Day: April 9, 2010

The Evolution of the Epidemic of Charcoal-Burning Suicide in Taiwan: A Spatial and Temporal Analysis

/ Matt Artz / 1 Comment

PLoS Medicine, 2010, Volume 7 (1): e1000212

Shu-Sen Chang, David Gunnell, Benedict W. Wheeler, Paul Yip, and Jonathan A. C. Sterne

“Background: An epidemic of carbon monoxide poisoning suicide by burning barbecue charcoal has occurred in East Asia in the last decade. We investigated the spatial and temporal evolution of the epidemic to assess its impact on the epidemiology of suicide in Taiwan.

“Methods and Findings: Age-standardised rates of suicide and undetermined death by charcoal burning were mapped across townships (median population aged 15 y or over = 27,000) in Taiwan for the periods 1999–2001, 2002–2004, and 2005–2007. Smoothed standardised mortality ratios of charcoal-burning and non-charcoal-burning suicide and undetermined death across townships were estimated using Bayesian hierarchical models. Trends in overall and method-specific rates were compared between urban and rural areas for the period 1991–2007. The epidemic of charcoal-burning suicide in Taiwan emerged more prominently in urban than rural areas, without a single point of origin, and rates of charcoal-burning suicide remained highest in the metropolitan regions throughout the epidemic. The rural excess in overall suicide rates prior to 1998 diminished as rates of charcoal-burning suicide increased to a greater extent in urban than rural areas.

“Conclusions:  The charcoal-burning epidemic has altered the geography of suicide in Taiwan. The observed pattern and its changes in the past decade suggest that widespread media coverage of this suicide method and easy access to barbecue charcoal may have contributed to the epidemic. Prevention strategies targeted at these factors, such as introducing and enforcing guidelines on media reporting and restricting access to charcoal, may help tackle the increase of charcoal-burning suicides.”

Land Use Dynamic Simulator (LUDAS): A Multi-agent System Model for Simulating Spatio-temporal Dynamics of Coupled Human-landscape System

/ Matt Artz

Ecological Informatics, In Press, Accepted Manuscript, Available online 13 February 2010

Quang Bao Le, Soo Jin Park, Paul L.G. Vlek

“Assessment of future socio-ecological consequences of land-use policies is useful for supporting decisions about what and where to invest for the best overall environmental and developmental outcomes. However, the task faces a great challenge due to the inherent complexity of coupled human-landscape systems and the long-term perspective required for sustainability assessment. Multi-agent system models have been recognised to be well suited to express the co-evolutions of the human and landscape systems in response to policy interventions. This paper applies the Land Use Dynamics Simulator (LUDAS) framework presented by Le et al. [Ecological Informatics 3 (2008) 135] to a mountain watershed in central Vietnam for supporting the design of land-use policies that enhance environmental and socio-economical benefits in long term. With an exploratory modelling strategy for complex integrated systems, our purpose is to assess relative impacts of policy interventions by measuring the long-term landscape and community divergences (compared with a baseline) driven from the widest plausible range of options for a given policy. Model’s tests include empirical verification and validation of sub-models, rational evaluation of coupled model’s structure, and behaviour tests using sensitivity/uncertainty analyses. We design experiments of replicated simulations for relevant policy factors in the study region that include (i) forest protection zoning, (ii) agricultural extension and (iii) agrochemical subsidies. As expected, the stronger human-environment interactions the performance indicators involve, the more uncertain the indicators are. Similar to the findings globally summarised by Liu et al. [Science 317 (2007) 1513], time lags between the implementation of land-use policies and the appearance of socio-ecological consequences are observed in our case. Long-term legacies are found in the responses of the total cropping area, farm size and income distribution to changes in forest protection zoning, implying that impact assessment of nature conservation policies on rural livelihoods must be considered in multiple decades. Our comparative assessment of alternative future socio-ecological scenarios shows that it is challenging to attain better either household income or forest conservation by straightforward expanding the current agricultural extensions and subsidy schemes without improving the qualities of the services. The results also suggest that the policy intervention that strengthens the enforcement of forest protection in the critical areas of the watershed and simultaneously create incentives and opportunities for agricultural production in the less critical areas will likely promote forest restoration and community income in long run. We also discuss limitations of the simulation model and recommend future directions for model development.”

Quantifying Aggregated Uncertainty in Plasmodium falciparum Malaria Prevalence and Populations at Risk via Efficient Space-Time Geostatistical Joint Simulation

/ Matt Artz

PLoS Computational Biology 2010 6(4): e1000724. doi:10.1371/journal.pcbi.1000724

Peter W. Gething, Anand P. Patil, and Simon I. Hay

“Risk maps estimating the spatial distribution of infectious diseases are required to guide public health policy from local to global scales. The advent of model-based geostatistics (MBG) has allowed these maps to be generated in a formal statistical framework, providing robust metrics of map uncertainty that enhances their utility for decision-makers. In many settings, decision-makers require spatially aggregated measures over large regions such as the mean prevalence within a country or administrative region, or national populations living under different levels of risk. Existing MBG mapping approaches provide suitable metrics of local uncertainty—the fidelity of predictions at each mapped pixel—but have not been adapted for measuring uncertainty over large areas, due largely to a series of fundamental computational constraints. Here the authors present a new efficient approximating algorithm that can generate for the first time the necessary joint simulation of prevalence values across the very large prediction spaces needed for global scale mapping. This new approach is implemented in conjunction with an established model for P. falciparum allowing robust estimates of mean prevalence at any specified level of spatial aggregation. The model is used to provide estimates of national populations at risk under three policy-relevant prevalence thresholds, along with accompanying model-based measures of uncertainty. By overcoming previously unchallenged computational barriers, this study illustrates how MBG approaches, already at the forefront of infectious disease mapping, can be extended to provide large-scale aggregate measures appropriate for decision-makers.”

Rock Glacier Activity in the South Shetland Islands: DINSAR, Ground-truth and GIS Analysis. Methodology and First Results

/ Matt Artz

Paper accepted for presentation at the 2010 European Space Agency Living Planet Symposium, Bergen, Norway, 28 June to 2 July 2010:

Jorge, Marco; Vieira, Gonçalo; Catalão, João; Ramos, Miguel

“Rock glaciers are distinct lobate or tongue-shaped bodies of permafrost that flow in response to the deformation of the ice within. Rock glaciers are relatively rare in oceanic environments so that their study is particularly important and relevant in maritime Antarctic (Serrano & Lopez-Martinez, 2000). Furthermore, being located in a region where the climate warming is particularly strong, the South Shetlands archipelago is a privileged place for investigation on the response of permafrost degradation and deformation rates to the climatic forcing. The ice-free coastal zones where the rock glaciers occur show mean annual air temperatures slightly below 0°C, making this region one of the best places on Earth to study the response of rock glaciers to climate change.

“In the South Shetlands, the field work logistics are complex, mainly due to the limitations on transport, harsh weather conditions, but also accouting for the environmental impact restrictions imposed by the Antarctic Treaty. Therefore, the use of active remote sensing systems is an excellent way to monitor the deformation of the terrain where rock glaciers occur. Serrano & Lopez-Martinez (2000) have surveyed most of the rock glaciers in the archipelago, but data on movement rates is still lacking. Differential interferometry of SAR images (DINSAR) from ERS 1-2 and ENVISAT sensors allow to monitor the activity of rock glaciers parsimoniously (good spatial resolution and measurement accuracy in a large area), in a way that no other technique would permit.

“Our approach focuses on different timescales of activity reflecting distinct climatic controls. “Permanent Scatterers pixels” identified in long temporal series of interferometric SAR images will be used to obtain the inter-annual movement rates of the rock glaciers. Interferograms with temporal baselines from 1 day (tandem pairs) to 1 year will allow to explore the DINSAR signal of each rock glacier. Following the methodology proposed by Lambiel et al. (2009), a classification of all features according to the rate of activity will be made. The specific physical conditions of the study area, the small dimensions of the features being monitored and large differences in rates of activity (i.e., the very distinct DINSAR signals) demand a preliminary focus on the specificity of the DINSAR analysis, a task whose results we will present in the 2010 ESA conference. Field test sites will be installed in Livingston and King George islands in order to obtain ground truth for validation and complement DINSAR results. Hurd rock glacier, in Livingston Island will be the main target of one-year interval detailed geodetic ground surveys using DGPS and Total Laser Station measurements.

“The high rates of geomorphic dynamics of the periglacial terrain provides an opportunity to perform an innovative spatial analysis using the DINSAR deformation grid. Ground deformation data will be analysed using empiro-statistical techniques accouting for different independent variables (e.g., bivariate analysis – informative value and GLM – logistic regression), such as: i) detailed geomorphological surveys; ii) geographical variables derived from the DEM; iii) and field data from monitoring sites maintained by our group, such as weather stations, shallow and deep boreholes for permafrost monitoring, active layer thickness (CALM sites) and snow mantle thickness. The deformation grid is a clear dependent variable, with no problems of multicollinearity with the variables assumed and inputted in the models as explanatory-independent variables, that can be used in two distinct but related levels of analysis: i) the relationship between the classified geomorphic features (geomorphological mapping) and the movement of the terrain; ii) the influence of the geographical factors on the terrain deformation. By combining i and ii we should reach a better level of knowledge on periglacial dynamics.”

RAMAS GIS: Linking Spatial Data with Population Viability Analysis

/ Matt Artz

“RAMAS GIS is designed to link your GIS with a metapopulation model for population viability analysis and extinction risk assessment. Habitats used by most species are becoming increasingly fragmented, requiring a metapopulation modeling approach to risk analysis. Recognizing habitat patchiness from an endangered species’ point of view requires spatial information on habitat suitability. RAMAS GIS meets both these requirements by linking metapopulation modeling with landscape data and GIS technology.”