3rd Quarter 2007
In This Issue
- Solving Environmental Problems Using Geospatial Analysis
- The Ecological Effects of Nanomaterials: A Challenge for the Future
- New Faces
- Recent/Upcoming Publications
- Recent/Upcoming Conferences & Presentations
- PDF Version
Past Issues
Solving Environmental Problems
Using Geospatial Analysis
Introduction
“Now I see it!” is a phrase that indicates successful communication and enlightenment. The ability to accomplish both with illustrations and maps is critical for making sense of otherwise dense and complicated technical data sets and analyses. In particular, powerful analytical tools such as advanced event-specific projection models (e.g., oil spill models), multi-media transport and fate models, and spatially-explicit wildlife exposure models, generate large and complex data sets that can be challenging to understand when presented only in tables of results without a clear geographical frame of reference. And maps alone do not do the trick.
Geospatial analyses using geographic information systems (GIS) have proven particularly helpful, offering useful visual displays of information together with underlying analytical power. GIS relies on digital maps, photographs, satellite images, and other visual media to capture user-specified geographic data. Using these base mapping and visualization tools, data sets are “overlaid” on the maps and can be presented, visualized, and analyzed in “layers.” Physical, chemical, and biological stresses on landscapes, watersheds, and coastal areas can be represented and viewed within a GIS framework and further analyzed with GIS tools. These tools can elucidate subtle changes that occur over time and that are manifested at particular spatial scales. Such information is critical for reconstructing the history of events, forecasting future trends, determining the causes of environmental problems, supporting other forensic analysis, and giving insight on possible solutions. In addition to its analytical capabilities, GIS can be used to communicate information to a broad audience. Most contemporary environmental assessment, problem-solving, and litigation support activities rely on a GIS tool as a central platform for analysis and presentation to stakeholders, including regulators, technical audiences, and juries. This enhances the utility of the underlying analyses and information for insurance cases, regulatory proceedings, voluntary environmental programs, and litigation. The versatility and value of GIS is illustrated by a variety of cases completed by our scientists over the past several years.
Case Examples of GIS Applications
CASE 1: Aerial Deposition Analysis
Exponent used GIS combined with other spatial data to analyze allegations that our client was contributing to air pollution impacts on farms and native plants in an arid region. This international project in the Middle East benefited from GIS mapping, field-program georeferencing, aerial photo interpretation, and multiple lines of evidence analysis. The analysis focused on desert-based farms in the vicinity of oil exploration and refining operations and alleged impacts from nitrogen oxides. Soil and water chemistry data, photographs, observations, aerial photographs, interviews, and plant pathological reviews all provided the information required to analyze the intersection of emissions deposition patterns and agricultural damage to reach a risk-based conclusion. GIS provided the tool needed to evaluate patterns in the evidence at different scales. Evaluating the region from a satellite photo (image 1), it became apparent that trends in observed crop stress were inconsistent with an airborne stressor. At the scale of a single farm, aerial photographs clearly supported this finding as well. Stressed vegetation was located immediately adjacent to healthy vegetation (image 2). Review of the plant stress indicated that nutrients, water quality/salinity, and diseases impacted the health of the plants. Making use of GIS to organize and analyze the data in relation to potential airborne sources, we conducted a causal analysis procedure known as stressor identification, developed by the U.S. Environmental Protection Agency
(U.S. EPA 2000) and elaborated by Suter et al. (2007) as the basis for identifying causes of impairments. This procedure has its basis in epidemiology. It relies on several types of observations to eliminate causes that are unlikely contributors to the observed conditions and also to evaluate the strength of association between candidate causes and the stress. Using GIS tools, we evaluated the lines of evidence based on co-occurrence between stressor and evidence of stress, gradients of effects, plausible mechanisms, consistency of association between the stressor and stress, and specificity.
CASE 2: Alternative Analysis—Predictions of Shoreline Impacts
In another international project, the task was to evaluate the implications of different oil spill response strategies on shoreline impacts. Our work focused on the development of the GIS from base shoreline maps obtained from aerial photographs. The analysis of possible shoreline impacts from oil spills focuses, in part, on the type of shoreline being affected. Our team of aerial imagery and GIS specialists evaluated the shoreline typing, and determined that the usability of aerial photographs to populate a GIS system and hence to assess oil spill impact and persistence is highly dependent on the timing and quality of the aerial images. This finding is especially important when it comes to the timing of tides and image acquisition. Significant offsets and errors in shoreline typing can occur without such recognition.
CASE 3: Historical Time-Series Analysis
Remote sensing tools offer a view into historic development at subject properties. Depending on the location, a property may have aerial photographic documentation extending back to the early 1900s. This rich database can be compiled and digitally reviewed to track activities that influence the current conditions. In many cases, an activity may have started and been discontinued prior to arrival of our team. Through aerial photographic reconnaissance, this activity can be reviewed with respect to the current conditions. Evidence of historical waterways may provide insights into chemical distribution and sources. In addition to activities at the study site, historical activities in neighboring and/or upgradient locations may also have affected current conditions, and would be included in the aerial time series.
CASE 4: Risk Communication
In addition to adding analytical depth and flexibility to environmental assessments, GIS can also provide a powerful communication approach. When Exponent was asked to monitor a mine site to ensure that plants and wildlife in the surrounding area were not adversely impacted by mine activities, GIS allowed us to compile multiple, complex data into a single map. In the example shown, concentrations of a particular analyte can easily be seen in relationship to property boundaries and dominant waterways.
CASE 5: Vulnerability Analysis
With any disaster, determining the vulnerability of the impacted area plays a critical role in developing a plan of action and recovery from the disaster. GIS provides a tool to integrate a wide variety of spatial data to allow the user to see the potential impact and use the combined data to analyze how a set of specific data will be affected. In the case of an earthquake, the user can quickly obtain modeled data of the earthquake from the USGS (image 1). Combining these USGS layers with client-specific information can produce data that will be useful to determine the impact to the client’s data set from the earthquake (image 2). In the example shown, client location information is overlaid onto the earthquake modeled intensity contours. The locations that will be affected by the greatest earthquake intensity are quickly and easily noted.
Summary
As scales shift from small, localized sites, to landscape and regional scales, the tools available for environmental assessment also expand. GIS offers benefits in the conceptual, analysis, risk characterization, and risk communication phases of environmental assessment. The goal of an environmental assessment is to ‘know where you are’ and to know the factors that influence the condition of that area. GIS allows our scientists to view a site from a multitude of scales, including but not limited to temporal, biological, economic, geological, hydrological, physical, and social. In addition, GIS tools are used to visualize unique characteristics of changes, which might be missed at one scale, but become apparent when evidence is integrated at another scale and even across time. Ultimately, multiple lines of evidence need to be integrated to reach a risk management conclusion. GIS fosters this integration and produces accessible and highly persuasive risk management summaries.
