Offspring sex ratio variation in the bridled nailtail wallaby, Onychogalea fraenata

The bridled nailtail wallaby is a sexually size dimorphic, promiscuous, solitary macropod. Sex ratios of pouch young were studied at two sites over 3 years, beginning with 14 months of severe drought. Females that were in better condition were more likely to have sons, and condition was dependent on body size. Females at one site were heavier, were consequently in better condition, and produced more sons than females at the other site. Females that declined in condition had more daughters during the most severe part of the drought than females that maintained condition, but endoparasite infection did not affect the pouch young sex ratio. Age also appeared to affect sex ratio adjustment, because weight was strongly influenced by age. Sex ratio bias was not caused by early offspring mortality, but occurred at conception. Mothers did not appear to bias energy expenditure on sons or daughters; males and females did not differ in condition at the end of pouch life. Pouch young sex ratio variation was most consistent with the Trivers-Willard hypothesis, but could also have been influenced by local resource competition, since sons dispersed further than daughters. Offspring condition was related to survival, and was correlated with maternal condition. Received: 14 April 1998 / Accepted after revision: 10 November 1998     

How does burrowing by the isopod <Emphasis Type="Italic">Limnoria agrostisa</Emphasis> (Crustacea: Limnoriidae) affect the leaf canopy of the southern Australian seagrass <Emphasis Type="Italic">Amphibolis griffithii</Emphasis>?

In south-western Australia, the isopod Limnoria agrostisa commonly burrows into leaf clusters and immature shoots of Amphibolis griffithii. The isopod also burrows into the sheath and rhizomes of Posidonia species. In A. griffithii, the isopod consumes new tissue within the sheath, damaging or destroying the meristem. This results in malformation of new leaves or destruction of whole leaf clusters with the potential to reduce the photosynthetic area of a shoot. The isopod has been found in all but one meadow of A. griffithii examined over 1,000 km of the Western Australian coastline. It was present throughout the year and showed little variation in abundance. Young were produced year round, but were more abundant in the summer months. Females, 3.5 mm in length or larger, produced 2–5 young that were brooded within the leaf cluster or base of an immature shoot. Within a meadow, 40–70% of shoots and 10–20% of leaf clusters were damaged by isopods. Seasonal trends were not consistent, but damage appeared to be higher in summer when isopod abundance was higher. Approximately 40% of clusters were destroyed by isopod damage. Isopods attack shoots of all ages, but damage was often located on apical clusters. There was no evidence that isopod damage initiated branching or leaf cluster formation. Estimations of clusters damaged or destroyed may be conservative, as only those clusters remaining on a shoot could be counted, and cluster loss could not be quantified. Examination of defoliated stems on upright shoots and horizontal rhizomes indicated that many were destroyed by isopods. The effect of L. agrostisa although substantial appears to be a feature of healthy seagrasses throughout southern Australia.     

Restoration Scaling Approaches to Addressing Ecological Injury: The Habitat-Based Resource Equivalency Method

Environmental Management - Natural resource trustee agencies must determine how much, and what type of environmental restoration will compensate for injuries to natural resources that result from...     

Manganese and trace-metal mobility under reducing conditions following in situ oxidation of TCE by KMnO4: a laboratory column experiment

The stability of Mn oxides, and the potential for mobilization of associated trace metals, were assessed by simulating the onset of microbially-mediated reducing conditions in a continuous-flow column experiment. The column had previously been used for an in situ chemical oxidation (ISCO) experiment in which trichloroethylene was reacted with permanganate in the presence of aqueous trace metals, which produced Mn oxyhydroxides (MnO(x)) that sequestered the trace metals and coated the column sand. The column influent solution represented the incursion of ambient groundwater containing dissolved organic carbon (DOC) into an ISCO treatment zone. The influx of DOC-containing groundwater initiated a series of cation-exchange, surface-complexation and reductive-dissolution reactions that controlled the release of aqueous metals from the system. Peak concentrations in the effluent occurred in the order Na, Mo, Cr, Zn, K, Mn, Fe, Pb, Mg, Ni, Cu and Ca. Manganese release from the column was controlled by a combination of cation exchange, reductive dissolution and precipitation of rhodochrosite. The trend in Fe concentrations was similar to that of Mn, and also resulted from a combination of reductive dissolution and cation exchange. Cation exchange and/or surface-complexation were the primary mechanisms controlling Cu, Ni, Mo and Pb release to solution, while Zn and Cr concentrations did not display coherent trends. Although metal release from the treatment zone was evident in the data, concentrations of trace metals remained below 0.05 mg L(-1) with the exception of Mo which reached concentrations on the order of 1 mg L(-1). The establishment of anaerobic conditions in ISCO-treated aquifers may result in a prolonged flux of aqueous Mn(II), but with the exception of MoO(4)(2-), it is unlikely that trace metals sequestered with MnO(x) during ISCO will be released to the groundwater in elevated concentrations.     

Community Perception of Water Quality in a Mining-Affected Area: A Case Study for the Certej Catchment in the Apuseni Mountains in Romania

Mining-contaminated sites and the affected communities at risk are important issues on the agenda of both researchers and policy makers, particularly in the former communist block countries in Eastern Europe. Integrated analyses and expert based assessments concerning mining affected areas are important in providing solid policy guidelines for environmental and social risk management and mitigation. Based on a survey for 103 households conducted in a former mining site in the Certej Catchment of the Apuseni Mountains, western Romania, this study assesses local communities’ perceptions on the quality of water in their living area. Logistic regression was used to examine peoples’ perception on the quality of the main river water and of the drinking water based on several predictors relating to social and economic conditions. The results from the perception analysis were then compared with the measurements of heavy metal contamination of the main river and drinking water undertaken in the same study area. The findings indicate that perception and measurement results for the water quality in the Certej Catchment are convergent, suggesting an obvious risk that mining activities pose on the surface water. However, the perception on drinking water quality was little predicted by the regression model and does not seem to be so much related to mining as to other explanatory factors, such as special mineralogy of rock and soils or improper water treatment infrastructure, facts suggested by the measurements of the contaminants. Discussion about the implications of these joint findings for risk mitigation policies completes this article.     

Constrained Choice and Ethical Dilemmas in Land Management: Environmental Quality and Food Safety in California Agriculture

As environmental and conservation efforts increasingly turn towards agricultural landscapes, it is important to understand how land management decisions are made by agricultural producers. While previous studies have explored producer decision-making, many fail to recognize the importance of external structural influences. This paper uses a case study to explore how consolidated markets and increasing corporate power in the food system can constrain producer choice and create ethical dilemmas over land management. Crop growers in the Central Coast region of California face conflicting demands regarding environmental quality and industry imposed food safety standards. A mail survey and personal interviews were used to explore growers’ perceptions and actions regarding these demands. Results indicate that in many cases growers face serious ethical dilemmas and feel pressured by large processing and retail firms to adopt measures they find environmentally destructive and unethical. Future strategies to address environmental issues on agricultural landscapes should consider the economic constraints producers face and the role of large firms in creating production standards.     

Monitoring and assessment of radionuclide discharges from Temelín Nuclear Power Plant into the Vltava River (Czech Republic)

The paper summarizes impacts of the Temelín Nuclear Power Plant (NPP) on the Vltava and Labe River basins. The study is based on the results of long-term monitoring carried out before the plant operation (1989–2000), and subsequently during the plant operation (2001–2005). In the first period, the main objective was to determine background radionuclide levels remaining in the environment after global fallout and due to the Chernobyl accident. A decrease in the concentrations of ⁹⁰Sr, ¹³⁴Cs and ¹³⁷Cs, which was observed before the plant operation, continued also during the subsequent period. Apart from tritium, the results of the observation did not indicate any impacts of the plant on the concentrations of activation and fission products in the hydrosphere. The annual average tritium concentrations in the Vltava River were in agreement with predicted values. The maximum annual average tritium concentration (13.5 Bq L⁻¹) was observed in 2004 downstream from the wastewater discharge in the Vltava River at Solenice. Estimated radiation doses for adults due to intakes of river water as drinking water contaminated by tritium are below 0.1 μSv y⁻¹.     

Effects of meteorology on diurnal and nocturnal levels of priority polycyclic aromatic hydrocarbons and elemental and organic carbon in PM10 at a source and a receptor area in Mexico City

PM₁₀ levels of the 16 US-EPA Priority Pollutant polycyclic aromatic hydrocarbons (PAHs) were measured from March 17 to 31, 2003, in 8-h time bins (morning, afternoon and nighttime) at Merced, a source site dominated by vehicular traffic emissions near the center of Mexico City, and at Pedregal, a receptor area located downwind in a residential area of low traffic. Along with PAH, elemental (EC) and organic carbon (OC), mass, and prevailing meteorological parameters were measured. At the source location, measured concentrations of benzo[a]pyrene (BAP), an agent suspected of being carcinogenic to humans and of causing oxidative DNA damage, reached concentrations as high as 2.04 and 2.11 ng m^?3 during the morning of a weekday and the night period of a holiday. Compared with source dominated areas in Central Los Angeles, the BAP levels found in Central Mexico City are approximately 6 times higher. Benzo[ghi]perylene (BGP) levels were, in general, the highest among the target PAH, both at the source (7.2 ng m^?3) and the receptor site (2.8 ng m^?3), suggesting that, at both locations, exhaust emission by light-duty (LD) vehicles is an important contributor to the atmospheric PAH burden. Higher PAH concentrations were observed during the morning period (5:00–13:00 h) at the source and the receptor site. The concentrations of PAHs found predominantly in the particle-phase (MW > 202) correlated well (r = 0.57–0.71) with the occurrence of surface thermal inversions and with mixing heights (r = ?0.57 to ?0.72). Organic and elemental carbon ratios also indicated that Pedregal is impacted by secondary aerosols during the afternoon hours.     

Risk to water security for small islands: an assessment framework and application

The freshwater resources of small islands are particularly vulnerable to the impacts of climate change and human stressors due to their limited extent and adaptive capacity. A water security approach is useful for effective management of the water resources; however, understanding risk to water security is critical in order to effectively plan and adapt to future changes. Currently available assessment tools generally do not incorporate risk and are not suitable for application on small islands, where the hydrogeological setting has unique vulnerabilities. The aim of this work is to provide a framework to characterize risk to water security for small islands. The risk assessment was developed using Andros Island, the Bahamas, as a case study area. Numerical modelling characterizes the response of the water system to potential future stressors related to climate change and human development, the results of which are integrated into the assessment framework. Based on risk assessment principles, indicators are determined for susceptibility, hazard threat, vulnerability and loss, in order to define the risk to water security. The resulting indicators are presented in geospatial maps that rank areas of risk to water security. These maps were provided to local water managers and policy-makers in the Bahamas as a tool to identify high-risk areas for near-term action and to inform long-term planning. The maps have also been used as a platform to engage local residents and raise awareness about the impact climate change and land-use activities may have on water security.     

Armed conflict distribution in global drylands through the lens of a typology of socio-ecological vulnerability

Motivated by an inconclusive debate over implications of resource scarcity for violent conflict, and common reliance on national data and linear models, we investigate the relationship between socio-ecological vulnerability and armed conflict in global drylands on a subnational level. Our study emanates from a global typology of smallholder farmers’ vulnerability to environmental and socioeconomic stresses in drylands. This typology is composed of eight typical value combinations of variables indicating environmental scarcities, resource overuse, and poverty-related factors in a widely subnational spatial resolution. We investigate the relationships between the spatial distribution of these combinations, or vulnerability profiles, and geocoded armed conflicts, and find that conflicts are heterogeneously distributed according to these profiles. Four profiles distributed across low- and middle-income countries comprise all drylands conflicts. Comparing models for conflict incidence using logit regression and receiver operator characteristic analysis based on (1) the set of all seven indicators as independent variables and (2) a single, only vulnerability profile-based variable proves that the nonlinear typology-based variable is the better explanans for conflict incidence. Inspection of the profiles’ value combinations makes this understandable: A systematic explanation of conflict incidence and absence across all degrees of natural resource endowments is only reached through varying importance of poverty and resource overuse depending on the level of endowment. These are nonlinear interactions between the explaining variables. Conflict does not generally increase with resource scarcity or overuse. Comparison with conflict case studies showed both good agreement with our results and promise in expanding the set of indicators. Based on our findings and supporting literature, we argue that part of the debate over implications of resource scarcity for violent conflict in drylands may be resolved by acknowledging and accounting for nonlinear processes.