Earth and Ecosystem Sciences

The present study is focused on the capabilities of remote sensing data and techniques to help in better understanding the role of community forest ecosystems as carbon sinks and carbon sources, with special reference to distinguishing between forest degradation and deforestation, and well-managed forests. It examined the statistical relationships between satellite-derived spectral vegetation indices (SVI) data from ASTER and biomass field measurements carried out with the help of forest user groups in community forests. Statistically weak relationships were obtained when correlating these datasets from 30 plots surveyed. International definitions of forest degradation were compared with the definitions understood by local people and by national experts to determine common understandings of forest degradation. Reduced canopy cover and loss of biodiversity were most frequently used in defining of forest degradation.The suitability of satellite data (ASTER and Landsat ETM) in separating degraded national forests and non-degraded community forests was tested using statistical and graphical methods. The results did not reveal significant differences in spectral signatures of these forests. Moreover, forest canopy density (FCD) mapper was employed to determine the degree of forest degradation in these forests by predicting their canopy density. The results indicated that subtle forest degradation is not possible to be captured in the satellite images currently available. The possibility of detecting forest degradation, as opposed to deforestation, from remotely sensed data depends largely on the rate, magnitude and spatial extent of the degradation.

Public opinion polls in Venezuela are unreliable, and so are the election results. It has been argued that there is a fear bias in traditional polls. On the other hand it is now easy to conduct polls on Facebook, but the online responses are very different both from the public opinion polls and from the election results. This study was made to evaluate the accuracy of different polling methods, and to estimate the true regime support. To evaluate the factors that influence the response, a set of questions were asked on different topics at the door, on the street, and on Facebook. In each poll the respondents were assured anonymity, but the analysis suggests that the respondents distrust the pollster to various degrees depending on polling method. An analysis of the correlation between media use and responses reveals a correlation on certain issues that biases the Facebook results. Traditional polls are found to severely underestimate the support for the opposition, and the Facebook polls to underestimate the support for the regime. Based on this study, the true support for the regime is estimated to be 10% ±5%.

Erlingsson, U., Lake Vostok behaves like a 'captured lake' and may be near to creating an Antarctic jökulhlaup. Geogr. Ann. 88A (1): 1-7. ABSTRACT. The most well known sub-glacial lake is probably Grímsvötn under Vatnajökul, Iceland, from where jökulhlaups regularly burst forth. It is created by thermal melting under the ice cap. The Antarctic Lake Vostok, on the other hand, is considered to be located over a region with normal geothermal heat transfer, where it can exist because the ice is so thick that its base is at the pressure melting point. This makes it a candidate for testing the Captured Ice Shelf (CIS) hypothesis, which states that the motion of a totally confined ice shelf creates a hydrostatic seal in the form of an ice rim over the threshold. The CIS hypothesis may offer a source of water for the controversial Laurentian jökulhlaups inferred from field data, implicated in dramatic climatic changes. Here I show that Lake Vostok agrees with the hypothesis, and that it may be on the verge of a jökulhlaup, which could create an ice stream and regional downdraw. The result also implies that the lake may well be of pre-glacial origin, and that it may have experienced jökulhlaups also during previous interglacials.

The risk of natural disasters is one of the factors that need to be taken into account in physical planning. However, the more unusual the hazard, the more likely it is to be neglected. This article describes an expert system for natural hazard mitigation, implemented at Instituto Nicaragüense de Estudios Territoriales (INETER), Nicaragua, to be an integral part of their physical planning process. The main objectives are to allow an automatic calculation of risk, and to provide expert information about the full spectrum of hazards for any chosen location or region. The ultimate goal is to reduce the total risk level in the most cost-effective manner possible.

"The images acquired by ESA's Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activité ́ (OMEGA) hyperspectral spectrometer on Mars Express of the surface of Mars are affected by noise and large pixel sizes. Spectra from these images have been used to identify surficial mineralogy, but their stability has not been studied in detail across different scenes and spatial resolutions. A modified image processing method and an analysis of correlation between spectra is proposed to evaluate how selected image spectra of key rock-forming minerals relate across different OMEGA image resolutions and to laboratory measurements of mineralogical spectra.
The Nili Fossae region at the western edge of the Isidis impact basin on Mars was the area chosen to be studied due to the diverse geological processes and mineralogy that have been associated with it. Here, spectra were extracted from regions identified with spectral parameters or summary products where groups of rock-forming minerals occurred. Image-extracted spectra were used as endmembers to produce a spectral library with which the statistical method of spectral angle mapping was applied to map the mineralogical distribution in OMEGA images of different resolutions. The extracted spectra were also compared to observed laboratory spectra via their spectral angles.
Results showed low angles and high correlation between the extracted spectra in different resolutions, and relatively low correlation between the extracted spectra and the laboratory spectra. Spectral angle mapping of the images revealed that some spatial coherence of the mapped mineralogy existed, but spectra from the maps were highly correlated for all endmembers. A cross-validation between processed images from OMEGA and the higher resolution Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on NASA’s Mars Reconnaissance Orbiter (MRO) showed relatively low correlation between their corresponding mineral spectra. Visual identification of mineralogical spectra was more precise at identifying mineral species than summary products were.
Extracted spectra were stable across different resolutions but were not identifying precise minerals based on their spectral properties because the chosen summary products are not effective at identifying precise mineralogical spectra. These summary products should therefore be used with care in future mineralogical analysis of Mars’ surface with remote sensing. Analysis with OMEGA imagery would benefit from using spectral angles to map with a library of minerals confirmed to be present by rovers, the direct sensors on the surface."

The origin of secondary carbonate minerals in the oldest known martian meteorite ALH84001 have been intensely debated in the literature, with widely different thermal origins considered: ranging from hydrothermal alteration (possibly impactinduced) [e.g. 1, 2, 3] to low temperature alteration conditions [e.g. 4, 5, 6]. Recent isotopic evidence suggests the carbonates precipitated from evaporating water at 18±4 ºC under near-surface conditions .

Evidence abounds for liquid water existing on Mars prior to the late heavy bombardment (LHB) ∼ 3.9 Ga ago and physicochemically interacting with rocks to form distinct geomorphological landforms and mineralogical alteration products (e.g. ). ALH84001, the oldest (∼4.5-4.1 Ga ) known martian meteorite, contains secondary carbonate minerals formed on Mars ∼3.9-4.0 Ga ago , roughly contemporaneous to the LHB. Recent isotopic evidence supports their formation at low temperature (∼18°C [9]) and also by fluids derived from aqueous weathering in the Noachian/Phyllosian, due to the elevated 87 Sr/ 86 Sr ratios in the carbonates and bulk rock of ALH84001 [1].

Introduction: Secondary carbonate minerals produced by low temperature aqueous processes [1] in the martian meteorite ALH 84001 are evidence of an early active hydrosphere on Mars when they were formed ~3.9 Ga ago [2]. Further evidence for an early hydrosphere includes orbital and surface observations of diverse alteration mineral assemblages [e.g. 3-5] and fluvial geomorphology . While carbonates are observed in ALH 84001, unusually, there is no evidence of secondary phyllosilicates associated to low temperature aqueous alteration of the meteorite, and there is a lack of textural evidence for intensive fluid interaction [7] We have used geochemical modelling techniques to show that the carbonates in ALH 84001 can be produced in a two stage process in which low temperature fluids percolate and leach clay-bearing layers prior to encountering the unweathered host of ALH 84001.