Browsing by Subject "Geographic information science and geodesy"

Tropical Cyclones (TCs) intensity and frequency are expected to be impacted by climate change. Despite their destructive potential, these phenomena, which can produce heavy precipitation, are also an important source of freshwater. Therefore any change in frequency, seasonal timing and intensity of TCs is expected to strongly impact the regional water cycle and consequently the freshwater availability and distribution. This is critical, due to the fact that freshwater resources in the US are under stress due to the population growth and economic development that increasingly create more demands from agricultural, municipal and industrial uses, resulting in frequent over-allocation of water resources.

In this study we concentrate on monitoring the impact of hurricanes and tropical storms on vegetation activity along their terrestrial tracks and investigate the underlying physical processes. To characterize and monitor the spatial organization and time of recovery of vegetation disturbance in the aftermath of major hurricanes over the entire southeastern US, a remote sensed framework based on MODIS enhanced vegetation index (EVI) was developed. At the SE scale, this framework was complemented by a water balance approach to estimate the variability in hurricane groundwater recharge capacity spatially and between events. Then we investigate the contribution of TCs (season totals and event by event) to the SE US annual precipitation totals from 2002 to 2011. A water budget approach applied at the drainage basins scale is used to investigate the partitioning of TCs' precipitation into surface runoff and groundwater system in the direct aftermath of major TCs. This framework allows exploring the contribution of TCs to annual precipitation totals and the consequent recharge of groundwater reservoirs across different physiographic regions (mountains, coastal and alluvial plains) versus the fraction that is quickly evacuated through the river network and surface runoff.

Then a Land surface Eco-Hydrological Model (LEHM), combining water and energy budgets with photosynthesis activity, is used to estimate Gross Primary Production (GPP) over the SE US The obtained data is compared to AmeriFlux and MODIS GPP data over the SE United States in order to establish the model's ability to capture vegetation dynamics for the different biomes of the SE US. Then, a suite of numerical experiments is conducted to evaluate the impact of Tropical Cyclones (TCs) precipitation over the SE US. The numerical experiments consist of with and without TC precipitation simulations by replacing the signature of TC forcing by NARR-derived climatology of atmospheric forcing ahead of landfall during the TC terrestrial path. The comparison of these GPP estimates with those obtained with the normal forcing result in areas of discrepancies where the GPP was significantly modulated by TC activity. These areas show up to 10% variability over the last decade.

Abstract

Legal and illegal gold mining in the Madre de Dios area cause several environmental concerns linked with mercury pollution and deforestation, which make hydrological and sediment transport processes central for any assessment of ongoing and future environmental impacts. This thesis addresses the problem of estimating flow and transport processes in the virtually ungauged Madre de Dios basin (Peru) to provide a first basis on which transport of mercury adsorbed on the sediment may be evaluated. The thesis first applies a recent method to derive the probability distribution of liquid and solid discharges to gauged basins in the Tropical Zone (Puerto Rico). This application allows the evaluation of the uncertainty associated with estimates of flow and transport pdf's. Once the iuncertainty is quantified, the same tool is applied to provide the first evaluation of the frequency distributions of discharge and sediment fluxes in the Madre de Dios area.

Global climate change is largely due to human induced increases in the emission of greenhouse gases to the atmosphere. Although this fact does not directly motivate this research, it does set the backdrop for the impressive increase in research that topic has garnered across disciplines over the past 30 plus years. The goals of the research presented herein were to investigate the spatial and temporal dynamics of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) flux dynamics in a snowmelt dominated, semi-arid watershed in central Montana and to assess if and how these fluxes were related to patterns imposed by the topographic structure of the watershed. In the process, it has become apparent that a conceptual model that incorporates all three of these important GHGs, and their relationships with environmental variables does not exist. This is certainty at least in part due to the high variability of these fluxes within and between ecosystems. However, a concise conceptual model is necessary to compare empirical evidence and test alternative scaling methods across systems. Explicitly incorporating hydrologic processes into a conceptual framework will not only be important, but imperative, to predicting and assessing responses of these biogeochemical fluxes to a changing climate. This will be particularly relevant in locations that are likely to experience a change in the timing of precipitation such as snow versus rain dominated in sub-alpine zones or change in the timing and frequency of rain events.

In this study, we assessed the spatial and temporal dynamics of three major GHGs using a spatially distributed sampling campaign over two growing seasons. Real time sensors (5 locations) and local spatial variability plots (700 m2, n = 7, with 30 samples in each) were nested within a landscape scale sampling design (n=52). The sites that were distributed across the landscape (n = 52) were organized by transects that either exemplified specific landscape elements (e.g. uplands vs riparian area) or crossed significant environmental gradients (e.g. riparian – uplands or clearcut – forest). Total annual precipitation was similar between the two focal years (2012 = 764 mm 2013 = 749 mm). However, the contribution from rain versus snow shifted from 76% snow and 24% rain in 2012 to 56% snow and 44% rain in 2013. The influential rain events in 2013 began on 17 July and were observed through 14 August.

In this study, we observed that the strength of the relationship between soil water content and topographic metrics of water redistribution increased as the average wetness of the watershed declined. Soil water content and CO2 flux (fCO2) exhibited distinct spatial and temporal variability at the plot and landscape scales in 2013. The legacy effects of clearcutting remained prevalent with regards to fCO2 (which was significantly higher in the forest than in the clearcut regrowth), while differences in the spatial and temporal variability of \theta were not evident between the two landcover types.

Relationships between fluxes of CO2, CH4, and N2O and \theta were variable. The relationship between each gas and soil water content was not consistent between riparian and upland landscape elements. Although the transition zone between riparian and upland locations has been a focal point in watershed biogeochemistry, it appears that focusing on the shifting hydrodynamics, or the dominant hydrologic processes themselves, might be more important than focusing on specific, pre-defined locations in the landscape.

We capitalized on the significant relationships between terrain mediated \theta in the uplands and cumulative seasonal flux of CH4 to empirically scale our weekly measurements of CH4 flux to the watershed scale. We determined that incorporating multiple terrain metrics in the model produced the strongest fit between modeled and observed CH4 flux. This scaling exercise showed that the best fit model predicted over twice as much CH4 consumption in the uplands than predicted with an individual topographic wetness index or by extrapolating the mean/median CH4 flux to the watershed. Additionally, we determined that even if we used the maximum value of seasonal CH4 efflux in the riparian area to estimate riparian contributions, the riparian CH4 efflux only constituted 1– 4% of the net watershed CH4 flux (depending on which value of net influx is used).

While searching for the mechanisms that create biogeochemical optima can interesting and valuable, moving forward, it seems equally important to investigate the spatiotemporal dynamics of fluxes (or times/ places) that we expect to exhibit more landscape scale characteristic levels of a given flux/pool/process. It is also critical that we do not treat the hydrologic dynamics that can influencing those pools/fluxes as a “black box”. Field studies that measure these hydrologic dynamics can provide rich data sets to test accepted and proposed conceptual models and provide useful calibration data for process-based models. The combination of these techniques will most certainly advance our understanding of the spatial and temporal dynamics of greenhouse gas fluxes across given systems. However, evolved conceptual models will be key to assessing how each unique field site or modeling exercise contributes to greater process understanding and predictive capacity. Here we contribute to an updated conceptual model of the relationship between the processes that influence these GHG fluxes and soil water content. We hope that these conceptual contributions will spur new research questions that span systems and scales, while the empirical contributions highlight a few ways that this can be done in practice.

Background: Greenspaces have been shown to promote psychological health; they are understudied in regions facing epidemiologic and demographic shifts towards increased mental illness burden and a more urban population, including Ethiopia. This exploratory cross-sectional analysis characterizes greenspace distribution in Addis Ababa and estimates the overall and stratified (income and sex) associations between greenspaces and depression symptomology. Methods: Data are from young adults living in Addis Ababa in the Positive Outcomes for Orphans study. The normalized difference vegetation index (NDVI) measured greenspace exposure. The Patient Health Questionnaire 8-item scale measured depressive symptoms. Tests of spatial clustering characterized greenspace distribution. Adjusted linear regression models estimated associations between greenspace and depressive symptoms. Results: Among our analytic population (n=206; 51% male; 49% female) the median age was 22(IQR: 20-23), mean NDVI was 0.14(SD:0.44), and mean PHQ-8 was 5.33(SD:4.60). Tests of clustering revealed green-rich areas in the northeast region of the city and green-deprived areas in the center of the city. Adjusted models suggest a slight association between greenspace and depressive symptoms (β = -1.10, 95% CI: -2.76,0.57). The association was strengthened among those with income (β = -1.52, 95% CI: -4.09,1.05) and among males (β = -2.58, 95%CI: -5.38,0.21), but null among those with no income (β = -0.01, 95%CI: -1.89,1.87), and females (β = 0.26, 95%CI: -1.08, 1.58). Conclusion: Though the sample is small and estimates imprecise, this analysis suggests there may be an association between greenspace and depressive symptoms that should be explored further in pursuit of population mental health in Ethiopia.

Compared to full weight infants, low birth weight infants are at greater risk for short and long term health consequences. Maternal exposure to air pollution is associated with low birth weight, although these studies did not extend to rural sources of air pollution[1]. The aim of this study was to investigate the association of maternal exposure to swine CAFO air emissions with birth weight. Information on all North Carolina births from 2004-2008 was extracted from the NCDBR. Maternal exposure to swine CAFO air emissions were estimated using NC CAFO water release permitting in a geographic information system. Using ordinary least squares regression modeling, this study implicates a statistically, but not clinically significant association with exposure to swine CAFO emissions and a decrease in birth weight. As the metric of estimated maternal exposure to swine CAFO air emissions became more refined (binary< interaction< exponential decay) the association between swine CAFO exposure and decreased birth weight was increased. Prior studies have found associations between swine CAFOs and poor health in proximate communities, but none have addressed birth weight [2-8]. The results of this research indicate rural sources of air pollution could potentially adversely impact birth outcomes of especially sensitive mothers.

Habitat loss, fragmentation, and degradation threaten the World’s ecosystems and species. These, and other threats, will likely be exacerbated by climate change. Due to a limited budget for conservation, we are forced to prioritize a few areas over others. These places are selected based on their uniqueness and vulnerability. One of the most famous examples is the biodiversity hotspots: areas where large quantities of endemic species meet alarming rates of habitat loss. Most of these places are in the tropics, where species have smaller ranges, diversity is higher, and ecosystems are most threatened.

Species distributions are useful to understand ecological theory and evaluate extinction risk. Small-ranged species, or those endemic to one place, are more vulnerable to extinction than widely distributed species. However, current range maps often overestimate the distribution of species, including areas that are not within the suitable elevation or habitat for a species. Consequently, assessment of extinction risk using these maps could underestimate vulnerability.

In order to be effective in our quest to conserve the World’s most important places we must: 1) Translate global and national priorities into practical local actions, 2) Find synergies between biodiversity conservation and human welfare, 3) Evaluate the different dimensions of threats, in order to design effective conservation measures and prepare for future threats, and 4) Improve the methods used to evaluate species’ extinction risk and prioritize areas for conservation. The purpose of this dissertation is to address these points in Colombia and other global biodiversity hotspots.

In Chapter 2, I identified the global, strategic conservation priorities and then downscaled to practical local actions within the selected priorities in Colombia. I used existing range maps of 171 bird species to identify priority conservation areas that would protect the greatest number of species at risk in Colombia (endemic and small-ranged species). The Western Andes had the highest concentrations of such species—100 in total—but the lowest densities of national parks. I then adjusted the priorities for this region by refining these species ranges by selecting only areas of suitable elevation and remaining habitat. The estimated ranges of these species shrank by 18–100% after accounting for habitat and suitable elevation. Setting conservation priorities on the basis of currently available range maps excluded priority areas in the Western Andes and, by extension, likely elsewhere and for other taxa. By incorporating detailed maps of remaining natural habitats, I made practical recommendations for conservation actions. One recommendation was to restore forest connections to a patch of cloud forest about to become isolated from the main Andes.

For Chapter 3, I identified areas where bird conservation met ecosystem service protection in the Central Andes of Colombia. Inspired by the November 11th (2011) landslide event near Manizales, and the current poor results of Colombia’s Article 111 of Law 99 of 1993 as a conservation measure in this country, I set out to prioritize conservation and restoration areas where landslide prevention would complement bird conservation in the Central Andes. This area is one of the most biodiverse places on Earth, but also one of the most threatened. Using the case of the Rio Blanco Reserve, near Manizales, I identified areas for conservation where endemic and small-range bird diversity was high, and where landslide risk was also high. I further prioritized restoration areas by overlapping these conservation priorities with a forest cover map. Restoring forests in bare areas of high landslide risk and important bird diversity yields benefits for both biodiversity and people. I developed a simple landslide susceptibility model using slope, forest cover, aspect, and stream proximity. Using publicly available bird range maps, refined by elevation, I mapped concentrations of endemic and small-range bird species. I identified 1.54 km2 of potential restoration areas in the Rio Blanco Reserve, and 886 km2 in the Central Andes region. By prioritizing these areas, I facilitate the application of Article 111 which requires local and regional governments to invest in land purchases for the conservation of watersheds.

Chapter 4 dealt with elevational ranges of montane birds and the impact of lowland deforestation on their ranges in the Western Andes of Colombia, an important biodiversity hotspot. Using point counts and mist-nets, I surveyed six altitudinal transects spanning 2200 to 2800m. Three transects were forested from 2200 to 2800m, and three were partially deforested with forest cover only above 2400m. I compared abundance-weighted mean elevation, minimum elevation, and elevational range width. In addition to analyzing the effect of deforestation on 134 species, I tested its impact within trophic guilds and habitat preference groups. Abundance-weighted mean and minimum elevations were not significantly different between forested and partially deforested transects. Range width was marginally different: as expected, ranges were larger in forested transects. Species in different trophic guilds and habitat preference categories showed different trends. These results suggest that deforestation may affect species’ elevational ranges, even within the forest that remains. Climate change will likely exacerbate harmful impacts of deforestation on species’ elevational distributions. Future conservation strategies need to account for this by protecting connected forest tracts across a wide range of elevations.

In Chapter 5, I refine the ranges of 726 species from six biodiversity hotspots by suitable elevation and habitat. This set of 172 bird species for the Atlantic Forest, 138 for Central America, 100 for the Western Andes of Colombia, 57 for Madagascar, 102 for Sumatra, and 157 for Southeast Asia met the criteria for range size, endemism, threat, and forest use. Of these 586 species, the Red List deems 108 to be threatened: 15 critically endangered, 29 endangered, and 64 vulnerable. When ranges are refined by elevational limits and remaining forest cover, 10 of those critically endangered species have ranges < 100km2, but then so do 2 endangered species, seven vulnerable, and eight non-threatened ones. Similarly, 4 critically endangered species, 20 endangered, and 12 vulnerable species have refined ranges < 5000km2, but so do 66 non-threatened species. A striking 89% of these species I have classified in higher threat categories have <50% of their refined ranges inside protected areas. I find that for 43% of the species I assessed, refined range sizes fall within thresholds that typically have higher threat categories than their current assignments. I recommend these species for closer inspection by those who assess risk. These assessments are not only important on a species-by-species basis, but by combining distributions of threatened species, I create maps of conservation priorities. They differ significantly from those created from unrefined ranges.

This study used Landsat 8 satellite imagery to identify environmental variables of households with malaria vector breeding sites in a malaria endemic rural district in Western Kenya. Understanding the influence of environmental variables on the distribution of malaria has been critical in the strengthening of malaria control programs. Using remote sensing and GIS technologies, this study performed a land classification, NDVI, Tasseled Cap Wetness Index, and derived land surface temperature values of the study area and examined the significance of each variable in predicting the probability of a household with a mosquito breeding site with and without larvae. The findings of this study revealed that households with any potential breeding sites were characterized by higher moisture, higher vegetation density (NDVI) and in urban areas or roads. The results of this study also confirmed that land surface temperature was significant in explaining the presence of active mosquito breeding sites (P< 0.000). The present study showed that freely available Landsat 8 imagery has limited use in deriving environmental characteristics of malaria vector habitats at the scale of the Bungoma East District in Western Kenya.

The Etruscan-Roman city of Vulci is one of many Etruscan cities which lacks a detailed and holistic understanding of its urban development. Vulci represents a rare site that was not covered by modern structures and thus presents a unique opportunity for a city-scale examination of the transformation of urban space over a millennium of occupation. In order to address this query while most of the site is still unexcavated, an innovative method was created for this project. This ‘n’-dimensional approach layers a series of geospatial and historical data, largely relying on new, non-invasive remote sensing surveys. The main sensors and data sets include a series of older aerial photographs (1954, 1975, 1986), a geological and landscape survey from 2014, multi-spectral aerial images from surveys between 2015 and 2017 ranging from normal-colored to red edge to near infrared bands, and two ground penetrating radar (GPR) surveys from 2015 and 2018. The analyses and interpretations from this multi-modal method builds a more holistic and nuanced understanding of the urbanization and transformation of Vulci. Conclusions from spatial analysis suggest a relative order for the development of the Etruscan-Roman street-grid, offering a new framework for the contextualization of other urban features. Further, evidence points to the northeast area with its unique structure orientation and connection to Northeastern Acropolis as the first settled space on the plateau during the 8th century BCE after shifting away from the Villanovan era settlement on La Pozzatella. Analysis also indicates numerous new features, including multiple public buildings in the Western Forum with major phases of transformation first in the 6th-5th century BCE while under Etruscan control and then again during the early Imperial period while under Roman control. Other features include a ‘basilica’-like/Augusteum structure, at least one additional temple, several administrative buildings, and multiple residential structures with atriums and impluviums. The urban development of Vulci implies a revitalization of the city and re-emergence of power during the Roman Imperial period, contradicting the previous notion that Vulci slowly but steadily declined post-conquest. These conclusions situate Vulci in a new place in not only in Etruscan urbanization but also in period the cultural transformation during Rome’s expansion into Etruria. Furthermore, the success of the multi-perspective, layered approach allows for its use in other studies as well as further refinement and advancement of the methodology.