Why are metapopulations so rare?

Roughly 40 years after its introduction, the metapopulation concept is central to population ecology. The notion that local populations and their dynamics may be coupled by dispersal is without any doubt of great importance for our understanding of population-level processes. A metapopulation describes a set of subpopulations linked by (rare) dispersal events in a dynamic equilibrium of extinctions and recolonizations. In the large body of literature that has accumulated, the term "metapopulation" is often used in a very broad sense; most of the time it simply implies spatial heterogeneity. A number of reviews have recently addressed this problem and have pointed out that, despite the large and still growing popularity of the metapopulation concept, there are only very few empirical examples that conform with the strict classical metapopulation (CM) definition. In order to understand this discrepancy between theory and observation, we use an individual-based modeling approach that allows us to pinpoint the environmental conditions and the life-history attributes required for the emergence of a CM structure. We find that CM dynamics are restricted to a specific parameter range at the border between spatially structured but completely occupied and globally extinct populations. Considering general life-history attributes, our simulations suggest that CMs are more likely to occur in arthropod species than in (large) vertebrates. Since the specific type of spatial population structure determines conservation concepts, our findings have important implications for conservation biology. Our model suggests that most spatially structured populations are panmictic, patchy, or of mainland-island type, which makes efforts spent on increasing connectivity (e.g., corridors) questionable. If one does observe a true CM structure, this means that the focal metapopulation is on the brink of extinction and that drastic conservation measures are needed.     

Stochastic Multi-species MSY to Achieve Ecological-Economic Sustainability of a Coral Reef Fishery System in French Polynesia

Environmental Modeling & Assessment - This paper investigates the ecological-economic sustainability of coral reef socio-ecological systems under fishing and environmental pressures. To achieve...     

Performance evaluation of a completely stirred anaerobic reactor treating pig manure at a low range of mesophilic conditions

Many Chinese biogas plants run in the lower range of mesophilic conditions. This study evaluated the performance of a completely stirred anaerobic reactor treating pig manure at different temperatures (20, 28 and 38 °C). The start-up phase of the reactor at 20 °C was very long and extremely poor performance was observed with increasing organic loading rate (OLR). At an OLR of 4.3 g ODM L^?1 d^?1, methane production at 28 °C was comparable (3% less) with that at 38 °C, but the risk of acidification was high at 28 °C. At low OLR (1.3 g ODM L^?1 d^?1), the biogas process appeared stable at 28 °C and gave same methane yields as compared to the reactor operating at 38 °C. The estimated sludge yield at 28 °C was 0.065 g VSS g^?1 COD_removed, which was higher than that at 38 °C (0.016 g VSS g^?1 COD_removed).     

Braucht Substitution mehr Staat oder mehr Markt?

Ziel und Hintergrund

In den bisherigen REACH-Verordnungsentwürfen wird als einer der wichtigen Gründe für die Gesetzes-initiative ‘die Schaffung von Anreizen für die Substitution gefährlicher durch weniger gefährliche Stoffe’ genannt (REACH 2003, 61). Damit wird die Frage aktuell, was denn Unternehmen als Wirtschaftssubjekte ‘anreizen’ oder eben auch ‘nicht anreizen’ kann, gefährliche chemikalien zu substituieren: Welche Marktkräfte wirken bereits positiv, die durch regulative Vorgaben eventuell verstärkt werden können, und welche die Substitution behindernden Marktkräfte sollten durch regulative Maßnahmen abgeschwächt werden?

Schwerpunkte

Die Autoren untersuchen auf Basis ihrer Vorarbeiten und Fallstudien zur Substitution die Rahmenbedingungen — Treiber und blockierende Faktoren — für Substitution. Dabei werden auch aktuelle Positionen zur Substitutionsproblematik einbezogen, so z.B. die Stellungnahme des Ausschusses für Umwelt, Gesundheit und Sicherheit der Royal Society of Chemistry (UK), des UK Chemicals Stakeholder Forums sowie die gegenwärtigen Kompromisse zwischen Europäischem Rat und Europäischem Parlament zur Regelung der Substitution unter REACH.

Ergebnisse und Schlussfolgerungen

Gegenwärtig fördern weder die Marktdynamik noch die Gesetzgebung Substitution effektiv genug. Die Unternehmen selbst sind zögerlich, wenn Kosten und Haftungsfragen sowie Kundenprioritäten der Substitution entgegenstehen. Substitution wird vom Gesetzgeber oft nur als Rahmengebot, als Generalklausel, als Anspruch, als Vorrangstrategie oder als Priorität gefordert. Dennoch gibt es sowohl in der Gesetzgebung als auch in der Marktentwicklung positive Ansätze, die regulativ unterstützt werden können.

Perspektive

Der entscheidende Punkt für die Frage der regulativen Substitutionsvorgaben ist, auf welche Weise der Staat die Marktdynamik durch Setzen von Innovationszielen befördern kann. Der Staat sollte in Kooperation mit den Stakeholdern in technischen Dossiers die bekannten Substitutionsmöglichkeiten und Risikominderungsmaßnahmen zusammen stellen, einen Realisierungszeitpunkt vorgeben, Mindeststandards vorschrieben und auch detaillierte Regulation androhen, falls nichts geschieht. Eine case-to-case-Beurteilungs-Methode ist der Substitutionsproblematik in der Regel angemessen, um den Aufwand und die erforderlichen Maßnahmen annähernd genau zu bestimmen.     

Perceived and measured levels of environmental pollution: interdisciplinary research in the subarctic lowlands of northeast European Russia

Using interdisciplinary field research in the Usa Basin, northeast European Russia, we compared local inhabitants' perception of environmental problems with chemical and remote-sensing signatures of environmental pollution and their local impacts. Extensive coal mining since the 1930s around Inta and Vorkuta has left a legacy of pollution, detected by measuring snowpack, topsoil, and lichen chemistry, together with remote-sensing techniques and analysis of lake water and sediments. Vorkuta and its environs suffered the worst impacts, with significant metal loading and alkalization in lakes and topsoils, elevated metals and cations in terricolous (reindeer) lichens, and changes in vegetation communities. Although the coal industry has declined recently, the area boasts a booming oil and gas industry, based around Usinsk. Local perceptions and concerns of environmental pollution and protection were higher in Usinsk, as a result of increased awareness after a major oil spill in 1994, compared with Vorkuta's inhabitants, who perceived air pollution as the primary environmental threat. Our studies indicate that the principal sources of atmospheric emissions and local deposition within 25 to 40 km of Vorkuta were coal combustion from power and heating plants, coal mines, and a cement factory. Local people evaluated air pollution from direct observations and personal experiences, such as discoloration of snow and respiratory problems, whereas scientific knowledge played a minor role in shaping these perceptions.