Endemic avifaunal biodiversity and tropical forest loss in Makira, a mountainous Pacific island

Anthropogenic habitat changes and the introduction of pigs, dogs, cats and rats have caused a catastrophic decline in the terrestrial biodiversity of Pacific archipelagos. At present, economic globalization and an increased demand for timber are promoting industrial logging and plantation expansion. Commercial logging can be sustainable but in practice it more often leads to land degradation, especially on small flat islands. On large and mountainous islands, however, more modest impacts can be expected as the narrowly endemic species tend to inhabit montane forests where logging is difficult. In this study we use ornithological data collected at different elevations to assess the extent to which the avifauna of Makira, a large mountainous island in Melanesia, will be affected by deforestation of the lowlands, most of which are under timber concessions. Our data suggest that a majority of the endemic bird species use lowland forest to some extent and that this may even apply to species hitherto associated with montane forest. If current commercial forestry programmes are continued, the forest habitat may be disturbed or lost over large parts of Makira, potentially undermining the natural resource base for the local subsistence economy, exacerbating climate change and threatening the integrity of one of the most important areas for biodiversity conservation on earth. Our study highlights the importance of understanding the habitat requirements of endemic species and the urgency of establishing and effectively managing community-based protected areas in suitable lowland forests of the Pacific.     

Fast approximate 1D modelling and inversion of transient electromagnetic data

A novel, fast, and approximate forward modelling routine for time‐domain electromagnetic responses is presented. It is based on the separation of the forward problem into a configuration‐independent part, mapping conductivity as a function of depth onto apparent conductivity as a function of time, and a configuration‐dependent part, i.e., the half‐space step response. The response of a layered model is then found as the half‐space response for a half‐space conductivity equal to the apparent conductivity. The mapping is ten times faster than traditional accurate forward modelling routines, and through stochastic modelling, it is found that the standard deviation of the modelling error is 0.7 %. The forward mapping lends itself to integration in a modern state‐of‐the‐art inversion formulation in exactly the same way as traditionally computed responses, and a field example is included where inversion results using the approximate forward response are compared with those of an accurate forward response for helicopterborne transient electromagnetic data. In addition to being used in its own right in inversion of transient data, the speed and accuracy of the approximate inversion mean that it is well suited for quality control and fast turnaround data delivery of survey results to a client. It can also be used in hybrid inversion formulations by supplying initial iterations and high‐quality derivatives in an inversion based on accurate forward modelling.     

Accumulation of Pesticides in Anaerobic Clayey Till‐Controls and Implications for Groundwater

Pesticide residuals after point‐source pesticide spills in clay‐rich aquitards may potentially affect underlying groundwater for many decades due to slow release of accumulated pollution in the clayey matrix material of the aquitard. In this study, we evaluated factors behind different degrees of accumulation of phenoxy acids (MCPP, dichlorprop, 2,4‐D MCPA) and triazines (simazine and terbutylazine) observed in an old pesticide pollution described by Jørgensen et al. (2016a, this issue). By using leaching experiments, it was shown that a zone of maximum concentrations of MCPP and dichlorprop (mg/L) observed by Jørgensen et al. (2016a, this issue) represented accumulated potentially mobile pollution in anaerobic, however largely immobile pore water of the clayey matrix in the upper few meters of the unoxidized aquitard zone. By using sorption experiments, we determined 9 to16 times higher mobility by diffusion and flow for the phenoxy acids (R = 1 to 2) than for the triazines (R = 9 to 16) in the clayey matrix material of the aquitard. This indicated that more rapid and greater accumulation could occur for the phenoxy acids in the clayey matrix than for the triazines. In contrast, the relative mobility of the phenoxy acids and triazines was much closer in sand‐filled fractures and thin sand layers/lamina in the clay, suggesting that the migration of the same compounds along these textural preferential flow paths into the underlying aquifer was less different. Despite that a greater mass had originally been spilled of 2,4‐D and MCPA having similar mobility as the accumulated MCPP and dichlorprop, these compounds were not accumulated in the zone of maximum concentrations. It is suggested that the controls, which initially allowed for the observed separate accumulation of MCPP and dichlorprop as a zone of maximum pollution, were due to the combination of high persistence and high mobility for these specific pesticides in the clayey till matrix material of the aquitard. The investigation showed that over time the initial high concentrations of the accumulated phenoxy acids (MCPP, dichlorprop) transformed into high concentrations of related mobile degradation products (e.g., 4‐CPP and 2‐CPP), which extended the total time of groundwater pollution beyond the disappearance of the original phenoxyacids.     

Unified multi‐depth‐level field decomposition

Wavefield decomposition forms an important ingredient of various geophysical methods. An example of wavefield decomposition is the decomposition into upgoing and downgoing wavefields and simultaneous decomposition into different wave/field types. The multi‐component field decomposition scheme makes use of the recordings of different field quantities (such as particle velocity and pressure). In practice, different recordings can be obscured by different sensor characteristics, requiring calibration with an unknown calibration factor. Not all field quantities required for multi‐component field decomposition might be available, or they can suffer from different noise levels. The multi‐depth‐level decomposition approach makes use of field quantities recorded at multiple depth levels, e.g., two horizontal boreholes closely separated from each other, a combination of a single receiver array combined with free‐surface boundary conditions, or acquisition geometries with a high‐density of vertical boreholes. We theoretically describe the multi‐depth‐level decomposition approach in a unified form, showing that it can be applied to different kinds of fields in dissipative, inhomogeneous, anisotropic media, e.g., acoustic, electromagnetic, elastodynamic, poroelastic, and seismoelectric fields. We express the one‐way fields at one depth level in terms of the observed fields at multiple depth levels, using extrapolation operators that are dependent on the medium parameters between the two depth levels. Lateral invariance at the depth level of decomposition allows us to carry out the multi‐depth‐level decomposition in the horizontal wavenumber–frequency domain. We illustrate the multi‐depth‐level decomposition scheme using two synthetic elastodynamic examples. The first example uses particle velocity recordings at two depth levels, whereas the second example combines recordings at one depth level with the Dirichlet free‐surface boundary condition of zero traction. Comparison with multi‐component decomposed fields shows a perfect match in both amplitude and phase for both cases. The multi‐depth‐level decomposition scheme is fully customizable to the desired acquisition geometry. The decomposition problem is in principle an inverse problem. Notches may occur at certain frequencies, causing the multi‐depth‐level composition matrix to become uninvertible, requiring additional notch filters. We can add multi‐depth‐level free‐surface boundary conditions as extra equations to the multi‐component composition matrix, thereby overdetermining this inverse problem. The combined multi‐component–multi‐depth‐level decomposition on a land data set clearly shows improvements in the decomposition results, compared with the performance of the multi‐component decomposition scheme.     

Production of gas from coal seams in the Upper Silesian Coal Basin in Poland in the post-injection period of an ECBM pilot site

A pilot site for CO₂ storage in coal seams was set-up in the Upper Silesian Coal Basin in Poland in the scope of the RECOPOL project, funded by the European Commission. About 760 tons CO₂ were injected into the reservoir from August 2004 to June 2005. Breakthrough of the injected CO₂ was established, which resulted in the production of about 10% of the injected CO₂ in this period. This paper reports on activities performed under the European Commission project MOVECBM that aimed at the assessment of the storage performance of the reservoir in the follow-up period, i.e. whether the injected CO₂ was adsorbed onto the coal or whether it was still present as free gas in the pore space. The injection well was used for this purpose, as the production well had to be abandoned for permitting reasons. Several operational periods can be defined between the last injection in June 2005 and the abandonment of the well in October 2007. In the first period the well was shut-in to observe the pressure fall-off, from about 15.0 MPa at the wellhead after the last injection until about 4.5 MPa at the end of 2005. This pressure fall-off curve showed that the reservoir permeability was very low. This seemed to confirm the observed swelling of the coal during the injection period. In the first months of 2006 the pressure at the wellhead was decreased by releasing gas in a controlled way. The amount and composition of the gas were measured. As a result of the pressure reduction, the well flooded with water. A production pump was placed on the former injection well, enabling active production from the coal from March to September 2007. Results of these operations showed that whereas the gas production rates were as expected based on the experience with the production well, the water production was remarkably low. This could be related to permeability issues or, alternatively, indicate a drying effect of the CO₂ in the reservoir. Further, the gas composition showed a predominance of CO₂ over CH₄ during the gas release that changed gradually into a predominance of CH₄ over CO₂ during the production phase. Although stabilization was not reached within the given production period, the composition approached a 60% methane, 40% CO₂ ratio. This indicates that the exchange of these gases is more complex than often envisaged. After removal of the pump the well was filled with water, which ceased the gas release. This indicates that the pressure in the reservoir was back to its original, hydrostatic, state. As the total volume of CO₂ produced was only a fraction of the amount that was injected, it can be concluded that the CO₂ was taken up by the coal and is currently adsorbed. This gives confidence in the long-term stability of the injected CO₂.     

Implications of tree species–environment relationships for the responsiveness of Himalayan krummholz treelines to climate change

Climate warming is expected to advance treelines to higher elevations. However, empirical studies in diverse mountain ranges give evidence of both advancing alpine treelines as well as rather insignificant responses. In this context, we aim at investigating the sensitivity and responsiveness of the near-natural treeline ecotone in Rolwaling Himal, Nepal, to climate warming. We analysed population densities of tree species along the treeline ecotone from closed forest stands via the krummholz belt to alpine dwarf shrub heaths (3700-4200 m) at 50 plots in 2013 and 2014. We quantified species - environment relationships, i.e. the change of environmental conditions (e.g., nutrient and thermal deficits, plant interactions) across the ecotone by means of redundancy analyses, variation partitioning and distance-based Moran's eigenvector maps. In particular, we focus on explaining the high competitiveness of Rhododendron campanulatum forming a dense krummholz belt and on the implications for the responsiveness of Himalayan krummholz treelines to climate change. Results indicate that treeline trees in the ecotone show species-specific responses to the influence of environmental parameters, and that juvenile and adult tree responses are modulated by environmental constraints in differing intensity. Moreover, the species - environment relationships suggest that the investigated krummholz belt will largely prevent the upward migration of other tree species and thus constrain the future response of Himalayan krummholz treelines to climate warming.     

Gamma-burst positions - are they reliable?

Ever since the discovery of the Cosmic Gamma-Ray Bursts we have searched for the quiescent counterparts of these mysterious flashes. Without definite counterparts our pictures of the sources must remain vague. The review discusses a number of techniques which have been applied to the gamma burst localization problem and their limitations. The most accurate technique to-date is the Interplanetary Network (IPN) timing technique. Considering the lack of success in the searches for counterparts in even the smallest gamma burst error boxes, it seems, that the next generation of satellite gamma burst detectors must be designed to allow immediate follow-up with sensitive telescopes. Concepts to achieve this goal are discussed.     

Photo's from Proceedings of the Third MicroQuasar Workshop; Granada Worshop on Galactic Relativistic Jet Sources – Granada,Spain, 11–13 September 2000

The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm²). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin² . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations.