The Blue Ridge ecoregion is located in the southern Appalachian Mountains, and is the easternmost of the Appalachian highland ecoregions (fig. 1). At more than 1100 km long and ranging between 8 and 80 km wide, it covers approximately 47,791 km² (18,452 mi²). The ecoregion is primarily forested with cool summers and cold winters. Almost one-third of the ecoregion is under public ownership, including two National parks—the Great Smoky Mountains National Park and Shenandoah National Park, the Blue Ridge Parkway, seven National forests, and 29 wilderness areas (Nash, 1999). Areas within the Great Smoky Mountains National Park have been declared an International Biosphere Reserve because of the high number of endemic species of flora and fauna (Bousquet, 2000). The overall landscape is a mosaic of large continuous blocks of forest intermixed with agriculture and dotted with small parcels of developed land.

Figure 1: The Blue Ridge ecoregion. The underlying land cover is taken from the 1992 National Land Cover Database (Vogelmann and others, 2001). Click on image to enlarge

The Blue Ridge ecoregion is stable. The overall spatial change—the percentage of land area within the ecoregion where land cover changed at least once between 1973 and 2000—was 2.0 percent, the lowest of all Eastern U.S. ecoregions (fig. 2). Three fourths of the converted land changed only one time, while one-fourth changed twice (table 1).

Estimated changes in each of the time periods selected for this study were low, ranging from 0.5 percent in the 1973 to 1980 period to 0.9 percent in the 1992 to 2000 period (table 2). The estimates of land cover change have an associated margin of error that is shown in table 2. After normalizing the land cover change per period to an annual rate of change to avoid comparison of unequal time intervals, change was lowest in the 1980 to 1986 period, at 0.07 percent per year, and highest in the 1992 to 2000 period, at 0.11 percent per year (fig. 3).

Table 1: Amount of overall spatial change detected in ecoregion and proportion of ecoregion that experienced change during one or multiple time period

Table 2: Raw estimates of percent change in ecoregion computed for each of four time periods and associated margin of error at 85-percent confidence level (Estimates of change per period are normalized to an annual rate of change for each of the four time periods.).

Figure 2: The overall spatial change in all Eastern U.S. ecoregions. Each bar chart shows the proportion of the ecoregion that experienced change on 1, 2, 3, or 4 dates. Click on image to enlarge

Figure 3: The estimates of land cover change per time interval normalized to an annual rate of change. Click on image to enlarge

Three classes of land cover (forest, agricultural land, and developed land) account for 99 percent of the ecoregion. Table 3 lists the percentage of each individual land cover class during each of the five mapped dates. Forest is the most common cover and makes up nearly 80 percent of the ecoregion. Over the entire study period, forest cover decreased from 79.6 percent of the ecoregion in 1972 to 78.3 percent in 2000, a 1.3 percent decrease. Changes to forest cover included both unidirectional conversions and cyclical conversions during the study period. Some forest was converted to developed land, while some was harvested for timber, and then returned to forest in subsequent years. Agriculture was the second most common land cover, occupying approximately 13.7 percent of the ecoregion. Over the entire study period, agricultural cover remained relatively stable with minor gains and losses in each time period. Developed land, the third most common land cover, increased 1.1 percent, from 6.1 percent in 1972 to 7.2 percent in 2000 (fig. 4).

Table 3: Proportion of ecoregion covered by each land cover class during each of five mapped dates.

Figure 4: The percentage of net land cover change in each time interval. Click on image to enlarge