Land Use–Land Cover Changes in the Lower Eastern Shore Watersheds and Coastal Bays of Maryland: 1986–2006

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Land Use–Land Cover Changes in the Lower Eastern Shore Watersheds andCoastal Bays of Maryland: 1986–2006Author(s): Osarodion K. Nosakhare, Isoken T. Aighewi, Albert Y. Chi, Ali B. Ishaque, and GodwinMbamaluSource: Journal of Coastal Research, 28(1A):54-62. 2012.Published By: Coastal Education and Research FoundationDOI: http://dx.doi.org/10.2112/JCOASTRES-D-09-00074.1URL: http://www.bioone.org/doi/full/10.2112/JCOASTRES-D-09-00074.1

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Land Use–Land Cover Changes in the Lower Eastern ShoreWatersheds and Coastal Bays of Maryland: 1986–2006

Osarodion K. Nosakhare{*, Isoken T. Aighewi{**, Albert Y. Chi1, Ali B. Ishaque{, andGodwin Mbamalu{

{Department of Natural SciencesUniversity of Maryland Eastern ShorePrincess Anne, MD 21835

{Benedict CollegeDepartment of BiologyChemistry and Environmental Health

Science1600 Harden StreetColumbia, SC [email protected]

1Department of Mathematics and ComputerScience

University of Maryland Eastern ShorePrincess Anne, MD 21853

ABSTRACT

NOSAKHARE, O.K.; AIGHEWI, I.T.; CHI, A.Y.; ISHAQUE, A.B., and MBAMALU, G., 2012. Land use–land coverchanges in the lower Eastern Shore watersheds and coastal bays of Maryland: 1986–2006. Journal of Coastal Research,28(1A), 54–62. West Palm Beach (Florida), ISSN 0749-0208.

Changes in land use influence surface-water quality and thus present a potential threat to coastal ecosystem health.Land use–land cover changes (LULCC) in the lower Eastern Shore watersheds of Maryland have been rapid in the lastdecade, with increase in real estate development an obvious indicator. The objective of this study was to evaluate theextent of historical LULCC in the lower Eastern Shore watershed and coastal bays of Maryland from 1986 to 2006. Landuse–land cover data were derived by supervised classification of Landsat TM 5 satellite imagery acquired in 1986, 1996,and 2006 using the Anderson level-1 classification system in Environment for Visualizing Images (ENVI 4.5), whileLULCCs were detected in an Arc-GIS 9.2 environment.

The results showed that while urban and forest lands increased by 121.8% and 8.5%, respectively, in the lower EasternShore from 1986 to 2006, croplands and wetlands decreased by 19.6% and 21.3%, respectively. Area covered by surface waterincreased by 10%, submerging mostly wetlands of 150 km2 in 17 of the 23 subwatersheds studied. The loss of these coastalwetlands is attributable in part to the changing climate and the resultant sea-level rise and in part to the activities of theinvasive rodent Nutria (Myocastor coypus), reported to be a major menace in Maryland’s Eastern Shore. The decliningwetlands have serious ecological health implications for the Chesapeake Bay and its watersheds for several species and thusrequire urgent attention. More intensive and frequent monitoring of this delicate estuarine ecosystem is suggested.

www.JCRonline.org

INTRODUCTION

Land use and water resources are intimately liked. Indeed,

one of the most important factors that can affect the quality of a

surface-water body is the land use within its watershed. Land

use and land cover largely determine the type and amount of

contaminants entering streams, lakes, and underground

pathways (Dale et al., 2000; Gergel et al., 2002). In addition,

increasing human population density can directly and indi-

rectly influence waste generation and discharge and thus

influence the concentration of chloride, nitrate, and a variety of

pesticides in streams that drain urban and suburban settings.

The watershed of the Chesapeake Bay, the largest estuary in

the United States, drains 166,534 km2 of land in six states:

Maryland, Virginia, Delaware, Pennsylvania, West Virginia,

and New York, as well as the District of Columbia. The

population of this area has increased over the years, resulting

in negative effects on the surface-water systems and the fragile

coastal ecosystem. Approximately 17 million people live in the

Chesapeake watershed, and about 10 million people live along

its shores or near them. Between 1950 and 1980, approximately

1.09 million hectares of land was lost to development

(Chesapeake Eco-Check, 2009). Such changes in land use have

been specifically correlated with the degradation of biological,

chemical, and physical properties of streams within the

Chesapeake Bay watershed (Palmer et al., 2002). The lower

Eastern Shore watershed and coastal bays of Maryland

(subsets of the Chesapeake Bay watershed) in particular have

experienced several episodes of hypoxia during the summer

months as a result of such nutrient loading from natural and

anthropogenic activities (Chesapeake Bay Program, 2010).

Jantz, Goetz, and Jantz (2004) observed a 61% increase in

developed land within the Chesapeake Bay watershed between

1990 and 2000, with 64% of the new development occurring on

agricultural lands and grasslands, while 33% occurred on

forested lands. The U.S. Environmental Protection Agency

(Boward et al., 1999) has since confirmed these statistics and

has stated that if the rate of urban sprawl continued, more

streams will likely degrade. In 1999, about 16% of Maryland’s

land area was urban, and urban area was expected to grow to

21% in the next 25 years, while only 42% of the state was

forested. The availability of remotely sensed satellite data from

DOI: 10.2112/JCOASTRES-D-09-00074.1 received 28 June 2009;accepted in revision 25 March 2010.* Present address: Purdue University, West Lafayette, IN 47904.** Corresponding author.’ Coastal Education & Research Foundation 2012

Journal of Coastal Research 28 1A 54–62 West Palm Beach, Florida January 2012

satellites such as Landsat, SPOT, and IKONOS, as well as the

evolving geospatial technologies–remote sensing and geo-

graphic information systems (GIS), is creating new opportuni-

ties for enhanced evaluation of land use changes and impact on

ecosystems worldwide. For example, these data have been used

for assessing land use change impact on water quality in

several studies worldwide, e.g., in Alabama (Bhuttarai et al.,

2008) and California (Charbonneau and Kondolf, 2006) in the

United States; in China (Liu et al., 2003); in Turkey

(Baspehlivan et al., 2004); and in several other areas. In the

United States, a geospatial technology–based Coastal Change

Analysis Program was initiated by the National Oceanic and

Atmospheric Administration (NOAA) for monitoring land use–

land cover (LULC) changes of the coastal regions on a 5-year

basis starting from 1996 (NOAA, 2007) and is currently

investigating techniques for trend analysis as they apply to

land cover change data. Similarly, the Multi-Resolution Land

Characteristics Consortium (MRLC) national land cover data

also exist for 1973, 1992, and 2001 (MRLC, 2008). However, no

published analysis of long-term trends in LULC exists—

particularly in view of the rapidly changing demography and

in view of changes in the agronomic and poultry industries of

the coastal Eastern Shore of Maryland since the 1980s. This

study was therefore initiated to quantify the historical LULC

changes in the lower Eastern Shore watersheds of Maryland

over a 20-year period (1986–2006) using remote sensing

techniques as a possible strategy for driving future manage-

ment decisions of this fragile ecosystem.

STUDY AREA

This study was conducted in the lower Eastern Shore

watershed and coastal bays of Maryland, which lies between

longitudes 74u59915.20W and 76u1795.60W and latitudes

37u54912.40N and 38u53910.70N. This study area is located

between the Atlantic Ocean and the Chesapeake Bay and

drains approximately 5596.69 km2 in Wicomico, Somerset, and

Worcester counties, and some portions of Caroline and

Dorchester counties. The major land use in this area includes

cropland, forestry, pasture, and urban; and water bodies

include estuary, river/stream, and abundant wetlands. The

area that is less than 30.5 meters above sea level includes a

total of 23 subwatersheds (U.S. EPA, 2009) (see Figure 1). The

main economic activities in the lower Eastern Shore are poultry

production and grain farming of corn, soybeans, and barley.

Other important economic activities include a declining fishing

industry, which remains important in the Chesapeake Bay

area, as well as tourism.

DATA AND METHODS

Satellite Image Data Acquisition

Landsat 5 TM satellite data of Maryland (Path 14, rows 33

and 34) for 1986 (May 6), 1996 (May 1), and 2006 (April 27)

were obtained in geotiff format from the U.S. Geological Survey

(USGS) Center for Earth Resources Observation and Science.

These images were of 10 days temporal variability (1986–2006)

due to cloud cover and were systematically corrected; the

data were of very high acquisition quality and had been

georeferenced and atmospherically corrected. The reflective

bands 1–5 and 7 were of pixel size of 30 m, while the thermal

band 6 was 60 m. All maps were projected using NAD83

Universal Transverse Mercator Zone 18.

Classification and Geospatial Analysis

Study area LULC classification was done in Environment for

Visualizing Images (ENVI 4.5) acquired from ITT Visual

Information Solutions (ITT VIS, 2008). Bands 7, 4, and 2 were

selected for supervised classification using the Mahalanobis

distance method after several trials. The reference group or

regions of interest selection was guided by aerial photos, Google

Earth (2009), and some ground truthing and personal

knowledge of the study area. The LULC classification system

of Anderson et al. (1976) was used. It classifies LULC into nine

major categories: urban or built-up land, agricultural land,

rangeland, forest land, water, wetland, barren land, tundra,

and perennial snow or ice at the level 1. However, range-

land, tundra, and perennial snow land cover types are absent

in the study location and were eliminated from the classifica-

tion scheme. The classified images were exported into a

GIS environment (ESRI, 2007), where spatial analysis was

completed.

The 1986 Landsat images for rows 33 and 34 were merged,

and each subwatershed was masked and extracted. Areas of

various land use in each watershed were quantified by

multiplying the number of pixels for each land use by the

spatial resolution (30 m 3 30 m) of the Landsat images from

which the LULC data were derived. Land use changes at 10-

year intervals (1986–1996 and 1996–2006) and 20-year

interval (1986–2006) were derived by overlaying the respective

LULC maps for each interval. The Kruskal-Wallis one-way

nonparametric analysis of variance test and the post hoc paired

test were employed to evaluate the how significantly the LULC

changed between each time interval for the same area.

Figure 1. Study area showing the lower Eastern Shore subwatersheds

of Maryland.

Land use changes in Maryland’s Eastern Shore 55

Journal of Coastal Research, Vol. 28, No. 1A (Supplement), 2012

RESULTS AND DISCUSSION

The LULC of the lower Eastern Shore subwatersheds for

1986, 1996, and 2006 are shown in Figures 2, 3, and 4,

respectively. The extent of LULC change by class from 1986 to

2006 is shown in Figure 5 and summarized in Table 1. During

this period, forestlands and area covered by water increased by

8.5% and 10%, respectively, while urban land increased by

121.8%. However, there was a net loss of agricultural lands

(19.6%), wetlands (21.3%), and barren lands (51.3%) within the

same period. The following sections outline specific changes

that occurred in the subwatersheds with respect to the major

LULC.

Urban Land Use of Subwatersheds

All the subwatersheds in the study area experienced an

increase in urban land use between 1986 and 2006 (Fig. 6)

except the narrow coastal bays bordering the Atlantic Ocean

consisting of basically water (99.6%) and beaches (0.2%). The

largest net gain in urban land occurred in the Lower Wicomico

subwatershed. Urban land increased by 18.26 km2 in the Lower

Wicomico River subwatershed during the study period

(11.37%). Using the Kruskal-Wallis test and the post hoc

paired comparisons, this subwatershed increased significantly

(p , 0.05, H 5 9.87, n 5 23) in urban land area between 1986

and 2006 after a total of 227.29 km2 of other land uses were

Figure 2. Land and use–land cover of the lower Eastern Shore of

Maryland in 1986.

Figure 3. Land use–land cover of the lower Eastern Shore of Maryland

in 1996.

Figure 4. Land use–land cover of the lower Eastern Shore of Maryland

in 2006.

Figure 5. Land use–land cover change of lower Eastern Shore of

Maryland (1986–2006).

56 Nosakhare et al.


converted to urban lands. However, changes between the

1986–1996 and 1996–2006 intervals were not significant.

Most of the gains in urban land (56% or 127.20 km2) occurred

on agricultural lands, with the greatest changes occurring in

the Lower Wicomico River subwatershed (18.3 km2), Nanticoke

River (13.1 km2), Upper Pocomoke River (11 km2), Marshyhope

Creek (10.2 km2), and Lower Pocomoke River (10.5 km2)

subwatersheds. This trend is not unexpected considering the

fact that residential developments and commercial growth

attendant to increasing world population growth are not only

occurring in urban centers but also in previously small towns

and lands previously used for agricultural purposes (Carlson

and Arthur, 2000). About 33% (75.17 km2) of urban land growth

occurred on forested lands, and the most significant loss to

urbanization also occurred in the Lower Wicomico (8.1 km2),

Marshyhope Creek (8.1 km2), Nanticoke River (8.0 km2), and

Lower Pocomoke River (7.1 km2) subwatersheds. This trend is

similar to that reported previously (Jantz, Goetz, and Jantz,

2004), where a 61% increase in developed lands within the

Chesapeake Bay watershed from 1990 to 2000 occurred due to

new urban development occurring on agricultural lands,

grasslands, and forested lands. The National Oceanic and

Atmospheric Administration (NOAA) data also showed a

similar trend for the lower Eastern Shore between 1996 and

2005 (NOAA, 2007). A total loss of approximately 12.65 km2 of

wetlands to urbanization occurred, while 8.19 km2 of barren

land were converted to urban lands during the 20-year study

period.

The total populations of the lower Eastern Shore counties

(Dorchester, Somerset, Wicomico, and Worcester counties)

were approximately 155,708 in 1986, 176,905 in 1996, and

198,155 in 2006. At an average annual growth rate of 0.98%,

the projected population for 2030 is 249,700, which would be

double the population in 1970 (Maryland Department of

Planning, 2006). Therefore, the gains in urban land can be

attributed to the changes in the demography of the major cities/

towns in the subwatersheds. For example, Salisbury, in the

Lower Wicomico River subwatershed, has been experiencing a

rapid growth in housing development due to increase in

population from approximately 16,850 in 1986 to 27,172 in

2006: a 61% increase (Maryland Department of Planning,

2006). Such growth in urban lands creates impervious surfaces

and thus reduces infiltration and increases nutrient, sediment,

and other pollutant loadings into the aquatic ecosystems,

which lowers quality of the surface waters (Mallin et. al., 2001;

Tang et al., 2005, and Van Buren et. al., 2000). Urbanization in

Marshyhope Creek (12.22 km2) can be attributed to population

growth in Federalsburg and Hurlock, while population growth

in towns such as Hebron, Vienna, Mardela Springs, and

Sharptown is responsible for the 15.42 km2 increase in urban

land use observed in the Nanticoke River subwatershed.

Population growth in Pocomoke City and Snow Hill are mainly

responsible for the 11.67 km2 increase in urban land use in the

Lower Pocomoke River subwatershed. A combined urban land

gain of 7.23 km2 in Isle of Wight and Assawoman Bay is due to

population growth in Ocean City, a popular tourist city in the

Eastern Shore of Maryland.

Agricultural Land Use of Subwatersheds

There was a net loss of about 256.16 km2 (19.6%) of

agricultural land in the lower Eastern Shore subwatersheds

between 1986 and 2006 in general. The largest net loss of

agricultural lands occurred in the Lower Wicomico River

subwatershed (Table 2). In this subwatershed, agricultural

lands decreased from 108.62 to 74.92 km2 from 1986 to 2006.

However, there were no significant differences in agricultural

land use between 1986 and 1996, 1996 and 2006, or 1986 and

2006 (p , 0.70, H 5 0.83, n 5 23). This finding was corroborated

with the Census of Agriculture conducted by the United States

Department of Agriculture (USDA) every 5 years that showed a

decline in the use of land for crop production (USDA 2009).

Croplands in Maryland decreased consistently over the years

Figure 6. Net change in urban lands for lower Eastern Shore of Maryland

subwatersheds (1986–2006).

Table 1. Historical land use–land cover in Maryland lower Eastern Shore (1986–2006).

LULC

1986 1996 2006 Net Change

(km2) (%) (km2) (%) (km2) (%) (km2) (%)

Urban 115.37 2.1 161.36 2.9 255.94 4.6 140.57 121.8

Agriculture 1306.94 23.4 1121.53 20.0 1050.78 18.8 2256.16 219.6

Forest 2022.60 36.2 2136.08 38.2 2193.87 39.2 171.27 8.5

Water 1365.46 24.4 1439.05 25.7 1501.35 26.8 135.89 10.0

Wetland 704.25 12.6 719.60 12.9 554.23 9.9 2150.02 221.3

Barren 80.22 1.4 17.22 0.3 38.67 0.7 241.55 251.3

Sum 5594.84 100.0 5594.84 100.0 5594.84 100.0 0.00



from 686,964 ha in 1987 to 553,324 ha in 2007, representing a

19.5% loss. However, the poultry industry in Maryland has

been on a steady rise. Broilers and other meat-type chickens

sold have increased from 257,070,110 in 1987 to 296,373,113 in

2007 (up by 13.3% between 1987 and 2007).

The greatest loss of agricultural lands occurred in the Lower

Wicomico River subwatershed, followed by Nanticoke River

and Upper Pocomoke River subwatersheds. Agricultural lands

lost 127.20 km2 to urban sprawl. A large land mass (457.31 km2)

of agricultural lands was converted into forested lands during

the study period. Nanticoke River (58.4 km2), Upper Pocomoke

River (49.9 km2), Marshyhope Creek (42.5 km2), Lower

Wicomico River (39.2 km2), Lower Pocomoke River (41.1 km2),

and Transquaking River (36.2 km2) subwatersheds experi-

enced large changes from agricultural land to forested land.

Forest lands were also lost to agriculture (301.61 km2) be-

tween 1986 and 2006 in the lower Eastern Shore, with most of

those changes occurring in Marshyhope Creek (40.5 km2),

Nanticoke River (40.8 km2), Upper Pocomoke River (33.3 km2),

Lower Pocomoke River (18.3 km2), and Transquaking

River (27.6 km2) subwatersheds. Agricultural to wetland

change was 54.83 km2, while an approximate 21.59 km2 of

agricultural land in 1986 became barren in 2006. Marshyhope

Creek and Nanticoke River subwatersheds have lost 7.5 km2

and 4.6 km2 of agricultural lands, respectively, to barren

lands. About 636.89 km2 (about 47% of agricultural lands)

remained unaltered during the same period especially in the

Upper Pocomoke River (109.3 km2) and the Nanticoke River

subwatersheds (75.2 km2). While a total of 250.16 km2

agricultural land was lost to other land uses during the study

period, an average of 11.14 6 1.50 km2 were lost per

subwatershed.

Forest Land Use of Subwatersheds

Very substantial areas of forest lands (1447.29 km2 or 71%)

remained unaltered between 1986 and 2006 for Lower

Pocomoke River, Upper Pocomoke River, Nanticoke River,

Fishing Bay, and Marshyhope Creek. Forest land in the lower

Eastern Shore occupied 2022.6 km2 in 1986 and grew to

2193.9 km2 in 2006 (Table 1), with a net gain of 171.27 km2

(8.5%) during the 20-year period. The recent U.S. Census of

Agriculture (USDA, 2009) reported increases in woodlands and

pastures in Maryland in general. However, this change was not

significant between all time intervals investigated (p , 0.90,

H 5 0.28, n 5 23). Although forested lands increased in most

subwatersheds, Marshyhope Creek subwatershed actually

experienced a net loss of 8.20 km2 (Table 3). This result is

corroborated by the NOAA land use–land cover data, which

also showed an increase in forested lands for the lower Eastern

Shore between 1996 and 2005 (NOAA, 2007). Increase in

forested land in the lower Eastern Shore can be attributed to

natural forest regrowth and the Maryland Forest Conservation

Act enacted in 1991. This Act stipulates that, ‘‘gaining approval

of the required Forest Conservation Plan (development of more

than 0.404 hectare) may require long-term protection of

included priority areas or planting/replanting (aforestation or

reforestation) a sensitive area off-site’’ (Maryland Department

of Natural Resources, 1995). The largest net gain in forest land

(21.07 km2) during the study period was in the Lower Wicomico

Table 2. Changes in agricultural lands in the lower Eastern Shore subwatersheds (1986–2006).

Subwatersheds 1986 (km2) 1996 (km2) 2006 (km2) Net Change (km2)

Marshyhope Creek 124.26 140.98 112.39 211.87

Big Annemessex River 18.78 19.98 11.33 27.45

Nanticoke River 155.52 136.02 126.69 228.83

Transquaking River 96.3 97.22 81.1 215.20

Fishing Bay 58.8 51.2 37.49 221.31

Wicomico River Head 42.46 34.64 32.21 210.25

Upper Pocomoke River 177.28 111.74 149.31 227.97

Lower Wicomico River 108.62 92.45 74.92 233.70

Honga River 11.42 9.09 6.89 24.53

Nassawango Creek 49.6 38.98 40.05 29.55

Dividing Creek 30.4 30.61 27.81 22.59

Wicomico Creek 28.34 23.89 22.4 25.94

Monie Bay 15.05 14.38 10.84 24.21

Manokin River 58.82 48.63 45.05 213.77

Lower Pocomoke River 121.82 113.81 110.39 211.43

Tangier Sound 3.82 5.93 2.84 20.98

Pocomoke Sound 29.83 26.78 19 210.83

Assawoman Bay 10.63 7.32 7.76 22.87

Isle of Wight Bay 61.08 35.56 45.06 216.02

Atlantic Ocean 0.30 0.32 0.08 20.22

Newport Bay 43.17 28.11 33.98 29.19

Sinepuxent Bay 10.40 7.41 6.63 23.77

Chincoteague Bay 50.25 46.49 46.56 23.69

Sum 1306.94 1121.53 1050.78 2256.16

Mean 56.82 48.76 45.69 211.14

SD1 50.26 43.75 43.07 27.18

SE1 10.48 9.12 8.98 21.50

1 SD, standard deviation; SE, standard error.

58 Nosakhare et al.


subwatershed. Gains in forest land from other land uses

decreased in the following order: agricultural land to forest

(457.31 km2), wetland to forest (204.45 km2), urban to forest

(38.48 km2), water to forest (27.53 km2), and barren land to

forest (19.38 km2).

Surface-Water Cover

There was a net gain of about 135.89 km2 (10%) of areas

covered by water in the lower Eastern Shore subwatersheds

between 1986 and 2006. During the study period, however,

154.61 km2 of wetlands became inundated. Most of this

inundation occurred in Fishing Bay (55.77 km2) (Fig. 7 and 8)

situated at the edge of Chesapeake Bay in Dorchester county.

Conversely, only 31.44 km2 of water-covered areas in 1986

became wetlands in 2006, with Fishing Bay also experiencing

the most change of 6.4 km2. Some forested lands (32.2 km2)

were also inundated by water during the study period, while

9.6 km2 of agricultural lands also became inundated with

water. About 6.6 km2 of urban lands similarly became

inundated by water, while a total change from barren land to

water in the lower Eastern Shore was 1.63 km2 during the

study period. New areas covered by land between 1986 and

2006 are shown in Figure 8. Increase in water cover in the

lower Eastern Shore of Maryland is due in part to sea-level

rise—perhaps a global warming effect on the estuarine

tributaries of the Chesapeake Bay, which empties into the

Atlantic Ocean. This rise is indicated by the decrease in the

extent of wetlands and salt marshes (by 22%) through

submergence, and a decrease in barren land (by 2%) during

the study period. Hilbert (2006) reported a similar trend in the

Grand Bay National Estuarine Research Reserve area of

Mississippi in the northern coast of the Gulf of Mexico from

1974 to 2001.

Wetlands

Loss of wetlands was observed in 17 out of the 23

subwatersheds in the study area (Table 4). There was a 23%

net loss (150.02 km2) of wetlands from 1986 to 2006 in the study

area (Table 2). But these losses were not significant (p , 0.50,

H 5 1.80, n 5 23) for the periods between 1986 and 1996, 1996

and 2006, or 1986 and 2006. Similar results were observed in

Table 3. Changes in forest land in the lower Eastern Shore subwatersheds (1986–2006).




Nanticoke River 214.78 232.33 232.6 17.82


Fishing Bay 153.47 194.07 165.15 11.68




Honga River 30.86 30.09 38.94 8.08


Dividing Creek 111.84 111.4 112.87 1.03

Wicomico Creek 40.64 43.88 45.92 5.28

Monie Bay 38.1 42.03 43.8 5.70

Manokin River 113.41 127.96 131.34 17.93


Tangier Sound 13.89 14.66 21.92 8.03

Pocomoke Sound 66.67 69.18 73.66 6.99

Assawoman Bay 5.72 8.52 7.11 1.40

Isle of Wight Bay 55.76 66.16 61.89 6.13

Atlantic Ocean 0.01 0.08 0.01 0.00

Newport Bay 48.71 51.91 52.88 4.17

Sinepuxent Bay 8.67 9.10 9.75 1.08


Sum 2022.60 2136.08 2193.87 171.27

Mean 87.94 92.87 95.39 7.45

SD 69.10 72.58 72.29 3.18

SE 14.41 15.13 15.07 0.66

Figure 7. Net surface-water cover change in lower Eastern Shore

subwatersheds of Maryland (1986–2006).



NOAA LULC data, which also showed loss of wetlands for the

lower Eastern Shore between 1996 and 2005 (NOAA, 2007).

The vital ecological functions of wetlands, which include water

quality improvement/preservation, fish and wildlife habitats,

reduction of flood damage, shoreline erosion protection, etc.,

make their decline of great ecological concern. The Congaree

Bottomland Hardwood Swamp in South Carolina was estimat-

ed to remove pollutants equivalent to what is removed annually

by a $5 million wastewater treatment plant (U.S. EPA, 2008).

The decreasing extent of wetlands in the lower Eastern Shore

has the potential to compromise several ecological services

performed by this habitat.

Our results also indicate that during the study period,

154.61 km2 of wetlands became covered by water. Most of this

wetland inundation by water (55.77 km2 representing 41%)

occurred in Fishing Bay, where the largest net loss of 53.16 km2

(35%) of wetlands occurred. Nutria (Myocastor coypus) has

been a primary force in accelerating wetland loss in the

Blackwater basin—where Fishing Bay is located—as well as

other subwatersheds in Maryland. Nutria feed on marsh

vegetation, expose the mud, and thereby predispose marshes

to erosion. Consequently, the marsh surface sinks and the

vegetation is lost to flooding. Large area of marsh lands in the

Blackwater National Wildlife Refuge (BNWR) within the same

watershed have been reported lost to nutria (U.S. Fish and

Wildlife Service, 2009). Although this destructive rodent has

been eradicated from BNWR (Washington Post, 2004), 53% of

the remaining marshes in BNWR are considered unhealthy

and are likely to be lost in the future (U.S. Fish and Wildlife

Service, 2009). It is obvious, therefore, that the activities of

these nonnative rodents on the wetlands may have contributed

in part to the decreasing wetlands and increasing extent of

water cover in the lower Eastern Shore of Maryland.

Reciprocally, only 31.44 km2 of areas covered by water in

1986 have become wetlands in 2006, with Fishing Bay also

experiencing the most change of 6.4 km2. This indicates

fluctuations between areas covered by water and wetland in

Fishing Bay but with more wetlands becoming flooded. Of the

704.25 km2 of wetlands in 1986, only 299.56 km2 of wetlands

(which represents about 43%) have remained unaltered

between 1986 and 2006 especially in Fishing Bay (79.3 km2),

Figure 8. New areas covered by water between 1986 and 2006 in the

lower Eastern Shore of Maryland.

Table 4. Changes in wetlands in the lower Eastern Shore subwatersheds (1986–2006).




Nanticoke River 60.32 61.28 52.6 27.72


Fishing Bay 163.85 106.17 110.69 253.16




Honga River 56.02 45.63 42.34 213.68


Dividing Creek 16.58 16.2 14.88 21.70

Wicomico Creek 7.58 8.19 5.15 22.43

Monie Bay 31.01 28.61 25.64 25.37

Manokin River 60.45 52.98 46.96 213.49


Tangier Sound 40.47 35.01 23.04 217.43

Pocomoke Sound 41.3 36.74 38.5 22.80

Assawoman Bay 6.48 7.67 5.43 21.05

Isle of Wight Bay 7.77 22.71 9.61 1.85

Atlantic Ocean 0.04 0.16 0.01 20.04

Newport Bay 14.30 24.41 14.54 0.24

Sinepuxent Bay 6.99 7.13 4.64 22.35


Sum 704.25 719.60 554.23 2150.02

Mean 30.62 31.29 24.10 26.52

SD 35.09 23.82 23.76 211.33

SE 7.32 4.97 4.96 22.36

60 Nosakhare et al.


Nanticoke River (35.4 km2), Honga River (29.6 km2), and

Manokin River (25.9 km2) subwatersheds. Approximately

204.45 km2 of wetlands became forested between 1986 and

2006. Most of this change has occurred in the Lower Pocomoke

River (25 km2) and Manokin River (23.7 km2) watersheds, as

well as Fishing Bay (21.6 km2). A total of 34.09 km2 of wetlands

was lost to agricultural land use in the study region between

1986 and 2006. Small areas of wetlands also changed to

agricultural land in the Lower Pocomoke River (5.4 km2),

Manokin River (3.4 km2), and Fishing Bay (3.0 km2). About

12.65 km2 of wetlands became urbanized in 2006. Lost areas of

wetland between 1986 and 2006 are shown in Figure 9.

Barren Lands

There was a decrease in barren lands (51.3%) in all the

subwatersheds except for Marshyhope Creek (with a net gain of

2.22 km2), and Sinepuxent Bay (1.05 km2), while Assawoman

Bay experienced no net gain (Table 5). Barren lands, which are

mainly beaches in Assawoman Bay and Isle of Wight Bay

where Ocean City (a popular tourist city) is located, experi-

enced increase in water-covered areas by 2.07 km2 in Assa-

woman Bay and 2.56 km2 in Isle of Wight Bay (Figure 9). This

may be due to the rising sea level—a trend that has also been

reported by Hilbert (2006) in the Grand Bay National

Estuarine Research Reserve area of Mississippi in the northern

coast of the Gulf of Mexico from 1974 to 2001. The lower

Eastern Shore subwatersheds recorded a significant net loss of

about 41.55 km2 of barren lands between 1986 and 2006 (P ,

0.05, H 5 13.28, n 5 23). Barren land significantly (P , 0.05)

decreased from 80.22 km2 in 1986 to 17.22 km2 in 1996;

however, changes between 1996 and 2006 were not significant.

About 43.20 km2 of barren land was converted to agricultural

land, while 8.19 km2 of barren land became urbanized. As of

2006, approximately 19.38 km2 of barren lands became forested

within the 20-year period, with the largest changes occurring

in the Lower Wicomico River (2.7 km2), Marshyhope Creek

(2.4 km2), and Nanticoke River (2.0 km2) subwatersheds. Only

6.68 km2 of barren land remained unaltered, mostly in the

Marshyhope Creek (1.6 km2).

Figure 9. Lost areas of wetland between 1986 and 2006 in the lower

Eastern Shore of Maryland.

Table 5. Changes in barren lands in the lower Eastern Shore subwatersheds (1986–2006).




Nanticoke River 9.05 1.65 6.7 22.35


Fishing Bay 2.09 0.05 0.21 21.88




Honga River 0.41 0.00 0.01 20.40


Dividing Creek 0.78 0.09 0.15 20.63

Wicomico Creek 1.39 0.34 0.23 21.16

Monie Bay 0.19 0.01 0.03 20.16

Manokin River 2.26 0.09 0.15 22.11


Tangier Sound 0.08 0.07 0.02 20.06

Pocomoke Sound 0.58 0.05 0.04 20.54

Assawoman Bay 0.61 0.13 0.65 0.04

Isle of Wight Bay 2.38 0.28 1.06 21.32

Atlantic Ocean 1.14 2.02 0.11 21.04

Newport Bay 2.40 0.50 0.24 22.17

Sinepuxent Bay 2.35 2.78 3.40 1.05


Sum 80.22 17.22 38.67 241.55

Mean 3.49 0.75 1.68 21.81

SD 3.55 1.00 2.96 20.59

SE 0.74 0.21 0.62 20.12



CONCLUSIONS

Urban land increased by an average of 121.8%, followed by

areas covered by water (10%) and forest lands (8.5%) in the

lower Eastern Shore watersheds from 1986 to 2006. There were

net losses of agricultural land (19.6%), wetlands (21.3%), and

barren land (51.3%) in the past 20 years in the study area. Most

of the urban land gain (56% equivalent to 127.2 km2) occurred

on agricultural land, while 33% (75.17 km2) occurred on

forested land. The largest gains in urban land, as well as loss

of agricultural, forest, and barren lands, occurred in Lower

Wicomico River subwatershed. Net area covered by water

increased by 135.9 km2 from 1986 to 2006 for all subwater-

sheds, and 154.61 km2 of wetlands was inundated or covered by

water. Most of such coverage (41%) occurred in Fishing Bay, in

Dorchester County, and was attributed to the rising sea level,

since these tributaries of the Chesapeake Bay empty into the

Atlantic Ocean. Seventeen out of 23 subwatersheds in the

lower Eastern Shore experienced decreased wetlands areas

from 1986 to 2006. The net area of wetlands lost was 150 km2,

especially in Fishing Bay (35%) where BNWR is located. This

signals change in the coastal ecology attributable in part to

global climate change and the consequent sea-level rise, as well

as wetland subsidence due to the destructive feeding activities

of M. coypus (Nutria)—a nonnative rodent species that feeds on

marsh vegetation. Declining wetlands have serious ecological

implications with respect to the various ecological services

wetlands provide, e.g., habitat for shellfish and waterfowls,

flood buffer, and wastes filter.

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Documents

Land Use–Land Cover Changes in the Lower Eastern Shore Watersheds and Coastal Bays of Maryland: 1986–2006