A Strategy for Prioritizing Threats and Recovery Actions for At-Risk Species

Ensuring the persistence of at-risk species depends on implementing conservation actions that ameliorate threats. We developed and implemented a method to quantify the relative importance of threats and to prioritize recovery actions based on their potential to affect risk to Mojave desert tortoises (Gopherus agassizii). We used assessments of threat importance and elasticities of demographic rates from population matrix models to estimate the relative contributions of threats to overall increase in risk to the population. We found that urbanization, human access, military operations, disease, and illegal use of off highway vehicles are the most serious threats to the desert tortoise range-wide. These results suggest that, overall, recovery actions that decrease habitat loss, predation, and crushing will be most effective for recovery; specifically, we found that habitat restoration, topic-specific environmental education, and land acquisition are most likely to result in the greatest decrease in risk to the desert tortoise across its range. In addition, we have developed an application that manages the conceptual model and all supporting information and calculates threat severity and potential effectiveness of recovery actions. Our analytical approach provides an objective process for quantifying threats, prioritizing recovery actions, and developing monitoring metrics for those actions for adaptive management of any at-risk species.     

Field test of best management practice pollutant removal efficiencies in Shenzhen, China

This paper presents a study on the use of best management practices (BMPs) for controlling nonpoint pollution in the Xikeng Reservoir watershed located in Shenzhen, China. A BMP treatment train design, including a pond, a wetland, and a buffer strip placed in series was implemented at the reservoir location. A separate grass swale was also constructed at the site. Low impact development (LID) BMPs, namely a planter box and bioboxes, were used at the parking lot of the reservoir’s Administration Building. Samples were collected during storm events and were analyzed for total suspended solids (TSS), biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃-N), and total phosphorus (TP). The removal efficiencies of both BMP systems were evaluated using the Efficiency Ratio (ER) method based on the event mean concentration (EMC) data. In summary, the pond/wetland treatment train removed 70%–90% of TSS, 20%–50% of BOD₅, and 30%–70% of TP and NH₃-N. The swale removed 50%–90% of TSS, 30%–55% of BOD₅, − 10%–35% of NH₃-N, and 25%–70% of TP. For the planter box and biobox, the ranges of removal rates were 70%–90%, 20%–50%, and 30%–70% for TSS, BOD₅, and ammonia and phosphorus, respectively.     

A value-based approach to infrastructure resilience

This paper includes the findings of MMI Thornton Tomasetti’s investigation into the measurement of resilience within infrastructure using systems thinking and focussed on value delivery. This paper provides a review of current practise across critical infrastructure sectors, based on a series of interviews undertaken with stakeholders from various UK infrastructure organisations. Gaps and opportunities were identified and an outline for a value-based approach to diagnosing, measuring and building resilience suggested. The performance of critical infrastructure sectors was also comparatively assessed using the suggested approach value metrics.     

Treatability aspects of urban stormwater stressors

Pollution from diffuse sources (pollution from contaminants picked up and carried into surface waters by stormwater runoff) has been identified as a significant source of water quality problems in the U.S. scientists and engineers continue to seek solutions that will allow them to optimize existing technologies and develop new ones that will provide the best possible protection to people, wildlife, and the environment. This paper addresses the various pollutants or stressors in urban stormwater, including flow (shear force), pathogens, suspended solids/sediment, toxicants (organic and metals), nutrients, oxygen demanding substances, and coarse solids. A broad overview of the pollutants removed and the removal mechanisms by and of conventional best management practices (BMPs) is also presented. The principal treatment mechanisms of conventional wet ponds, vegetative swales/buffer strips, and wetlands are sedimentation and filtration. These mechanisms have the capability to remove significant amounts of suspended solids or particulate matter and are a vital component of strategies to reduce pollutant loads to receiving waters. In addition, because most of the nation??s receiving water violations are caused by pathogen indicator bacteria, it is of utmost importance that research efforts address this problem. Further research is also needed on the treatment of emerging contaminants in BMPs and on the costs and affects of maintenance and maintenance schedules on the long-term performance of BMPs.     

Environmental filtering and land-use history drive patterns in biomass accumulation in a mediterranean-type landscape

Aboveground biomass (AGB) reflects multiple and often undetermined ecological and land-use processes, yet detailed landscape-level studies of AGB are uncommon due to the difficulty in making consistent measurements at ecologically relevant scales. Working in a protected mediterranean-type landscape (Jasper Ridge Biological Preserve, California, USA), we combined field measurements with remotely sensed data from the Carnegie Airborne Observatory's light detection and ranging (lidar) system to create a detailed AGB map. We then developed a predictive model using a maximum of 56 explanatory variables derived from geologic and historic-ownership maps, a digital elevation model, and geographic coordinates to evaluate possible controls over currently observed AGB patterns. We tested both ordinary least-squares regression (OLS) and autoregressive approaches. OLS explained 44% of the variation in AGB, and simultaneous autoregression with a 100-m neighborhood improved the fit to an r2 = 0.72, while reducing the number of significant predictor variables from 27 variables in the OLS model to 11 variables in the autoregressive model. We also compared the results from these approaches to a more typical field-derived data set; we randomly sampled 5% of the data 1000 times and used the same OLS approach each time. Environmental filters including incident solar radiation, substrate type, and topographic position were significant predictors of AGB in all models. Past ownership was a minor but significant predictor, despite the long history of conservation at the site. The weak predictive power of these environmental variables, and the significant improvement when spatial autocorrelation was incorporated, highlight the importance of land-use history, disturbance regime, and population dynamics as controllers of AGB.     

Field test of best management practice pollutant removal efficiencies in Shenzhen, China

This paper presents a study on the use of best management practices (BMPs) for controlling nonpoint pollution in the Xikeng Reservoir watershed located in Shenzhen, China. A BMP treatment train design, including a pond, a wetland, and a buffer strip placed in series was implemented at the reservoir location. A separate grass swale was also constructed at the site. Low impact development (LID) BMPs, namely a planter box and bioboxes, were used at the parking lot of the reservoir’s Administration Building. Samples were collected during storm events and were analyzed for total suspended solids (TSS), biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃—N), and total phosphorus (TP). The removal efficiencies of both BMP systems were evaluated using the Efficiency Ratio (ER) method based on the event mean concentration (EMC) data. In summary, the pond/wetland treatment train removed 70%―90% of TSS, 20%―50% of BOD₅, and 30%―70% of TP and NH₃—N. The swale removed 50%―90% of TSS, 30%―55% of BOD₅, −10%―35% of NH₃—N, and 25%―70% of TP. For the planter box and biobox, the ranges of removal rates were 70%―90%, 20%―50%, and 30%―70% for TSS, BOD₅, and ammonia and phosphorus, respectively.     

Group size, queuing and helping decisions in facultatively eusocial hover wasps

In facultatively eusocial hover wasps, some females leave their natal nests while others choose to stay and become helpers. We tested whether the decisions of 126 newly emerged females to stay or leave depended on group size: the number of females already resident on their natal nests. We predicted that females would be less likely to stay in larger groups, where the benefits of helping are probably smaller and there is a smaller chance of inheriting the dominant position. We also predicted that unrelated females would be less likely to join larger groups. We manipulated group size by removing residents from nests. Newly emerged females disappeared from their natal nests at a rate of 2.5% per day, but did not disappear from manipulated nests at higher rates than controls. Experimentally reducing group size also did not increase the frequency of joiners. Newly emerged females disappeared at twice the rate of older subordinate females, suggesting the existence of a `leaving window' early in life. One problem is the difficulty of distinguishing between leaving and death. Received: 7 July 1998 / Accepted after revision: 25 October 1998     

Toxicity of TiO2, ZrO2, Fe,Fe2O3, and Mn2O3 nanoparticles to the yeast, Saccharomyces cerevisiae

The growing application of engineered nanomaterials is leading to an increased occurrence of nanoparticles (NPs) in the environment. Thus, there is a need to better understand their potential impact on the environment. This study evaluated the toxicity of nanosized TiO₂, ZrO₂, Fe⁰, Fe₂O₃, and Mn₂O₃ towards the yeast Saccharomyces cerevisiae based on O₂ consumption and cell membrane integrity. In addition, the state of dispersion of the nanoparticles in the bioassay medium was characterized.     

Molecular approaches to microbiological monitoring: fecal source detection

Molecular methods are useful both to monitor natural communities of bacteria, and to track specific bacterial markers in complex environments. Length-heterogeneity polymerase chain reaction (LH-PCR) and terminal restriction fragment length polymorphism (T-RFLP) of 16S rDNAs discriminate among 16S rRNA genes based on length polymorphisms of their PCR products. With these methods, we developed an alternative indicator that distinguishes the source of fecal pollution in water. We amplify 16S rRNA gene fragments from the fecal anaerobic genus Bacteroides with specific primers. Because Bacteroides normally resides in gut habitats, its presence in water indicates fecal pollution. Molecular detection circumvents the complexities of growing anaerobic bacteria. We identified Bacteroides LH-PCR and T-RFLP ribosomal DNA markers unique to either ruminant or human feces. The same unique fecal markers were recovered from polluted natural waters. We cloned and sequenced the unique markers; marker sequences were used to design specific PCR primers that reliably distinguish human from ruminant sources of fecal contamination. Primers for more species are under development. This approach is more sensitive than fecal coliform assays, is comparable in complexity to standard food safety and public health diagnostic tests, and lends itself to automation and high-throughput. Thus molecular genetic markers for fecal anaerobic bacteria hold promise for monitoring bacterial pollution and water quality.