Middle Atlantic Coastal Plain
By Roger F. Auch 1
Click to see available downloads for this ecoregion
Figure 1. The Middle Atlantic Coastal Plain ecoregion. The
underlying land cover is from the 1992 National Land Cover Database (Vogelmann
and others, 2001).
Ecoregion Description
The Middle Atlantic Coastal Plain
is a linear ecoregion covering approximately 89,691 km2 (34,630 mi2)
that stretches from Delaware Bay and the Delmarva Peninsula in the north to nearly
Jacksonville in the south (fig. 1). Portions of nine states are included (New Jersey, Pennsylvania, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida) (fig. 1). The ecoregion ranges in width from only a few miles (inland of
Delaware Bay and extreme northeast Florida) to approximately 70 miles in areas
of North and South Carolina. The topography is primarily flat, and many soil
types are poorly drained (U.S. Environmental Protection Agency, 1997). The
dominant land uses are farming and forestry, with urban development being
locally significant. The land cover is primarily a mosaic of forest, wetlands,
and agriculture. Agricultural land consists mainly of cropland—growing
soybeans, cotton, and some tobacco in the south and soybeans and corn further
north (fig. 2). Livestock production is most pronounced as confined animal
feeding operations, such as for hogs in North Carolina and poultry on the Delmarva Peninsula (fig. 3)(U.S. Department of Agriculture, 1999). Upland forest land
cover consists predominantly of pine or mixed pine and hardwood communities (fig.
4). Wetlands are quite common across the ecoregion and include coastal
marshes, bottomland hardwood forests, and shrub bogs (pocosins) (fig. 5a &
5b). Other land covers with less extensive areas include water and
mechanically disturbed land. The climate has moderate to mild winters and hot,
humid summers, with 1,000 to 1,500 mm (40 to 60 in) of average annual
precipitation.
Contemporary Land Cover Change (1973 to 2000)
The Middle Atlantic Coastal Plain
experienced a large amount of land cover change when compared with other
ecoregions in the Eastern United States, ranking third in the proportion of
area changed (overall spatial change) (fig. 6). Eighteen percent of the land
area changed from one land cover to another at least once during the 1973 to
2000 study period (table 1). The amount of area changed per time interval was
relatively high and appeared to increase over time, with the 1973 to1980
interval experiencing the least change and the 1992 to 2000 interval
experiencing the most (table 2). Normalizing the amount of change to an
annual rate to adjust for unequal time intervals still shows that 1973 to 1980
had the lowest rate of change, but indicates that 1986 to 1992 actually had the
highest rate. Although the interval from 1986 to 1992 was the most dynamic, two
other intervals (1980 to1986 and 1992 to 2000) also had normalized rates
exceeding one percent per year, a high rate of change among those estimated for
all eastern ecoregions (fig. 7). The margin of error in our statistical
estimates was relatively high, ranging from +/–1.6 percent to +/–2.6 percent at
the 85-percent confidence level, indicating that land cover change had high
variability across the ecoregion.
Two of the Middle Atlantic Coastal
Plain’s dominant land covers, forest and wetlands, experienced considerable net
change, although there was a temporal unevenness for each of these classes
across time periods (table 3). Forest cover decreased in the first three time
intervals, ranging from –0.61 to –1.58 percent, but increased +0.21 percent in
the last time interval, for a net loss in area of –3.3 percent between 1973 and
2000 (fig. 8). Some of the net loss between 1992 and 2000 was due to the
conversion of forest to mechanically disturbed land associated with timber
harvesting and is expected to return to forest cover at a later date. Two time
intervals (1980 to 1986 and 1992 to 2000) had noticeable decreases (–0.55 and
–0.71 percent) in wetlands land cover, but the other two intervals had almost
no change. Wetlands had a net decrease of –1.29 percent during the study
period, but some of the wetlands-to-mechanically disturbed land cover change
between 1992 and 2000 will likely return to wetlands at a later date. The third
most common land cover, agriculture, did not have a noticeable net change
between 1973 and 2000, although the 1973 to 1980 interval had a small gain
(+0.23 percent) that was offset by decreases during two subsequent time
intervals (–0.1 percent and –0.15 percent), respectively. The less prevalent
land covers of developed and mechanically disturbed lands had substantial net
gains in area but experienced somewhat different pulses of change. The total
amount of development had a nearly consistent increase across each time
interval, ranging from +0.55 to +0.66 percent, to have a net change of +2.59
percent, whereas the mechanically disturbed land cover class changes showed
more fluctuation of change, ranging from +0.17 for the 1992 to 2000 interval to
+0.76 percent for the 1973 to 1980 period. Overall, mechanically disturbed
land had a net areal increase of +2.46 percent.
Urban development almost always has
a net increase, as it tends to be a permanent change, whereas other land
covers, such as forest, agriculture, wetlands, and mechanically disturbed, may
experience fluctuating net changes as part of cyclic land uses. Forest parcels may be clear-cut for wood harvesting and, subsequently, return to forest.
Land used for farming or forestry may be switched to another use to take
advantage of changing economic markets.
The leading changes in the Middle
Atlantic Coastal Plain were those indicative of cyclic wood production (table
4). Conversions from forest to mechanically disturbed land and mechanically
disturbed land to forest were the leading land cover conversions for each time
interval (fig. 9a & 9b). Overall, 18,995 km2 of land fluctuated
between these two land cover classes. Another way to consider forest cover in this
ecoregion is to compare the percentage of land that was consistently forest
between 1973 and 2000 (“stable” forest) with the percentage of land that was
forest only part of the time (“dynamic” forest). More than half (59.5 percent)
of the forest area remained as forest throughout the study period, while 40.5
percent was converted to or from forest land (table 5). The percentage of
stable forest (unaltered forest that is at least 30 years of age) in the Middle
Atlantic Coastal Plain was one of the lowest of all eastern ecoregions.
Other, leading land cover changes
included disturbances in wetlands and increased development (fig. 10). The
transitions back and forth between wetlands and mechanically disturbed land
were the third (wetlands to mechanically disturbed land) and fifth
(mechanically disturbed land to wetlands) leading changes overall. Timber
harvesting of forested wetlands, such as bottomland hardwoods, appeared to
account for a majority of these transitions. The conversion of forest to developed
land was either the third or fourth most common land cover change in area by
time interval. The ecoregion gained an estimated 2,247 km2 of new
developed land during the study period, a majority of it from forest (1,747 km2)
and most of the rest from either agricultural land (253 km2) or
wetlands (134 km2).
References
U.S. Department
of Agriculture, 1999, 1997 Census of agriculture—agricultural atlas of the United States v. 2, subject series, part 1: Washington, D.C., U.S. Government Printing Office, 163
p.
U.S.
Environmental Protection Agency, 1997, Descriptions of level III ecological
regions for the CEC report on ecological regions of North America, accessed
April 12, 2006, at http://www.epa.gov/wed/pages/ecoregions/na_eco.htm#Downloads
Vogelmann, J. M., Howard, S.M., Yang, L., Larson,
C.R., Wylie, B.K., and Van Driel, N., 2001, Completion of the 1990s National
Land Cover Data set for the conterminous United States from Landsat Thematic
Mapper data and ancillary data sources: Photogrammetric Engineering &
Remote Sensing, v. 67, p. 650-662.
Table 1. Percentage of the ecoregion that experienced
change
[Most of the sample pixels remained unchanged (82.0
percent), whereas 18.0 percent changed at least once through the study period]
|
Overall
|
Number of changes
|
|
spatial change
|
1
|
2
|
3
|
4
|
Percent of
ecoregion
|
18.0
|
8.1
|
8.7
|
1.0
|
0.1
|
Table 2. Estimated amount of change by time interval,
85-percent confidence interval, and normalized annual rates of change
|
Period
|
|
1973-1980
|
1980-1986
|
1986-1992
|
1992-2000
|
Total
change (% of ecoregion)
|
5.9%
|
6.8%
|
7.6%
|
9.1%
|
Margin of
error (85% confidence level)
|
+/-1.6%
|
+/-2.3%
|
+/-2.5%
|
+/-2.6%
|
Average
annual rate of change (%/year)
|
0.8%
|
1.1%
|
1.3%
|
1.1%
|
Table 3. Estimated ecoregion land cover classes by percent
and area (km2)
|
1973
|
1980
|
1986
|
1992
|
2000
|
Net change 1973-2000
|
Land-use/land-cover
class
|
km²
|
%
|
km²
|
%
|
km²
|
%
|
km²
|
%
|
km²
|
%
|
km²
|
%
|
Water
|
5980
|
6.7
|
5987
|
6.7
|
5996
|
6.7
|
6004
|
6.7
|
5996
|
6.7
|
16
|
0.0
|
Developed
|
5800
|
6.5
|
6299
|
7.0
|
6900
|
7.7
|
7510
|
8.4
|
8047
|
9.0
|
2247
|
2.5
|
Mechanically
disturbed
|
2061
|
2.3
|
2757
|
3.1
|
3022
|
3.4
|
3618
|
4.0
|
3768
|
4.2
|
1707
|
1.9
|
Mining
|
37
|
0.0
|
49
|
0.1
|
75
|
0.1
|
109
|
0.1
|
114
|
0.1
|
77
|
0.1
|
Naturally
barren
|
132
|
0.1
|
126
|
0.1
|
120
|
0.1
|
124
|
0.1
|
143
|
0.2
|
10
|
0.0
|
Forest
|
31814
|
35.5
|
30365
|
33.9
|
29807
|
33.2
|
28593
|
31.9
|
28782
|
32.1
|
-3031
|
-3.4
|
Grassland/Shrubland
|
243
|
0.3
|
252
|
0.3
|
426
|
0.5
|
516
|
0.6
|
424
|
0.5
|
180
|
0.2
|
Agriculture
|
20343
|
22.7
|
20556
|
22.9
|
20549
|
22.9
|
20458
|
22.8
|
20320
|
22.7
|
-23
|
0.0
|
Wetland
|
23280
|
26.0
|
23302
|
26.0
|
22796
|
25.4
|
22758
|
25.4
|
22096
|
24.6
|
-1184
|
-1.3
|
Non-mechanically
disturbed
|
0
|
0
|
0
|
0
|
0
|
0.0
|
0
|
0.0
|
0
|
0.0
|
0
|
0.0
|
Table 4. Leading land cover changes by time interval
|
|
|
Area changed
|
% of all
|
Period
|
From
class
|
To
class
|
(km2)
|
changes
|
1973-1980
|
Forest
|
Mechanically
disturbed
|
2,408
|
46
|
|
Mechanically
disturbed
|
Forest
|
1,646
|
31
|
|
Forest
|
Developed
|
444
|
8
|
|
Forest
|
Agriculture
|
277
|
5
|
|
Mechanically
disturbed
|
Wetland
|
191
|
4
|
|
Other
classes
|
Other
classes
|
295
|
6
|
|
|
|
5,261
|
100
|
|
|
|
|
|
1980-1986
|
Forest
|
Mechanically
disturbed
|
2,128
|
35
|
|
Mechanically
disturbed
|
Forest
|
2,116
|
35
|
|
Wetland
|
Mechanically
disturbed
|
592
|
10
|
|
Forest
|
Developed
|
498
|
8
|
|
Mechanically
disturbed
|
Grassland/Shrubland
|
179
|
3
|
|
Other
classes
|
Other
classes
|
595
|
10
|
|
|
|
6,108
|
100
|
|
|
|
|
|
1986-1992
|
Forest
|
Mechanically
disturbed
|
2,805
|
41
|
|
Mechanically
disturbed
|
Forest
|
1,928
|
28
|
|
Forest
|
Developed
|
503
|
7
|
|
Mechanically
disturbed
|
Wetland
|
426
|
6
|
|
Wetland
|
Mechanically
disturbed
|
392
|
6
|
|
Other
classes
|
Other
classes
|
771
|
11
|
|
|
|
6,825
|
100
|
|
|
|
|
|
1992-2000
|
Mechanically
disturbed
|
Forest
|
3,097
|
38
|
|
Forest
|
Mechanically
disturbed
|
2,866
|
35
|
|
Wetland
|
Mechanically
disturbed
|
791
|
10
|
|
Forest
|
Developed
|
302
|
4
|
|
Mechanically
disturbed
|
Agriculture
|
191
|
2
|
|
Other
classes
|
Other
classes
|
931
|
11
|
|
|
|
8,178
|
100
|
Overall:
|
|
|
|
|
1973-2000
|
Forest
|
Mechanically
disturbed
|
10,207
|
39
|
|
Mechanically
disturbed
|
Forest
|
8,788
|
33
|
|
Wetland
|
Mechanically
disturbed
|
1,903
|
7
|
|
Forest
|
Developed
|
1,747
|
7
|
|
Grassland/Shrubland
|
Grassland/Shrubland
|
1,113
|
4
|
|
Other
classes
|
Other
classes
|
2,613
|
10
|
|
|
|
26,371
|
100
|
Table 5. Sample block forest pixels-stability vs. change
|
Number
|
Percentage of
|
Land
cover from 1973 to 2000
|
of pixels
|
Forest pixels
|
Forest at any time
|
464,020
|
100.0%
|
Stable Forest (unchanged)
|
276,005
|
59.5%
|
Dynamic Forest (affected by
|
188,015
|
40.5%
|
or
resulting from change)
|
|
|
Figure 1. The Middle Atlantic Coastal Plain ecoregion. The
underlying land cover is from the 1992 National Land Cover Database (Vogelmann
and others, 2001). The Land Cover Trends
20 km x 20 km sample blocks are shown as hollow yellow
squares.
Figure 2. Farm growing corn and soybeans near Salisbury, Md. Photo Thomas Loveland
Figure 3. Cotton field and confined animal feeding units,
raising either hogs or poultry, on a farm in North Carolina. Photo Thomas
Loveland
Figure 4. Even age (a forestry management term) loblolly
pine forest parcels near Marion, S.C. Photo Thomas Loveland
Figure 5a (top). Forested wetland (bottomland hardwoods) in
the South Carolina part of Ecoregion 63. Figure 5b (bottom). Coastal wetland
located in extreme southeast Georgia. Photos Thomas Loveland
Figure 6. 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.
Figure 7. The estimates of land cover change per time
interval normalized to an annual rate of change.
Figure 8. Estimated net percentage change by land cover
class by time interval and overall study period.
Figure 9a (top). Tree debris, or slash, left over from a forest
clear-cut on the eastern shore of Maryland. This is classified as mechanically
disturbed land. Figure 9b (bottom). Field of young pine trees west of Charleston, S.C. Photos Thomas Loveland
Figure 10. Newer subdivision located just off Interstate 95
west of St. Mary’s, Ga.
Photo Thomas Loveland