Citation:

NASH, M. S., T. G. WADE, D. T. HEGGEM, AND J. D. WICKHAM. DOES ANTHROPOGENIC ACTIVITIES OR NATURE DOMINATE THE SHAPING OF THE LANDSCDAPE IN THE OREGON PILOT STUDY AREA FOR 1990-1999? Presented at EnviroExpo: Moving Towards Balance Open House, Las Vegas, NV, December 09, 2004.

Impact/Purpose:

There are four basic objectives of the project:

Demonstrate the application of a comparative landscape assessment in analyzing the vulnerability of surface and coastal water conditions to declines based on landscape conditions (as estimated by landscape indicators as demonstrated in the mid-Atlantic landscape atlas) in western environments;

Develop and apply landscape assessment approaches relative to specific issues, including an ability to prioritize the vulnerability of areas relative to the Clean Water Act 303(d) designations; Quantify relationships between landscape conditions (as measured by landscape indicators) and surface and coastal waters in the west to reduce the uncertainty in comparative landscape assessments, and issue-specific, landscape assessments (e.g., Total Maximum Daily Load (TMDLs);

Complete a west-wide, comparative landscape assessment relative to surface and coastal water vulnerability;

Transfer landscape assessment technologies to Regional Offices so that they can conduct landscape assessments at many scales.

Description:

Climatic variation and human activities are major factors resulting in land degradation in arid and semi-arid lands. In the Mediterranean region and over history, climatic drying was coincidental with developing agricultural technology and the rapid increase of the population and their dependence on the grain field, timber, and animal products. As a result of human population demand, it is evident that depletion of natural resources, such as water (surface or ground) and soil (e.g. soil erosion), and reduction of farm productivity lead many farmers to move to alternative lands or to urban areas. This has a major impact on socio economics by decreasing per-capita food production and enhancing poverty that affect the political stability of the The region.

Desertification can be evaluated using environmental degradation, however, it is important to separate degradation that occurred naturally (fire, flood, drought, etc.) or as a result of anthropogenic human activities (urbanization, livestock grazing, etc). Here we report the use of advanced technology to map changes in vegetation cover that enable managers to geographically locate major changes in loss or gain of vegetation cover. Vegetation greenness was assessed over a ten-year period (1990- 1999) using 1 km Normalized Difference Vegetation Index (NDVI) data derived from Advanced Very High Resolution Radiometer (A VHRR) bi-weekly composites. A regression model of NDVI with time was developed to identify long-term trends in greenness for each pixel in a study area State of Oregon, USA. Greenness is highly correlated with precipitation, so general precipitation trends were also calculated for each station in the study area. Localized analysis was also performed around precipitation stations, comparing NDVI and rainfall trends in a 3 km x 3 km neighborhood centered on each station. A decreasing trend in vegetation greenness was an indicator of some type of stress, either natural (drought, fire) or anthropogenic (excessive grazing, urban growth) in origin. The method presented here allows mapping greenness trends over large areas quickly and inexpensively, providing land managers a useful tool in locating areas in most in need of remediation or protection efforts.

Results were mapped using ArcView for visualization and assessments. Three patches of decreasing greenness were identified and analyzed, along with two patches of increasing greenness. Analysis was performed using ancillary data and people with extensive knowledge of the area. Degradation causes were identified as urban growth and fire, increased greenness was attributed to recovery in timber harvest areas.

Record Details: