Fuelwood consumption in two tribal villages of the Nanda Devi Biosphere Reserve of the Indian Himalaya and strategies for fuelwood sustainability

Fuelwood is the only important source of energy in the mountainous region of the Garhwal Himalaya, India. Since the commercial source of energy is generally beyond the reach of ordinary people due to their poor socio-economic conditions and due to limited supply and lack of communication facilities for transport of LPG, the villages of the inner region of the Garhwal Himalaya depend on their fuel requirement from the forest. In the present study, two villages of the Nanda Devi Biosphere Reserve in Uttarakhand part of the Indian Himalaya i.e. Lata and Dunagiri located at 2,415 and 3,600 m altitudes, respectively, were selected for the study of socio-economic profile and vegetation and for estimation of per capita fuelwood consumption and the degree of disturbance. The study was conducted from 2002–2005. The population of these villages is migratory and belongs to the Bhotiya community, a scheduled tribe consisting of two subgroups known as Tolcha and Marchha. They grow traditional crops as well as cash crops. Important tree species used for fuelwood include Cedrus deodara, Pinus wallichiana, Cupressus torulosa, Taxus wallichiana, Acer indicum, Quercus dilatata and Viburnum cotinifolium. Maximum density among trees was shown by Pinus wallichiana (169.6 trees ha⁻¹) in village Lata and by Cedrus deodara (89.6 trees ha⁻¹) in village Dunagiri. The average per capita consumption of fuelwood in villages Lata and Dunagiri was 4.03 and 4.77 kg capita⁻¹ day⁻¹. Maximum number of trees (29 and 31% lopping for Lata and Dunagiri, respectively) belonged to disturbance class 1 (1–20% lopping) followed by the disturbance class 2 (20–40% lopping). Due to location of these villages in the buffer zone of the biosphere reserve, the fuelwood consumption may cause an adverse impact on the ecological status of this reserve, which urgently requires employing strategies for the conservation and management of this biosphere in terms of fuelwood sustainability e.g. regulation of livestock stock and grazing, using alternative sources of fuels, plantation of multipurpose trees and adoption of ecotourism.     

Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

Results of groundwater and seawater analyses for radioactive (³H, ²²²Rn, ²²³Ra, ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra) and stable (D and ¹⁸O) isotopes are presented together with in situ spatial mapping and time series ²²²Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d⁻¹ to 360 cm d⁻¹; the unit represents cm³/cm²/day), as well as during a few hours (from 0 cm d⁻¹ to 110 cm d⁻¹), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous ²²²Rn measurements is 17 ± 10 cm d⁻¹. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7 × 10³ m³ d⁻¹ per km of the coast. The isotopic composition (δD and δ¹⁸O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of ²²²Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1–2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.     

The mortality effect of ship-related fine particulate matter in the Sydney greater metropolitan region of NSW,Australia

This study investigates the mortality effect of primary and secondary PM_2.5 related to ship exhaust in the Sydney greater metropolitan region of Australia. A detailed inventory of ship exhaust emissions was used to model a) the 2010/11 concentration of ship-related PM_2.5 across the region, and b) the reduction in PM_2.5 concentration that would occur if ships used distillate fuel with a 0.1% sulfur content at berth or within 300 km of Sydney. The annual loss of life attributable to 2010/11 levels of ship-related PM_2.5 and the improvement in survival associated with use of low-sulfur fuel were estimated from the modelled concentrations.In 2010/11, approximately 1.9% of the region-wide annual average population weighted-mean concentration of all natural and human-made PM_2.5 was attributable to ship exhaust, and up to 9.4% at suburbs close to ports. An estimated 220 years of life were lost by people who died in 2010/11 as a result of ship exhaust-related exposure (95% CI_β: 140–290, where CI_β is the uncertainty in the concentration-response coefficient only). Use of 0.1% sulfur fuel at berth would reduce the population weighted-mean concentration of PM_2.5 related to ship exhaust by 25% and result in a gain of 390 life-years over a twenty year period (95% CI_β: 260–520). Use of 0.1% sulfur fuel within 300 km of Sydney would reduce the concentration by 56% and result in a gain of 920 life-years over twenty years (95% CI_β: 600–1200).Ship exhaust is an important source of human exposure to PM_2.5 in the Sydney greater metropolitan region. This assessment supports intervention to reduce ship emissions in the GMR. Local strategies to limit the sulfur content of fuel would reduce exposure and will become increasingly beneficial as the shipping industry expands. A requirement for use of 0.1% sulfur fuel by ships within 300 km of Sydney would provide more than twice the mortality benefit of a requirement for ships to use 0.1% sulfur fuel at berth.     

Impacts of arsenic contamination in groundwater: case study of some villages in Bangladesh

The contamination of groundwater in Bangladesh by arsenic is a widespread and serious environmental problem, affecting mainly the rural population who rely extensively on groundwater for drinking and cooking. The study conducted survey work in a few affected villages of the Northwest region in Bangladesh. The household survey gathered information on the respondents (affected by arsenic) water usage and sources, knowledge of the arsenic problem, changes in the source of water for drinking and cooking, arsenic mitigation technologies and socio-economic information on the households. The survey work shows that percentage of male patient is higher than female patient among the same level of household income in each study villages. Prevalence of arsenicosis is more among poorer sections and it is directly related to the poverty situation of the community. People know more about the health problems caused by arsenicosis but lack knowledge about mitigation aspects. In one of the study areas, every year an extra 4% tubewell is getting contaminated by arsenic. Arsenic contamination in groundwater also affects the environment and the ecology negatively. The NGOs have been found contributing to a knowledge creation process in the village community as the villagers are showing marked behavioral changes in water-use practice.

Use and knowledge of fuelwood in three rural caatinga (dryland) communities in NE Brazil

The woody species known, used, and preferred as fuelwood were examined in three rural communities within the county of Soledade, Paraíba State, NE Brazil. Ethnobotanical information was collected using semi-structured interviews with more than 90% of the local households (55 adult residents; 31 women, and 24 males). The interviewees cited 36 plant species as fuelwoods, distributed among 30 genera and 15 families, in addition to two unidentified plants. The plant families represented by the largest numbers of species were Euphorbiaceae, Anacardiaceae, Mimosaceae, Caesalpiniaceae, Sapotaceae, and Fabaceae. The species Caesalpinia pyramidalis Tul. (“catingueira”) was cited with the greatest frequency in all three communities. Within the communities we found significant differences on the number of plants cited and actually used (p < 0.05), indicating that the residents knew more fuelwood species than they effectively harvest. The different distances from the communities to the urban centers were not related to differences on the use or the size of the stocks of fuelwood. Additionally, the study revealed that the communities examined still maintain a significant knowledge of the use of energy-providing plants in spite of the widespread use of liquefied petroleum gas (LPG). Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Effects of cadmium on forearm bone density after reduction of exposure for 10 years in a Chinese population

The main focus of this study was to evaluate long term effects of cadmium on forearm bone mineral density after stopping ingestion of cadmium-polluted rice for 10 years in a Chinese population. A total of 532 persons (338 women and 194 men), living in control, moderately and heavily polluted areas, were included in this study. The residents living in the polluted area ceased ingesting cadmium-polluted rice in 1996. All participants were require to answer a questionnaire and the bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA) at the proximal radius and ulna. Samples of urine and blood were collected for determination of cadmium in urine (UCd) and blood (BCd).The BMD of subjects living in the heavily polluted area was significantly lower than that of those living in control area in both men and women (p < 0.01). For the people living in the moderately polluted area, only the women's BMD was greatly lower compared to that in the control area (p < 0.05). The BMD declined with the increasing BCd and UCd in both sexes, especially in the highest level (BCd > 5 µg/L, UCd > 10 µg/g crea) groups (p < 0.01). It was found that there were significant differences in the prevalence of osteoporosis among the different areas (χ² = 13.046, p = 0.0003) and different UCd groups (χ² = 4.511, p = 0.0337) in women, but not in men (χ² = 0.962, p = 0.3268; χ² = 1.906, p = 0.1675). But a significant difference exists in the prevalence of osteoporosis among different BCd groups in both genders (χ² = 9.304, p = 0.00229, in women; χ² = 4603, p = 0.0319, in men). This study suggested that cadmium could play a long-term role on bone and more attention should be paid to cadmium effects on bone metabolism after reduction of exposure.     

Levels of polychlorinated dibenzo-p-dioxins,dibenzofurans (PCDD/Fs) and biphenyls (PCBs) in blood of informal e-waste recycling workers from Agbogbloshie,Ghana, and controls

The formation and environmental release of highly toxic organohalogen compounds associated with informal recycling of waste electric and electronic equipment (e-waste) is a growing problem at e-waste dumps/recycling sites (EWRSs) in many developing countries worldwide. We chose a cross-sectional study design to measure the internal exposure to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) as well as polychlorinated biphenyls (PCBs) of individuals working on one of the largest EWRSs of Africa, located at Agbogbloshie, Accra, Ghana, and in controls from a suburb of Accra without direct exposure to EWRS activities. In whole blood samples of 21 age matched male exposed individuals (mean age: 24.7 years, SD 6.0) and 21 male controls (mean age: 24.4 years, SD 5.7) 17 PCDD/F congeners were determined. Moreover three indicator PCB congeners (#138, #153 and #180) were measured in blood of 39 exposed (mean age: 27.5 years, SD 11.7) and 19 non-exposed (mean age: 26.8 years, SD 9.7) patients. Besides a health examination, biometric and demographic data, residential and occupational history, occupational exposures and working conditions were recorded using a standardized questionnaire. In the exposed group, median PCDD/F-concentrations were 6.18 pg/g lipid base WHO₂₀₀₅-TEq (range: 2.1–42.7) and significantly higher compared to the control group with 4.60 pg/g lipid base WHO₂₀₀₅-TEq (range: 1.6–11.6). Concentrations were different for 2,3,7,8-TetraCDD, three HexaCDD and all 10 PCDF congeners, indicating a combustion pattern. Using a multivariate regression analysis exposure to EWRS activities was the most important determinant for PCDD/F exposure. Median PCB levels for the indicator congeners #138, #153 and #180 were 0.011, 0.019 and 0.008 μg/l whole blood (ranges: 0.002–0.18, 0.003–0.16, 0.002–0.078) in the exposed group and, surprisingly, significantly higher in the controls (0.037, 0.062 and 0.022; ranges: 0.005–0.46, 0.010–0.46, 0.004–0.21). In a multivariate regression approach e-waste related activities had no positive influence on internal PCB exposure, but rather the time living in Accra. The internal PCB exposure is in particular notable for a country where PCBs have historically never been produced or used. The impact of EWRS activities on organohalogen compound exposure of individuals working at and living in the surroundings of the Agbogbloshie EWRS, and the surprisingly high PCB exposure of people living in Accra not involved in e-waste activities require further investigation.     

Community-based natural resources management (CBNRM) in Xinhui, Guangdong Province, China

Using institutional appraisal focused groups (FG) and participatory appraisals with Dillman Total Design Method (TDM), this study examines community interaction with and utilization of wetland resources in Xinhui, Guangdong Province, China. Field results show high commercial activities and corresponding impacts on coastal environment. Other interacting factors identified include: legislation and ecosystem management, stakeholders’ participation, international guidelines criteria, and utilization of mangrove resources in the region. Sensitivity index and community-based natural resources management collaboration comparison percentile showed significant differences between cumulative distributions of respondents (D = 0.2568, P = 0.078). Likert statement of 11 sensitivity optional indexes in EMS of K–S test at 0.05 level of P = 0.078 also show significant differences in interaction between respondent groups and sensitivity factors. This indicates a dysfunction between regional environmental management systems and CBNRM in Xinhui coastal district. Considering the high tourism potential and economic quest of the region, there is the need for coordinated community enlightenment and further studies on the social, ecological and economic value of wetland resources. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Po determination in urines of people living in Central Italy

This paper presents the results of the monitoring programme on the urines of people living in an area of Central Italy (near the Republic of S. Marino) to evaluate the background level of the ²¹⁰Po excretion rate (mBq day⁻¹) in this region. The volunteers were subdivided in five age classes and in every age class groups of males and females, cigarette smokers and non-smokers were taken into account. The results indicated that the ²¹⁰Po excretion rate was widely distributed within each group of volunteers. The ²¹⁰Po excretion rate was <30 mBq day⁻¹ for 93.2% of people. The obtained results are discussed and some conclusion, based upon the average values, was drawn.     

Environmental self-efficacy, attitude and behavior among small scale farmers in Zambia

The rural livelihood system in Zambia is essentially agriculture, and agriculture is the main link between people and their environment. Through agricultural activities, people seek to husband the available soil, water and biological resources so as to ‘harvest’ a livelihood for themselves. The aim of this study is to examine Zambian farmers’ awareness and attitude toward the degradation of the environment and their relationships with a set of beliefs to evaluate their perceived capacity to take actions to improve the environment. Results of the study revealed that perception of the severity of environmental degradation had a positive influence on both awareness of and attitude toward land degradation (β = 0.47; p < .001). Perception of susceptibility and benefits significantly influence farmers’ attitude toward environmental degradation (β = 0.51; p < .001). Awareness of environmental degradation is a significant precursor of environmental self-efficacy and behavior (β = 0.38; p < .001). Increasing severity of environmental degradation tends to promote a positive attitude of Zambian farmers toward the environment (β = 0.27; p < .001). Greater awareness of environmental degradation enhances farmers’ capacity in making decisions to improve the situation. Greater environmental awareness leads to greater involvement in land management programs. Greater awareness of the degradation of the environment leads to a more positive environmental behavior. The more individuals are aware of the existence of the degradation of the environment and of its consequences, the more likely they are to do something about it in order to ameliorate the situation (β = 0.36; p < .001). Farmers’ environmental self-efficacy also plays a significant role in their decision to change their behavior. Greater perception of one’s capability to improve the environment is significantly associated with a more positive environmental behavior (β = .39; p < .001).     

Co-Partnership in Forest Management: The Gwira-Banso Joint Forest Management Project in Ghana

The involvement of local communities, as well as the private sector and the government in forest management is now an important principle of tropical forestry policy and practice and a major component of most international forestry aid programmes. This paper present an analysis on the Joint Forest Management Project initiated by two timber companies (Ghana Primewood Products Ltd and Dalhoff Larsen & Horneman) in collaboration with local people in Gwira-Banso of Ghana. Conditions required for enhancing responsibility for and commitment to local forest management, and for an effective local participatory process were also analysed. The study began with the premise that incentives and good communication will enhance participation in joint forest management.The assumption was valid and the results from the survey showed that five broad issues prioritised by respondents to be essential for co-partnership in forest management are communication, financial support, tree planting, multiple land use and benefit sharing. The Project enjoys a great deal of support from the local community, but a number of factors make the continued support of local people a challenging task, including questions of immediate livelihood sources and tenure arrangements. Although this participatory forest management has been implemented over a relatively short period, there is evidence that government and private sectors can successfully involve local people in sustainable management of the forests.     

Redressing cultural erosion and ecological decline in a far North Queensland aboriginal community (Australia): the Aurukun ethnobiology database project

Traditional environmental knowledge (usually imparted orally) is being lost from many regions of the world, requiring novel forms of transmission if this situation is to be redressed. Loss of this knowledge may be a significant contributory factor towards ecological decline. Undoubtedly, disruption to ecosystems and societies that depend on these has impacted on traditional land management practices, with negative ramifications for biodiversity. From an environmental perspective, scientists in northern Australia need to understand traditional Aboriginal methods of ‘caring for country’, such as burning regimes, so that these can be incorporated into strategies today for maintaining Australia’s rich biodiversity. However, information exchange should be two-way: as well as learning from local people, science can in turn benefit people who may have little experience of, for example, invasive species. The challenge is how can the complexity of biological knowledge from within different ontologies be represented and integrated in a way that it can be of use to scientists and local people, in order to ensure a sustainable future? The main aim of this study was to record existing local knowledge of biodiversity for the community of Aurukun (far north Queensland), integrating this knowledge with scientific data, while giving parity to both knowledge systems and protecting intellectual property rights. A cross-cultural collaboration between community members and ethnobiologists resulted in development of the Aurukun Ethnobiology Database. An interdisciplinary approach was taken to effectively model autochthonous biological knowledge and scientific data to create a database with a number of practical applications.     

Urban water-related environmental transitions in Southeast Asia

This article reviews water-related urban environmental conditions in Southeast Asia. It argues that the development of urban environmental challenges in the region follows a unique pattern compared with those experienced in the now developed world. The new pattern is defined by the so called time–space telescoping of the development process. The process of time–space telescoping reduces the levels of income at which environmental challenges emerge and forces their appearance in a simultaneous fashion, as sets of problems. During previous eras, cities experienced sequential environmental transitions. Urban water-related environmental burdens emerged on local scales and expanded geographically and temporally in impact, with growing levels of affluence. Moreover, certain environmental challenges appeared later in economic growth because the technologies and practices that induced these problems emerged at higher levels of income. The article has two main findings. First, except for wealthy urban centers, for example Singapore, cities in the region are experiencing multi-scaled water burdens simultaneously. Second, low-income and middle-income cities are experiencing burdens at lower levels of income than did their contemporaries in the north.

Pre-concentration of naturally occurring radionuclides and the determination of (212)Pb from fresh waters

A novel technique has been developed for determining the ²¹²Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from ²¹²Pb varies, and is difficult to experimentally measure due to its relatively short half-life (t_½ = 10.6 h) and low environmental activity (<0.1 Bq l⁻¹). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l⁻¹ with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of ²¹²Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.     

Social and ecological facets of pest management in Honduran subsistence agriculture: implications for IPM extension and natural resource management

In subsistence farming systems of the developing world, adoption of resource-conserving practices such as integrated pest management (IPM) is often strikingly low. This has partially been ascribed to researchers’ limited understanding of how technologies develop at the interface of the systems’ social and ecological components. In Honduras (Central America), there exists concern about limited adoption and diffusion of IPM technologies in certain smallholder production systems. In this study, we determine social and ecological drivers of IPM adoption in subsistence maize production in the country’s hillside environment. Honduran small-scale maize production is typified by a key insect pest (the fall armyworm, Spodoptera frugiperda) being partly kept at bay through action of a diverse natural enemy complex, including ants, social wasps, carabid beetles, and spiders. Local agricultural landscapes, primarily shaped through shifting cultivation, provide key resources to maintain this natural enemy diversity. These local ecological conditions and related natural enemy abundance strongly influence farmers’ agroecological knowledge and pest management practices. In the meantime, farmer practices are also affected by local communication networks, which help validate and spread IPM concepts and technologies. Based on our findings, we advocate a holistic approach to improve IPM extension through mapping of agroecological opportunities, visualization of regional patterns in farmer knowledge, and associated priority setting. Local IPM capacity could be built through institutional strengthening and adaptive comanagement, while IPM training should be linked with natural resource management initiatives. These approaches may eventually improve the way IPM is delivered to small-scale farmers who operate in the ecologically diverse environments of the tropics.     

Consumptive values and local perception of dry forest decline in Burkina Faso,West Africa

Traditional ecological knowledge and local experience of resource management and the usefulness of plant species can make important contributions to attempts to understand forest ecosystems and to develop effective sustainable management strategies for them. Therefore, the utilization of tree species by local people, their perceptions of changes in the surrounding forests, and suggested solutions for associated problems, were studied in the Sissili province of southern Burkina Faso. Information was collected through a combination of participatory rural appraisals, household interviews, and observational methods. Principal component analysis was used to analyze the consumptive values of woody species and their respective parts. A total of 82 species were identified, 90% of them were used for medicinal purposes, 78% for fodder, 73% for food, 67% for house construction, and 58% for wood carving. This suggests that forests play a key role in sustaining the rural livelihood and contributing to poverty reduction. The various stakeholders perceived that vegetation clearing for cultivation of cash crops (agribusiness) was the main driver of the change in forest cover. Species reported to be declining in the area included Parkia biglobosa, Pterocarpus erinaceus, Afzelia africana, Bombax costatum, Tamarindus indica, and Diospyros mespiliformis. Thus, a concerted effort should be made to manage the remaining natural forests in the country. Appropriate management strategies should be developed jointly by the local communities and external support groups to integrate the valuable local knowledge about forest species with the stakeholders’ suggestions in order to promote sustainable management of the region’s forest ecosystems.     

The cost effectiveness of radon reduction programmes in domestic housing in England and Wales: The impact of improved radon mapping and housing trends

In the UK, excessive levels of radon gas have been detected in domestic housing. Areas where 1% of existing homes were found to be over the Action Level of 200 Bq · m^− 3 were declared to be Radon Affected Areas. Building Regulations have been introduced which require that, for areas where between 3% and 10% of existing houses are above the Action Level, new homes should be built with basic radon protection using a membrane, and that, where 10% or more of existing homes exceed this level, new homes should be built with full radon protection.Initially these affected areas followed administrative boundaries, known as Counties. However, with increasing numbers of measurements of radon levels in domestic homes recorded in the national database, these areas have been successively refined into smaller units – 5 km grid squares in 1999, down to 1 km grid squares in 2007.One result is the identification of small areas with raised radon levels within regions where previously no problem had been identified. In addition, some parts of areas that were previously considered radon affected are now considered low, or no, risk. Our analysis suggests that the net result of improved mapping is to increase the number of affected houses. Further, the process is more complex for local builders, and inspectors, who need to work out whether radon protection in new homes is appropriate.Our group has assessed the cost-effectiveness of radon remediation programmes, and has applied this analysis to consider the cost-effectiveness of providing radon protection in both new and existing homes. This includes modelling the potential failure rate of membranes, and whether testing radon levels in new homes is appropriate. The analysis concludes that it is more cost effective to provide targeted radon protection in high radon areas, although this introduces more complexity.The paper also considers the trend in housing to a greater proportion of apartments, the regional variations in types of housing and the decreasing average number of occupants in each dwelling, and concludes that data and methods are now available to respond to the health risks of radon at a local level, in keeping with a general initiative to prioritise responses to health and social welfare issues at a more local level.     

Effects of acute γ-irradiation on the aquatic microbial microcosm in comparison with chemicals

Effects of acute γ-irradiation were investigated in the aquatic microcosm consisting of green algae (Chlorella sp. and Scenedesmus sp.) and a blue–green alga (Tolypothrix sp.) as producers; an oligochaete (Aeolosoma hemprichi), rotifers (Lecane sp. and Philodina sp.) and a ciliate protozoan (Cyclidium glaucoma) as consumers; and more than four species of bacteria as decomposers. At 100 Gy, populations were not affected in any taxa. At 500–5000 Gy, one or three taxa died out and populations of two or three taxa decreased over time, while that of Tolypothrix sp. increased. This Tolypothrix sp. increase was likely an indirect effect due to interspecies interactions. The principal response curve analysis revealed that the main trend of the effects was a dose-dependent population decrease. For a better understanding of radiation risks in aquatic microbial communities, effect doses of γ-rays compared with copper, herbicides and detergents were evaluated using the radiochemoecological conceptual model and the effect index for microcosm.     

Exposure and vulnerability to climate extremes: population and asset exposure to coastal flooding in Dar es Salaam, Tanzania

The paper provides a first quantitative estimate of the potential number of people and value of assets exposed to coastal flooding in Dar es Salaam, Tanzania. The study used an elevation-based geographic information system-analysis based on physical exposure and socio-economic vulnerability under a range of climate and socio-economic scenarios. It particularly considered a worst-case scenario assuming even if defences (natural and/or man-made) exist, they are subjected to failure under a 100-year flood event. About 8% of Dar es Salaam lies within the low-elevation coastal zone (below the 10 m contour lines). Over 210,000 people could be exposed to a 100-year coastal flood event by 2070, up from 30,000 people in 2005. The asset that could be damaged due to such event is also estimated to rise from US35 million (2005) to US35 million (2005) to US10 billion (2070). Results show that socio-economic changes in terms of rapid population growth, urbanisation, economic growth, and their spatial distribution play a significant role over climate change in the overall increase in exposure. However, the study illustrates that steering development away from low-lying areas that are not (or less) threatened by sea-level rise and extreme climates could be an effective strategic response to reduce the future growth in exposure. Enforcement of such policy where informal settlements dominate urbanisation (as in many developing countries) could undoubtedly be a major issue. It should be recognised that this analysis only provides indicative results. Lack of sufficient and good quality observational local climate data (e.g. long-term sea-level measurements), finer-resolution spatial population and asset distribution and local elevation data, and detailed information about existing coastal defences and current protection levels are identified as limitations of the study. As such, it should be seen as a first step towards analysing these issues and needs to be followed by more detailed, city-based analyses.     

Ecologically optimal nitrogen application rates for rice cropping in the Taihu Lake region of China

Excessive nitrogen (N) fertilization in intensive agricultural areas in the Taihu Lake region of East China has resulted in low N utilization efficiency and serious environmental problems, giving rise to the need for an urgent reduction in the N fertilization rate. However, no holistic evaluations of rice (Oryza sativa L.) yield effect and environmental effects of N fertilization have been conducted when recommending an optimal N rate. The current study provides an economic indicator and an evaluation model to account for the environmental effects of different N losses after N fertilizer application in the ecological and economic N rate for one rice season in the Taihu Lake region. Based on the assembled data and economic index, a general economic evaluation model to measure efficiently the cascading costs of the chemical N cycle at the regional scale was developed. Thereafter, fertilizer-stimulated benefit curves and fertilizer-induced cost curves were generated to determine an economically and ecologically optimal N application rate. The results revealed that the maximum net benefits were 3,123 yuan ha⁻¹ at 202 kg N ha⁻¹ for one rice season in the Taihu Lake region. Additional N application up to a rate of 263 kg N ha⁻¹ would increase rice production, but the increase in the total marginal costs would be slightly greater than the increase in marginal benefits. Among the marginal costs, the fertilizer and acidification costs were the greatest expenses, amounting to 1,716 yuan at 263 kg N ha⁻¹, followed by eutrophication and global warming costs. When compared with the conventional N fertilization rate, this recommended rate could decrease the amount of N applied to rice from 10 to 40%, thereby, enabling optimum economic and ecological results.