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Satellite Imagery (satellite + imagery)

Distribution by Scientific Domains

Earth and Environmental Science	44%
Life Sciences	38%
Humanities and Social Sciences	8%

Distribution within Earth and Environmental Science

Ecology & Organismal Biology	25%
Atmospheric Sciences	18%

Selected Abstracts

Hemeroby, urbanity and ruderality: bioindicators of disturbance and human impact

JOURNAL OF APPLIED ECOLOGY, Issue 5 2002
M. O. Hill
Summary 1Species vary according to whether they benefit from or are harmed by disturbance and intensive human activity. This variation can be quantified by indices of disturbance and unnaturalness. 2An urban flora was characterized by comparing quadrat data from cities with several large data sets from the countryside. Existing scales of species response to disturbance and unnaturalness, ruderality (a plant's ability to survive in disturbed conditions) and hemeroby (a measure of human impact) were contrasted with derived scales based on the number of associated annuals and aliens and with ,urbanity', defined as the proportion of urban land in the vicinity of each quadrat. 3Species presence data were available from 26 710 quadrats distributed through Great Britain, with urban sites only in central England. Satellite imagery was used to measure the proportion of urban land cover in the vicinity of each quadrat; 2595 quadrats were located in 1-km squares having at least 40% cover of urban land. 4The 20 species having highest urbanity were all alien to Britain, comprising 12 neophytes and eight archaeophytes. 5Of the 20 most frequent species in quadrats situated in 1-km squares with at least 40% urban land cover, 18 were natives. The two exceptions were Artemisia vulgaris , an archaeophyte, and Senecio squalidus , a neophyte. 6Both ruderal and hemerobic species, as usually defined, include many non-urban arable species. The hemeroby scale of Kowarik (1990 ), designed for Berlin, does not work well in Britain. 7The proportion of associated annuals (annuality) and the proportion of associated neophytes (alien richness or xenicity) can be developed into good indices. The annuality scale is very well defined because annuals tend to occur with other annuals. Plants with high annuality are mostly arable weeds. 8Urban specialists in central England are, with a few exceptions, character-species of the phytosociological classes Artemisietea , Galio-Urticetea and Stellarietea . Most of them have numerous non-urban associates and they do not form a very well defined group. They have intermediate levels of annuality combined with relatively high levels of xenicity. 9While it is possible to develop indices of hemeroby, urbanity and ruderality, these concepts are relatively complicated. Annuality and xenicity are simpler measures that can complement Ellenberg values, but definitive values for Great Britain would require additional data from southern England. [source]

A multiscale approach for reconstructing archaeological landscapes: Applications in Northern Apulia (Italy)

ARCHAEOLOGICAL PROSPECTION, Issue 3 2009
Marcello Ciminale
Abstract This paper is focused on the joint use of multiscale remote sensing technologies for supporting archaeological prospection. Satellite imagery, aerial photographs and high-resolution magnetic surveys were adopted for studying the Tavoliere, an extended agricultural region located in Northern Apulia (Italy) that is characterized by an abundant presence of archaeological sites. A first recognition of the archaeological features was performed by historical aerial photographs and satellite QuickBird images were used to obtain an up-to-date synoptic view of the study area. Archaeological features extracted from both aerial and satellite images, were further investigated by high-resolution magnetic survey, which provided detailed identification of buried remains. All data were stored in a GIS in order to integrate them properly. This database was used to cross-check information of different types and determine significant correlations. The multilayer analysis in the GIS environment allowed for a comprehensive reconstruction of ancient landscapes and their palaeoenvironmental context, as well as the present geomorphological and territorial setting. Moreover it represents an open information system that could always be upgraded by inputting new data from future studies. Results from our analyses suggest that this multidisciplinary and multiscale approach, in addition to its important scientific implications, could yield meaningful information for the preservation, monitoring and management of the cultural resource, from a single site to a landscape perspective; thus this integrated tool could play a strategic role in defining proper policies of sustainable development in this region. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Soil erosion assessment using geomorphological remote sensing techniques: an example from southern Italy

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2010
Sergio Lo Curzio
Abstract The aim of this study is to assess of the distribution and map the geomorphological effects of soil erosion at the basin scale identifying newly-formed erosional landsurfaces (NeFELs), by means of an integration of Landsat ETM 7+ remotely sensed data and field-surveyed geomorphological data. The study was performed on a 228·6,km2 -wide area, located in southern Italy. The study area was first characterized from a lithological, pedological, land-use and morpho-topographic point of view and thematic maps were created. Then, the georeferenced Landsat ETM 7+ satellite imagery was processed using the RSI ENVI 4.0 software. The processing consisted of contrast stretching, principal component analysis (PCA), decorrelation stretching and RGB false colour compositing. A field survey was conducted to characterize the features detected on the imagery. Particular attention was given to the NeFELs, which were located using a global positioning system (GPS). We then delimited the Regions of Interest (ROI) on the Landsat ETM 7+ imagery, i.e. polygons representing the ,ground-truth', discriminating the NeFELs from the other features occurring in the imagery. A simple statistical analysis was conducted on the digital number (DN) values of the pixels enclosed in the ROI of the NeFELs, with the aim to determine the spectral response pattern of such landsurfaces. The NeFELs were then classified in the entire image using a maximum likelihood classification algorithm. The results of the classification process were checked in the field. Finally, a spatial analysis was performed by converting the detected landsurfaces into vectorial format and importing them into the ESRI ArcViewGIS 9.0 software. Application of these procedures, together with the results of the field survey, highlighted that some ,objects' in the classified imagery, even if displaying the same spectral response of NeFELs, were not landsurfaces subject to intense soil erosion, thus confirming the strategic importance of the field-checking for the automatically produced data. During the production of the map of the NeFELs, which is the final result of the study, these ,objects' were eliminated by means of simple, geomorphologically-coherent intersection procedures in a geographic information system (GIS) environment. The overall surface of the NeFELs had an area of 22·9,km2, which was 10% of the total. The spatial analysis showed that the highest frequency of the NeFELs occurred on both south-facing and southwest-facing slopes, cut on clayey-marly deposits, on which fine-textured and carbonate-rich Inceptisols were present and displaying slope angle values ranging from 12° to 20°. The comparison of two satellite imageries of different periods highlighted that the NeFELs were most clearly evident immediately after summer tillage operations and not so evident before them, suggesting that these practices could have played an important role in inducing the erosional processes. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Remote sensing and GIS-based flood vulnerability assessment of human settlements: a case study of Gangetic West Bengal, India

HYDROLOGICAL PROCESSES, Issue 18 2005
Joy Sanyal
Abstract Flooding due to excessive rainfall in a short period of time is a frequent hazard in the flood plains of monsoon Asia. In late September 2000, a devastating flood stuck Gangetic West Bengal, India. This particular event has been selected for this study. Instead of following the conventional approach of flooded area delineation and overall damage estimation, this paper seeks to identify the rural settlements that are vulnerable to floods of a given magnitude. Vulnerability of a rural settlement is perceived as a function of two factors: the presence of deep flood water in and around the settlement and its proximity to an elevated area for temporary shelter during an extreme hydrological event. Landsat ETM+ images acquired on 30 September 2000 have been used to identify the non-flooded areas within the flooded zone. Particular effort has been made to differentiate land from water under cloud shadow. ASTER digital elevation data have been used to assess accuracy and rectify the classified image. The presence of large numbers of trees around rural settlements made it particularly difficult to extract the flooded areas from their spectral signatures in the visible and infrared bands. ERS-1 synthetic aperture radar data are found particularly useful for extracting the settlement areas surrounded by trees. Finally, all information extracted from satellite imageries are imported into ArcGIS, and spatial analysis is carried out to identify the settlements vulnerable to river inundation. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Possible Environmental Factors Underlying Amphibian Decline in Eastern Puerto Rico: Analysis of U.S. Government Data Archives

CONSERVATION BIOLOGY, Issue 4 2001
Robert F. Stallard
I examined changes in environmental conditions by examining time-series data sets that extend back at least into the 1980s, a period when frog populations were declining. The data include forest cover; annual mean, minimum, and maximum daily temperature; annual rainfall; rain and stream chemistry; and atmospheric-dust transport. I examined satellite imagery and air-chemistry samples from a single National Aeronautics and Space Administration aircraft flight across the Caribbean showing patches of pollutants, described as thin sheets or lenses, in the lower troposphere. The main source of these pollutants appeared to be fires from land clearing and deforestation, primarily in Africa. Some pollutant concentrations were high and, in the case of ozone, approached health limits set for urban air. Urban pollution impinging on Puerto Rico, dust generation from Africa ( potential soil pathogens), and tropical forest burning ( gaseous pollutants) have all increased during the last three decades, overlapping the timing of amphibian declines in eastern Puerto Rico. None of the data sets pointed directly to changes so extreme that they might be considered a direct lethal cause of amphibian declines in Puerto Rico. More experimental research is required to link any of these environmental factors to this problem. Resumen: Las pasadas tres décadas han visto grandes disminuciones poblacionales de especies de anfibios en altas elevaciones de Puerto Rico oriental, una región única en los trópicos húmedos debido al grado de monitoreo ambiental que se ha llevado a cabo mediante los esfuerzos de las agencias de gobierno de los Estados Unidos. Examiné los cambios en condiciones ambientales mediante el análisis de datos de series de tiempo que se extienden hasta los 1980s, un periodo en el que las poblaciones de ranas estaban declinando. Los datos incluyen cobertura forestal; temperatura diaria media, mínima y máxima anual; precipitación anual; química de la lluvia y arroyos; y el transporte atmosférico de polvo. Examiné imágenes de satélite y muestras de química del aire obtenidos de un solo vuelo de una nave de la NASA a lo largo del Caribe que mostraba parches de contaminantes descritas como capas delgadas de lentes en la inferior troposfera. La mayor fuente de contaminantes parece ser los incendios de tierras clareadas y la deforestación, principalmente en África. Algunas concentraciones de contaminantes fueron altas y en el caso del ozono, se aproximó a los límites de salud establecidos para aire urbano. La contaminación urbana afectando a Puerto Rico, la generación de polvo en África ( patógenos del suelo potenciales) y la quema de bosque tropical (contaminantes gaseosos) han incrementado durante las últimas tres décadas, superponiéndose con el periodo en que oturrieron las disminuciones de anfibios en Puerto Rico oriental. Ninguno de estos conjuntos de datos señaló directamente hacia cambios tan extremos que debieran ser considerados como una causa letal directa de las disminuciones en Puerto Rico. Se requiere de más investigación experimental que vincule a estos factores ambientales con este problema. [source]

Satellite Remote Sensing as a Tool in Lahar Disaster Management

DISASTERS, Issue 2 2002
Norman Kerle
At least 40,000 deaths have been attributed to historic lahars (volcanic mudflows). The most recent lahar disaster occurred in 1998 at Casita volcano, Nicaragua, claiming over 2,500 lives. Lahars can cover large areas and be highly destructive, and constitute a challenge for disaster management. With infrastructure affected and access frequently impeded, disaster management can benefit from the synoptic coverage provided by satellite imagery. This potential has been recognised for other types of natural disasters, but limitations are also known. Dedicated satellite constellations for disaster response and management have been proposed as one solution. Here we investigate the utility of currently available and forthcoming optical and radar sensors as tools in lahar disaster management. Applied to the Casita case, we find that imagery available at the time could not have significantly improved disaster response. However, forthcoming satellites, especially radar, will improve the situation, reducing the benefit of dedicated constellations. [source]

Effects of species and habitat positional errors on the performance and interpretation of species distribution models

DIVERSITY AND DISTRIBUTIONS, Issue 4 2009
Patrick E. Osborne
Abstract Aim, A key assumption in species distribution modelling is that both species and environmental data layers contain no positional errors, yet this will rarely be true. This study assesses the effect of introduced positional errors on the performance and interpretation of species distribution models. Location, Baixo Alentejo region of Portugal. Methods, Data on steppe bird occurrence were collected using a random stratified sampling design on a 1-km2 pixel grid. Environmental data were sourced from satellite imagery and digital maps. Error was deliberately introduced into the species data as shifts in a random direction of 0,1, 2,3, 4,5 and 0,5 pixels. Whole habitat layers were shifted by 1 pixel to cause mis-registration, and the cumulative effect of one to three shifted layers investigated. Distribution models were built for three species using three algorithms with three replicates. Test models were compared with controls without errors. Results, Positional errors in the species data led to a drop in model performance (larger errors having larger effects , typically up to 10% drop in area under the curve on average), although not enough for models to be rejected. Model interpretation was more severely affected with inconsistencies in the contributing variables. Errors in the habitat layers had similar although lesser effects. Main conclusions, Models with species positional errors are hard to detect, often statistically good, ecologically plausible and useful for prediction, but interpreting them is dangerous. Mis-registered habitat layers produce smaller effects probably because shifting entire layers does not break down the correlation structure to the same extent as random shifts in individual species observations. Spatial autocorrelation in the habitat layers may protect against species positional errors to some extent but the relationship is complex and requires further work. The key recommendation must be that positional errors should be minimised through careful field design and data processing. [source]

Patterns of spatial autocorrelation of assemblages of birds, floristics, physiognomy, and primary productivity in the central Great Basin, USA

DIVERSITY AND DISTRIBUTIONS, Issue 3 2006
Erica Fleishman
ABSTRACT We fitted spatial autocorrelation functions to distance-based data for assemblages of birds and for three attributes of birds' habitats at 140 locations, separated by up to 65 km, in the Great Basin (Nevada, USA). The three habitat characteristics were taxonomic composition of the vegetation, physical structure of the vegetation, and a measure of primary productivity, the normalized difference vegetation index, estimated from satellite imagery. We found that a spherical model was the best fit to data for avifaunal composition, vegetation composition, and primary productivity, but the distance at which spatial correlation effectively was zero differed substantially among data sets (c. 30 km for birds, 20 km for vegetation composition, and 60 km for primary productivity). A power-law function was the best fit to data for vegetation structure, indicating that the structure of vegetation differed by similar amounts irrespective of distance between locations (up to the maximum distance measured). Our results suggested that the spatial structure of bird assemblages is more similar to vegetation composition than to either vegetation structure or primary productivity, but is autocorrelated over larger distances. We believe that the greater mobility of birds compared with plants may be responsible for this difference. [source]

Soil erosion assessment using geomorphological remote sensing techniques: an example from southern Italy

Assessing the variability of hydrographic processes influencing the life cycle of the Sicilian Channel anchovy, Engraulis encrasicolus, by satellite imagery

FISHERIES OCEANOGRAPHY, Issue 1 2005
JESÚS GARCÍA LAFUENTE
Abstract Three oceanographic surveys carried out in the Sicilian Channel during the spawning season (June to July) of anchovy (Engraulis encrasicolus) showed a close relationship between anchovy reproductive strategy and important hydrographic structures. A time series of satellite-derived sea surface temperature images of the Sicilian Channel were analysed by means of empirical orthogonal functions and the dominant empirical modes were studied in detail. The first empirical mode captured much of the original variance and reproduced the trajectory of the Atlantic Ionian Stream (AIS), the principal hydrodynamic feature of the area. The time coefficients of modes 1 and 2 had seasonal signals which, when combined, accounted for the enhancement of the thermal front, clearly visible off Cape Passero (southernmost coast of Sicily) during summer. As the area constituted the principal nursery ground of the Sicilian Channel anchovy, the combination of the time coefficients of these modes was considered a potential indicator of the food particle concentration usually associated with oceanic fronts, which provided the energy requirements for larval growth. Mode 3 described the north/south displacements of the mean AIS trajectory, which modified the surface temperature regime of the anchovy spawning habitat. Therefore, the time coefficients of this mode were used as a potential indicator of anchovy spawning habitat variability. The capability of time coefficients of modes 2 and 3 to modify the main pattern depicted by mode 1 were tested successfully against in situ oceanographic observations. [source]

Fire, flow and dynamic equilibrium in stream macroinvertebrate communities

FRESHWATER BIOLOGY, Issue 2 2010
ROBERT S. ARKLE
Summary 1. The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a central Idaho wilderness, USA. We conducted a 4-year retrospective analysis of unburned (n = 7) and burned (n = 6) catchments, using changes in reflectance values (,NBR) from satellite imagery to quantify the percentage of each catchment's riparian and upland vegetation that burned at high and low severity. 2. For this wildland fire complex, increasing riparian burn severity and extent were associated with greater year-to-year variation, rather than a perennial increase, in sediment loads, organic debris, large woody debris (LWD) and undercut bank structure. Temporal changes in these variables were correlated with yearly peak flow in burned catchments but not in unburned reference catchments, indicating that an interaction between fire and flow can result in decreased habitat stability in burned catchments. 3. Streams in more severely burned catchments exhibited increasingly dynamic macroinvertebrate communities and did not show increased similarity to reference streams over time. Annual variability in macroinvertebrates was attributed, predominantly, to the changing influence of sediment, LWD, riparian cover and organic debris, as quantities of these habitat components fluctuated annually depending on burn severity and annual peak streamflows. 4. These analyses suggest that interactions among fire, flow and stream habitat may increase inter-annual habitat variability and macroinvertebrate community dynamics for a duration approaching the length of the historic fire return interval of the study area. [source]

Simulated and observed fluxes of sensible and latent heat and CO2 at the WLEF-TV tower using SiB2.5

GLOBAL CHANGE BIOLOGY, Issue 9 2003
Ian Baker
Abstract Three years of meteorological data collected at the WLEF-TV tower were used to drive a revised version of the Simple Biosphere (SiB 2.5) Model. Physiological properties and vegetation phenology were specified from satellite imagery. Simulated fluxes of heat, moisture, and carbon were compared to eddy covariance measurements taken onsite as a means of evaluating model performance on diurnal, synoptic, seasonal, and interannual time scales. The model was very successful in simulating variations of latent heat flux when compared to observations, slightly less so in the simulation of sensible heat flux. The model overestimated peak values of sensible heat flux on both monthly and diurnal scales. There was evidence that the differences between observed and simulated fluxes might be linked to wetlands near the WLEF tower, which were not present in the SiB simulation. The model overestimated the magnitude of the net ecosystem exchange of CO2 in both summer and winter. Mid-day maximum assimilation was well represented by the model, but late afternoon simulations showed excessive carbon uptake due to misrepresentation of within-canopy shading in the model. Interannual variability was not well simulated because only a single year of satellite imagery was used to parameterize the model. [source]

Macroecology meets macroevolution: evolutionary niche dynamics in the seaweed Halimeda

GLOBAL ECOLOGY, Issue 4 2009
Heroen Verbruggen
ABSTRACT Aim Because of their broad distribution in geographical and ecological dimensions, seaweeds (marine macroalgae) offer great potential as models for marine biogeographical inquiry and exploration of the interface between macroecology and macroevolution. This study aims to characterize evolutionary niche dynamics in the common green seaweed genus Halimeda, use the observed insights to gain understanding of the biogeographical history of the genus and predict habitats that can be targeted for the discovery of species of special biogeographical interest. Location Tropical and subtropical coastal waters. Methods The evolutionary history of the genus is characterized using molecular phylogenetics and relaxed molecular clock analysis. Niche modelling is carried out with maximum entropy techniques and uses macroecological data derived from global satellite imagery. Evolutionary niche dynamics are inferred through application of ancestral character state estimation. Results A nearly comprehensive molecular phylogeny of the genus was inferred from a six-locus dataset. Macroecological niche models showed that species distribution ranges are considerably smaller than their potential ranges. We show strong phylogenetic signal in various macroecological niche features. Main conclusions The evolution of Halimeda is characterized by conservatism for tropical, nutrient-depleted habitats, yet one section of the genus managed to invade colder habitats multiple times independently. Niche models indicate that the restricted geographical ranges of Halimeda species are not due to habitat unsuitability, strengthening the case for dispersal limitation. Niche models identified hotspots of habitat suitability of Caribbean species in the eastern Pacific Ocean. We propose that these hotspots be targeted for discovery of new species separated from their Caribbean siblings since the Pliocene rise of the Central American Isthmus. [source]

Near real time satellite imagery to support and verify timely flood modelling

HYDROLOGICAL PROCESSES, Issue 5 2009
Giuliano Di Baldassarre
Abstract The study investigates the capability of coarse resolution synthetic aperture radar (SAR) imagery to support flood inundation models. A hydraulic model of a 98-km reach of the River Po (Northern Italy) was calibrated on the October 2000 high-magnitude flood event with extensive and high-quality field data. During the June 2008, low-magnitude flood event a SAR image was acquired and processed in near real time (NRT) in order to provide adequate data for quick verification and recalibration of the hydraulic model. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Development of a historical ice database for the study of climate change in Canada

HYDROLOGICAL PROCESSES, Issue 18 2002
Frédéric Lenormand
Abstract The Canadian government has been compiling various observations on freshwater and coastal sea ice conditions for many years. However, the records are not easily accessible and are dispersed within different government departments. Given this, a major effort was undertaken in order to gather all available observations into a common database,the Canadian Ice Database (CID). This database will respond to the needs for climate monitoring in Canada, the validation and improvement of numerical ice models and the development of new remote-sensing methods. Indeed, several studies have shown that freshwater ice and sea ice are good proxy indicators of climate variability and change. The first version of CID contains in situ observations from 757 sites distributed across Canada, which were originally kept on digital or paper records at the Meteorological Service of Canada Headquarters and the Canadian Ice Service (CIS). The CID holds 63 546 records covering the period from ice season 1822,23 to 2000,01. An analysis of the database allows one to trace the temporal evolution of the ice networks. The freeze-up/break-up network of 2000,01 only represents 4% of what it was in 1985,86. A drastic decline of the ice thickness and the snow on ice network is also observable. In 1997,98, it represented only 10% of the network that existed in 1984,85. The major budget cuts in Canadian government agencies during the late 1980s and the 1990s offer the most plausible explanation for the drastic decline in the ice observation networks. Weekly ice coverage determination on large lakes from satellite imagery by the CIS and the national volunteer ice monitoring program, IceWatch, may provide a means of reviving, at least, the freeze-up/break-up network. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Europe's 2003 heat wave: a satellite view of impacts and land,atmosphere feedbacks

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2006
Benjamin F. Zaitchik
Abstract A combination of satellite imagery, meteorological station data, and the NCEP/NCAR reanalysis has been used to explore the spatial and temporal evolution of the 2003 heat wave in France, with focus on understanding the impacts and feedbacks at the land surface. Vegetation was severely affected across the study area, especially in a swath across central France that corresponds to the Western European Broadleaf (WEB) Forests ecological zone. The remotely sensed surface temperature anomaly was also greatest in this zone, peaking at +15.4 °C in August. On a finer spatial scale, both the vegetation and surface temperature anomalies were greater for crops and pastures than for forested lands. The heat wave was also associated with an anomalous surface forcing of air temperature. Relative to other years in record, satellite-derived estimates of surface-sensible heat flux indicate an enhancement of 48,61% (24.0,30.5 W m,2) in WEB during the August heat wave maximum. Longwave radiative heating of the planetary boundary layer (PBL) was enhanced by 10.5 W m,2 in WEB for the same period. The magnitude and spatial structure of this local heating is consistent with models of the late twenty-first century climate in France, which predict a transitional climate zone that will become increasingly affected by summertime drought. Models of future climate also suggest that a soil-moisture feedback on the surface energy balance might exacerbate summertime drought, and these proposed feedback mechanisms were tested using satellite-derived heat budgets. Copyright © 2006 Royal Meteorological Society. [source]

Indirect effects of invasive species removal devastate World Heritage Island

JOURNAL OF APPLIED ECOLOGY, Issue 1 2009
Dana M. Bergstrom
Summary 1Owing to the detrimental impacts of invasive alien species, their control is often a priority for conservation management. Whereas the potential for unforeseen consequences of management is recognized, their associated complexity and costs are less widely appreciated. 2We demonstrate that theoretically plausible trophic cascades associated with invasive species removal not only take place in reality, but can also result in rapid and drastic landscape-wide changes to ecosystems. 3Using a combination of population data from of an invasive herbivore, plot-scale vegetation analyses, and satellite imagery, we show how a management intervention to eradicate a mesopredator has inadvertently and rapidly precipitated landscape-wide change on sub-Antarctic Macquarie Island. This happened despite the eradication being positioned within an integrated pest management framework. Following eradication of cats Felis catus in 2001, rabbit Oryctolagus cuniculus numbers increased substantially although a control action was in place (Myxoma virus), resulting in island-wide ecosystem effects. 4Synthesis and applications. Our results highlight an important lesson for conservation agencies working to eradicate invasive species globally; that is, risk assessment of management interventions must explicitly consider and plan for their indirect effects, or face substantial subsequent costs. On Macquarie Island, the cost of further conservation action will exceed AU$24 million. [source]

Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: aggregation during drought and suggestions of long distance movement

JOURNAL OF APPLIED ECOLOGY, Issue 5 2007
ANTHONY R. POPLE
Summary 1Wildlife surveys usually focus on estimating population size, and management actions such as commercial harvesting, culling and poison baiting are referenced commonly to population size alone, without taking into account the way in which those animals are distributed. This paper outlines how point-based aerial survey data can be converted to continuous density surfaces using spatial analysis techniques. Using this approach, we describe and explore the spatial patterns of density of two species of kangaroos in an area exceeding 200 000 km2 in South Australia over a 26-year period. 2Densities of red and western grey kangaroos were estimated in 2 km2 segments along aerial survey transect lines, yielding point density estimates. Universal kriging provided an unbiased interpolation of these data using the spatial autocorrelation structure described by the semi-variogram. The Getis statistic identified clusters of high and low kangaroo density. 3Considerable year-to-year variation in the spatial patterns of kangaroo density was observed. In many cases, annual rates of increase over large areas were too high to be explained by vital rates alone, implying immigration from surrounding areas. These large shifts in distribution were occasionally to areas that had received better rainfall than the surrounding areas. For both species, there was no obvious local spatial autocorrelation pattern or clustering of kangaroo density beyond that described by average density and the present set of management regions, suggesting the latter are appropriate divisions for harvest management. 4Data for both species fitted the power law relationship extremely well. During dry times, red kangaroos, but not western grey kangaroos, were more aggregated, supporting past ground observations at a fine spatial scale. 5Synthesis and applications. Kriged density surfaces enable estimation of kangaroo density on individual properties, which are the management units at which harvest quotas or culling approvals are allocated. These estimates will be marked improvements over systematic sampling estimates when sampling intensity is low. Predictions of shifts in kangaroo distribution using rainfall or satellite imagery will allow more accurate allocation of harvest quotas. Similarly, predictions of more even kangaroo dispersion following high rainfall will allow managers to anticipate downturns in harvest rate. [source]

Climate change and its impact on the forests of Kilimanjaro

AFRICAN JOURNAL OF ECOLOGY, Issue 2009
Andreas Hemp
Abstract Cloud forests are of great importance in the hydrological functioning of watersheds in subhumid East Africa. However, the montane forests of Mt. Kilimanjaro are heavily threatened by global change impacts. Based on an evaluation of over 1500 vegetation plots and interpretation of satellite imagery from 1976 and 2000, land-cover changes on Kilimanjaro were evaluated and their impact on the water balance estimated. While the vanishing glaciers of Kilimanjaro attract broad interest, the associated increase of frequency and intensity of fires on the slopes of Kilimanjaro is less conspicuous but ecologically far more significant. These climate change-induced fires have lead to changes in species composition and structure of the forests and to a downward shift of the upper forest line by several hundred metres. During the last 70 years, Kilimanjaro has lost nearly one-third of its forest cover, in the upper areas caused by fire, on the lower forest border mainly caused by clearing. The loss of 150 km2 of cloud forest , the most effective source in the upper montane and subalpine fog interception zone , caused by fire during the last three decades means a considerable reduction in water yield. In contrast to common belief, global warming does not necessarily cause upward migration of plants and animals. On Kilimanjaro the opposite trend is under way, with consequences more harmful than those due to the loss of the showy ice cap of Africa's highest mountain. [source]

Widespread dispersal of Icelandic tephra: how does the Eyjafjöll eruption of 2010 compare to past Icelandic events?,

JOURNAL OF QUATERNARY SCIENCE, Issue 5 2010
Siwan M. Davies
Abstract The Eyjafjöll AD 2010 eruption is an extraordinary event in that it led to widespread and unprecedented disruption to air travel over Europe , a region generally considered to be free from the hazards associated with volcanic eruptions. Following the onset of the eruption, satellite imagery demonstrated the rapid transportation of ash by westerly winds over mainland Europe, eventually expanding to large swathes of the North Atlantic Ocean and the eastern seaboard of Canada. This small-to-intermediate size eruption and the dispersal pattern observed are not particularly unusual for Icelandic eruptions within a longer-term perspective. Indeed, the Eyjafjöll eruption is a relatively modest eruption in comparison to some of the 20 most voluminous eruptions that have deposited cryptotephra in sedimentary archives in mainland Europe, such as the mid Younger Dryas Vedde Ash and the mid Holocene Hekla 4 tephra. The 2010 eruption, however, highlights the critical role that weather patterns play in the distribution of a relatively small amount of ash and also highlights the spatially complex dispersal trajectories of tephra in the atmosphere. Whether or not the preservation of the Eyjafjöll 2010 tephra in European proxy archives will correspond to the extensive distributions mapped in the atmosphere remains to be seen. The Eyjafjöll 2010 event highlights our increased vulnerability to natural hazards rather than the unparalleled explosivity of the event. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Using hyperspectral satellite imagery for regional inventories: a test with tropical emergent trees in the Amazon Basin

JOURNAL OF VEGETATION SCIENCE, Issue 2 2010
M. Pape
Abstract Questions: Understanding distributions of tree species at landscape scales in tropical forests is a difficult task that could benefit from the recent development of satellite imaging spectroscopy. We tested an application of the EO-1 Hyperion satellite sensor to spectrally detect the location of five important tree taxa in the lowland humid tropical forests of southeastern Peru. Location: Peru, Departamento de Madre de Díos. Methods: We used linear discriminant analysis with a stepwise selection procedure to analyze two Hyperion datasets (July and December 2006) to choose the most informative narrow bands for classifying trees. Results: Optimal channels selected were different between the two seasons. Classification was 100% successful for the five taxa when using 25 narrow bands and pixels that represented >40% of tree crowns. We applied the discriminant functions developed separately for the two seasons to the entire study area, and found significantly nonrandom overlap in the anticipated distributions of the five taxa between seasons. Conclusions: Despite known issues, such as signal-to-noise ratio and spatial resolution, Hyperion imaging spectroscopy has potential for developing regional mapping of large-crowned tropical trees. [source]

Post-fire tree establishment patterns at the alpine treeline ecotone: Mount Rainier National Park, Washington, USA

JOURNAL OF VEGETATION SCIENCE, Issue 1 2009
Kirk M. Stueve
Abstract Questions: Does tree establishment: (1) occur at a treeline depressed by fire, (2) cause the forest line to ascend upslope, and/or (3) alter landscape heterogeneity? (4) What abiotic and biotic local site conditions are most important in structuring establishment patterns? (5) Does the abiotic setting become more important with increasing upslope distance from the forest line? Location: Western slopes of Mount Rainier, USA. Methods: We performed classification analysis of 1970 satellite imagery and 2003 aerial photography to delineate establishment. Local site conditions were calculated from a LIDAR-based DEM, ancillary climate data, and 1970 tree locations in a GIS. We used logistic regression on a spatially weighted landscape matrix to rank variables. Results: Considerable establishment after 1970 caused forest line elevation to increase over 150 m in specific locations. Landscape heterogeneity increased with distance from the 1970 forest line. At a broad spatial context, we found establishment was most common near existing trees (0-50 m) and at low elevations (1250-1350 m). Slope aspect (W, NW, N, NE, and E), slope angle (40-60°), and other abiotic factors emerged as important predictors of establishment with increasing upslope distance from the forest line to restricted spatial extents. Conclusions: Favorable climatic conditions likely triggered widespread tree establishment. Readily available seed probably enhanced establishment rates near sexually mature trees, particularly in the less stressful environment at low elevations. The mass effect of nearly ubiquitous establishment in these areas may have obscured the importance of the abiotic setting to restricted spatial extents. Topographic variability apparently produced favorable sites that facilitated opportunistic establishment with increasing upslope distance from the forest line, thereby enabling additional trees to invade the alpine tundra. [source]

Use of METEOSAT water-vapour images for the diagnosis of a vigorous stratospheric intrusion over the central Mediterranean

METEOROLOGICAL APPLICATIONS, Issue 3 2000
K Lagouvardos
The diagnosis of a vigorous dry intrusion over the central Mediterranean is performed using water-vapour images from METEOSAT. This dry intrusion was located on the rear side of a cold front (propagating from Italy to Greece) and played an important role in the onset of thunderstorms over the western Greek coasts. A combination of satellite imagery and potential vorticity analyses showed that the dry air originated in the lower-stratospheric and higher-tropospheric layers. The interaction of the dry air with the moist air masses within the warm conveyor belt ahead of the cold front (overrun of warm air by low equivalent potential temperature air) produced a potentially unstable region over the area of reported thunderstorms. Copyright © 2000 Royal Meteorological Society [source]

Change in vegetation cover in East Timor, 1989,1999

NATURAL RESOURCES FORUM, Issue 1 2004
George A. Bouma
Abstract Forest resources play a key role and provide many basic needs to communities in developing economies. To assess the patterns of vegetation cover change, as a corollary of resource utilization, satellite imagery, ground truth data, and image processing techniques can be useful. This article is concerned with identifying change in major vegetation types in East Timor between 1989 and 1999, using Landsat Thematic Mapper data. The results highlight a significant level of deforestation and decline in foliage cover. All major vegetation cover types declined from 1989 to 1999, and there was a sizeable increase in degraded woodlands. This decline has had considerable impact on the livelihoods of rural and urban communities. Causes for these changes include: economic exploitation of abundant resources; and implications of transmigration policies implemented during Indonesian rule, resulting in increased competition for land and woodland resources. As the new nation of Timor-Leste establishes itself, it must consider its current stock and distribution of natural capital to ensure that development efforts are geared towards sustainable outcomes. Without the knowledge of historical patterns of resource consumption, development efforts may, unwittingly, lead to continuing decline in forest resources. [source]

Evolution of the Irrawaddy delta region since 1850

THE GEOGRAPHICAL JOURNAL, Issue 2 2010
PETER J HEDLEY
We present a time series of coastline change for the Irrawaddy delta region of Myanmar using the earliest available navigation chart from 1850, and a set of topographic maps and satellite imagery dating from 1913 to 2006. Despite the large sediment load delivered annually to the gulf by the Irrawaddy and Salween Rivers, the coastline has been largely stable for 156 years, advancing at an average rate of no more than 0.34 km per century since 1925. The long-term average rate of increase in land area across the study area between 1925 and 2006 is 4.2 km2/year, but this masks a period of more rapid accumulation between 1925 and 1989 (8.7 km2/year), followed by a period of net erosion at a rate of 13 km2/year until 2006. Less than 9% of the sediment load delivered to the study region by the Irrawaddy, Salween and Sittoung Rivers has contributed to the observed progradation, with the remainder being exported into the Gulf of Martaban to depths below low tide level, or filling any accommodation space created due to subsidence or sea level rise. In contrast to many deltas worldwide, we suggest that the coastline encompassing the Irrawaddy delta and the Salween River is more or less in equilibrium, and that sediment deposition currently balances subsidence and sea level rise. Myanmar has fewer large dams relative to its Asian neighbours, and the Salween is currently undammed. This is forecast to change in the next 5,10 years with extensive damming projects on the mainstem of the Salween under consideration or construction, and the sediment retention will cause losses in sediment supply to the Gulf of Martaban, and retreat of the delta. This could impact the densely populated delta region and Yangon, and further exacerbate the impacts of extreme events such as Cyclone Nargis in 2008. [source]

The sting at the end of the tail: Damaging winds associated with extratropical cyclones

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 597 2004
K. A. Browning
Abstract Strong surface winds often accompany the low-level jets that occur along the cold fronts of extratropical cyclones, but there is evidence that the strongest surface winds occur in a distinctly different part of a certain class of cyclone. The most damaging extratropical cyclones go through an evolution that involves the formation of a bent-back front and cloud head separated from the main polar-front cloud band by a dry slot. When the cyclone attains its minimum central pressure, the trailing tip of the cloud head bounding the bent-back front forms a hook which goes on to encircle a seclusion of warm air. The most damaging winds occur near the tip of this hook,the sting at the end of the tail. Observations of the Great Storm of October 1987 in south-east England are re-examined in some detail to study this phenomenon. The cloud head is shown to have a banded structure consistent with the existence of multiple mesoscale slantwise circulations. Air within these circulations leaves the hooked tip of the cloud head (and enters the dry slot) much faster than the rate of travel of the cloud-head tip, implying rapid evaporation and diabatic cooling immediately upwind of the area of damaging surface winds. The circumstantial evidence from the observational study leads one to hypothesize that the mesoscale circulations and the associated evaporative heat sinks may play an active role in strengthening the damaging winds. Regardless of how important this role may be, the evolution of the cloud pattern seen in satellite imagery is a useful tool for nowcasting the occurrence and location of the worst winds. Copyright © 2004 Royal Meteorological Society [source]

Landscape-scale detection and mapping of invasive African Olive (Olea europaea L. ssp. cuspidata Wall ex G. Don Ciferri) in SW Sydney, Australia using satellite remote sensing

APPLIED VEGETATION SCIENCE, Issue 2 2009
P. Cuneo
Abstract Question: Is satellite imagery an effective tool for mapping and examining the distribution of the invasive species Olea europaea L. ssp. cuspidata at a regional landscape scale? Location: Southwest Sydney, Australia. Methods: Remote sensing software was used to classify pixels of Olea europaea L. ssp. cuspidata (African Olive) and major vegetation types from satellite imagery, using a "supervised classification" technique across a 721 km2 study area in the Cumberland Plain region of western Sydney. A map of African Olive distribution was produced from the image analysis and checked for accuracy at 337 random locations using ground observation and comparison with existing vegetation maps. The African Olive distribution data were then used in a GIS analysis with additional spatial datasets to investigate the relationship between the distribution of African Olive and environmental factors, and to quantify the conservation threat to endangered native vegetation. Results: A total area of 1907 ha of dense African Olive infestation was identified, with an omission error of 7.5% and a commission error of 5.4%. African Olive was found to occur on the steepest slopes (mean slope 14.3°) of the vegetation classes examined, with aspect analysis identifying a high prevalence on south- and southwest-facing slopes. The analysis also quantified the level of African Olive infestation in endangered ecological communities, with Western Sydney Dry Rainforest (25% affected) and Moist Shale Woodland (28% affected) identified as most vulnerable to African Olive invasion. Conclusion: The distribution of African Olive can be efficiently mapped at a landscape scale. This technique, used in association with additional spatial datasets, identified African Olive as a significant environmental weed in SW Sydney, occupying a greater area than previously recognised and threatening several endangered native vegetation communities. [source]

Mapping the roots of agriculture in southern Arabia: the application of satellite remote sensing, global positioning system and geographic information system technologies

ARCHAEOLOGICAL PROSPECTION, Issue 1 2002
M. Harrower
Abstract Satellite remote sensing, global positioning system (GPS) and geographical information system (GIS) technologies form a powerful methodological and analytical triad for archaeological research, particularly in remote regions where few large-scale maps are available. This paper outlines the application of these technologies as a component of the Roots of Agriculture in Southern Arabia (RASA) research project and provides a review for archaeologists interested in potential applications, particularly in arid and semi-arid environments. We used LANDSAT satellite imagery and GPS data to construct a GIS and provide a foundation for the management and analysis of archaeological, geomorphological and palaeoecological evidence of middle Holocene environmental conditions and human land-use in the remote highlands of southern Yemen. Using both supervized and unsupervized multispectral landscape classification procedures we categorized the landscape into seven classes based on landform and sedimentary cover characteristics. The resulting GIS helps us evaluate the relationship between landscape characteristics, site location, site preservation, and investigate associations with sociocultural and environmental variables. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Evidence from traditional and new technologies for northward migrations of Australian plague locusts (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) to western Queensland

AUSTRAL ECOLOGY, Issue 8 2005
E. D. DEVESON
Abstract The development of recent infestations of the Australian plague locust (Chortoicetes terminifera) (Walker) (Orthoptera: Acrididae) has been traced using traditional survey data combined with information from several modern technologies including simulation of windborne transport trajectories, direct observation with entomological radar and satellite imagery. The results indicate that migration from spring generations in the southern and eastern parts of the species range, including agricultural areas, to the summer rainfall areas in arid western Queensland (Qld) has contributed to the development of infestations on several occasions. Migration from swarm populations in New South Wales to western Qld in November and December 1999 contributed to a rapid population increase that, over a sequence of generations, led to the major infestation of agricultural areas in March and April 2000. There is evidence that northward migrations also occurred in 1995, 1997 and 2000. These contributed to the early summer populations in Qld, but did not result in large migrations to the south in autumn. These observations suggest that a pattern of exchange migration across much of the geographical range of the species between regions of winter and summer rainfall characterizes the spatial dynamics of this species. This pattern appears to be adaptive and suggests migration in C. terminifera is sustained by contemporary natural selection. [source]

Fold evolution and drainage development in the Zagros mountains of Fars province, SE Iran

BASIN RESEARCH, Issue 1 2008
Lucy A. Ramsey
ABSTRACT A central question in structural geology is whether, and by what mechanism, active faults (and the folds often associated with them) grow in length as they accumulate displacement. An obstacle in our understanding of these processes is the lack of examples in which the lateral growth of active structures can be demonstrated definitively, as geomorphic indicators of lateral propagation are often difficult, or even impossible to distinguish from the effects of varying lithology or non-uniform displacement and slip histories. In this paper we examine, using the Zagros mountains of southern Iran as our example, the extent to which qualitative analysis of satellite imagery and digital topography can yield insight into the growth, lateral propagation, and interaction of individual fold segments in regions of active continental shortening. The Zagros fold-and-thrust belt contains spectacular whaleback anticlines that are well exposed in resistant Tertiary and Mesozoic limestone, are often >100 km in length, and which contain a large proportion of the global hydrocarbon reserves. In one example, Kuh-e Handun, where an anticline is mantled by soft Miocene sediments, direct evidence of lateral fold propagation is recorded in remnants of consequent drainage patterns on the fold flanks that do not correspond to the present-day topography. We suggest that in most other cases, the soft Miocene and Pliocene sediments that originally mantled the folds, and which would have recorded early stages in the growth histories, have been completely stripped away, thus removing any direct geomorphic evidence of lateral propagation. However, many of the long fold chains of the Zagros do appear to be formed from numerous segments that have coalesced. If our interpretations are correct, the merger of individual fold segments that have grown in length is a major control on the development of through-going drainage and sedimentation patterns in the Zagros, and may be an important process in other regions of crustal shortening as well. Abundant earthquakes in the Zagros show that large seismogenic thrust faults must be present at depth, but these faults rarely reach the Earth's surface, and their relationship to the surface folding is not well constrained. The individual fold segments that we identify are typically 20,40 km in length, which correlates well with the maximum length of the seismogenic basement faults suggested from the largest observed thrusting earthquakes. This correlation between the lengths of individual fold segments and the lengths of seismogenic faults at depth suggest that it is possible, at least in some cases, that there may be a direct relationship between folding and faulting in the Zagros, with individual fold segments underlain by discrete thrusts. [source]