Hydraulic and hydrologic modeling has been moving to larger spatial scales with increased spatial resolution, and such models require a global database of river widths and depths to facilitate ...accurate river flow routing. Hydraulic geometry relationships have a long history in estimating river channel characteristics as a function of discharge. A simple near‐global database of bankfull widths and depths (along with confidence intervals) was developed based on hydraulic geometry equations and the HydroSHEDS hydrography data set. The bankfull width estimates were evaluated with widths derived from Landsat imagery for reaches of nine major rivers, showing errors ranging from 8 to 62% (correlation of 0.88), although it was difficult to verify whether the satellite observations corresponded to bankfull conditions. Bankfull depth estimates were compared with in situ measurements at sites in the Ohio and Willamette rivers, producing a mean error of 24%. The uncertainties in the derivation approach and a number of caveats are identified, and ways to improve the database in the future are discussed. Despite these limitations, this is the first global database that can be used directly in hydraulic models or as a set of constraints in model calibration.
Key Points
Developed a global river database
Used hydraulic geometry equations
Leveraged existing hydrologic datasets
Nature based recreation such as wildlife viewing, hiking, running, cycling, canoeing, horse riding and dog walking can have negative environmental effects. A review of the recreation ecology ...literature published in English language academic journals identified 69 papers from 1978 to 2010 that examined the effect of these activities on birds. Sixty-one of the papers (88%) found negative impacts, including changes in bird physiology (all 11 papers), immediate behaviour (37 out of 41 papers), as well as changes in abundance (28 out of 33 papers) and reproductive success (28 out of 33 papers). Previous studies are concentrated in a few countries (United States, England, Argentina and New Zealand), mostly in cool temperate or temperate climatic zones, often in shoreline or wetland habitats, and mostly on insectivore, carnivore and crustaceovore/molluscivore foraging guilds. There is limited research in some regions with both high bird diversity and nature based recreation such as mainland Australia, Central America, Asia, and Africa, and for popular activities such as mountain bike riding and horse riding. It is clear, however, that non-motorised nature based recreation has negative impacts on a diversity of birds from a range of habitats in different climatic zones and regions of the world.
► We reviewed 69 research papers on the effects on birds of nature-based recreation activities. ► 88% report negative impacts, including in physiology, behaviour, abundance and reproduction. ► Most research was in cool or temperate zones, often in shoreline or wetland habitats. ► There was limited research for mainland Australia, Central America, Asia, and Africa. ► Most research was on hiking, with few studies on mountain bike riding and none on horse riding.
Climate, conflict and forced migration Abel, Guy J.; Brottrager, Michael; Crespo Cuaresma, Jesus ...
Global environmental change,
January 2019, 2019-01-00, 20190101, Volume:
54
Journal Article
Peer reviewed
Open access
•Growing public interest on climate driver of conflict and migration but evidence is scarce.•Climate change is responsible for increase in asylum seeking through conflict.•Reduced rainfall increases ...conflict which in turn drive outflow of asylum seekers.•Established causal relationship between climate, conflict and asylum seeking only in the recent period.
Despite the lack of robust empirical evidence, a growing number of media reports attempt to link climate change to the ongoing violent conflicts in Syria and other parts of the world, as well as to the migration crisis in Europe. Exploiting bilateral data on asylum seeking applications for 157 countries over the period 2006–2015, we assess the determinants of refugee flows using a gravity model which accounts for endogenous selection in order to examine the causal link between climate, conflict and forced migration. Our results indicate that climatic conditions, by affecting drought severity and the likelihood of armed conflict, played a significant role as an explanatory factor for asylum seeking in the period 2011–2015. The effect of climate on conflict occurrence is particularly relevant for countries in Western Asia in the period 2010–2012 during when many countries were undergoing political transformation. This finding suggests that the impact of climate on conflict and asylum seeking flows is limited to specific time period and contexts.
Human crowds often bear a striking resemblance to interacting particle systems, and this has prompted many researchers to describe pedestrian dynamics in terms of interaction forces and potential ...energies. The correct quantitative form of this interaction, however, has remained an open question. Here, we introduce a novel statistical-mechanical approach to directly measure the interaction energy between pedestrians. This analysis, when applied to a large collection of human motion data, reveals a simple power-law interaction that is based not on the physical separation between pedestrians but on their projected time to a potential future collision, and is therefore fundamentally anticipatory in nature. Remarkably, this simple law is able to describe human interactions across a wide variety of situations, speeds, and densities. We further show, through simulations, that the interaction law we identify is sufficient to reproduce many known crowd phenomena.
Very high resolution synthetic aperture radar (SAR) sensors represent an alternative to aerial photography for delineating floods in built-up environments where flood risk is highest. However, even ...with currently available SAR image resolutions of 3 m and higher, signal returns from man-made structures hamper the accurate mapping of flooded areas. Enhanced image processing algorithms and a better exploitation of image archives are required to facilitate the use of microwave remote-sensing data for monitoring flood dynamics in urban areas. In this paper, a hybrid methodology combining backscatter thresholding, region growing, and change detection (CD) is introduced as an approach enabling the automated, objective, and reliable flood extent extraction from very high resolution urban SAR images. The method is based on the calibration of a statistical distribution of "open water" backscatter values from images of floods. Images acquired during dry conditions enable the identification of areas that are not "visible" to the sensor (i.e., regions affected by "shadow") and that systematically behave as specular reflectors (e.g., smooth tarmac, permanent water bodies). CD with respect to a reference image thereby reduces overdetection of inundated areas. A case study of the July 2007 Severn River flood (UK) observed by airborne photography and the very high resolution SAR sensor on board TerraSAR-X highlights advantages and limitations of the method. Even though the proposed fully automated SAR-based flood-mapping technique overcomes some limitations of previous methods, further technological and methodological improvements are necessary for SAR-based flood detection in urban areas to match the mapping capability of high-quality aerial photography.
Phosphorus has been identified as an important determinant of nutrition-related biological variation. The macronutrients protein (P) and carbohydrates (C), both alone and interactively, are known to ...affect animal performance. No study, however, has investigated the importance of phosphorus relative to dietary protein or carbohydrates, or the interactive effects of phosphorus with these macronutrients, on fitness-related traits in animals. We used a nutritional geometry framework to address this question in adult field crickets (Gryllus veletis). Our results showed that lifespan, weight gain, acoustic mate signalling and egg production were maximized on diets with different P : C ratios, that phosphorus did not positively affect any of these fitness traits, and that males and females had different optimal macronutrient intake ratios for reproductive performance. When given a choice, crickets selected diets that maximized both lifespan and reproductive performance by preferentially eating diets with low P : C ratios, and females selected diets with a higher P : C ratio than males. Conversely, phosphorus intake was not regulated. Overall, our findings highlight the importance of disentangling the influences of different nutrients, and of quantifying both their individual and interactive effects, on animal fitness traits, so as to gain a more integrative understanding of their nutritional ecology.
Here we show the extent to which the expected world population growth could be lowered by successfully implementing the recently agreed-upon Sustainable Development Goals (SDGs). The SDGs include ...specific quantitative targets on mortality, reproductive health, and education for all girls by 2030, measures that will directly and indirectly affect future demographic trends. Based on a multidimensional model of population dynamics that stratifies national populations by age, sex, and level of education with educational fertility and mortality differentials, we translate these goals into SDG population scenarios, resulting in population sizes between 8.2 and 8.7 billion in 2100. Because these results lie outside the 95% prediction range given by the 2015 United Nations probabilistic population projections, we complement the study with sensitivity analyses of these projections that suggest that those prediction intervals are too narrow because of uncertainty in baseline data, conservative assumptions on correlations, and the possibility of new policies influencing these trends. Although the analysis presented here rests on several assumptions about the implementation of the SDGs and the persistence of educational, fertility, and mortality differentials, it quantitatively illustrates the view that demography is not destiny and that policies can make a decisive difference. In particular, advances in female education and reproductive health can contribute greatly to reducing world population growth.
The wellbeing of soils is crucial for securing food production worldwide. The soil health (SH) concept has been introduced due to an evolving understanding that soil is not just a growing medium for ...crops but that it provides a foundation for other essential ecosystem services (ES). The SH concept requires development of a holistic index for reliable and quantitative assessment of soil wellbeing related to the effects of different soil management practices and land uses. The aims of this paper are to: (1) review current approaches and methods to assess SH, (2) highlight the role of soil ES in characterizing soil function and (3) propose a new approach to assess SH via monitoring of ES provided by soils. We introduce a brief critical review of the following three main steps required for assessment of common SH indices: (1) selection of relevant attributes; (2) quantification and scoring approaches; and (3) integration of the selected attributes to construct the SH index. These steps usually include statistical or expert opinion-based approaches. In addition, we present a new approach that highlights the relevance and importance of soil ES, i.e., provisioning, regulating and supporting services that must be quantified for comprehensive assessment of soil functions and for fitting models that relate selected soil attributes to ES. This will allow practitioners and scholars to identify the most significant and universal attributes, quantify the relative contribution of each attribute to each ES, and subsequently assess the overall health of soils.
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•A holistic approach for soil health assessment is crucial to sustain land resources.•Current approaches and essential steps to assess soil health are briefly reviewed.•Soil health index should reflect soil ability to provide ecosystem services (ES).•The relationship between soil attributes and ES should be quantified.
Agriculture is a major contributor to global greenhouse gas (GHG) emissions and must feature in efforts to reduce emissions. Organic farming might contribute to this through decreased use of farm ...inputs and increased soil carbon sequestration, but it might also exacerbate emissions through greater food production elsewhere to make up for lower organic yields. To date there has been no rigorous assessment of this potential at national scales. Here we assess the consequences for net GHG emissions of a 100% shift to organic food production in England and Wales using life-cycle assessment. We predict major shortfalls in production of most agricultural products against a conventional baseline. Direct GHG emissions are reduced with organic farming, but when increased overseas land use to compensate for shortfalls in domestic supply are factored in, net emissions are greater. Enhanced soil carbon sequestration could offset only a small part of the higher overseas emissions.
Microwave remote sensing of flood inundation Schumann, Guy J.-P.; Moller, Delwyn K.
Physics and chemistry of the earth. Parts A/B/C,
2015, 2015-00-00, 20150101, Volume:
83-84
Journal Article
Peer reviewed
•SAR for flood applications has grown considerably over the past decade.•Multitemporal SAR can monitor flood dynamics.•High-resolution SAR can map flooding in urban areas.•Long radar wavelengths can ...detect flooding under dense vegetation.•New SAR sensors expected to have significant impacts on flood applications.
Flooding is one of the most costly natural disasters and thus mapping, modeling and forecasting flood events at various temporal and spatial scales is important for any flood risk mitigation plan, disaster relief services and the global (re-)insurance markets. Both computer models and observations (ground-based, airborne and Earth-orbiting) of flood processes and variables are of great value but the amount and quality of information available varies greatly with location, spatial scales and time. It is very well known that remote sensing of flooding, especially in the microwave region of the electromagnetic spectrum, can complement ground-based observations and be integrated with flood models to augment the amount of information available to end-users, decision-makers and scientists. This paper aims to provide a concise review of both the science and applications of microwave remote sensing of flood inundation, focusing mainly on synthetic aperture radar (SAR), in a variety of natural and man-made environments. Strengths and limitations are discussed and the paper will conclude with a brief account on perspectives and emerging technologies.
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