidence for their importance is uneven. We assessed the effects of these factors on three monkey species, guerezas ( Colobus guereza ) , blue monkeys ( Cercopithecus mitis ) and redtails ( Cercopithecus ascanius ), in four areas of the Kakamega Forest, Kenya. Group densities of guerezas and blue monkeys were higher in areas where disturbance levels were also higher. Food availability measured as basal area density of food trees did not correlate significantly with the group densities of any of the three monkeys. The diversity of food trees, another potential measure of food abundance did, however, correlate with group densities of guerezas and blue monkeys suggesting that food availability may positively influence monkey density, and may sometimes increase with disturbance. Group densities of redtails did not correlate with any habitat variable examined, suggesting that factors other than those we considered may have influenced the abundance of this species particularly.