least 85% across all classifications, whereas the accuracies of
developed, barren, and emergent herbaceous wetland classes
varied considerably from year to year (Table 4).
Our
AASG
classifications provide a new long-term record of
widespread land cover change across the Southeast (Figures 4
and 5), which we briefly discuss here. A detailed discussion
of land cover change in the Southeast is beyond the scope of
this article, which focuses primarily on methods and charac-
teristics of the product. In Figure 4, we show two examples
of rapid urban expansion in distinctly different Southeastern
cities. The periphery of the Dallas-Fort Worth metropolitan
region experienced rapid expansion of developed land uses
from 1986-2011, particularly along the northern periphery of
Dallas (Figure 4a). Proportionally, the North Carolina Re-
search Triangle experienced even more rapid urban expansion
(Figure 4 b), particularly in the area between the major urban
areas of Durham and Raleigh. The overall percentage of land
mapped as developed land uses (classes 22-24) increased
from about 3.6% (roughly 8.5 million ha) in the 1986
AASG
classification to 4.6% (roughly 10.9 million ha) in the 2006
AASG
classification (Figure 5b). These trends are consistent
with the 2001-2011
NLCD
trends in this region, though our ar-
eal estimates of developed land in
AASG
are much lower than
those of the
NLCD
due to our exclusion of “Developed, Open
Space” (class 21) in the
AASG
classifications.
Our classifications also extend the record of forest cover
loss (Figure 5c) and reduction in cultivated cropland (Figure
5d) in the Southeast. Following an initial increase of nearly
1.5 million ha of forest between 1986 and 1991 (including all
three forest classes plus woody wetlands), there was a steady,
monotonic decline in total mapped forest cover between 1991
to 2006 in our new
AASG
classifications, with a total of nearly
3 million ha of forest loss, amounting to an average rate of
roughly −200,000 ha yr
−1
. The
NLCD
showed a continued and
accelerated loss of roughly −375,000 ha yr
−1
over the 2001-
2011 period. Notably, this change was not constant across
all forest classes, but mostly came at the expense of decidu-
ous forests and woody wetlands, which decreased by about
−110,000 ha yr
−1
and −165,000 ha yr
−1
, respectively, from 1991
to 2006. The area mapped as evergreen forest, on the other
Figure 4. Examples of urban growth in Dallas-Fort Worth, TX and Raleigh-Durham-Chapel Hill, NC from 1986-2011. 1986-
2006 classifications from
AASG
classifications, with 2011 data derived from the
NLCD
classification. Colors represent the
earliest year when a given pixel was mapped as Developed (including Low, Medium, and High Intensity). X- and Y-scales are
in units of meters. Note that the scales of (a) and (b) are not identical.
Figure 5. Summary of Southeast land cover change from 1986-2011. (a) Mapped proportions of each class from both
AASG
and
NLCD
over the period 1986-2011. The classes and color scale are the same as the
NLCD
modified Anderson Level II
classification shown in Figure 1. Trends in total area of the Southeast that are mapped by
AASG
as: (b) Developed area, (c)
forest cover (including Woody Wetland), and (d) Cultivated Crops.
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