Migration,remittances, livelihood trajectories,and social resilience

We argue that all aspects of demographic change, including migration, impact on the social resilience of individuals and communities, as well as on the sustainability of the underlying resource base. Social resilience is the ability to cope with and adapt to environmental and social change mediated through appropriate institutions. We investigate one aspect of the relationship between demographic change, social resilience, and sustainable development in contemporary coastal Vietnam: the effects of migration and remittances on resource-dependent communities in population source areas. We find, using longitudinal data on livelihood sources, that emigration and remittances have offsetting effects on resilience within an evolving social and political context. Emigration is occurring concurrently with, not driving, the expansion of unsustainable coastal aquaculture. Increasing economic inequality also undermines social resilience. At the same time diversification and increasing income levels are beneficial for resilience.     

Insectivorous birds consume an estimated 400–500 million tons of prey annually

In this paper, we present an estimate of the predation impact of the global population of insectivorous birds based on 103 (for the most part) published studies of prey consumption (kg ha^?1 season^?1) of insectivorous birds in seven biome types. By extrapolation—taking into account the global land cover of the various biomes—an estimate of the annual prey consumption of the world’s insectivorous birds was obtained. We estimate the prey biomass consumed by the world’s insectivorous birds to be somewhere between 400 and 500 million metric tons year^?1, but most likely at the lower end of this range (corresponding to an energy consumption of ≈?2.7?×?10¹⁸ J year^?1 or ≈?0.15% of the global terrestrial net primary production). Birds in forests account for >?70% of the global annual prey consumption of insectivorous birds (≥?300 million tons year^?1), whereas birds in other biomes (savannas and grasslands, croplands, deserts, and Arctic tundra) are less significant contributors (≥?100 million tons year^?1). Especially during the breeding season, when adult birds feed their nestlings protein-rich prey, large numbers of herbivorous insects (i.e., primarily in the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, and Orthoptera) supplemented by spiders are captured. The estimates presented in this paper emphasize the ecological and economic importance of insectivorous birds in suppressing potentially harmful insect pests on a global scale—especially in forested areas.     

A new generic approach for estimating the concentrations of down-the-drain chemicals at catchment and national scale

A new generic approach for estimating chemical concentrations in rivers at catchment and national scales is presented. Domestic chemical loads in waste water are estimated using gridded population data. River flows are estimated by combining predicted runoff with topographically derived flow direction. Regional scale exposure is characterised by two summary statistics: PEC(works), the average concentration immediately downstream of emission points, and, PEC(area), the catchment-average chemical concentration. The method was applied to boron at national (England and Wales) and catchment (Aire-Calder) scales. Predicted concentrations were within 50% of measured mean values in the Aire-Calder catchment and in agreement with results from the GREAT-ER model. The concentration grids generated provide a picture of the spatial distribution of expected chemical concentrations at various scales, and can be used to identify areas of potentially high risk.     

Mass balance modelling of contaminants in river basins: application of the flexible matrix approach

It is useful to have available a variety of catchment-scale water quality models that range in complexity, spatial resolution and data requirements. In a previous paper [Warren, C., Mackay, D., Whelan, M., Fox, K., 2005. Mass balance modelling of contaminants in river basins: a flexible matrix approach. Chemosphere 61, 1458-1467] a series of simple to intermediately complex mass balance models was presented which can be used for tiered exposure assessments in river basins. The connectivity of the segments is expressed using a matrix that permits flexibility in application, enabling the model to be re-segmented and applied to different catchments as required. In this paper, the intermediate models, QWASI matrix-rate constant (QMX-R) and QWASI matrix-fugacity (QMX-F) are used to estimate concentrations of linear alkylbenzene sulfonates (LAS) in the rivers Aire and Calder, UK, and of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the Fraser River basin, Canada. The results compare satisfactorily with monitoring data, suggesting that these QWASI-based models for exposure and risk assessment may be applicable under data-limited conditions. The use of QWASI-based models for regulatory purposes in an evaluative river system is also discussed with reference to assessments of para-dichlorobenzene (pDCB), trichloroethylene (TCE), bis(2-ethylhexyl) phthalate (DEHP) and toluene. It is shown that multi-media QWASI model predictions can be usefully depicted graphically on chemical space diagrams and used to highlight regions in which advection, partitioning to sediments and volatilization may be important determinants of chemical fate in river systems.     

Study of biological stabilization processes of cattle and poultry manure by thermogravimetric analysis and (13)C NMR

The biological stabilization process of cattle and poultry manure was studied using thermogravimetric analysis and (13)C nuclear magnetic resonance. The stabilization processes carried out were composting, anaerobic digestion and a mixed process (partly aerobic, partly anaerobic). It was observed from the analyzed samples that the biological stabilization processes reduce the volatile content of the bio-wastes and increase the degree of aromaticity. The stabilization of cattle manure by means of aerobic processes was able to further oxidize and enriched in aromatic compounds the bio-waste when compared with the digestion process. On the other hand, the stabilization of poultry manure resulted in a greater aromatization under the digestion process. Stabilized samples with a high degree of aromaticity presented a lower volatile content accompanied by a reduction in the intensity of the differential thermogravimetry peak registered under an inert atmosphere, indicative of the thermal decomposition of the organic matter. The thermal decomposition of all the analyzed materials (fresh and stabilized samples) commenced at around 200 degrees C but for the digested poultry manure, which decomposition initiated close to 250 degrees C. All stabilized samples yielded a lower degree of volatilization to that one observed in fresh samples.     

A comparison of river water quality sampling methodologies under highly variable load conditions

When river water quality fluctuates over relatively short periods of time with respect to the sampling frequency, the collection of grab samples may be inappropriate for characterising average water quality. This paper presents the results of a water quality monitoring study carried out on a stretch of the river Lambro (northern Italy) dominated by a periodically overloaded sewage treatment works (STW) located near its upstream end. Water quality was strongly influenced by a pronounced diurnal cycle in pollutant loads caused by the regular emission of untreated waste water during periods of high domestic flow (daytime). Two different sampling techniques were employed: grab sampling and 24-h composite sampling using automatic samplers. Samples were collected at the plant overflow and at several sites along the river and analysed for two common ingredients of household detergents, linear alkylbenzene sulphonate (LAS) and boron (B) and for routine water quality variables. The results obtained show that: (1) The diurnal variability of point-source-derived chemical concentrations in the river downstream of the undersized STW increased with increasing removal efficiency in sewage treatment. (2) The shape of the diurnal concentration signal remained relatively intact for a considerable distance downstream of the STW for several water quality variables, suggesting that hydrodynamic dispersion plays a relatively minor role in controlling concentration patterns in this river. (3) In-stream degradation of LAS was consistent with first order kinetics with a rate constant of 0.05-0.06 h(-1). (4) Grab sampling is a relatively inefficient methodology for capturing mean concentrations for rivers subjected to highly variable loads, especially when it is restricted to office hours. The inefficiency of grab sampling is more marked for substances (e.g. LAS) which are effectively removed during sewage treatment than for substances which are not. (5) For LAS, diurnal variability in the concentration signal decreases with distance downstream, making grab sampling an increasingly reliable methodology for estimating mean concentrations. (6) 24-h composite sampling is an efficient way of eliminating the effect of diurnal variations in load strength.     

A Molecular Genetic Assessment of Mating-System Variation in a Naturally Bird-Pollinated Shrub: Contributions from Birds and Introduced Honeybees

Abstract: Introductions of European honeybees have occurred globally, potentially affecting the natural pollination ecology of many plants. Introduced honeybees are now the most frequent visitors to the inflorescences of the self-compatible, bird-pollinated Australian shrub Grevillea macleayana and may therefore be expected to have altered the mating system. To examine the degree to which birds continue to play a role in determining the mating system of G. macleayana in this disturbed system, we compared outcrossing rates in open-pollinated inflorescences with inflorescences from which birds had been selectively excluded. Outcrossing rates were estimated from the microsatellite genotypes of over 100 seeds per population in three populations. Outcrossing rates (  t ) in open-pollinated seeds were surprisingly low (0.062–0.225) and did not vary significantly among the three populations. Nevertheless, outcrossing was significantly lower when birds were excluded (data pooled from all populations). Two lines of evidence suggest that there are temporal fluctuations in outcrossing rate and hence that birds usually have a major effect on the mating system of G. macleayana . First, at one site, t was substantially lower than estimates from an earlier study (0.06 in 1995 cf. 0.85 in 1990). Second, fixation indices based on seeds were high in all populations (  >0.68), whereas values for the established plants ( parental generation) were much lower in two of the three populations (0.06–0.32). Our findings suggest that honeybee activity is so high that the contribution of birds to pollination in G. macleayana is sometimes relatively trivial.     

Movement of diuron and hexazinone in clay soil and infiltrated pond water

Pre-emergence herbicide residues were detected in domestic wells sampled near Tracy, CA. This study sought to determine the source of contamination by comparing soil distribution of diuron [N'-(3,4-dichlorophenyl)-N,N-dimethylurea] and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] in an agricultural field where the soil was a cracking clay to infiltration of residues in water captured by an adjacent holding pond. Diuron and hexazinone were applied in December to a 3-yr-old alfalfa (Medicago sativa L.) crop. Water content of soil taken after major rainfall but before irrigation at 106 d after application was elevated at the lowest depth sampled centered at 953 mm, indicating water was available for percolation. Herbicide residues (reporting limit 8 microg kg(-1)) were confined above the 152 mm soil depth, even after subsequent application of two border-check surface irrigations. The pattern of distribution and concentration of residues in the soil were similar to results obtained from the LEACHM model, suggesting that macropore flow was limited to a shallow depth of soil. Herbicide residues were measured in runoff water at the first irrigation at 20 microg L(-1) for diuron and 1 microg L(-1) for hexazinone. Runoff water captured in the pond rapidly infiltrated into the subsurface soil, causing a concomitant rise in ground water elevation near the pond. Herbicide residues were also detected in the sampled ground water. We concluded that the pond was the predominant source for movement to ground water. Since addition of a surfactant to the spray mixture did not reduce concentrations in runoff water, mitigation methods will focus on minimizing infiltration of water from the pond.