The effects of road and bridge construction on the bank-root macrobenthic invertebrates of a Southern Nigerian stream

A comparative study was conducted at three stations on a fourth order Nigerian stream to evaluate the effects of a road and bridge construction on the macrobenthic invertebrates of the bank-root biotope. Siltation and sedimentation appear to be the important factors affecting macroinvertebrates. At station 2, the construction site, there was a considerable reduction in the occurrence and abundance of invertebrate taxa; different groups of invertebrates showed varying responses to perturbational stress; the taxa richness, general diversity and evenness were also low. Irregular fluctuations in diversity and evenness suggested that the benthic community of station 2 was less stable than those of upstream and downstream stations. The concentrated dominance of Ephemeroptera and Coleoptera at station 2, despite low diversity, reflected the ability of a few tolerant taxa to occur there in high abundance. Faunal comparisons of the three stations confirmed the perturbational stress caused by construction activities.     

Disease suppression on greenhouse tomatoes using plant waste compost

This study investigated the disease suppression abilities of a compost amendment that was added to the conventional growing medium, yellow cedar sawdust, used in most British Columbia vegetable greenhouses. The compost amendment was produced in a controlled, in-vessel process primarily from greenhouse crop waste materials. The pathogen and cultivar under study were Fusarium oxysporum f. sp. radicis-lycopersici (FORL) on Dombito (FORL-susceptible) beefsteak greenhouse tomatoes. Significant reduction of Fusarium crown and root rot was also realized in tomato seedlings by applying compost amendment from several different batches, as a seed cover or plug substitute. In a greenhouse trial, disease suppression using a mixture of 2:1 sawdust to amendment by volume was shown to be most effective. As a result, the tomato yield over a nine-month growing season was improved by 74% where the medium was deliberately infested with FORL.     

A novel gas purification system for biologically produced gases

A novel gas purification system employing membrane contactors with dense membranes in the absorption as well as the desorption unit has been tested concerning the separation efficiency of CO₂. The separation efficiency of potassium carbonate (K₂CO₃) promoted by piperazine (PZ) as absorption medium has been tested in the absorption unit. Since the absorbent will be regenerated in the desorption unit, the influence of temperature, sweep flow rate and absorbent type (0.5 M K₂CO₃ and 0.5 M K₂CO₃/0.5 M PZ) on the separation efficiency of CO₂ in the desorption unit has been investigated. Desorption by vacuum has been considered as well.In addition experimental results of the coupling of a bioreactor producing hydrogen by anoxygenic photosynthesis (low and fluctuating product gas flow rates and fluctuating compositions) with a membrane contactor for gas purification are reported. This was done in order to show the applicability of this system to processes producing biogases.     

Organotin pollution in Malta coastal zone

The speciation of organotins in seawater, surface microlayer and sediments in the marine environment of Malta is described. Concentrations of tributyltin (TBT) in bulk seawater inside the harbours were as high as 0.3 μg Sn L^‐1 but were below detection limits (5 ng Sn L^‐1) in open sea, 1.6 km offshore. In sediments, TBT levels were highest for the yacht marinas and ranged between 0.03 and 1.5 ug Sn g^‐1. Dibutyltin is more common in the surface microlayer than TBT. Diphenyl and monophenyltin were found infrequently in bulk seawater and in sediments. Tetrasubstituted organotins, namely, Me_nBu₍₄__n)Sn, where n = 1, 2, and 3, were found frequently in TBT‐contaminated sediments (0.1–9μg Sng^‐1), in seawater and in the microlayer where concentrations as high as 140 μg Sn L^‐1 (Me₃BuSn) were measured. Direct environmental methylation of TBT and that of its debutylated analogues may play a significant role in the geochemical cycling of tin under certain environmental conditions.     

Sovereign financial disaster risk management: The case of Mexico

In 2006, Mexico became the first transition country to transfer part of its public-sector natural catastrophe risk to the international reinsurance and capital markets. The Mexican case is of considerable interest to highly exposed transition and developing countries, many of which are considering similar transactions. Risk financing instruments can assure governments of sufficient post-disaster capital to provide emergency response, disaster relief to the affected population and repair public infrastructure. The costs of financial instruments, however, can greatly exceed expected losses, and for this reason it is important to closely examine their benefits and alternatives. This paper analyzes the Mexican case from the perspective of the risk cedent (the Ministry of Finance and Public Credit), which was informed by analyses provided by the International Institute for Applied Systems Analysis (IIASA). The rationale for a government to insure its contingent liabilities is presented along with the fiscal, legal and institutional context of the Mexican transaction. Using publicly available data, the paper scrutinizes the choice the authorities faced between two different risk-transfer instruments: reinsurance and a catastrophe bond. Making use of IIASA's catastrophe simulation model (CATSIM), this financial risk management decision is analyzed within the context of a public investment decision.     

Influence of fuel load and weather on timing of nocturnal spring migratory departures in European robins, <Emphasis Type="Italic">Erithacus rubecula</Emphasis>

Time of departure and landing of nocturnal migrants are of great importance for understanding migratory strategy used by birds. It allows us to estimate flying time and hence the distance that migrants cover during a single night. In this paper, I studied the temporal schedule of nocturnal departures of European robins during spring migration. The study was done on the Courish Spit on the Baltic Sea in 1998–2003 by retrapping 51 ringed birds in high mist nets during nocturnal migratory departure. Take-offs of individual birds occurred between the first and tenth hour after sunset (median 176 min after sunset). Departure time was not related to fuel stores at arrival and departure, stopover duration and progress of the season. The results suggest that one reason for temporal variation in take-off time was differential response of European robins with high and low motivation to depart to such triggers as air pressure and its trend. If these parameters reach a certain minimum threshold shortly before sunset, robins with a high migratory motivation take off in the beginning of the night. When air pressure or its trend reaches a maximum, it may trigger to take off later during the night birds with lower initial motivation for departure, including those that have low refuelling efficiency. In regulation of timing of take-offs of robins, an important role is also played by their individual endogenous circadian rhythm of activity which is related to the environment in a complex way.     

Epiphyte metapopulation dynamics are explained by species traits, connectivity, and patch dynamics

The colonization-extinction dynamics of many species are affected by the dynamics of their patches. For increasing our understanding of the metapopulation dynamics of sessile species confined to dynamic patches, we fitted a Bayesian incidence function model extended for dynamic landscapes to snapshot data on five epiphytic lichens among 2083 mapped oaks (dynamic patches). We estimate the age at which trees become suitable patches for different species, which defines their niche breadth (number of suitable trees). We show that the colonization rates were generally low, but increased with increasing connectivity in accordance with metapopulation theory. The rates were related to species traits, and we show, for the first time, that they are higher for species with wide niches and small dispersal propagules than for species with narrow niches or large propagules. We also show frequent long-distance dispersal in epiphytes by quantifying the relative importance of local dispersal and background deposition of dispersal propagules. Local stochastic extinctions from intact trees were negligible in all study species, and thus, the extinction rate is set by the rate of patch destruction (tree fall). These findings mean that epiphyte metapopulations may have slow colonization-extinction dynamics that are explained by connectivity, species traits, and patch dynamics.     

The new geometry of climate governance

ABSTRACT

Scholars and practitioners have focused in recent years on the potential for achieving cooperation in small “clubs” of countries. While solutions to global climate change will eventually require widespread cooperation, club strategies could help to catalyze that outcome. Unlike the Paris Agreement, which has achieved widespread but relatively shallow cooperation, it could be easier to tailor agreements that allow deep cooperation within smaller groups. This essay extends that logic to clubs whose geometry varies two-dimensionally across countries but also along a third dimension: within countries. Most of the key elements of international relations and international law theory that explain how clubs achieve cooperation are directly applicable to three-dimensional clubs. Most of the relevant experience for these clubs has occurred in the west; overdue is a close assessment of how key units – such as provinces and firms – within China and other emerging economies.