Atoll island vulnerability to flooding and inundation revealed by historical reconstruction: Fongafale Islet, Funafuti Atoll, Tuvalu

The reef islands formed on coral atolls are generally small, low, and flat, with elevations of only a few meters. These islands are thus highly vulnerable to elevated sea levels caused by extreme events and global warming. Such vulnerability was recently evidenced at Fongafale Islet, the capital of Tuvalu, when it flooded during accelerated spring high tides possibly related to sea level rise caused by global warming. Many factors, not only environmental but also economic and social, determine the vulnerability of an island to sea level rise. In this study, we used data spanning 108 yrs to reconstruct changes in topography, land use/cover, population, and the distribution of buildings at Fongafale Islet. The results indicate that the vulnerability of Fongafale Islet relates to its original landform characteristics: the central part of the island was formerly dominated by swampland that flooded at high tides. Fongafale Islet experienced greater population in-migration and centralization beginning in the 1970s following the independence of Tuvalu and Kiribati. Migrants were also responding to declines in overseas mining operations and limited options for paid employment. As the population increased, construction took place in vulnerable swampland areas. Our results clearly demonstrate that examinations of global environmental issues should focus on characteristics specific to the region of interest. These characteristics should be specified using historical reconstruction to understand and address the vulnerability of an area to global environmental changes.     

Impacts of agriculture and urbanization on the climate of the Northeastern United States

The climate sensitivity to specification of agricultural and urban land cover was investigated using the climate version of the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) for 1990 over northeastern United States. The simulations were for 5 yr at a spatial resolution of 36 km. Urbanization resulted in near-surface temperature increases of more than 1 K over the urban sites during both winter and summer. The increase in summer temperature due to urbanization was more widespread than that due to the effect of agricultural land use. The conversion of forest to agricultural land resulted in a decrease in temperature of more than 0.5 K during winter and an increase of more than 1 K during summer over the sites of perturbation. The reduced temperature during winter is related to snow cover. Agricultural lands are covered by snow while the trees in non-agricultural areas protrude through the snow, reducing the albedo of the surface. The warming during summer reflects reduced evaporation. Urbanization also reduces the diurnal temperature range (DTR) by about 0.4 K.     

Scenarios of land cover in China

A method for surface modeling of land cover change (SMLC) is developed on the basis of establishing transition probability matrixes between land cover types and HLZ types. SMLC is used to simulate land cover scenarios of China for the years 2039, 2069 and 2099, for which HLZ scenarios are first simulated in terms of HadCM3 climatic scenarios that are downscaled in zonal model of spatial climate change in China. This paper also analyzes spatial distribution of land cover types, area change and mean center shift of each land cover type, ecotope diversity, and patch connectivity under the land cover scenarios. The results show that cultivated land would decrease and woodland would expand greatly with climatic change, which coincides with consequences expected by implementation of Grain-for-Green policy. Nival area would shrink, and desertification area would expand at a comparatively slow rate in future 100 years. Climate change would generally cause less ecotope diversity and more patch connectivity. Ecosystems in China would have a pattern of beneficial cycle after efficient ecological conservation and restoration. However, if human activities would exceed regulation capacity of ecosystems themselves, the ecosystems in China might deteriorate more seriously.     

Agricultural impacts on ecosystem functioning in temperate areas of North and South America

Land use has a large impact on ecosystem functioning, though evidences of these impacts at the regional scale are scarce. The objective of this paper was to analyze the impacts of agricultural land use on ecosystem functioning (radiation interception and carbon uptake) in temperate areas of North and South America. From land cover maps generated using high-resolution satellite images we selected sites dominated by row crops (RC), small grain crops (SG), pastures (PA), and rangelands (RA) in the Central Plains of USA and the Pampas of Argentina. These two regions share climatic characteristics and the agricultural conditions (crop types) are also very similar. Both areas were originally dominated by temperate grasslands. In these sites we extracted the temporal series of the normalized difference vegetation index (NDVI) from the NOAA satellites for the period 1989–1998 and calculated the mean seasonal NDVI curve for each site. Additionally, we calculated the mean annual NDVI, the maximum NDVI, the date of the year when the max NDVI was recorded and the interannual variability of these three attributes. We compared the mean values of each NDVI-derived attribute between land cover types and between continents. The NDVI seasonal patterns for each land cover type were roughly similar between the Central Plains and the Pampas during the growing season. The largest differences were observed during the winter and spring, when the NDVI of all land cover types in the Central Plains remained at lower values than in the Pampas. This was probably caused by the high annual thermal amplitude in the Central Plains that results in a much more restricted growing season. As a result of these differences in the shape of the NDVI curve, the mean annual NDVI in the Central Plains was lower than in the Pampas for all land cover types but the maximum NDVI did not differ importantly. In both regions, row crops delayed the date of the NDVI peak, small grain crops advanced it and pastures did not change it importantly, compared with rangelands. The interannual variability of the NDVI attributes was higher for small grains than for row crops in both regions. However, small grains crops were consistently more variable between years in the Central Plains than in the Pampas. The opposite occurred with pastures and rangelands, which were more variable in the Pampas than in the Central Plains. This paper confirms and generalizes previous findings that showed important imprints of land use on ecosystem functioning in temperate ecosystems. Our results support the idea that the changes in land cover that have occurred in the Central Plains and the Pampas leaded to similar changes in the way that ecosystems absorb solar radiation and in the patterns of carbon uptake.     

Modeling the impacts of grazing land management on land-use change for the Jordan River region

In this article, we describe a simulation method for investigating the impacts of different grazing land management strategies on the productivity of (semi-)natural vegetation and the resulting feedback on land-use change. In a first application, we analyze the effects of sustainable and intensive grazing land management in the Jordan River region. For this purpose, we adapt and use the regional version of the spatially explicit modeling framework LandSHIFT. Our simulation experiments indicate that the modeled feedback mechanism has a strong effect on the spatial extent of grazing land. Consequently, the results of our study underline that the inclusion of such feedback mechanisms in land-use models can help to represent and analyze the complex interactions between humans and the environment in a more differentiated and realistic way, but they also identify the demand for more detailed empirical data on grazing land degradation in order to further improve the explanatory power of the model.     

Improving the methodology for assessing natural hazard impacts

The impacts of natural hazards such as cyclones have been conventionally measured through changes in human, social and economic capital, typically represented by stock variables such as population, built property and public infrastructure, livestock, agricultural land, etc. This paper develops an alternative approach that seeks to detect and quantify impacts as changes in flow variables. In particular, we explore whether changes in annual agricultural output, when measured at an appropriate spatial level, could be used to measure impacts associated with tropical cyclones in coastal regions of India. We believe that such an approach may have a number of benefits from a policy perspective, particularly with regard to the debate between relief versus recovery as disaster management strategies. A focus on flow variables is also likely to be more relevant and useful in developing countries; the maintenance of economic activity directly affects livelihood and is perhaps of greater importance than loss of built property or other physical capital.     

The history of environmental change and adaptation in eastern Saloum–Senegal—Driving forces and perceptions

Environmental change in the Sahel–Sudan zone of West Africa has been a major issue in development debates over the last decades. Using remote sensing based land cover change analysis, archival data, national and international statistical data, and household interviews, we analyze the drivers of environmental change in Eastern Saloum in Central East Senegal as well as the local perceptions of these changes and adaptation. Being part of the ground nut basin, Eastern Saloum has witnessed rapid environmental degradation caused by the conversion of forest and savanna areas to agricultural land during the last 20–30 years and by a combination of decline in precipitation, soil degradation, a diversity of policies with little concern for the environment, fluctuating markets and population pressure. Farmers perceive the environmental change mainly as land degradation and poor soil fertility, though recent extensification of agriculture counters this effect and has led to increased vegetation cover in marginal areas. They identified erratic climate, agricultural policies, insufficient food production and desire to increase income as the main drivers of change in the area. We conclude that while climate variability has influenced environmental change in the area, various types of State interventions in agriculture and global market fluctuations appear to have been the main underlying causes of environmental degradation.     

Geology and impact features of Riachão structure,northern Brazil

Riachão, located at S7°42′/W46°38′ in Maranhão State, northeastern Brazil, is a complex impact structure of about 4.1 km diameter, formed in Pennsylvanian to Permian sedimentary rocks of the Parnaíba Basin sequence. Although its impact origin was already proposed in the 1970s, information on its geology and shock features is still scarce in the literature. We present here the main geomorphological and geological characteristics of the Riachão impact structure obtained by integrated geophysical and remote sensing analysis, as well as geological field work and petrographic analysis. The identified lithostratigraphic units consist of different levels of the Pedra de Fogo Formation and, possibly, the Piauí Formation. Our petrographic analysis confirms the presence of shock‐diagnostic planar microdeformation structures in quartz grains of sandstone from the central uplift as evidence for an impact origin of the Riachão structure. The absence of crater‐filling impact breccias and melt rocks, shatter cones, as well as the restricted occurrence of microscopic shock effects, suggests that intense and relatively deep erosion has occurred since crater formation.     

A new type of magnetograph

A solar magnetograph without electronics or any moving parts has been designed. The principle is the use of a subtracting double-dispersion optical system. The exposure time is of the order of 1 sec.Preliminary results obtained at the Swedish Astrophysical Observatory at Anacapri indicate that this method could be convenient to use in space vehicles when aiming at high spatial resolution of solar magnetic fields.     

Thread safe astronomy

Observational astronomy is the beneficiary of an ancient chain of apprenticeship. Kepler's laws required Tycho's data. As the pace of discoveries has increased over the centuries, so has the cadence of tutelage (literally, “watching over”). Naked eye astronomy is thousands of years old, the telescope hundreds, digital imaging a few decades, but today's undergraduates will use instrumentation yet unbuilt – and thus, unfamiliar to their professors – to complete their doctoral dissertations. Not only has the quickening cadence of astronomical data‐taking overrun the apprehension of the science within, but the contingent pace of experimental design threatens our capacity to learn new techniques and apply them productively. Virtual technologies are necessary to accelerate our human processes of perception and comprehension to keep up with astronomical instrumentation and pipelined dataflows. Necessary, but not sufficient. Computers can confuse us as efficiently as they illuminate. Rather, as with neural pathways evolved to meet competitive ecological challenges, astronomical software and data must become organized into ever more coherent ‘threads’ of execution. These are the same threaded constructs as understood by computer science. No datum is an island. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical Simulations of Oscillation Modes of the Solar Convection Zone

The ACIS front-illuminated CCDs on board the Chandra X-Ray Observatory were damaged in the extreme environment of the Earth's radiation belts, resulting in enhanced charge transfer inefficiency (CTI). This produces a row dependence in gain, event grade, and energy resolution. We model the CTI as a function of input photon energy, including the effects of detrapping (charge trailing), shielding within an event (charge in the leading pixels of the 3x3 event island protects the rest of the island by filling traps), and nonuniform spatial distribution of traps. This technique cannot fully recover the degraded energy resolution, but it reduces the position dependence of gain and grade distributions. By correcting the grade distributions as well as the event amplitudes, we can improve the instrument's quantum efficiency. We outline our model for CTI correction and discuss how the corrector can improve astrophysical results derived from ACIS data.     

Uncertainties in estimates of cropland area in China: a comparison between an AVHRR-derived dataset and a Landsat TM-derived dataset

The large uncertainties in estimates of cropland area in China may have significant implications for major cross-cutting themes of global environmental change—food production and trade, water resources, and the carbon and nitrogen cycles. Many earlier studies have indicated significant under-reporting of cropland area in China from official agricultural census statistics datasets. Space-borne remote sensing analyses provide an alternative and independent approach for estimating cropland area in China. In this study, we report estimates of cropland area from the National Land Cover Dataset (NLCD-96) at the 1:100,000 scale, which was generated by a multi-year National Land Cover Project in China through visual interpretation and digitization of Landsat TM images acquired mostly in 1995 and 1996. We compared the NLCD-96 dataset to another land cover dataset at 1-km spatial resolution (the IGBP DIScover dataset version 2.0), which was generated from monthly Advanced Very High Resolution Radiometer (AVHRR)-derived Normalized Difference Vegetation Index (NDVI) from April, 1992 to March, 1993. The data comparison highlighted the limitation and uncertainty of cropland area estimates from the DIScover dataset.     

Variation of Lunar-Solar Tidal Force and Earthquakes in Taiwan Island of China

This paper considers the relationship between 21 major earthquakes(M_s ≥ 7.0) in land and the offshore area of Taiwan island in the 20th century and thevariance ratio of the lunar-solar tidal force. The result indicates that the time of these earthquakes is closely related to the variance ratio of the lunar-solar tidal force, and therefore that the tidal force possibly plays an important role in triggering earthquakes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gender-specific out-migration, deforestation and urbanization in the Ecuadorian Amazon

The Ecuadorian Amazon, one of the richest reserves of biodiversity in the world, has faced one of the highest rates of deforestation of any Amazonian nation. Most of this forest elimination has been caused by agricultural colonization that followed the discovery of oil fields in 1967. Since the 1990s, an increasing process of urbanization has also engendered new patterns of population mobility within the Amazon, along with traditional ways by which rural settlers make their living. However, while very significant in its effects on deforestation, urbanization and regional development, population mobility within the Amazon has hardly been studied at all, as well as the distinct migration patterns between men and women. This paper uses a longitudinal dataset of 250 farm households in the Northern Ecuadorian Amazon to understand differentials between men and women migrants to urban and rural destinations and between men and women non-migrants. First, we use hazard analysis based on the Kaplan–Meier (KM) estimator to obtain the cumulative probability that an individual living in the study area in 1990 or at time t, will out-migrated at some time, t+n, before 1999. Results indicate that out-migration to other rural areas in the Amazon, especially pristine areas is considerably greater than out-migration to the growing, but still incipient, Amazonian urban areas. Furthermore, men are more likely to out-migrate to rural areas than women, while the reverse occurs for urban areas. Difference-of-means tests were employed to examine potential factors accounting for differentials between male and female out-migration to urban and rural areas. Among the key results, relative to men younger women are more likely to out-migrate to urban areas; more difficult access from farms to towns and roads constrains women's migration; and access to new lands in the Amazon–an important cause of further deforestation–is more associated with male out-migration. Economic factors such as engagement in on-farm work, increasing resource scarcity–measured by higher population density at the farm and reduction in farm land on forest and crops–and increase in pasture land are more associated with male out-migration to rural areas. On the other hand, increasing resource scarcity, higher population density and weaker migration networks are more associated with female out-migration to urban areas. Thus, a “vicious cycle” is created: Pressure over land leads to deforestation in most or all farm forest areas and reduces the possibilities for further agricultural extensification (deforestation); out-migration, especially male out-migration, occurs to other rural or forest areas in the Amazon (with women being more likely to choose urban destinations); and, giving continuing population growth and pressures in the new settled areas, new pressures promote further out-migration to rural destinations and unabated deforestation.     

Resolving the 180° Ambiguity in Solar Vector Magnetic Field Data: Evaluating the Effects of Noise,Spatial Resolution,and Method Assumptions

The objective testing of algorithms for performing ambiguity resolution in vector magnetic field data is continued, with an examination of the effects of noise in the data. Through the use of analytic magnetic field models, two types of noise are “added” prior to resolving: noise to simulate Poisson photon noise in the observed polarization spectra, and a spatial binning to simulate the effects of unresolved structure. The results are compared through the use of quantitative metrics and performance maps. We find that while no algorithm severely propagates the effects of Poisson noise beyond very local influences, some algorithms are more robust against high photon-noise levels than others. In the case of limited spatial resolution, loss of information regarding fine-scale structure can easily result in erroneous solutions. Our tests imply that photon noise and limited spatial resolution can act so as to make assumptions used in some ambiguity resolution algorithms no longer consistent with the observed magnetogram. We confirm a finding of the earlier comparison study that results can be very sensitive to the details of the treatment of the observed boundary and the assumptions governing that treatment. We discuss the implications of these findings, given the relative sensitivities of the algorithms to the two sources of noise tested here. We also touch on further implications for interpreting observational vector magnetic field data for general solar physics research.     

Toward high spatial resolution in solar observations

To achieve high spatial resolution capability for IR solar observations, we suggest the use of a special mask placed before the entrance aperture of large conventional optical telescopes. Such a mask would match well the resolution of a non-redundant array and would provide safe operation of a large telescope used for solar observations. The proposed solution has the additional advantage of relatively low cost because already-existing optical telescopes are used.     

Solar wind,non-force-free magnetic field and two-ribbon flares

With the assumption that the magnetic field lines are radial at some quite high level in the solar corona, a non-constant shearing magnetic field is introduced into the magnetohydrostatic equations. It is found that a same critical amount of shearing a magnetic island is formed and then breaks out to form an open magnetic configuration in which resistive tearing-mode instability may occur, and may initiate a two-ribbon flare. In addition, high shearing magnetic fields are investigated. It is shown that high shearing magnetic configurations are weak two-dimensional neutral sheets, the instability of which has been studied by Janicke (1982).     

Crystal spectrometer studies of the Sun employing a rotation modulation collimator

The use of rotating modulation collimators in high resolution solar X-ray spectroscopy is discussed with reference to the recent flight of a sounding rocket payload. This rocket carried an experiment which combined a modulation collimator and a Bragg crystal spectrometer to make moderately high resolution spectral and spatial measurements simultaneously. The response of the instrument to extended sources is described. It is shown that the technique is particularly suited to long term observations of active region emission, but that useful measurements can be made even during a short rocket flight.Our observations were made in 1972 October 26 between 0432 UT and 0436 UT. During the flight a scan of the solar X-ray spectrum was made which covered the wavelength range 1.45–1.71 nm. A small flare commenced at about 0432 UT in McMath calcium plage region 12094; the emission from this provided the major contribution to the observed spectrum. X-ray emission from a group of active regions in the SW and the small McMath region 12090 has also been detected.Spectral and spatial observations have been combined to investigate the conditions in both active region and flare plasmas.     

Observations of very low-contrast white-light solar structures utilizing differential photometry

The spatial derivative of the intensity structure of the photosphere has been investigated utilizing a differential photometer system capable of recording intensity variations on the solar disc of 0.05% per arc sec. Time evolution images of the differential intensity profile for a 562.5 arc sec segment of the solar photosphere show a high degree of structure. To a large extent the observed structure persists for times greater than one hour and is rather highly ordered in spatial distribution. Power spectra of the spatial structure averaged over one hour show maxima at 28000 km and 16000 km, close to the spatial scale expected for intensity perturbations from supergranulation.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.