Computing the limits of risk aversion

Utility theory can be used to model the decision process involved in evaluating the cost-effectiveness of systems that protect against a risk to assets. A key variable in the model is the coefficient of relative risk aversion (or simply “risk-aversion”) which reflects the decision maker's reluctance to invest in such safety systems. This reluctance to invest is the scaled difference in expected utility before and after installing the safety system and has a minimum at some given value of risk-aversion known as the “permission point”, and it has been argued that decisions to sanction safety systems would be made at this point. As the cost of implementing a safety system increases, this difference in utility will diminish. At some point, the “point of indiscriminate decision”, the decision maker will not be able to discern any benefit from installing the safety system. This point is used to calculate the maximum reasonable cost of a proposed safety system. The value of the utility difference at which the decision maker is unable to discern any difference is called the “discrimination limit”.By considering the full range of accident probabilities, costs of the safety system and potential loss of assets, an average risk-aversion can be calculated from the model. This paper presents the numerical and computational techniques employed in performing these calculations. Two independent approaches to the calculations have been taken, the first of which is the derivative-based secant method, an extension of the referred derivative method employed in previous papers. The second is the Golden Bisection Method, based on a Golden Section Search algorithm, which was found to be more robust but less efficient than the secant method. The average risk-aversion is a function of several key parameters: the organisation's assets, the probability and maximum cost of an incident, and the discrimination limit. An analysis of the sensitivity of the results to changes in these parameters is presented. An average risk-aversion of 0.8–1.0 is found for a wide range of parameters appropriate to individuals or small companies, while an average risk-aversion of 0.1 is found for large corporations. This reproduces the view that large corporations will be risk neutral until faced with risks that pose a threat to their viability.     

If not here, then perhaps not anywhere: urban growth management as a tool for sustainability planning in British Columbia's capital regional district

In 1995 the provincial government of British Columbia, Canada, passed new legislation encouraging regional districts to prepare Regional Growth Strategies. The strategies were to be means of coordinating municipal action on regional issues. They were also meant to facilitate pursuit of sustainability objectives, including reducing urban sprawl, protecting environmentally sensitive areas, providing affordable housing and decreasing pollution. This paper examines the experience so far in one region that chose to prepare a growth strategy: the Capital Regional District (CRD) at the south end of Vancouver Island. Growth-management planning in the CRD has been and remains both critical and difficult. The region expects a substantial population increase over the next couple of decades and has a limited land base for urban expansion. Many citizens recognise that their quality of life is high, but vulnerable and, as a result, public support for effective growth management is stronger in the CRD than in many other provincial growth areas. However, BC does not have a tradition of strong regional governance and the CRD as a regional authority is the creature of sixteen municipalities and electoral areas. Seven years into the process, effective growth management still faces substantial challenges, including the persistent jurisdictional protectionism of CRD municipalities. Nevertheless, there have been positive achievements and an admirable diversity of individuals, organisations and initiatives continue to push municipal and regional officials towards a more sustainable future.     

Measuring the environmental performance of IPPC industry: I. Devising a quantitative science-based and policy-weighted Environmental Emissions Index

This paper describes the derivation of an Environmental Emissions Index (EEI) intended to quantify the environmental performance of Integrated Pollution Prevention and Control (IPPC) installations and sectors. Characterisation and normalisation methods used in lifecycle analyses were applied to 20 routinely reported emissions parameters, pertaining to six environmental impact categories. Distance to policy targets for relevant emissions were used to weight impact categories, and link the EEI to policy priorities. Ireland and the EU15 were considered as scales of context. The European Pollutant Emission Register was a convenient source of normalisation data, but restricted the context of the EEI to industrial emissions, and distorted outputs. Using national and EU15 total loading estimates for normalisation resulted in an EEI that better reflected the relative contribution of reported emissions towards overall environmental pressures. Using Ireland's pharmaceutical sector as a case study indicated that weighting factors, and the toxicity range of NMVOC emissions, were the largest sources of EEI uncertainty. Through the integration of inventory data, scientific characterisation, and policy targets, the EEI translates reported emissions data from IPPC installations and sectors into a benchmark of environmental performance. It may be regarded as an evolving tool of potential utility to regulators and policy makers.     

Home range and movement patterns of the Redlip Parrotfish (Scarus rubroviolaceus) in Hawaii

The activity and movement of the Redlip Parrotfish, Scarus rubroviolaceus, near Wawaloli reef, Hawaii (19°43′06″N, 156°03′11″W), was investigated with active and passive tracking techniques from April through November 2007. Site fidelity was determined and home range sizes were measured for 21 individuals. All individuals showed strong diurnal activity patterns and relatively stable home ranges. Terminal phase individuals had larger home range areas than initial phase fish, and home range size increased with depth. Occasional long forays from the home range were observed in many individuals. Forays often occurred in crepuscular hours and may represent migrations to/from nocturnal sheltering sites. Findings from this study underscore the importance of depth and nighttime shelter migrations as design considerations for effective marine protected areas (MPA) for large parrotfishes.     

Optic gland enlargement and female gonad maturation in a population of the octopuseledone cirrhosa: a multivariate analysis

Eleven principal component analyses were performed on morphometric data from a series of monthly samples of the octopusEledone cirrhosa (Lamarck) collected from March 1978 through January 1979 in the Aberdeen (Scotland) area. This technique has allowed a partitioning of general growth effects from variation in the reproductive system. Optic gland size varies as a reproductive character together with ovary and oviducal glands. Optic gland size not clearly associated with other cerebral organs, the brain and optic lobes. The association between the reprountive characters developed during the onset of the main period of reproductive maturation in the early summer of 1978 and persisted for the remainder of that year. This result supports the experimental evidence linking optic gland enlargement with female gonad maturation and suggests that this process occurs normally in the field population.     

Soil responses to management, increased precipitation, and added nitrogen in ponderosa pine forests.

Forest management, climatic change, and atmospheric N deposition can affect soil biogeochemistry, but their combined effects are not well understood. We examined the effects of water and N amendments and forest thinning and burning on soil N pools and fluxes in ponderosa pine forests near Flagstaff, Arizona (USA). Using a 15N-depleted fertilizer, we also documented the distribution of added N into soil N pools. Because thinning and burning can increase soil water content and N availability, we hypothesized that these changes would alleviate water and N limitation of soil processes, causing smaller responses to added N and water in the restored stand. We found little support for this hypothesis. Responses of fine root biomass, potential net N mineralization, and the soil microbial N to water and N amendments were mostly unaffected by stand management. Most of the soil processes we examined were limited by N and water, and the increased N and soil water availability caused by forest restoration was insufficient to alleviate these limitations. For example, N addition caused a larger increase in potential net nitrification in the restored stand, and at a given level of soil N availability, N addition had a larger effect on soil microbial N in the restored stand. Possibly, forest restoration increased the availability of some other limiting resource, amplifying responses to added N and water. Tracer N recoveries in roots and in the forest floor were lower in the restored stand. Natural abundance delta15N of labile soil N pools were higher in the restored stand, consistent with a more open N cycle. We conclude that thinning and burning open up the N cycle, at least in the short-term, and that these changes are amplified by enhanced precipitation and N additions. Our results suggest that thinning and burning in ponderosa pine forests will not increase their resistance to changes in soil N dynamics resulting from increased atmospheric N deposition or increased precipitation due to climatic change. Restoration plans should consider the potential impact on long-term forest productivity of greater N losses from a more open N cycle, especially during the period immediately after thinning and burning.     

What can we learn from benefit transfer errors? Evidence from 20 years of research on convergent validity

We develop a nonparametric approach to meta-analysis and use it to identify modeling decisions that affect benefit transfer errors. The meta-data describe the results from 31 empirical studies testing the convergent validity of benefit transfers. They evaluated numerous methodological procedures, collectively reporting 1071 transfer errors. Our meta-regressions identify several important findings, including: (1) the median absolute error is 39%; (2) function transfers outperform value transfers; (3) transfers describing environmental quantity generate lower transfer errors than transfers describing quality changes; (4) geographic site similarity is important for value transfers; (5) contingent valuation generates lower transfer errors than other valuation methods; and (6) combining data from multiple studies tends to reduce transfer errors.     

Flexible foraging strategies in a diving seabird with high flight cost

How central-place foragers change search strategy in response to environmental conditions is poorly known. Foragers may vary the total distance travelled and how far they range from the central place in response to variation in the distribution of their prey. One potential reason as to why they would extend the length of their foraging trip and its distance from the colony would be to increase prey quality or quantity, despite incurring higher transit costs. To test this trade-off hypothesis in a species with high flight costs, we recorded the foraging behaviour of razorbills (Alca torca) using state-of-the-art techniques that log both individual horizontal (flight activity) and vertical (dive activity) movements. We show that the distance that razorbills travelled to foraging locations increased with sea-surface temperature, which may relate to higher prey quality or quantity. This relation is supported by an indirect index of patch quality, based on dive profiles, which also increased with travel distance from the colony. Furthermore, we show that this index was highest during the daily peak in diving activity, around midday. Taken together, these results suggest that razorbills are capable of adjusting their search strategies sensitively in response to proximate environmental cues.