Risk perception and decision-making: do farmers consider risks from climate change?

This paper provides one of the first empirical studies that examine the impact of climate change adaptation practices on technical efficiency (TE) among smallholder farmers in Nepal. An adaptation index is used to explore the impact of farmers’ adaptation on TE using the stochastic frontier analysis framework. Data for six districts of Nepal representing all three agro-ecological regions (terai, hill, and mountain) were collected from a focus group discussion, a stakeholder workshop and a household survey. The survey shows that about 91% of the farming households have adopted at least one practice to minimize the adverse impacts of climate change. Empirical results reveal that adaptation is an important factor explaining efficiency differentials among farming households. Those adopting a greater number of adaptation practices on a larger scale are, on average, found to be 13% more technically efficient than those adopting fewer practices on smaller scale. The empirical results also show that average TE is only 0.72, indicating that there are opportunities for farming households in Nepal to further improve productive efficiency, on average by 28%. Other important factors that explain variations in the productive efficiency across farming households include farmer’s education level, irrigation facilities, market access, and social capital such as farmer’s participations in relevant agricultural organizations and clubs. This study provides empirical evidence to policy makers that small scale adjustments made by farmers in response to climate change impacts are effective in improving farmers’ efficiency in agriculture production. This indicates a need for farmers’ involvement in climate change adaptation planning.     

Arsenic speciation and turnover in intact organic soil mesocosms during experimental drought and rewetting

Wetlands are significant sources and sinks for arsenic (As), yet the geochemical conditions and processes causing a release of dissolved arsenic and its association with the solid phase of wetland soils are poorly known. Here we present experiments in which arsenic speciation was determined in peatland mesocosms in high spatiotemporal resolution over 10 months. The experiment included a drought/rewetting treatment, a permanently wet, and a defoliated treatment. Soil water content was determined by the TDR technique, and arsenic, iron and sulfate turnover from mass balancing stocks and fluxes in the peat, and solid phase contents by sequential extractions. Arsenic content ranged from 5 to 25 mg kg⁻¹ and dissolved concentrations from 10 to 300 μg L⁻¹, mainly in form of As(III), and secondarily of As(V) and dimethylated arsenic (DMA). Total arsenic was mainly associated with amorphous iron hydroxides (R² > 0.95, α < 0.01) and deeper into the peat with an unidentified residual fraction. Arsenic release was linked to ferrous iron release and primarily occurred in the intensely rooted uppermost soil. Volumetric air contents of 2-13 % during drought eliminated DMA from the porewater and suppressed its release after rewetting for >30 d. Dissolved As(III) was oxidized and immobilized as As(V) at rates of up to 0.015 mmol m⁻³ d⁻¹. Rewetting mobilized As(III) at rates of up to 0.018 mmol m⁻³ d⁻¹ within days. Concurrently, Fe(II) was released at depth integrated rates of up 20 mmol m⁻³ d⁻¹. The redox half systems of arsenic, iron, and sulfur were in persistent disequilibrium, with H₂S being a thermodynamically viable reductant for As(V) to As(III). The study suggests that rewetting can lead to a rapid release of arsenic in iron-rich peatlands and that methylation is of lesser importance than co-release with iron reduction, which was largely driven by root activity.     

Extraordinary heat during the 1930s US Dust Bowl and associated large-scale conditions

Unusually hot summer conditions occurred during the 1930s over the central United States and undoubtedly contributed to the severity of the Dust Bowl drought. We investigate local and large-scale conditions in association with the extraordinary heat and drought events, making use of novel datasets of observed climate extremes and climate reanalysis covering the past century. We show that the unprecedented summer heat during the Dust Bowl years was likely exacerbated by land-surface feedbacks associated with springtime precipitation deficits. The reanalysis results indicate that these deficits were associated with the coincidence of anomalously warm North Atlantic and Northeast Pacific surface waters and a shift in atmospheric pressure patterns leading to reduced flow of moist air into the central US. Thus, the combination of springtime ocean temperatures and atmospheric flow anomalies, leading to reduced precipitation, also holds potential for enhanced predictability of summer heat events. The results suggest that hot drought, more severe than experienced during the most recent 2011 and 2012 heat waves, is to be expected when ocean temperature anomalies like those observed in the 1930s occur in a world that has seen significant mean warming.     

Some long period variations of microseismic activity

Summary The microseisms recorded at Uppsala have been studied for the time 1907–1947 with regard to long period variations. There is clear evidence of an 11 year variation and slight indications of a 28 month variation. The 11 year variation is from 1923 negatively correlated to the sunspot frequency and is explained by corresponding meridional displacements of the dominant cyclonic tracks.

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Zusammenfassung Die in Uppsala registrierte Bodenunruhe ist für die Zeit 1907–1947 betreffs langperiodischen Schwankungen untersucht worden. Eine 11-j?hrige Variation wird festgestellt und es gibt weiter Anzeichnungen einer Variation von 28 Monaten. Die 11-j?hrige Variation ist seit 1923 zur Sonnenflecken-frequenz negativ korreliert und ist durch entsprechende meridionale Verschiebungen der am meisten betretenen Zyklonenbahnen, erkl?rt.

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Riassunto L'agitazione microsismica registrata a Uppsala nel quarantennio 1907–1947 venne esaminata in vista di determinare le oscillazioni di lungo periodo. Si è accertata una oscillazione undecennale, trovandosi altresi indizi per una oscillazione di 28 mesi. Dal 1923 l'oscillazione undecennale manifesta una correlazione negativa con la frequenza delle macchie solari e viene spiegata con i corrispondenti spostamenti meridionali delle rotte cicloniche dominanti.

     

Arsenic in seawater and brown algae of the Baltic and the North Sea

A long-term study within the pilot environmental specimen bank programme of the Federal Republic of Germany on arsenic levels in coastal and open seawater and their reflection in the brown seaweed (Fucus vesiculosus) has been performed. Dissolved arsenic was on average 0.76 (range 0.45–1.11) μgl⁻¹ for 17 sampling stations in the Baltic Sea, whereas contents of dissolved arsenic are somewhat higher in shallow waters of the coastal zone of the North Sea. Total arsenic levels in algae ranged up to 40 mg kg⁻¹ (dry weight) and showed for the four locations studied obvious seasonal variations for comparatively nonpolluted or nondisturbed locations only. However, probably due to biological influences, the results obtained so far indicate that composite samples integrating a one year period are supposed to be the best strategy for future environmental specimen banking. Using a new efficient speciation technique the percentage of chemically stable organoarsenic compounds in the investigated algae has been found to be 95% of the total arsenic content and thus somewhat lower than in teleost fish. For comparison, typical data for a few other algae species from the Baltic and the Mediterranean Sea are also shown.     

Achieving a more realistic assessment of rockfall hazards by coupling three‐dimensional process models and field‐based tree‐ring data

Sound knowledge of the spatial and temporal patterns of rockfalls is fundamental for the management of this very common hazard in mountain environments. Process‐based, three‐dimensional simulation models are nowadays capable of reproducing the spatial distribution of rockfall occurrences with reasonable accuracy through the simulation of numerous individual trajectories on highly‐resolved digital terrain models. At the same time, however, simulation models typically fail to quantify the ‘real’ frequency of rockfalls (in terms of return intervals). The analysis of impact scars on trees, in contrast, yields real rockfall frequencies, but trees may not be present at the location of interest and rare trajectories may not necessarily be captured due to the limited age of forest stands. In this article, we demonstrate that the coupling of modeling with tree‐ring techniques may overcome the limitations inherent to both approaches. Based on the analysis of 64 cells (40 m × 40 m) of a rockfall slope located above a 1631‐m long road section in the Swiss Alps, we illustrate results from 488 rockfalls detected in 1260 trees. We illustrate that tree impact data cannot only be used (i) to reconstruct the real frequency of rockfalls for individual cells, but that they also serve (ii) the calibration of the rockfall model Rockyfor3D, as well as (iii) the transformation of simulated trajectories into real frequencies. Calibrated simulation results are in good agreement with real rockfall frequencies and exhibit significant differences in rockfall activity between the cells (zones) along the road section. Real frequencies, expressed as rock passages per meter road section, also enable quantification and direct comparison of the hazard potential between the zones. The contribution provides an approach for hazard zoning procedures that complements traditional methods with a quantification of rockfall frequencies in terms of return intervals through a systematic inclusion of impact records in trees. Copyright © 2014 John Wiley & Sons, Ltd.     

Knowledge-based building reconstruction from terrestrial video sequences

The paper presents an automatic method for the reconstruction of building models from video image sequences. These videos may be recorded using a hand-held camera or a camera mounted on a moving car. Such terrestrial video sequences are economic and flexible. Presenting buildings as geometric models–rather than for instance a representation from a simple meshing of 3D points–enables one to perform a wide range of analyses. However, sparse 3D points and 3D edges do not contain topological relations. Therefore, integrating building structure knowledge into the reconstruction steps plays an important role in our method. First, some rules are applied to reasonably group the extracted features. Then, a suitable outline and normal direction are specified for each surface patch. Based on these surface patches, a hybrid model- and data-driven method is used to recover a building model from both the extracted surface patches and hypothesized parts. Using the building structure knowledge leads to a simple and fast reconstruction method, and also enables one to obtain the main structures of buildings. The results show that this method correctly sets up topological relationships between generated surface patches and also obtains reasonable structure models in occluded areas. Therefore, the reconstructed models satisfy requirements for both visualization and analysis.