Perchlorate as an environmental contaminant

Perchlorate anion (ClO4-) has been found in drinking water supplies throughout the southwestern United States. It is primarily associated with releases of ammonium perchlorate by defense contractors, military operations, and aerospace programs. Ammonium perchlorate is used as a solid oxidant in missile and rocket propulsion systems. Traces of perchlorate are found in Chile saltpeter, but the use of such fertilizer has not been associated with large scale contamination. Although it is a strong oxidant, perchlorate anion is very persistent in the environment due to the high activation energy associated with its reduction. At high enough concentrations, perchlorate can affect thyroid gland functions, where it is mistakenly taken up in place of iodide. A safe daily exposure has not yet been set, but is expected to be released in 2002. Perchlorate is measured in environmental samples primarily by ion chromatography. It can be removed by anion exchange or membrane filtration. It is destroyed by some biological and chemical processes. The environmental occurrence, toxicity, analytical chemistry, and remediative approaches are discussed.     

Experimental interbreeding between geographically separated populations of the marine wood-boring isopod Limnoria tripunctata with preliminary indications of hybrid vigor

Populations of the marine wood-boring isopod Limnoria tripunctata Menzies were cultivated and interbred in the laboratory in order to determine whether geographically separated populations would interbreed. Two series of interbreeding studies were conducted. In the first, field populations from 11 Atlantic and Caribbean sites and 3 Pacific sites were interbred with a North Western Atlantic population from Beaufort, North Carolina (USA). Viable crossings, to at least F ₁, occurred in all but one case—that of a BeaufortxChatham (Massachusetts, USA) cross. In the second series of experiments, field populations from 9 Atlantic and Caribbean sites were crossed with populations from St. Teresa, Florida, Gulf of Mexico. In this case also, all crosses except one produced viable offspring, not only to the F ₁, but to the F ₂ generations as well. The St. Teresa x Chatham cross was not successful. Geographic distance was not a factor in the success of crossbreeding between disjunct populations. Chatham populations (mainly) are now believed to represent a valid but previously obscure species, Limnoria tuberculata Sowinski, and not a variant of L. tripunctata Menzies. Enhanced viality or vigor, as determined from rate of wood destruction, population growth rate and survival, was indicated in several crossings, but this was not necessarily correlated with distance between populations. Observations were made on the manner in which the species has achieved a worldwide distribution, and a hypothesis is put forward to explain the evolution of species related to L. tripunctata.Contribution from Zoology Department, Duke University, Durham, North Carolina, and Duke University Marine Laboratory, Beaufort, North Carolina, and the Department of Oceanography, No. 289, Florida State University, Tallahassee, Florida. Support in part from NSF Grant No. GB-6898.     

Inter-male competition for high-quality host-plants: the evolution of protandry in a territorial grasshopper

Summary Males of the desert grasshopper Ligurotettix coquilletti typically eclose 3–5 weeks prior to females. Early-eclosed males experience more female encounters than the later-eclosed individuals. Evidence suggests that the number of encounters may be proportional to male lifetime mating success. Early-eclosed males enjoyed greater adult lifespans, occupied and defended higher quality territories (Larrea shrubs), and tended to be dominant on these shrubs if several males were present. The elevated number of female encounters were not conferred on early-eclosed males by their extended survivorship, but rather by the high quality of their territories, which retained numerous females, and their dominant behavior. We evaluate several female-benefit and male-benefit hypotheses for the evolution of protandry and propose that in L. coquilletti, the phenomenon arose due to male-male competition for female-encounter sites, a mechanism not considered in earlier models. Finally, we discuss several reasons for the high variance in the date of male eclosion.     

Externalities, pigouvian corrections, and risk attitudes

We examine the influence of risk attitudes on the provision of an externality and on the proper size of Pigouvian correction when the externality is a random variable whose distribution is affected by an observable externality-generating activity. An intervening technology relates changes in this observable activity to the probability distribution of the relevant externality. Unlike the now-standard result in the theory of the firm involving the influence of risk attitudes on output levels, we cannot conclude that increases in risk aversion will lead necessarily to a reduction in the level of the externality. Our results are applied to a wide range of market failures.     

Road development, housing growth, and landscape fragmentation in northern Wisconsin: 1937-1999.

Roads remove habitat, alter adjacent areas, and interrupt and redirect ecological flows. They subdivide wildlife populations, foster invasive species spread, change the hydrologic network, and increase human use of adjacent areas. At broad scales, these impacts cumulate and define landscape patterns. The goal of this study was to improve our understanding of the dynamics of road networks over time, and their effects on landscape patterns, and identify significant relationships between road changes and other land-use changes. We mapped roads from aerial photographs from five dates between 1937 and 1999 in 17 townships in predominantly forested landscapes in northern Wisconsin, U.S.A. Patch-level landscape metrics were calculated on terrestrial area outside of a 15-m road-effect zone. We used generalized least-squares regression models to relate changes in road density and landscape pattern to concurrent changes in housing density. Rates of change and relationships were compared among three ecological regions. Our results showed substantial increases in both road density and landscape fragmentation during the study period. Road density more than doubled, and median, mean, and largest patch size were reduced by a factor of four, while patch shape became more regular. Increases in road density varied significantly among ecological subsections and were positively related to increases in housing density. Fragmentation was largely driven by increases in road density, but housing density had a significantly positive relationship with largest patch area and patch shape. Without protection of roadless areas, our results suggest road development is likely to continue in the future, even in areas where road construction is constrained by the physical environment. Recognizing the dynamic nature of road networks is important for understanding and predicting their ecological impacts over time and understanding where other types of development are likely to occur in the future. Historical perspectives of development can provide guidance in prioritizing management efforts to defragment landscapes and mitigate the ecological impacts of past road development.     

Antipoaching standards in onshore hydrocarbon concessions drawn from a Central African case study

Unsustainable hunting outside protected areas is threatening tropical biodiversity worldwide and requires conservationists to engage increasingly in antipoaching activities. Following the example of ecocertified logging companies, we argue that other extractive industries managing large concessions should engage in antipoaching activities as part of their environmental management plans. Onshore hydrocarbon concessions should also adopt antipoaching protocols as a standard because they represent a biodiversity threat comparable to logging. We examined the spatiotemporal patterns of small‐ and large‐mammal poaching in an onshore oil concession in Gabon, Central Africa, with a Bayesian occupancy model based on signs of poaching collected from 2010 to 2015 on antipoaching patrols. Patrol locations were initially determined based on local intelligence and past patrol successes (adaptive management) and subsequently with a systematic sampling of the concession. We generated maps of poaching probability in the concession and determined the temporal trends of this threat over 5 years. The spatiotemporal patterns of large‐ and small‐mammal poaching differed throughout the concession, and likely these groups will need different management strategies. By elucidating the relationship between site‐specific sampling effort and detection probability, the Bayesian method allowed us to set goals for future antipoaching patrols. Our results indicate that a combination of systematic sampling and adaptive management data is necessary to infer spatiotemporal patterns with the statistical method we used. On the basis of our case study, we recommend hydrocarbon companies interested in implementing efficient antipoaching activities in their onshore concessions to lay the foundation of long‐needed industry standards by: adequately measuring antipoaching effort; mixing adaptive management and balanced sampling; setting goals for antipoaching effort; pairing patrols with large‐mammal monitoring; supporting antipoaching patrols across the landscape; restricting access to their concessions; performing random searches for bushmeat and mammal products at points of entry; controlling urban and agricultural expansion; supporting bushmeat alternatives; and supporting land‐use planning.     

Changes in the salinity of the Euphrates River system in Iraq

The water salinity of the Euphrates River as it enters Iraq, expressed as total dissolved solids (TDS), has more than doubled compared to that of 1973. Downstream of Al Hindia Barrage, south of Baghdad, the salinity has increased gradually over the last 30 years. The annual average TDS at Al Nassiriah, in the lower reaches of the Euphrates, has increased from 1,080 ppm in 1979 to more than 4,500 ppm in 2001. Water quality of the Euphrates within Iraq has deteriorated due to the decreased flow that is entering Iraq, diverted flows to the river from Al Tharthar Lake, and irrigation-return flow. The decreased flow from upstream sources was due to reservoir construction projects. Water from Al Tharthar Lake and from irrigation return flow is being diverted to the Euphrates to compensate for the upstream deficit. An environmental flow rate of 178 m³/s (annual minimum flow, 5.6 bcm or about one-third of historic minimum flow) is proposed as the minimum discharge that must be flowing into Iraq to preserve the environment of the Euphrates River in Iraq. A flow of twice this amount would allow more reasonable downstream management with an input average salinity of 760 ppm.