Land Cover Trends Project

Western Allegheny Plateau

By Kristi L. Sayler 1

Click to see available downloads for this ecoregion

map of Central Appalachians Ecoregion

Figure 1. Western Allegheny Plateau and surrounding ecoregions. The 40 randomly selected 100-km² sample blocks are shown along with land use/land cover from the 1992 National Land Cover Dataset.

 

Ecoregion Description

 

The Western Allegheny Plateau ecoregion, as defined by Omernik (1987), covers portions of eastern Ohio, southwestern Pennsylvania, northwestern West Virginia, and a small piece of northeastern Kentucky. The ecoregion covers approximately 84,500 km2 (32,630 mi2) (fig. 1) and is about 72 percent forest and 23 percent agriculture.  The forest area is mostly mixed oak and mixed temperate forests that still exist today on most of the remaining rounded hills.  Dairy, livestock, and general farming, as well as residential developments, are concentrated in the valleys (fig. 2).  Pittsburgh, Pennsylvania is the largest urban area in the ecoregion and has shown some expansion despite an overall population decline in the ecoregion.  Coal mining is still active in the Pennsylvania, West Virginia, and Kentucky portions of the ecoregion and in Ohio to a lesser extent (fig. 3 and 4).  The Ohio and Allegheny River systems in the ecoregion have been adversely affected by acid mine drainage and industrial pollution, which has caused degradation of the stream habitats and loss of fish species (Cooper, 1983).  Water quality has improved somewhat, and a few species have returned. 

 

Contemporary Land Cover Change (1973 to 2000)

 

The overall spatial change from 1973 to 2000 for the Western Allegheny Plateau was 6.0 percent, which was a low amount of change compared to other ecoregions in the East (fig. 5).  An estimated 4 percent of the ecoregion changed only one time.  The other 2 percent changed multiple times and was likely the result of coal mining and timber harvesting activities (table 1), which tend to cycle through multiple land cover transitions. 

The change per time period ranged from 1.9 to 2.3 percent with margin of errors ranging from 0.4 to 0.7 percent (table 2).  The average annual rates of change show that the 1986 to 1992 period had the greatest amount of change with a rate of 0.4 percent per year (table 2 and fig. 6).  This was a period of transition for the coal mining regions of Ohio and West Virginia.  Ohio coal production was slowing down due to increasing regulations on surface mining and higher environmental emission standards (Crowell, 1995), whereas West Virginia saw an increase in the extraction of low-sulfur coal (Fox, 1999) in order to meet federal standards from the 1990 Clean Air Act.

The majority of land cover classes in the Western Allegheny Plateau experienced little change during the study period (table 3).  Forest and agriculture both showed steady declines since 1973, while developed lands increased during each time period resulting in an increase of 376 km2 (147 mi2) between 1973 and 2000 (fig. 7).  Grassland/shrubland increased from 1.5 percent of the ecoregion area in 1973 to 2.6 percent in 2000. 

Mining and forest clearing activities caused the most prominent net land cover changes in the Western Allegheny Plateau ecoregion.  Net changes in the land cover classes fluctuated throughout the 1973 to 2000 period (fig. 8).  Grassland/shrubland had net increases in all four time periods, while mining and forest showed decreases in most time periods. 

With a few exceptions for timber cutting, the top three leading land cover transitions during each time period were related to coal mining activities in the ecoregion (i.e., mining to grassland/shrubland, grassland/shrubland to forest, or forest to mining).  The top seven transitions contained at least 75 percent of the total change for each time period and affected between 1,090 and 1,400 km2 of land area (table 4).

 

References

 

Cooper, E.L., 1983, Fishes of Pennsylvania and the northeastern United States: University Park, Pa., Pennsylvania State University Press, 183 p.

 

Crowell, D.L., 1995, History of the coal-mining industry in Ohio: Ohio Division of Geological Survey Bulletin 72, 204 p.

 

Fox, J., 1999, Mountaintop removal in West Virginia—an environmental sacrifice zone:  Organization and Environment, v. 12, no. 2, p. 163-183.

 

Omernik, J.M., 1987, Ecoregions of the conterminous United States: Annals of the Association of American Geographers, v. 77, no. 1, p. 118-125.

 

 

 

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

 

 

Overall

Number of changes

 

spatial change

1

2

3

4

Percent of ecoregion

6.0

4.0

1.8

0.2

0.0

 

 

 

Table 2.  Raw estimates of percent change in the ecoregion computed for each of the four time periods and associated margin of error at a 85 percent level of confidence

 

 

Period

 

1973-1980

1980-1986

1986-1992

1992-2000

Total change (% of ecoregion)

2.1%

2.0%

2.3%

1.9%

Margin of error (85% confidence level)

+/-0.6%

+/-0.8%

+/-0.6%

+/-0.5%

Average annual rate of change (%/year)

0.3%

0.3%

0.4%

0.2%

 

 

 

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

 

 

1973

1980

1986

1992

2000

Net change 1973-2000

Land-use/land-cover class

km²

%

km²

%

km²

%

km²

%

km²

%

km²

%

Water

1079

1.3

1116

1.3

1118

1.3

1120

1.3

1126

1.3

47

0.1

Developed

5909

7.0

5976

7.1

6034

7.1

6192

7.3

6358

7.5

449

0.5

Mechanically disturbed

75

0.1

84

0.1

74

0.1

245

0.3

239

0.3

165

0.2

Mining

892

1.1

1024

1.2

863

1.0

574

0.7

511

0.6

-381

-0.4

Barren

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

Forest

54674

64.5

54298

64.1

54387

64.2

54159

63.9

53942

63.7

-732

-0.9

Grassland/Shrubland

1300

1.5

1581

1.9

1683

2.0

1965

2.3

2201

2.6

901

1.1

Agriculture

20682

24.4

20524

24.2

20445

24.1

20349

24.0

20216

23.9

-465

-0.5

Wetland

128

0.2

134

0.2

134

0.2

134

0.2

145

0.2

17

0.0

Non-mechanically disturbed

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

0

0.0

 

 

 


Table 4.  Leading land cover conversions during each of the four time periods

 

 

 

 

Area changed

% of all

Period

From class

To class

(km2)

changes

1973-1980

Forest

Mining

331

19

 

Mining

Grassland/Shrubland

258

15

 

Grassland/Shrubland

Forest

201

11

 

Forest

Grassland/Shrubland

174

10

 

Forest

Agriculture

119

7

 

Agriculture

Grassland/Shrubland

105

6

 

Agriculture

Mining

96

5

 

Other classes

Other classes

475

27

 

 

 

1,759

100

 

 

 

 

 

1980-1986

Grassland/Shrubland

Forest

414

24

 

Mining

Grassland/Shrubland

402

23

 

Forest

Mining

202

12

 

Forest

Agriculture

113

7

 

Agriculture

Mining

82

5

 

Agriculture

Grassland/Shrubland

74

4

 

Forest

Grassland/Shrubland

69

4

 

Other classes

Other classes

361

21

 

 

 

1,717

100

 

 

 

 

 

1986-1992

Mining

Grassland/Shrubland

372

20

 

Grassland/Shrubland

Forest

238

12

 

Forest

Mechanically disturbed

223

12

 

Forest

Mining

174

9

 

Forest

Grassland/Shrubland

159

8

 

Mining

Forest

124

7

 

Agriculture

Forest

110

6

 

Other classes

Other classes

507

27

 

 

 

1,907

100

 

 

 

 

 

1992-2000

Forest

Mechanically disturbed

214

13

 

Mining

Grassland/Shrubland

202

13

 

Grassland/Shrubland

Forest

141

9

 

Forest

Grassland/Shrubland

138

9

 

Mechanically disturbed

Forest

135

8

 

Agriculture

Forest

133

8

 

Forest

Mining

127

8

 

Other classes

Other classes

524

32

 

 

 

1,614

100

Overall:

 

 

 

 

1973-2000

Mining

Grassland/Shrubland

1,234

18

 

Grassland/Shrubland

Forest

993

14

 

Forest

Mining

835

12

 

Forest

Mechanically disturbed

580

8

 

Forest

Grassland/Shrubland

540

8

 

Forest

Agriculture

391

6

 

Agriculture

Forest

381

5

 

Other classes

Other classes

2,043

29

 

 

 

6,997

100

 

 

 

Refer to caption

 

Figure 1.  Western Allegheny Plateau and surrounding ecoregions. The 40 randomly selected 100-km² sample blocks are shown along with land use/land cover from the 1992 National Land Cover Dataset.

 

 

Refer to caption

 

Figure 2.  Forested hills with corn and oats in the valley.

 

 

Refer to caption

 

Figure 3.  Coal mining southwest of Brookville, Pennsylvania.

 

Refer to caption

 

Figure 4.  Coal mining south of East Palestine, Ohio.

 

 

Refer to caption

 

Figure 5.  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.

 

 

Refer to caption

 

Figure 6.  The estimates of land cover change per time interval normalized to an annual rate of change. The Western Allegheny Plateau is highlighted in black.

 

 

Refer to caption

 

Figure 7.  Suburban development southeast of Pittsburgh, Pennsylvania.

 

 

Refer to caption

 

Figure 8.  Per period net change for each land cover class. Areas above zero represent net gains for a land cover class, while areas below represent a net loss.

 

 

 



[1] U.S. Geological Survey, Center for Earth Resources Observation and Science, Sioux Falls, SD 57198

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