The time evolution of marginally trapped surfaces

In previous work we have shown the existence of a dynamical horizon or marginally trapped tube (MOTT) containing a given strictly stable marginally outer trapped surface (MOTS). In this paper we show some results on the global behavior of MOTTs assuming the null energy condition. In particular we show that MOTSs persist in the sense that every Cauchy surface in the future of a given Cauchy surface containing a MOTS also must contain a MOTS. We describe a situation where the evolving outermost MOTS must jump during the coalescence of two seperate MOTSs. We furthermore characterize the behavior of MOTSs in the case that the principal eigenvalue vanishes under a genericity assumption. This leads to a regularity result for the tube of outermost MOTSs under the genericity assumption. This tube is then smooth up to finitely many jump times. Finally we discuss the relation of MOTSs to singularities of a space-time.Comment: 21 pages. This revision corrects some typos and contains more detailed proofs than the original versio

The ecosystem approach in ecological impact assessment: Lessons learned from windfarm developments on peatlands in Scotland

The Ecosystem Approach introduced in 1994 through the Convention on Biological Diversity, together with related Ecosystem-based Management and Landscape Approaches are frequently called upon to improve ecological impact assessment. Current practice typically does not have such a systems focus and we explore the potential for explicitly adopting an Ecosystem Approach in the Environmental Impact Assessment process using wind energy development on peatland, in Scotland, as a case study. Based on a review of 21 windfarm projects (>50MW) approved by the Scottish Government we provide an overview of current practice and identify and discuss how the 12 principles of the Ecosystem Approach can help identify options for more appropriate impact assessment. These include defining functional units of analysis that reflect the spatial and temporal linkages of peatland elements through hydrological connections, rather than a focus on individual vegetation types and simple distance buffers. Our conclusions are not limited to peatland and are relevant wherever meaningful functional management units can be defined, including in marine environments. Our results also show that environmental statements for wind energy development in Scotland largely ignore ecosystem services and the people that benefit from them. As for threatened species and other biodiversity features, an Ecosystem Approach is a prerequisite to the meaningful inclusion of ecosystem services in impact assessment

Experimental investigation of drying by pore networks: influence of pore size distribution and temperature

Isothermal and non-isothermal drying of pore structures has been experimentally investigated using 2D square network models of interconnected etched channels with different (Gaussian) distributions of the channel width. In experiments with imposed temperature gradients, the temperatures either increase from the open side of the network with increasing network depth (referred to as the positive temperature gradient) or the temperatures decrease with increasing distance from the network opening (i.e. a negative temperature gradient). Experiments reveal that the observed phase patterns, or the distributions of liquid and gas, during drying are significantly depending on the direction of the temperature gradient; but also the presence of macro channels can have a strong effect on the phase patterns as well as on drying time

Assessing the Impacts of Changing Connectivity of Hydropower Dams on the Distribution of Fish Species in the 3S Rivers, a Tributary of the Lower Mekong

Hydropower plants (HPPs) create barriers across rivers and fragment aquatic ecosystems, river reaches and habitats. The reservoirs they create slow the flowing water and convert the riverine into lacustrine ecosystems. The barriers created by HPPs interrupt the seasonal migrations of many fish species, while the reservoirs drive away fish species that are dependent on flowing water habitats. This paper assesses the distribution of fish species in the 3S rivers—Sekong, Sesan and Sre Pok, in Cambodia, Laos and Viet Nam—using IUCN Red List-assessed species distribution by HydroBasin Level 8 from the freshwater reports of the Integrated Biodiversity Assessment Tool (IBAT) and their connectivity with the Mekong. There are currently 61 commissioned dams in the 3S basins and a further 2 under construction, 23 of which are larger than the 30 MW installed capacity. A further 24 HPPs are proposed or planned in these basins. The changes in connectivity caused by the dams are measured by adapting the River Class Connectivity Index (RCICLASS); the original connectivity of the 3S basin taking into account the two major waterfalls in the Sesan and Sre Pok rivers was estimated at 80.9%. With existing dams, the connectivity has been reduced to 23.5%, and with all planned dams, it is reduced further to 10.9%. The resulting re-distribution of fish species occurring throughout the 3S basins is explored, by focusing on migratory guilds and threatened and endemic fish species. With all dams built, it is predicted that the total numbers of species in HydroBasins above the dams will be reduced by 40–50%. The Threatened Species Index is estimated to fall from over 30 near the confluence of the three rivers to less than 10 above the lowest dams on the 3S rivers. The analysis demonstrates how widely available global and regional datasets can be used to assess the impacts of dams on fish biodiversity in this region

Mapping and assessing soil protection through an integrative ecosystem service framework.

Recent studies show that introducing the ecosystem service concept into policy and decisionmaking requires spatially explicit information on the state and trends of ecosystems and their services (Maes et al., 2012). Current spatially explicit approaches are often based on land cover assessments (Burkhard et al., 2009; Nelson et al., 2009), assigning values of ecosystem service provision to each land cover class. This approach fails to make a distinction between the actual service provision and the underlying ecosystem potential to provide a specific service. By focusing on actual ecosystem service provision (e.g. tonnes of soil that are fixated by vegetation) the potential of a given ecosystem or community under alternative management options is ignored (e.g. afforestation on a marginal grassland will increase soil fixation when comparing a grassland to a mature forest). The full potential value that the ecosystem service can provide (in this example to mitigate soil erosion) is therefore not taken into account