Deltaic environments are often densely populated with high socio-economic values, and thus are hotspots of climatic, environmental and anthropogenic change. Large scale engineered structures, such as dike systems, have played an important role in shaping both environmental and socio-economic conditions in deltas, with such interventions more likely where there is a high population and a wealthy economy. Engineered interventions interact with the morphological evolution of the delta, reducing or removing sedimentation and accelerating subsidence, increasing the consequences of flooding and necessitating further adaptation. They also encourage further development, reinforcing this feedback. Thus, in these cases, the deltaic landscape and associated livelihoods can be considered to be the result of a coevolution process between natural delta processes and human engineered interventions. This paper explores this hypothesis. It analyses the history of large scale engineering interventions and their implications in five representative, large, populated deltas across the globe (Ganges-Brahmaputra-Meghna, Yangtze, Rhine-Meuse-Scheldt, Mekong and Nile). The results demonstrate coevolution has occurred and indicate that the response type and the management approach of these engineered structures have significant implications for future delta development. To understand and manage unintended consequences and the development of lock-in trajectories in deltas, a systematic understanding of delta development, including these coevolution processes is essential.
Lead (Pb) exposure in wildlife is a widespread management and conservation concern. Quantitative determination of Pb concentrations in wildlife tissues is the foundation for estimating exposure and risk. Development of low-cost, portable instruments has improved access and cost-effectiveness of determining Pb concentrations in blood samples, while also facilitating the ability for wildlife researchers to conduct near real-time Pb testing. However, these instruments, which use anodic stripping voltammetry (ASV) methodology, may produce an analytical bias in wildlife-blood Pb concentrations. Additionally, their simplicity invites use without appropriate quality-assurance-quality-control measures. Together, these factors can reduce data quality and hamper the ability to evaluate it, raising concerns about use of these instruments to inform important conservation issues. We document the extent to which this bias is addressed in the wildlife toxicology literature, develop quantitative approaches for correcting the bias, and provide recommendations to ensure robust data quality when using these instruments. Of the 25 studies we reviewed that referenced ASV use for determining Pb exposure in wildlife, only 32% acknowledged the existence of bias from the instrument. Importantly, another 20% of the studies actually reported ASV and spectroscopic-based results together without acknowledging their lack of equivalence. Using a multispecies data set of avian blood Pb concentrations, we found that ASV-based estimates of paired blood Pb concentrations were 30-38% lower than those from standard spectrometric-based methods. We provide regression equations based on this analysis of 453 blood samples to allow users of ASV instruments to adjust Pb concentrations to spectrometricequivalent values, and propose a series of guidelines to follow when using these instruments to improve data validity. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.KEY WORDS anodic stripping voltammetry, blood lead, graphite-furnace atomic absorption spectrometry, inductively-coupled mass spectrometry, LeadCare 1 , portable lead analyzer.
We investigated threats to the California condor (Gymnogyps californianus), a flagship endangered species, using individual data on survival during a 20 year period of intensive recovery efforts. Over the two decades of reintroductions, condors in California had an estimated median survival time of 7.8 years suggesting that 50% of condors are expected to survive in the wild long enough to contribute to recruitment. In general, annual mortality rates exceeded levels necessary for a stable population; however, mortality declined, reaching levels needed for population stability, during the second decade of re-establishment. Intensive management practices, including utility pole aversion training and clinical interventions to prevent lead-related deaths likely contributed to the decrease in mortality rates. Utility line collision and/or electrocution was an important factor causing mortality over the two decades; though, this threat has largely been mitigated through management and targeted efforts in high-risk areas. In the past, wildfires were not considered a major threat to survival of freeflying condors. However, our analyses suggest that forest fires are significantly linked to the hazard of death, and increased wildfire activity in California highlights this population's vulnerability to catastrophic losses from forest fire. Lead poisoning, which was a major driver in the population's decline, was a leading cause of death accounting for the greatest adult mortality, and lead exposure remains the most significant threat. Recent lead ammunition reduction efforts in the condor range in California hold promise for improving the recovery potential for this population.
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