An optimized spatial proximity model for fine particulate matter air pollution exposure assessment in areas of sparse monitoring

GIS-based proximity models are one of the key tools for the assessment of exposure to air pollution when the density of spatial monitoring stations is sparse. Central to exposure assessment that utilizes proximity models is the ‘exposure intensity–distance’ hypothesis. A major weakness in the application of this hypothesis is that it does not account for the Gaussian processes that are at the core of the physical mechanisms inherent in the dispersion of air pollutants.

Building upon the utility of spatial proximity models and the theoretical reliability of Gaussian dispersion processes of air pollutants, this study puts forward a novel Gaussian weighting function-aided proximity model (GWFPM). The study area and data set for this work consisted of transport-related emission sources of PM_2.5 in the Houston-Baytown-Sugar Land metropolitan area. Performance of the GWFPM was validated by comparing on-site observed PM_2.5 concentrations with results from classical ordinary kriging (OK) interpolation and a robust emission-weighted proximity model (EWPM). Results show that the fitting R² between possible exposure intensity calculated by GWFPM and observed PM_2.5 concentrations was 0.67. A variety of statistical evidence (i.e., bias, root mean square error [RMSE], mean absolute error [MAE], and correlation coefficient) confirmed that GWFPM outperformed OK and EWPM in estimating annual PM_2.5 concentrations for all monitoring sites. These results indicate that a GWFPM utilizing the physical dispersing mechanisms integrated may more effectively characterize annual-scale exposure than traditional models. Using GWFPM, receptors’ exposure to air pollution can be assessed with sufficient accuracy, even in those areas with a low density of monitoring sites. These results may be of use to public health and planning officials in a more accurate assessment of the annual exposure risk to a population, especially in areas where monitoring sites are sparse.     

Long‐term spatial dynamics in vegetated seascapes: fragmentation and habitat loss in a human‐impacted subtropical lagoon

Vegetated coastal seascapes exhibit dynamic spatial patterning, some of which is directly linked to human coastal activities. Human activities (e.g. coastal development) have modified freshwater flow to marine environments, resulting in significant changes to submerged aquatic vegetation (SAV) communities. Yet, very little is known about the spatially complex process of SAV habitat loss and fragmentation that affects ecosystem function. Using habitat mapping from aerial photography spanning 71 years (1938–2009) for Biscayne Bay (Florida, USA), we quantify both SAV habitat loss and fragmentation using a novel fragmentation index. To understand the influence of water management practices on SAV seascapes, habitat loss and fragmentation were compared between nearshore and offshore locations, as well as locations adjacent to and distant from canals that transport freshwater into the marine environment. Habitat loss and fragmentation were significantly higher along the shoreline compared with offshore seascapes. Nearshore habitats experienced a net loss of 3.31% of the total SAV mapped (2.57 km²) over the time series. While areas adjacent to canals had significantly higher SAV cover, they still experienced wide fluctuations in cover and fragmentation over time. All sites exhibited higher fragmentation in 2009 compared with 1938, with four sites exhibiting high fragmentation levels between the 1990s and 2000s. We demonstrate that freshwater inputs into coastal bays modify the amount of SAV and the fragmentation dynamics of SAV habitats. Spatial changes are greater close to shore and canals, indicating that these coastal developments have transformative impacts on vegetated habitats, with undetermined consequences for the provisioning of ecosystem goods and services.     

Quantifying the reefscape transformation of a coastal Caribbean coral reef during a phase shift and the associated coastal landscape change

Caribbean coral reefs are under strong natural and human pressures and many have undergone phase shifts as a result of local and global change. However few studies have quantified the extent of these phase shifts and the potential impacts that they have on coral reef communities. A temporal comparative analysis of several coral reefscape and landscape metrics was conducted for data from Mahahual, Quintana Roo, Mexico, between the years 2000 and 2006, when a phase shift occurred. Landscape metrics were calculated from coral reef and coastal cover maps obtained by multispectral satellite image classification using IKONOS satellite imagery. These metrics showed that the coastal landscape and reefscape of Mahahual lost 85 ha of vegetation cover and 43 ha of coral cover over 6 years, respectively. Coastal landscape transformation was induced by the construction of a cruise ship pier and multiple associated tourist developments along the coast, such as hotels and restaurants, meanwhile alteration of the reefscape may be associated with potential stressors such as coastal development, bleaching events and hurricanes.     

Pursuing sustainable nitrogen management following the “5 Ps” principles: Production,People, Planet,Policy and Partnerships

Nitrogen (N) is an essential nutrient to support life, but if poorly managed, can adversely affect the environment, ecosystems and human health. The global challenge of achieving food security with minimal ecosystem degradation and human health impacts hinges on sustainable N management, which goes beyond farm level and requires concerted efforts from a range of stakeholders. While various metrics have been developed to inform N management, most of them focus on one or two stakeholders only. Few efforts have tried to integrate N metrics to derive a coherent set of actions for all stakeholders. Here we propose the “5 Ps” principles (Production, People, Planet, Policy and Partnerships) that shape guidelines for sustainable N management with multidimensional N metrics (i.e., N use efficiency, virtual N factor, N footprint, N neutrality, reactive N spatial intensity, N boundary, N price and N equity). The “5 Ps” principles address the environmental, social and economic dimensions of sustainability. These principles allow multidimensional evaluation of N management, highlight specific areas for improvement, direct future research, and support the design of effective policy and legislation. They facilitate collective actions of producers, consumers, researchers and policy makers towards sustainable N management regionally and globally.     

Spatial metrics to study urban patterns in growing and shrinking cities

This article reviews existing literature on spatial metrics, presenting a portfolio of metrics addressing the spatial patterns of growing and shrinking cities and discussing their potential and limitations. A wide and diverse set of spatial metrics was found. While these metrics address most of the identified spatial patterns of urban growth, spatial metrics used in urban shrinkage studies are much scarcer and not nearly sufficient to provide a comprehensive assessment of its spatial patterns. The article concludes that there is great potential for the development of new spatial metrics or mixed indicators, particularly in shrinkage contexts. The article builds on recent literature focusing on reviewing and developing metrics for particular spatial patterns (notably patterns of urban sprawl), while considering a very broad and multidisciplinary set of metrics. It focuses not only on the outcomes of urban growth but also on those of the increasingly common shrinking phenomenon.     

Temporal Extensions of Landscape Ecology Theory and Practice: Examples from the Peruvian Amazon*

The growing overlap between geographic information science (GIScience) and landscape ecology for landscape characterization has led to increasingly sophisticated measures of landscape site and situation. Scale, both temporal and spatial, has been injected into methodologies to improve our ability to derive process from pattern with the hope of defining, monitoring, and modeling ecological landscape function. This article addresses an evolving methodology of longitudinal or panel analysis designed to test the relative importance of thematic versus structural landscape configuration as well as interannual versus intra‐annual change. Landscape typologies for both temporal signature and dominant structural trajectories are offered as guideposts for rethinking dynamic landscape characterization. A case study from the Peruvian Amazon is provided to illustrate interpretive advances available via panel methods that allow for disentangling inter‐ and intra‐annual shifts as well as separating changes in composition versus configuration for improved understanding of landscape dynamics and dynamism.     

Reference conditions of German stream types analysed and revised with macroinvertebrate fauna

This study investigates reference conditions of German stream types using the top-down stream typology developed by Pottgiesser & Sommerhäuser (2004) and 264 macrozoobenthos samples selected as representing reference status. With the aid of discriminant and correlation analyses, the use of typological parameters is investigated as regards their relevancy and the study aims to show whether the metrics used in the newly developed type-specific indices (Böhmer et al. 2004b) reflect the reference conditions. The data cover 15 of the 24 German stream types. The use of stream size, of ecoregions as an indirect parameter for geographical altitude, and of the bottom substrate for the lowland stream types as typological factors can be confirmed, as can six stream types as separate and independent. As bottom substrate is an essential factor for the lowland stream types, their independency is at least probable. For the stream types of the lower mountain regions, a separation of siliceous and calcareous types seems not to be crucial for the bioassessment on metric level, while a new approach for and a possible splitting of the small streams in floodplains is recommended.     

基于邻近图的道路网络特征分析

基于邻近图理论针对北京道路网络数据并结合道路网络特征参数进行了试验分析,进而研究了北京道路网络特征。结果表明,相关邻近图能较好地反映北京道路网络特征,基于邻近图分析道路网络特征为道路网络分析提供了理论支撑。     

Impacts of river bank stabilization using riprap on fish habitat in two contrasting environments

Riverbank stabilization using rock riprap is commonly used for protecting road and bridge structures from fluvial erosion. However, little is known about how streams adjust to such perturbation or how this can affect fish habitat in different fluvial environments, particularly for non‐salmonid species in small streams. The objective of this study is to assess impacts of riprap on fish habitat quantity and quality through a pairwise comparison of 27 stabilized and non‐stabilized stream reaches in two physiographic regions, the Saint Lawrence Lowlands and the Appalachian highlands of Montérégie‐Est (Quebec, Canada). Both quantitative (Hydro‐morphological Index of Diversity, HMID) and qualitative (Qualitative Habitat Evaluation Index, QHEI) fish habitat assessment techniques are applied in order to compare results between methods. For each stream reach depth and velocity were measured to calculate HMID. In‐stream cover (woody debris, overhanging vegetation, undercut banks, aquatic macrophytes) and habitat units (pools, riffles, runs, glides) were also documented and used to determine QHEI. Results show that overall bank stabilization using riprap at bridge and stream crossings alters fish habitat characteristics. Loss of in‐stream covers and riparian vegetation lower QHEI scores at stabilized reaches, especially in more pristine Appalachian streams, but has less impact on already altered straightened Lowlands streams. In this latter context, some positive alterations of fish habitat were observed in riprapped reaches due to the coarsening of the substrate and an induced increase of slope. The two metrics (HMID and QHEI) revealed similar differences between stabilized and non‐stabilized sites for Lowlands sites, but their level of agreement was much less in the Appalachian streams, suggesting caution when interpreting habitat quality results based on a single metric. Copyright © 2016 John Wiley & Sons, Ltd.     

Protected nearshore shallow and deep subtidal rocky reef communities differ in their trophic diversity but not their nutritional condition

Large physical changes that alter reef macrobenthos and fish assemblages occur with increasing depth, so the biological processes that regulate communities at different depths are expected to diverge. We used analyses of stable isotopes (δ13C and δ15N) and fatty acids to establish whether shallow (11–25 m) and deep (45–75 m) warm-temperate reef communities within a South African marine protected area differ in their trophic organisation and nutritional condition. We found evidence of enhanced nutritional condition in plankton from the deeper reef as compared with the shallow reef based on the essential fatty acid content, but this effect was generally not observed in the macrobenthos or the fish communities. Community-based indices derived from the stable isotope data indicated that the shallow-reef community had significantly greater niche diversification (greater diversity of carbon sources at the base of the food web) and more niche space occupied than the deep-reef community. One obvious difference in available carbon sources between reef communities was the absence of benthic primary production on the deep reef, where light is limiting. Our results highlight that the decreased trophic diversity, and to an extent functional redundancy, associated with the simplification of food webs at depth may translate into greater vulnerability of deep reefs to disturbance.