The Northeastern Highlands ecoregion consists of four physically separate areas, which occupy 127,109 km² (49,077 mi²) in Maine, New Hampshire, Vermont, New York, Massachusetts, Connecticut, New Jersey, and Pennsylvania (fig. 1). The ecoregion is “a relatively sparsely populated region characterized by nutrient poor soils blanketed by northern hardwood and spruce fir forests. Land-surface form in the region grades from low mountains in the southwest and central portions to open high hills in the northeast” (U.S. Environmental Protection Agency, 2002). Numerous mountain ranges, including the White Mountains in New Hampshire, the Green Mountains in Vermont, and New York’s Catskills and Adirondacks, lie within the ecoregion. The ecoregion also shows many remnants of glaciation, including rocky soils, glacial lakes, and wetlands. Annual average rainfall varies from 940 to 1,397 mm (37 to 55 in), with significantly higher amounts in mountainous areas. The average daily temperature ranges from below –7^oC (20o F) in January to between 16 and 21^oC (60 and 70^oF) in July.

Though the ecoregion was heavily forested at the beginning of European settlement, much of it was cleared for farmland in the 19th century. Farmland abandonment, beginning in the mid-1800s and continuing through the study period, has led to a natural regrowth of forest. Forest harvesting for wood products has been an ongoing activity since the early 1800s—and clear-cutting of forest was evident during the study period in western Maine, where timber companies control large tracts of land. Paper and pulp processing is the leading manufacturing activity in Maine. Further south, in New Hampshire, Vermont, and New York, tourism and small-scale farming are more prevalent.

Figure 1. The Northeastern Highlands and surrounding ecoregions. The randomly selected sample blocks are shown along with land use/land cover data from the 1992 National Land Cover Dataset. Click on image to enlarge

A moderate amount of change was observed in the Northeastern Highlands ecoregion, with an estimated 8.9 percent of its area converting to another land cover at least once during the study period (fig. 2). Approximately 2.9 percent changed only once, while 3.1 percent and 2.8 percent changed two and three times, respectively. About one-tenth of 1 percent of the ecoregion’s area was converted four times. Of the thirty-five sample blocks in the ecoregion, five blocks in western Maine had rates of change exceeding 25 percent. The high rates of change were due primarily to forest clear-cutting and regrowth. Thirteen blocks had less than 2 percent change, most of which fell within State or Federally owned lands such as parks, forests, or refuges where forestry practices are restricted or disallowed altogether. Total change per interval increased from 2.3 percent between 1973 and 1980 to 6.2 percent between 1992 and 2000 (table 1). Average annual rates of change increased steadily in the first three intervals from 0.3 percent to 0.9 percent and then slowed to 0.8 percent between 1992 and 2000 (fig. 3).

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

Table 2: Estimated amount of change by time interval, 85-percent confidence interval, and normalized annual rates of change.

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. Estimates of land cover change per time interval normalized to annual rates of change. Click on image to enlarge

Primarily as a result of clear-cutting and some selective harvesting, forest decreased by an estimated 3.8 percent (table 2) or approximately 4,830 km² (1,865 mi²). However, forest remained the dominant land cover, extending over an estimated 81.4 percent of the ecoregion in 2000. As the amount of tree harvesting increased, the percent of mechanically disturbed land also increased—from 0.6 percent in 1973 to 2.1 percent in 2000. The amount of estimated land area in grassland/shrubland increased between 1973 and 1992 from 0.2 percent to 2.2 percent and then decreased slightly in the last interval to 2.1 percent. Developed land increased from 1.8 percent to 2.3 percent between 1973 and 2000, while farmland remained unchanged with approximately 3.3 percent of the ecoregion’s land area. Forest, mechanically disturbed land, and grassland/shrubland were by far the most active land covers, accounting for most of the net change in the ecoregion during the study period (fig. 4).

Figure 4. Net land cover changes by categories for each time interval and for the entire study period. Click on image to enlarge