Wildfire, landscape diversity and the Drossel-Schwabl model

How simple can a model be that still captures essential aspects of wildfire ecosystems at large spatial and temporal scales? The Drossel-Schwabl model (DSM) is a metaphorical forest-fire model developed to reproduce only one pattern of real systems: a frequency distribution of fire sizes resembling a power law. Consequently, and because it appears oversimplified, it remains unclear what bearings the DSM has in reality. Here, we test whether the DSM is capable of reproducing a pattern that was not considered in its design, the hump-shaped relation between the diversity of succession stages and average annual area burnt. We found that the model, once reformulated to represent succession, produces realistic landscape diversity patterns. We investigated four succession scenarios of forest-fire ecosystems in the USA and Canada. In all scenarios, landscape diversity is highest at an intermediate average annual area burnt as predicted by the intermediate disturbance hypothesis. These results show that a model based solely on the dynamics of the fuel mosaic has surprisingly high predictive power with regard to observed statistical properties of wildfire systems at large spatial scales. Parsimonious models, such as the DSM can be used as starting points for systematic development of more structurally realistic but tractable wildfire models. Due to their simplicity they allow analytical approaches that further our understanding under increasing complexity.     

Managing Swedish forestry’s impact on mercury in fish: Defining the impact and mitigation measures

Inputs of anthropogenic mercury (Hg) to the environment have led to accumulation of Hg in terrestrial and aquatic ecosystems, contributing to fish Hg concentrations well above the European Union standards in large parts of Fennoscandia. Forestry operations have been reported to increase the concentrations and loads of Hg to surface waters by mobilizing Hg from the soil. This summary of available forestry effect studies reveals considerable variation in treatment effects on total Hg (THg) and methylmercury (MeHg) at different sites, varying from no effect up to manifold concentration increases, especially for the bioavailable MeHg fraction. Since Hg biomagnification depends on trophic structures, forestry impacts on nutrient flows will also influence the Hg in fish. From this, we conclude that recommendations for best management practices in Swedish forestry operations are appropriate from the perspective of mercury contamination. However, the complexity of defining effective policies needs to be recognized.     

The Zambian Resource Curse and its influence on Genuine Savings as an indicator for “weak” sustainable development

The empirical evidence that economies predominantly reliant on their natural resources are characterized by slower economic growth—the so-called Resource Curse (RC)—is in many ways confirmed by the case of Zambia. Haber and Menaldo (Am Polit Sci Rev 105(1):1–26, 2011) identify Zambia’s extreme dependence on copper exports as one of the worldwide most striking examples for a country suffering from this “curse.” In topical literature, the RC is traced back to the generation of natural resource rents regardless of economic performance, which among other problems leads to suboptimal reinvestment. The World Banks indicator for the “weak” sustainable development of a country—the so-called Genuine Savings (GS)—considers exactly this reinvestment of rents from the depletion of natural capital rents into physical or human capital. Although it has been shown empirically that countries dependent on primary exports on average feature negative GS rates and that the determinants of the RC influence both present economic growth and future sustainability as measured by GS, no case studies have been conducted to confirm this. Against this background, we qualitatively survey the relationship between the most discussed determinants causing the RC in Zambia and the country’s GS rate. We show that all theoretical relationships between the GS rates of a country and RC determinants such as consumption behavior, volatile world market prices, the so-called Dutch disease as well as political and institutional structures apply to Zambia between 1964 and 2010: an extreme dependency on copper exports and insufficient reinvestments of income from the depletion of Zambia’s natural capital constitutes one of the main reasons for slow growth and negative GS until the copper price booms in the second half of the 2000s.     

Future agriculture with minimized phosphorus losses to waters: Research needs and direction

The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.     

Geophysical investigations for evaluation of environmental pollution in a mine tailings area

Sulfide-containing mill wastes of the Komsomolsk ore processing plant situated in the Kemerovo region (Russia) were examined in 2013–2015. Multipurpose studies of the mine tailings determined the composition of waste, pore water, mine drainages, and affected groundwater. Electrical resistivity tomography was used to trace the geoelectric zoning of the waste samples. Layers with low resistivity indicated areas with pore spaces filled with highly mineralized solutions with Fe, Cu, Zn, Cd, As, and Sb at total concentrations of up to 50 g/L. Anomalous zones can be specified as ‘geochemical barriers’ – specific layers where the mobility of the elements is reduced due to pH conditions, redox potential, and Fe(III) hydroxide precipitation. The zones of increased conductivity in oxidized mine tailings indicated local areas with high acid production potential and coexisting acidic pore solution. In non-oxidized tailings, high conductivity of the mineral skeleton was observed. There was a migration of drainage outside the tailings, its direction monitored by geophysical data. Chemical analysis confirmed that the concentrations of As in groundwater samples were higher than the maximum permissible concentration.     

Acute and chronic effects of nano- and non-nano-scale TiO2 and ZnO particles on mobility and reproduction of the freshwater invertebrate Daphnia magna

Among the emerging literature addressing the biological effects of nanoparticles, very little information exists, particularly on aquatic organisms, that evaluates nanoparticles in comparison to non-nanocounterparts. Therefore, the potential effects of nano-scale and non-nano-scale TiO₂ and ZnO on the water flea, Daphnia magna, were examined in 48-h acute toxicity tests using three different test media, several pigment formulations – including coated nanoparticles – and a variety of preparation steps. In addition, a 21-d chronic Daphnia reproduction study was performed using coated TiO₂ nanoparticles. Analytical ultracentrifugation analyses provided evidence that the nanoparticles were present in a wide range of differently sized aggregates in the tested dispersions. While no pronounced effects on D. magna were observed for nano-scale and non-nano-scale TiO₂ pigments in 19 of 25 acute (48-h) toxicity tests (EC50 > 100 mg L⁻¹), six acute tests with both nano- and non-nano-scale TiO₂ pigments showed slight effects (EC10, 0.5–91.2 mg L⁻¹). For the nano-scale and non-nano-scale ZnO pigments, the acute 48-h EC50 values were close to the 1 mg L⁻¹ level, which is within the reported range of zinc toxicity to Daphnia. In general, the toxicity in the acute tests was independent of particle size (non-nano-scale or nano-scale), coating of particles, aggregation of particles, the type of medium or the applied pre-treatment of the test dispersions. The chronic Daphnia test with coated TiO₂ nanoparticles demonstrated that reproduction was a more sensitive endpoint than adult mortality. After 21 d, the NOEC for adult mortality was 30 mg L⁻¹ and the NOEC for offspring production was 3 mg L⁻¹. The 21-d EC10 and EC50 values for reproductive effects were 5 and 26.6 mg L⁻¹, respectively. This study demonstrates the utility of evaluating nanoparticle effects relative to non-nano-scale counterparts and presents the first report of chronic exposure to TiO₂ nanoparticles in D. magna.     

Requirements for estimation of doses from contaminants dispersed by a ‘dirty bomb’ explosion in an urban area

The ARGOS decision support system is currently being extended to enable estimation of the consequences of terror attacks involving chemical, biological, nuclear and radiological substances. This paper presents elements of the framework that will be applied in ARGOS to calculate the dose contributions from contaminants dispersed in the atmosphere after a ‘dirty bomb’ explosion. Conceptual methodologies are presented which describe the various dose components on the basis of knowledge of time-integrated contaminant air concentrations. Also the aerosolisation and atmospheric dispersion in a city of different types of conceivable contaminants from a ‘dirty bomb’ are discussed.     

Modelling the long-term consequences of a hypothetical dispersal of radioactivity in an urban area including remediation alternatives

The Urban Remediation Working Group of the International Atomic Energy Agency's EMRAS (Environmental Modelling for Radiation Safety) program was organized to address issues of remediation assessment modelling for urban areas contaminated with dispersed radionuclides. The present paper describes the second of two modelling exercises. This exercise was based on a hypothetical dispersal of radioactivity in an urban area from a radiological dispersal device, with reference surface contamination at selected sites used as the primary input information. Modelling endpoints for the exercise included radionuclide concentrations and external dose rates at specified locations, contributions to the dose rates from individual surfaces, and annual and cumulative external doses to specified reference individuals. Model predictions were performed for a “no action” situation (with no remedial measures) and for selected countermeasures. The exercise provided an opportunity for comparison of three modelling approaches, as well as a comparison of the predicted effectiveness of various countermeasures in terms of their short-term and long-term effects on predicted doses to humans.     

Climate and land-use changes affecting river sediment and brown trout in alpine countries—a review

Background, aim, and scope

Catch decline of freshwater fish has been recorded in several countries. Among the possible causes, habitat change is discussed. This article focuses on potentially increased levels of fine sediments going to rivers and their effects on gravel-spawning brown trout. Indications of increased erosion rates are evident from land-use change in agriculture, changes in forest management practices, and from climate change. The latter induces an increase in air and river water temperatures, reduction in permafrost, changes in snow dynamics and an increase in heavy rain events. As a result, an increase in river sediment is likely. Suspended sediment may affect fish health and behaviour directly. Furthermore, sediment loads may clog gravel beds impeding fish such as brown trout from spawning and reducing recruitment rates. To assess the potential impact on fine sediments, knowledge of brown trout reproductive needs and the effects of sediment on brown trout health were evaluated.

Approach

We critically reviewed the literature and included results from ongoing studies to answer the following questions, focusing on recent decades and rivers in alpine countries.

Have climate change and land-use change increased erosion and sediment loads in rivers?

Do we have indications of an increase in riverbed clogging?

Are there indications of direct or indirect effects on brown trout from increased suspended sediment concentrations in rivers or from an increase in riverbed clogging?

Results

Rising air temperatures have led to more intensive precipitation in winter months, earlier snow melt in spring, and rising snow lines and hence to increased erosion. Intensification of land use has supported erosion in lowland and pre-alpine areas in the second half of the twentieth century. In the Alps, however, reforestation of abandoned land at high altitudes might reduce the erosion risk while intensification on the lower, more easily accessible slopes increases erosion risk. Data from laboratory experiments show that suspended sediments affect the health and behaviour of fish when available in high amounts. Point measurements in large rivers indicate no common lethal threat and suspended sediment is rarely measured continuously in small rivers. However, effects on fish can be expected under environmentally relevant conditions. River bed clogging impairs the reproductive performance of gravel-spawning fish.

Discussion

Overall, higher erosion and increased levels of fine sediment going into rivers are expected in future. Additionally, sediment loads in rivers are suspected to have considerably impaired gravel bed structure and brown trout spawning is impeded. Timing of discharge is put forward and is now more likely to affect brown trout spawning than in previous decades.

Conclusions

Reports on riverbed clogging from changes in erosion and fine sediment deposition patterns, caused by climate change and land-use change are rare. This review identifies both a risk of increases in climate erosive forces and fine sediment loads in rivers of alpine countries. Increased river discharge and sediment loads in winter and early spring could be especially harmful for brown trout reproduction and development of young life stages. Recently published studies indicate a decline in trout reproduction from riverbed clogging in many rivers in lowlands and alpine regions. However, the multitude of factors in natural complex ecosystems makes it difficult to address a single causative factor.

Recommendations and perspectives

Further investigations into the consequences of climate change and land-use change on river systems are needed. Small rivers, of high importance for the recruitment of gravel-spawning fish, are often neglected. Studies on river bed clogging are rare and the few existing studies are not comparable. Thus, there is a strong need for the development of methods to assess sediment input and river bed clogging. As well, studies on the effects to fish from suspended sediments and consequences of gravel beds clogging under natural conditions are urgently needed.     

Levels and homologue profiles of PCDD/Fs in sediments along the Swedish coast of the Baltic Sea

Background, aim, and scope  The primary aim of this study was to explore the variations in PCDD/F levels and homologue profiles of Baltic surface sediments by comprehensively analyzing polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in samples from a large number of sites, encompassing not only previously known hotspot areas, but also sites near other potential PCDD/F sources, in pristine reference areas (in which there was no industrial activity) and offshore sites. Materials and methods  Surface sediment samples (146 in total) were collected at various points along the Swedish coast and offshore areas. In addition, bulk deposition was sampled, monthly, at a single site in northern Sweden during 1 year. The concentrations of tetra- through octa-substituted CDD/Fs were determined in both matrices. Results  Highly elevated concentrations of PCDD/Fs were found at many sites in coastal areas and concentrations were also slightly elevated in some offshore areas. Homologue profiles varied substantially amongst samples from coastal sites, while those from offshore and other pristine sediments were relatively similar. The offshore sediments showed different profiles from those observed in the deposition samples. Sediment levels of PCDD/Fs were not generally significantly correlated to organic carbon levels, except in some pristine areas. Comparison of data obtained in this and previous studies suggest that both their levels and profiles are similar today to those observed 20 years ago in coastal and offshore areas. The only detected trend is that their levels appear to have decreased slightly in the offshore area of the Bothnian Sea. Discussion  The localization of hotspot areas along the coast, the lack of consensus between PCDD/F profiles of sediments and general background, and their weak correlations with organic carbon suggest that PCDD/Fs in the study area largely originate from local/regional emissions. However, due to complicating factors such as sediment dynamics and land upheaval, it is not possible to conclude whether these pollutants derive from recent emissions or from a combination of recent emissions and re-distribution of previous inputs. Conclusions  The results show that: elevated levels of PCDD/Fs are present in both coastal and offshore areas of the Baltic Sea, the major hotspots are close to the shore, and there are large variations in profiles, indicating that local emissions are (or have been) the major causes of pollution. Recommendations and perspectives  In order to identify other hotspot areas and trace sources, comprehensive analysis of PCDD/Fs in surface sediments is needed in all areas of the Baltic Sea that have not been previously investigated. The high levels of PCDD/Fs observed in surface sediments also indicate a need to elucidate whether they are due mainly to current emissions or a combination of recent pollution and re-distribution of historically deposited pollutants. To do so, better understanding of sediment dynamics and present-day inputs, such as riverine inputs, industrial effluents, and leakage from contaminated soil is required. There are indications that contaminated sediments have a regional impact on fish contamination levels. However, as yet there is no statistically robust evidence linking contaminated sediments with elevated levels in Baltic biota. It should also be noted that the Baltic Sea is being massively invaded by the deep-burrowing polychaete Marenzielleria ssp., whose presence in sediments has been shown to increase water concentrations of hydrophobic pollutants. In awareness of this, it is clear that high levels in sediments cannot be ignored in risk assessments. In order to investigate the emission trends more thoroughly, analysis of PCDD/Fs in offshore sediment cores throughout the Baltic Sea is also recommended. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.