Uncertainty representation and propagation in quantified risk assessment using fuzzy sets

It is generally acknowledged that there are substantial uncertainties present in any analysis of risk. This paper provides a brief overview of the current techniques used for uncertainty analyses, and highlights their inappropriateness for practical use in the complete risk assessment process. The concept of fuzzy sets as a means for quantifying uncertainty is introduced and a case study demonstrates the application of this method to a simple consequence analysis where parameter uncertainty is considered. The results of this fuzzy analysis are compared with those of a more traditional probabilistic approach using a Monte Carlo simulation. This comparison demonstrates that the novel approach of fuzzy sets is a more appropriate technique due to its non-statistical nature and that the amount of computation required is substantially reduced compared to the traditional probabilistic approach. The versatility of fuzzy set theory suggests that this approach could also be used to quantify other types of uncertainty present in the risk assessment process, including model uncertainty and expert opinion.     

Assessing trophic position from nitrogen isotope ratios: effective calibration against spatially varying baselines

Nitrogen isotope signatures (δ¹⁵N) provide powerful measures of the trophic positions of individuals, populations and communities. Obtaining reliable consumer δ¹⁵N values depends upon controlling for spatial variation in plant δ¹⁵N values, which form the trophic ‘baseline’. However, recent studies make differing assumptions about the scale over which plant δ¹⁵N values vary, and approaches to baseline control differ markedly. We examined spatial variation in the δ¹⁵N values of plants and ants sampled from eight 150-m transects in both unlogged and logged rainforests. We then investigated whether ant δ¹⁵N values were related to variation in plant δ¹⁵N values following baseline correction of ant values at two spatial scales: (1) using ‘local’ means of plants collected from the same transect and (2) using ‘global’ means of plants collected from all transects within each forest type. Plant δ¹⁵N baselines varied by the equivalent of one trophic level within each forest type. Correcting ant δ¹⁵N values using global plant means resulted in consumer values that were strongly positively related to the transect baseline, whereas local corrections yielded reliable estimates of consumer trophic positions that were largely independent of transect baselines. These results were consistent at the community level and when three trophically distinct ant subfamilies and eight abundant ant species were considered separately. Our results suggest that assuming baselines do not vary can produce misleading estimates of consumer trophic positions. We therefore emphasise the importance of clearly defining and applying baseline corrections at a scale that accounts for spatial variation in plant δ¹⁵N values.     

Are low infidelity rates in feral horses due to infanticide?

A growing number of studies conducted on diverse taxa have shown that extra-pair/group paternity is higher than what would be predicted from behavioral observations alone. While it may be beneficial for females to mate with multiple males, this often results in offspring not sired by the behavioral father, which could influence offspring survival, especially in social mammals. Feral horses (Equus caballus) maintain stable social relationships over several years, usually with one stallion defending a harem band of unrelated mares against other males. Sneak copulations by subordinate males have been observed and mares sometimes change bands, both of which can result in foals sired by males other than the dominant band stallion. We measured female fidelity in free-ranging feral horses in 23 bands, with 51 foals over four foaling seasons and tested offspring paternity against parental behaviors. We used 12 polymorphic microsatellite loci and the program CERVUS 2.0 to determine and exclude potential sires. The majority of mares remained in the band with the sire of their foal resulting in most foals being sired by the band stallion. Most foals that were not sired by the band stallion were born in the year after a round-up and we could not determine if they were the result of band changing or sneak copulations. Foals born into a band without their sire had lower survival rates and mothers were significantly more protective of foals not sired by the band stallion. These findings suggest that band stability increases the reproductive success of mares and support the importance of infanticide risk in equid social structure.     

Climate change and the cost of conserving species in Madagascar

We examined the cost of conserving species as climate changes. We used a Maxent species distribution model to predict the ranges from 2000 to 2080 of 74 plant species endemic to the forests of Madagascar under 3 climate scenarios. We set a conservation target of achieving 10,000 ha of forest cover for each species and calculated the cost of achieving this target under each scenario. We interviewed managers of projects to restore native forests and conducted a literature review to obtain the net present cost per hectare of management actions to maintain or establish forest cover. For each species, we added hectares of land from lowest to highest cost per additional year of forest cover until the conservation target was achieved throughout the time period. Climate change was predicted to reduce the size of species' ranges, the overlap between species' ranges and existing or planned protected areas, and the overlap between species' ranges and existing forest. As a result, climate change increased the cost of achieving the conservation target by necessitating successively more costly management actions: additional management within existing protected areas (US$0-60/ha); avoidance of forest degradation (i.e., loss of biomass) in community-managed areas ($160-576/ha); avoidance of deforestation in unprotected areas ($252-1069/ha); and establishment of forest on nonforested land within protected areas ($802-2710/ha), in community-managed areas ($962-3226/ha), and in unprotected areas ($1054-3719/ha). Our results suggest that although forest restoration may be required for the conservation of some species as climate changes, it is more cost-effective to maintain existing forest wherever possible.     

Development of an integrated decision-support model for density management within jack pine stand-types

The objectives of this study were to (1) develop a modular-based structural stand density management model (SSDMM) and corresponding algorithmic analogue for natural (naturally regenerated stands without a history of density regulation) and managed (naturally or artificially regenerated stands with a history of density regulation) jack pine (Pinus banksiana Lamb.) stand-types, and (2) demonstrate the utility of the model in operational density management decision-making. Employing an Ontario-centric database consisting of 262 and 221 tree-list measurements obtained from 91 and 139 permanent and temporary sample plots situated within natural and managed stand-types, respectively, combined with data derived from density control experiments and sawmill simulation studies, six integrated estimation modules were constructed: Module A consisted of the parameterization of the core yield–density relationships which together drive the entire yield prediction system (e.g., size–density relationships for quadratic mean diameter, dominant height, mean volume, and mean live crown ratio, and site-specific height–age relationships); Module B consisted of the development of Weibull-based parameter prediction equation systems for recovering diameter distributions and composite height-diameter equations for height estimation; Module C consisted of the development of composite taper equations for predicting log products and stem volumes; Module D consisted of the development of allometric-based composite biomass equations for each above-ground component (bark, stem, branch and foliage) from which biomass estimates and associated carbon-based equivalents were derived; Module E consisted of the development of sawmill-specific composite equations for estimating chip and lumber volumes; and Module F consisted of the development of composite equations for estimating wood density and mean maximum branch diameter. The utility of the model was demonstrated by simultaneously contrasting a set of complex density management regimes (commercial thinning and variable planting densities) in terms of a broad array of stand-level yield outcomes and performance measures: overall productivity, log-product distributions, biomass production and carbon yields, recoverable products (chip and lumber volumes) and associated monetary values, economic efficiency, duration of optimal site occupancy, structural stability, and fibre attributes (wood density and mean maximum branch diameter). In summary, the modular-based SSDMM provides the analytical foundation for evaluating the likelihood of realizing a multitude of stand-level objectives when designing density control regimes for jack pine stand-types.     

Processing Stability and Biodegradation of Polylactic Acid (PLA) Composites Reinforced with Cotton Linters or Maple Hardwood Fibres

Polylactic acid (PLA) composites comprising up to 25 wt% cotton linter (CL) or up to 50 % maple wood fibre (WF) were prepared by compounding and injection moulding. A reduction of crystallinity in the PLA matrix was observed as a result of the thermal processing method. These PLACL and PLAWF composites provided excellent improvements in both stiffness (with increases in tensile and flexural modulus) and toughness (increases in notched impact strength) properties over the neat PLA resin, while the tensile and flexural strengths of the composites were generally unchanged, while the strain at break values were reduced in comparison to the neat PLA. DMA results indicated incorporating these fibres caused the mechanical loss factor (tan δ) to decrease, suggesting better damping capabilities were achieved with the composites. SEM analysis of the impact fractured surfaces of the PLACL composites showed debonding-cavitation at the matrix-fibre interface while the PLAWF composites showed good wetting along its matrix-fibre interface. The composting of these composites up to 90 days showed that the degradation onset time was increased when increasing the fibre loadings, but the maximum degree of degradation and the maximum daily rates of degradation were decreased compared to neat PLA. On a weight basis of fibre loading, the PLACL composites had a quicker onset of biodegradation, a higher maximum daily rate of biodegradation and, overall, a higher degree of biodegradation at 90 days than the PLAWF composites, possibly due to the quicker thermal hydrolysis observed in the PLA matrix of the PLACL composites during processing and composting.     

Stable isotope analysis in two sympatric populations of bottlenose dolphins <Emphasis Type="Italic">Tursiops truncatus</Emphasis>: evidence of resource partitioning?

Skin and muscle from 43 bottlenose dolphins (38 juveniles/adults, 5 calves) stranded in NW Spain were analysed to determine whether stable isotope ratios (δ¹³C and δ¹⁵N) could be used to assess dietary variation, habitat segregation and population substructure. Results were compared with published stomach contents data. Stable isotope ratios from 17 known prey species were also determined. Isotope ratios of the main prey (blue whiting, hake) varied significantly in relation to fish body size. Dolphin calves showed significant heavy isotope enrichments compared to adult females. Excluding calves, δ¹⁵N decreased with increasing dolphin body size, probably related to an ontogenetic shift in diet towards species at lower trophic levels, e.g. on blue whiting as suggested by stomach content results. Bottlenose dolphins were divided into two putative populations (North, South) based on previous genetic studies, and values of δ¹³C and δ¹⁵N differed significantly between these two groups, confirming the existence of population structuring.