Malthusian overfishing and efforts to overcome it on Kenyan coral reefs

This study examined trends along a gradient of fishing intensity in an artisanal coral reef fishery over a 10-year period along 75 km of Kenya's most populated coastline. As predicted by Malthusian scenarios, catch per unit effort (CPUE), mean trophic level, the functional diversity of fished taxa, and the diversity of gear declined, while total annual catch and catch variability increased along the fishing pressure gradient. The fishery was able to sustain high (approximately 16 Mg x km(-2) x yr(-1)) but variable yields at high fishing pressure due to the dominance of a few productive herbivorous fish species in the catch. The effect of two separate management strategies to overcome this Malthusian pattern was investigated: fisheries area closure and elimination of the dominant and most "competitive" gear. We found that sites within 5 km of the enforced closure showed significantly lower total catch and CPUE, but increased yield stability and trophic level of catch than predicted by regression models normalized for fishing effort. Sites that had excluded illegal beach seine use through active gear management exhibited increased total catch and CPUE. There was a strong interaction between closure and gear management, which indicates that, for closures to be effective at increasing catch, there must be simultaneous efforts at gear management around the periphery of the closures. We propose that Malthusian effects are responsible for the variation in gear and catch and that active management through reduced effort and reductions in the most competitive gear have the greatest potential to increase the functional and trophic diversity and per-person productivity.     

Additive effects of aboveground polyphagous herbivores and soil feedback in native and range-expanding exotic plants

Plant biomass and plant abundance can be controlled by aboveground and belowground natural enemies. However, little is known about how the aboveground and belowground enemy effects may add up. We exposed 15 plant species to aboveground polyphagous insect herbivores and feedback effects from the soil community alone, as well as in combination. We envisaged three possibilities: additive, synergistic, or antagonistic effects of the aboveground and belowground enemies on plant biomass. In our analysis, we included native and phylogenetically related range-expanding exotic plant species, because exotic plants on average are less sensitive to aboveground herbivores and soil feedback than related natives. Thus, we examined if lower sensitivity of exotic plant species to enemies also alters aboveground-belowground interactions. In a greenhouse experiment, we exposed six exotic and nine native plant species to feedback from their own soil communities, aboveground herbivory by polyphagous insects, or a combination of soil feedback and aboveground insects and compared shoot and root biomass to control plants without aboveground and belowground enemies. We observed that for both native and range-expanding exotic plant species effects of insect herbivory aboveground and soil feedback added up linearly, instead of enforcing or counteracting each other. However, there was no correlation between the strength of aboveground herbivory and soil feedback. We conclude that effects of polyphagous aboveground herbivorous insects and soil feedback add up both in the case of native and related range-expanding exotic plant species, but that aboveground herbivory effects may not necessarily predict the strengths of soil feedback effects.     

Estimating the complexity of bird song by using capture-recapture approaches from community ecology

Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.Communicated by A. Cockburn     

Monoterpene chemodiversity of ponderosa pine in relation to herbivory and bark beetle colonization

Summary. Ponderosa pine, Pinus ponderosa Laws. (Pinaceae), forests in Arizona have suffered from a nine-year period of drought and bark beetle, Ips lecontei Swaine (Coleoptera: Scolytidae), outbreaks. Abiotic and biotic stress in ponderosa pine results in the induced synthesis of certain monoterpenes that may in turn affect bark beetle behavior and survival. In this study, we investigate whether induced monoterpene production could result in a different monoterpene composition that remains stored in the needles or the trunk resin of the tree. Needle and resin samples in addition to trunk cores were collected from ponderosa pines at three locations in Arizona. Ungulate browsing induced a significant increase in limonene (P=0.010) and in chemodiversity (P=0.009), a measure of the evenness of distribution among the monoterpenes present in needles. We compared the level of ‘stress’ of the trees by measuring the thickness of annual rings in living trees and those that were killed by bark beetles. Where drought occurred, the spacing of annual rings from the last 10 years of trees killed by bark beetles was significantly smaller (P=0.020) compared to living trees. There was no difference in the monoterpene composition between the core sections of closest spacing of annual rings (stressed years) compared to the sections of widest spacing, which indicates that monoterpenes are distributed evenly throughout the extended resin system. In the area where the degree of drought was less overall, none of the individual monoterpenes present in the resin was related to bark beetle killed trees. However, about half the living pines had resin in which one of the major monoterpenes (α-pinene, Δ³-carene, and limonene) was absent, and these trees had a lower monoterpene chemodiversity compared to trees killed by bark beetles. Trees with these three major monoterpenes, corresponding to the average relative proportion in living pines at that location, may sustain higher selection and colonization by bark beetles.     

The accumulation of metals and toxic effects in Nereis virens exposed to pulverised fuel ash

The marine polychaete worm Nereis virens was used to study the bioaccumulation patterns of metal exposures with pulverised fuel ash (PFA). Juvenile N. virens were exposed for 12 weeks to sediments comprised of 100% PFA, 50% PFA-50% clean sand, a reference sediment (contaminated harbour-dredged material) and a clean sand control. Mortality after the first 4 weeks was high at 32–45% in the four sediments. However, this declined to a few percent during the following 8 weeks. Growth expressed as biomass (wet weight) was reduced in bout PFA treatments and the reference sediment. Heavy metal accumulation in the tissues of N. virens was characterised as follows: a group of elements showed negligible to low accumulation (Cd, Cr, Ni, and Zn), As and Cu wich showed a definite, but moderate accumulation: and finally Se, which showed a low accumulation rate, where an uptake equilibrium was not reached after 9 weeks. It is concluded that acute toxic effects did not occur but a population of N. virens inhabiting a PFA dumping site could be affected by high Se concentrations.     

Biodegradation of an Epoxy-Based Thermoplastic Polyester, Poly(Hydroxy Ester Ether) in a Laboratory-Scale Compost System

An epoxy-based thermoplastic polyester, poly(hydroxy ester ether), was incubated under aerobic conditions in a laboratory-scale compost system for 168 days to evaluate its potential for biodegradation. Radiolabeled test polymer [uniformly ¹⁴C ring-labeled, poly(hydroxy ester ether)] was incorporated into a mature compost and a sludge-amended compost at a loading of 3 mg test polymer/g compost. ¹⁴C-Cellulose was used as the positive control and a biologically inhibited control reactor was used to assess abiotic degradation of the test polymer. Degradation of the test polymer was assessed by measuring the amount of ¹⁴C-CO₂ from each of the test reactors. In addition, at selected time intervals subsamples of the compost were collected and serially extracted with water, methanol, and dimethylformamide to monitor degradation of the ¹⁴C-test polymer and provide a partial characterization of the degradation intermediates. Extensive degradation of ¹⁴C-poly(hydroxy ester ether) was observed in the test reactors with degradation half-life of the parent polymer (t _1/2) of approximately 32 days. By the end of the study, only 2% of the total ¹⁴C activity in the test reactors was attributed to intact polymer, with most of the measurable ¹⁴C activity converted to either ¹⁴C-CO₂ (26% of total ¹⁴C activity) or nonextractable products (accounting for 60% of the total activity). In contrast to the test reactors, only 3% of the ¹⁴C-poly(hydroxy ester ether) added to the biologically inhibited control reactor was mineralized to ¹⁴C-CO₂. The results obtained from the microbially active and biologically inhibited compost systems indicate that the poly(hydroxy ester ether) polymer was degraded, at least in part, by a biologically mediated process.     

Determination of the minimum ignition energy on the basis of a statistical approach

Based on existing MIE test results and new measurements, a statistical analysis for the MIE of hydrogen, ethene and propane is made by means of the logistic regression. The conditions necessary to carry out such an approach are discussed. It is shown that MIE values which are connected with a certain ignition probability could be determined adequately and lead to a more sophisticated result, also with regard to measurement uncertainties. This, in turn, leads to a better comparability and a higher informative content. At the same time, the MIEs of hydrogen, ethene and propane are reviewed. In doing so, a useful contribution to the discussion concerning the MIE of propane is made.     

A Framework to Integrate Habitat Monitoring and Restoration with Endangered Insect Recovery

Monitoring is essential to track the long-term recovery of endangered species. Greater emphasis on habitat monitoring is especially important for taxa whose populations may be difficult to quantify (e.g., insects) or when true recovery (delisting) requires continuous species-specific habitat management. In this paper, we outline and implement a standardized framework to facilitate the integration of habitat monitoring with species recovery efforts. The framework has five parts: (1) identify appropriate sample units, (2) select measurable indicators of habitat requirements, (3) determine rating categories for these indicators, (4) design and implement appropriate data collection protocols, and (5) synthesize the ratings into an overall measure of habitat potential. Following these steps, we developed a set of recovery criteria to estimate habitat potential and initially assess restoration activities in the context of recovering an endangered insect, the Karner blue butterfly (Lycaeides melissa samuelis). We recommend basing the habitat potential grading scheme on recovery plan criteria, the latest information on species biology, and working hypotheses as needed. The habitat-based assessment framework helps to identify which recovery areas and habitat patches are worth investing in and what type of site-specific restoration work is needed. We propose that the transparency and decision-making process in endangered insect recovery efforts could be improved through adaptive management that explicitly identifies and tracks progress toward habitat objectives and ultimate population recovery.     

Living the green city: Freiburg's Solarsiedlung between narratives and practices of sustainable urban development

The solar settlement (Solarsiedlung) in Freiburg, Germany, has been widely hailed as an eco-city or green city neighbourhood and a blueprint for sustainable urban development. However, as there is a noticeable lack of critical analysis of what constitutes Solarsiedlung as an “eco-city”, this paper studies narratives and practices of sustainable urban development. First, we look at Solarsiedlung as a best-practice model – a narrative that was produced and perpetuated by architects, urban planners, investors and academics celebrating this neighbourhood as a technologically leapfrogging, economically sound and socially integrated project. Second, we explore the everyday practices and lived experience of the residents in Solarsiedlung. Bringing together these two perspectives, we contribute to a more comprehensive understanding and critical reading of the interplay between the ecological, economic and social dimensions of sustainable development as seen from different viewpoints. Findings indicate that Solarsiedlung as a best-practice model is embedded in growth-oriented neoliberal strategies that are in conflict with the everyday practices and lived experience of the residents. Our findings put into question the widely assumed transferability of best-practice models in sustainable urban development.