Research Highlights

Oliver W. Frauenfeld, Associate Professor

Department of Geography

An Observational 71-year History of Seasonally Frozen Ground Changes in the Eurasian High Latitudes

In recent decades, significant changes have occurred in high-latitude areas, particularly to the cryosphere. Sea ice extent and thickness have declined. In land areas, glaciers and ice sheets are experiencing negative mass balance changes, and there is substantial regional snow cover variability. Subsurface changes are also occurring in northern soils. This study focuses on these changes in the soil thermal regime, specifically the seasonally frozen ground region of Eurasia. We use a database of soil temperatures at 423 stations and estimate the maximum annual soil freezing depth at the 387 sites located on seasonally frozen ground. Evaluating seasonal freeze depth at these sites for 1930–2000 reveals a statistically significant trend of −4.5 cm/decade and a net change of −31.9 cm. Interdecadal variability is also evident such that there was no trend until the late 1960s, after which seasonal freeze depths decreased significantly until the early 1990s. From that point forward, likely through at least 2008, no change is evident. These changes in the soil thermal regime are most closely linked with the freezing index, but also mean annual air temperatures and snow depth. Antecedent conditions from the previous warm season do not appear to play a large role in affecting the subsequent cold season’s seasonal freeze depths. The strong decrease in seasonal freeze depths during the 1970s to 1990s was likely the result of strong atmospheric forcing from the North Atlantic Oscillation during that time period.

David M. Cairns, Professor

Department of Geography

The Changing Influence of Severe Storms on Salt Marsh Vegetation

A fundamental question in biogeography is how plant species composition changes over space and time in response to geomorphic and hydrologic processes at a range of spatial and temporal scales. The dynamic nature of these processes and their importance in vegetation succession makes coastal salt marshes excellent laboratories for the study of vegetation change. Traditionally, succession on salt marshes has been associated with the increase of surface elevation relative to mean high water levels and consequently decreased frequency of tidal flooding. This linkage is based on the notion of a positive feedback between plant growth and sediment accumulation in which the presence of vegetation increases sedimentation thereby facilitating growth due to lowered tidal inundation, salt stress, and edaphic amelioration. As sedimentation and elevation increase, this feedback process facilitates the establishment and growth of later successional species by further reducing the physical stress imposed by seawater.

The Gulf coast of Texas is an area undergoing rapid but spatially variable sea level rise that may also be affected by short-term wind-induced changes in over marsh flooding.

The objective of this research is to evaluate the importance of short-term events for the successional status of Texas salt marshes. Our specific research question is: What are the relative effects of storm tides (meteorological change) versus sea level rise (climatological change) on successional trajectories of vegetation communities? It is currently not clear for the Texas coast whether or not storm tides are important controls on the succession of marsh vegetation. This issue is of particular importance now due to the significant amount of vegetation die-back that occurred on the salt marshes that were in the path of Hurricane Ike. The Texas Chenier Plain National Wildlife Refuge Complex sustained a direct hit from Hurricane Ike in September 2008 and significant amounts of vegetation were either damaged or destroyed subsequent to overmarsh flooding.

In this project we are collecting field-based vegetation data to determine for use in classifying vegetation assemblages and relating these classifications to satellite and airborne imagery of the area. We have concentrated our efforts in the Smith Point region of the East Bay portion of Galveston Bay. We hope to relate vegetation changes to the changing frequency of large storms and wind-induced changes in over marsh flooding over the historic period of record.

Wendy Jepson, Professor

Department of Geography

Household Water Security in Low Income Rural and Peri-Urban Communities in South Texas

Social scientists recently exposed the myth of universal water services coverage in the United States: migrant farm workers, the rural poor, and urban homeless communities face substantial deficiencies in water and sanitation infrastructure. Although institutional and location factors are thought to explain limited water and sanitation services, scholars have overlooked two key aspects of the water-poverty problem:

(1) access to water infrastructure does not guarantee water security, which is defined as adequate, reliable, and affordable water and sanitation for a healthy life; and

(2) considerable water security variability exists within low-income communities.

Our study is filling these gaps by examining household water security variability in low-income Mexican-American communities in the lower Rio Grande Valley of Texas, one of the poorest regions with the largest population lacking suitable water supply and basic sanitation in the United States.

The project is being executed in three parts: 1) household case studies, group interviews, and semi-structured interviews to describe the meaning and experience of household water security in colonias, low-income rural and peri-urban communities; 2) develop and pretest a household water security survey instrument using information gathered in the first part of the project to – pre-testing and respondent evaluations will allow researchers to revise the survey for full implementation; and 3) administer survey instrument and analyze results. Descriptive analysis and multivariate relationships with predictors will be assessed using standard statistical analysis, and hypothesis testing will be conducted. These data will enable the identification of the variables that predict different levels of water insecurity, relationships between the degree of water insecurity and household characteristics, and relationships between the degree of water insecurity and type of water service provider.

This project will provide the basis for new empirical discoveries and advance conceptual innovations related to water security in low-income communities in the United States. Project outcomes include a new survey instrument that could be applied in other low-income areas where substantial water and sanitation deficiencies exist. In addition, the project changes the current understanding of water-poverty problems from 'infrastructure' at a regional scale to 'water security' at a household scale.

The focus on the household as the unit of analysis allows for fine-grained assessments of a broad array of water and sanitation issues, incorporating physical, relational and behavioral dimensions of water deficiency. Therefore, expected research results will advance current knowledge about water and poverty, transform policy and social scientific study about poverty and water, and provide scientifically informed recommendations to improve the human condition of economically excluded groups in the United States. This study is funded by the National Science Foundation and has led to a bi-national initiative to evaluate water security in the lower Rio Grande Valley under varied climate change scenarios.