Texas coastal wetlands status and trends, mid-1950s to early 1990s

              March, 1997
United States Department of the Interior
Fish and Wildlife Service
Southwestern Region
Albuquerque, New Mexico
D. W. Moulton
Texas Parks and
Wildlife Department
Austin, Texas
T. E. Dahl
U.S. Fish and Wildlife
Service
St. Petersburg, Florida
D. M. Dall
U.S. Fish and Wildlife
Service
Albuquerque, New
Mexico
Shrimp Harvest
ESTUARINE SYSTEM
TEXAS PARKS & WILDLIFE
DEPARTMENT
Texas Coastal Wetlands
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Executive Summary
Introduction
Survey Methods
Results and Discussion
Conclusions
Literature Cited
Appendix A: Habitat Categories
Appendix B: Data Tables
Acknowledgments
List of Figures
List of Tables
Cultivated Rice
PALUSTRINE
FARMED
Texas Parks and Wildlife
Department
English/Metric
Conversions
1 acre = 0.4 hectare
1 square mile = 259.1
hectares
1 mile = 1.61
kilometers
1 foot = 0.3 meter
Contents
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The U.S. Fish and Wildlife Service prepared this report on the
status and trends of coastal Texas wetlands in accordance with
the Coastal Wetlands Planning, Protection, and Restoration Act
of 1990 (Title III of Public Law 101-646). This report is a
product of the Coastal Texas Project completed by the Fish and
Wildlife Service in cooperation with the Texas Parks and
Wildlife Department and the Texas General Land Office.
This report analyzes data collected for the 12.8 million-acre
coastal Texas study area (Fig. 1). The design of the study
consisted of a stratified random sample of 754 four-square-mile
plots. Aerial photographs from the mid-1950s and early 1990s
(mean dates 1955 and 1992) for each of the plots were analyzed
to detect changes in wetlands, deepwater habitats, and uplands
acreage. Changes were determined to be either natural or
human-induced. The total wetlands acreage estimate for 1992
was subtracted from the 1955 total estimate and divided by the
37-year study period to give an estimate for average annual net
wetlands loss.
Figure 1.
Texas Physiographic
Regions and Coastal
Texas Study Area
An estimated 4.1 million acres of wetlands existed on the Texas
coast in the mid-1950s. By the early 1990s, wetlands had
decreased to less than 3.9 million acres including 3.3 million
acres of freshwater wetlands and 567,000 acres of saltwater
wetlands. About 1.7 million acres (52 percent) of the 3.3
million acres of freshwater wetlands were classified as farmed
wetlands. The total net loss of wetlands for the region was
approximately 210,600 acres, making the average annual net
loss of wetlands about 5,700 acres. The greatest losses were of
freshwater emergent and forested wetlands.
Estuarine (saltwater) wetlands decreased by about 9.5 percent,
with an estimated net loss of 59,600 acres, making the average
annual net loss approximately 1,600 acres. Loss of estuarine
emergent wetlands occurred primarily between Freeport in
Brazoria County and Port Arthur in Jefferson County. The
major cause was faulting and land subsidence, due to
withdrawal of underground water and oil and gas, which has
resulted in the submergence (drowning) of marshes.
Palustrine (freshwater) wetlands showed a net decline of
151,000 acres (4.3 percent). However, this average figure
includes a 96,500-acre net increase in palustrine farmed
Executive Summary
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wetlands.
Palustrine emergent wetlands (fresh marsh, wet prairie, etc.)
declined by about 29 percent, with an estimated net loss of
235,100 acres, making the average annual net loss about 6,400
acres. This was the largest acreage change for any wetland
category studied. Most of the palustrine emergent loss was to
upland agriculture and other upland land uses. Also, there was
conversion of palustrine emergents to the palustrine farmed and
palustrine scrub-shrub wetland types.
Over 96,000 acres (a 10.9 percent decrease) of forested
wetlands (swamps, hardwood bottomlands, etc.) were lost or
converted to other wetland types. Most of the losses were to
upland agriculture and other upland land uses, with conversions
to the palustrine scrub-shrub and palustrine farmed wetland
types and to lacustrine deepwater (reservoirs).
Palustrine scrub-shrub wetlands showed a net increase of over
63,000 acres (a 58.7 percent increase). This increase was
primarily at the expense of palustrine emergent and palustrine
forested wetland types. Invasion of fresh marsh and cut-over
forested wetlands by the introduced Chinese Tallow-tree may
be responsible for much of the expansion of scrub-shrub
wetlands.
Freshwater ponds showed a net gain of 21,700 acres (a 137
percent increase). About half of the increase came from
conversion of uplands to farm ponds, stock tanks, and other
small impoundments. The other half came from conversion of
palustrine emergent, palustrine farmed, and palustrine forested
wetlands to ponds. The proliferation of man-made ponds
obscured the loss of natural prairie potholes.
The largest land-use category in the region was agriculture (4.7
million acres). Agricultural acreage declined by 618,000 acres
even though 98,000 acres of palustrine wetlands were lost to
agriculture. Urban land use increased by 529,000 acres, mostly
at the expense of agriculture and other upland land uses. There
was also loss of palustrine farmed and other palustrine wetlands
to urban and rural development. Approximately 245,000 acres
of the upland "other" category, much of it originally native
hardwood and pine-hardwood forest, were converted to forested
plantation (silviculture).
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Figure 1.
Texas Physiographic Regions and Coastal Texas Study
Area (comprised of Gulf-Atlantic Coastal Flats and
Coastal Zone)
Figure 1
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The Texas Gulf Coast is one of the most ecologically complex
and biologically diverse regions of the state. The region is
comprised of three distinct segments -- upper, mid, and lower --
defined by geomorphologic, climatological, hydrologic, and
ecological characteristics. The upper coast, from Sabine Lake
west to the estuarine drainage area of Galveston Bay, is
characterized by extensive western Louisiana-type marshes
grading from salt to brackish to intermediate to fresh, with
coastal prairie and humid flatwoods inland.
The mid- and lower coasts are both characterized by barrier
islands and peninsulas and extensive bays or lagoons. The
mid-coast, Galveston Bay to Corpus Christi Bay, consists of
large bay and estuary systems supplied with freshwater inflow
by rivers, with extensive coastal prairies inland. The lower
coast consists of the upper and lower Laguna Madre, which are
frequently hypersaline due to lack of freshwater inflow (no
rivers and low rainfall) and restricted Gulf inlets. The lower
coast has extensive wind-tidal flats adjacent to the Laguna
Madre backed by semiarid rangeland inland and intensive
irrigated agriculture in the lower Rio Grande Valley.
More than one-third of the state's population and about 70
percent of its industrial base, commerce, and jobs are located
within 100 miles of the coastline (Texas General Land Office
1995). About 4.5 million people live in the 18 counties adjacent
to the Gulf. More than half of the nation's chemical and
petroleum production is located on the Texas coast, and the
state leads the nation in marine commerce with 10 deep-draft
ports and over 420 miles of the Gulf Intracoastal Waterway.
Every coastal county supports intensive agriculture or grazing.
Texas coastal waters support major commercial and
recreational fishing industries. Numerous recreational
opportunities are afforded by the beaches, bays, marshes,
prairies, and other fish and wildlife habitats of the Texas coast.
These resources have contributed to making tourism the third
largest industry in Texas, after oil and gas production and
agriculture (Texas Parks and Wildlife Dept. and Texas Dept. of
Commerce, no date).
The total economic impact on the Texas coastal region of
wetland-based recreation and wetland-dependent commercial
fisheries is substantial. In 1993, the dock-side value of shellfish
Introduction
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(brown, pink, and white shrimp; blue crab; and eastern oyster)
and finfish (black drum, flounder, sheepshead, and snapper)
landed commercially from the Galveston Bay system was about
$11.6 million (Robinson et al. 1994). The total economic
impact at the wholesale level from Galveston Bay alone was
estimated at $35 million. The total economic impact of
commercial fishing at the wholesale level coastwide is over
$400 million annually, providing jobs for about 30,000 coastal
residents.
There were about 850,000 saltwater sport fishers in Texas
during 1991 (Texas Parks & Wildlife Dept. 1993). Direct
expenditures by these anglers totaled about $380 million and
supported about 11,000 jobs in Texas (U.S. Fish & Wildlife
Service 1993). The total annual economic value of recreational
fishing to users of Galveston Bay living in the
Houston-Galveston area was estimated to be $75-150 million,
with the total annual value of the bay for all recreational uses (7
million user-days per year) in the range of $115-200 million
(Whittington et al. 1994).
In 1990-1994, 30-40,000 coastal waterfowl hunters pursued
waterfowl populations that averaged about 1 million geese and
1.5 million ducks (Texas Parks & Wildlife Dept. unpubl. data).
In 1991, the economic impact of waterfowl hunting and
nonconsumptive waterfowl use in Texas was about $96 million
and $240 million, respectively (Teisl and Southwick 1995). A
substantial portion of this activity took place on the coast. In the
spring of 1992, about 6,000 birdwatchers, an important segment
of the rapidly expanding nature tourism industry, poured into
tiny High Island in eastern Galveston County (Eubanks et al.
1993). The total economic impact was estimated to be $4-6
million over a 2-month period.
Although these estimates of wetlands-related economic impacts
were generated by mainstream economists, most classic market
economists have not yet fully recognized the concept that
ecological and economic concerns are not only related but
inseparable. From an economic point of view, market forces are
grossly underestimating the true economic value of existing
coastal wetlands to society (Whittington et al. 1994). Table 1
lists some known wetlands goods and services, many of which
provide undetermined monetary values. These ecological and
cultural values are important to the people of Texas and our
Nation.
Table 1.
Some valuable goods
and services
produced by coastal
Texas wetlands;
environmental quality
functions and
socioeconomic values
Introduction
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To conserve and manage Texas coastal wetlands resources, it is
necessary to understand the dynamics of the processes, both
natural and human-induced, that are affecting them. This report
presents data that estimate the extent (status) of Texas coastal
wetlands in the early 1990s and the changes in areal extent
(trends) that have taken place since the mid-1950s. These data
may indicate the impact of existing policies and programs
intended to conserve the state's valuable coastal wetlands
resources, and identify which wetland habitats are experiencing
change.
Introduction
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Table 1.
Some valuable goods and services produced by coastal
Texas wetlands; environmental quality functions and
socioeconomic values (after Tiner 1984 and Hefner et al.
1994).
Environmental Quality Functions
Water Quality Maintenance
l   Sediment Trapping & Stabilization
l   Chemical & Toxicant Trapping
l   Nutrient Absorption & Cycling
Hydrologic Functions
l   Groundwater Recharge/Discharge
l   Saltwater Intrusion Prevention
l   Flow Stabilization
Primary Production/Energy Transfer
Ecosystem Stabilization
Biological Diversity
Biogeochemical Cycling
Fish & Wildlife Habitat
l   Invertebrates
l   Fish & Shellfish
l   Reptiles & Amphibians
l   Waterfowl, Wading Birds, Shorebirds & Other Birds
l   Furbearers & Other Mammals
l   Endangered & Threatened Species
Socioeconomic Values
Products
l   Finfish & Shellfish
l   Forage & Hay
l   Timber
l   Food Products
l   Fur and Other Wildlife Products
Table 1
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l   Aquaculture/Mariculture
Recreation & Nature Tourism
l   Fishing & Crabbing
l   Hunting & Trapping
l   Nonconsumptive Fish & Wildlife Uses
l   Boating & Swimming
l   Camping & Picnicking
l   Hiking, Trail Walking/Jogging
l   Visual Aesthetics & Photography
Water Supply
Wastewater Treatment
Flood Control
Erosion Control
Storm Buffering
Education & Scientific Research
Cultural/Archaeological
Table 1
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Statistical sampling procedures for this study were developed
and first used by Frayer et al. (1983). Other national (Dahl and
Johnson 1991) and regional (Frayer et al. 1989, Frayer and
Hefner 1991, Hefner et al. 1994) wetlands status and trends
studies have also used the survey procedures.
The coastal Texas status and trends study consisted of 754
plots. Each plot was 4 square miles (2,560 acres). Plots were
randomly distributed within the Gulf-Atlantic Coastal Flats
subdivision (10,400,556 acres; 613 plots) of Hammond (1970)
plus a Coastal Zone stratum (2,417,589 acres; 141 plots) added
to incorporate estuarine and marine wetlands that extend
beyond the continuous land mass (Fig. 2). The Coastal Zone, as
described here, is not synonymous with any state or federal
jurisdictional coastal zone definitions. The total number of
sample plots used was derived to provide a statistically robust
estimate of coastal wetlands within this study area. The study
area encompassed approximately 20,028 square miles
(12,818,145 acres).
Figure 2.
Distribution of 754
sample plots within
the study area
Two sets of aerial photographs were analyzed for each sample
plot. The mean years of the aerial photos were 1955 and 1992.
This 37-year interval was used to estimate average annual
wetland acreage changes. The 1950s photos were black and
white and ranged in scale from 1:20,000 to 1:36,000. The 1990s
photos were color infrared at 1:40,000 or 1:62,500 scales.
Aerial photos were stereoscopically interpreted and cover types
delineated using procedures developed by the National
Wetlands Inventory (U.S. Fish and Wildlife Service 1990a,b).
Wetlands, deepwater habitats, and uplands identified on the
photos were assigned to one of 20 categories listed in Table 2
and described in Appendix A. All changes in category acreages
were classified as either natural (e.g., natural succession of
scrub-shrub to forested wetland) or human-induced (e.g., loss of
wetlands to agricultural or urban use). Upland areas were
assigned to 1 of 5 general land-use categories: agriculture,
urban, forested plantation, rural development, and "other." Field
verification of features on the aerial photos was done for
approximately 10 percent of the sample plots.
Table 2.
Wetland, deepwater,
and upland habitat
categories used in this
study.
Survey Methods
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Habitat-category delineations on the interpreted aerial photos
were transferred to mylar overlays on 1:24,000-scale U.S.
Geological Survey topographic maps. Digital measurements of
the various categories were made and acreages recorded. For
this study, wetlands 3 acres and larger composed the target
population. Changes in area of all categories from 1955 to 1992
for each sample plot were determined. Estimates of acreage
changes were developed from the sample plot data using
accepted statistical procedures developed by the U.S. Fish and
Wildlife Service and Colorado State University. This study, like
previous Fish and Wildlife Service status and trends studies,
measured wetlands acreages and made no assessment of
wetlands functional quality other than changes in areal extent.
Survey Methods
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Figure 2.
Distribution of 754 sample plots within the study area
Figure 2
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Table 2.
Wetland, deepwater, and upland habitat categories used
in this study. (Detailed descriptions in Appendix A)
Saltwater Habitats* Common Description
Marine Subtidal** Permanent open water of Gulf
Marine Intertidal Shore Gulf beaches, bars, and flats
Estuarine Subtidal** Permanent open water of bays
Estuarine Intertidal Emergent Salt, brackish, intermediate marsh
Estuarine Intertidal Scrub-Shrub Baccharis, Black Mangrove, other shrubs
Estuarine Intertidal Unconsolidated Shore Unvegetated bay beaches, bars, and flats
Freshwater Habitats* Common Description
Palustrine Forested Swamps, hardwood bottomlands, etc.
Palustrine Scrub-Shrub Shrub-sapling wetlands
Palustrine Emergent Fresh marshes, wet prairie, etc.
Palustrine Farmed Cultivated rice fields, some natural wetlands
Palustrine Unconsolidated Shore Unvegetated pond beaches, bars, and flats
Palustrine Unconsolidated Bottom Permanent open water of ponds
Palustrine Aquatic Beds Floating or submerged vegetation
Riverine** Open water of rivers, streams, canals
Lacustrine** Lakes and reservoirs
Upland Land Use Common Description
Agriculture*** Cropland, pasture, managed rangeland
Urban*** Cities, towns, other densely built-up areas
Forested Plantation Planted or intensively managed forests
Table 2
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Rural Development Nonurban built-up areas and infrastructure
Other Uplands***
Nonpatterned native forest, brush, and
grassland; barren land
* Adapted from Cowardin et al. (1979)
** Deepwater Habitats
*** Adapted from Anderson et al. (1976)
Table 2
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Acreage estimates for 1955 and 1992, and changes over the
37-year period, were developed for wetlands, deepwater
habitats, and upland categories within the coastal Texas study
area (Table 3). The complex dynamics of these conversions
were derived from Data Tables 1 and 2 in Appendix B.
STATUS AND DISTRIBUTION
An estimated 4,105,343 acres of coastal Texas wetlands existed
in 1955 (Fig. 3a). About 84.6 percent of the total was
freshwater palustrine (3,474,330 acres) (Fig. 4a), 15.3 percent
was saltwater estuarine (626,188 acres) (Fig. 5a), and 0.1
percent was marine intertidal (Fig. 3a). There were 1,664,698
acres of deepwater habitats consisting of rivers (59,303 acres),
reservoirs (67,544 acres), and estuarine subtidal bays
(1,537,851 acres; Fig. 6a) in 1955. In 1992, an estimated
3,894,753 acres of wetlands existed. About 85.3 percent of the
total was palustrine, 14.5 percent was estuarine, and 0.1 percent
was marine (Fig. 3b). There were 1,757,595 acres of deepwater
rivers (60,159 acres), reservoirs (147,363 acres), and estuarine
bays (1,550,073 acres) in 1992.
Areas of wetlands concentration did not change significantly
between 1955 and 1992. Wetlands distribution is shown in Fig.
7a and Fig. 7b. Areas of greatest wetlands concentration
appeared to be in Jefferson, Liberty, and Chambers Counties
(Fig. 7b). Substantial acreage also existed in Orange, Brazoria,
Fort Bend, Wharton, Matagorda, Jackson, Calhoun, and
Kenedy Counties.
Table 3.
Coastal Texas
wetland, deepwater
habitat, and upland
trends (acres), 1955
to 1992
Figures 3a-6b.
Change from 1955 to
1992 by type of
wetlands
Figures 7a-b.
Distribution of all
coastal Texas
wetlands in 1955 (a)
and 1992 (b)
Estuarine wetlands
Texas estuarine wetlands totaled about 566,570 acres in 1992 --
about 10 percent of all estuarine wetlands of the conterminous
U.S. About 62.8 percent (355,632 acres) was emergent, 36.3
percent (205,972 acres) was intertidal unvegetated
(unconsolidated shore) mud or sand flats and bars, and less than
1 percent (4,966 acres) was estuarine shrubs (Fig. 5b). There
were also 1,550,073 acres of estuarine subtidal open water
bays, classified as deepwater habitats, in 1992 (Fig. 6b).
Estuarine wetlands were most common in the areas around
Sabine Lake, Galveston Bay, Matagorda Bay, San Antonio
Bay, Aransas Bay, and the Laguna Madre (Fig. 8). Estuarine
Results and Discussion
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emergent wetlands were concentrated along the upper and
mid-coast (Sabine Lake to Aransas Bay), while estuarine
unvegetated flats were concentrated along the lower Laguna
Madre (Figs. 9 and 10). Estuarine shrubs were most abundant in
three areas: Galveston Island, the Sea Drift area in Calhoun
County, and the southern end of South Padre Island (Fig. 11).
Palustrine wetlands
There was a total of 3,323,282 acres of palustrine wetlands in
the study area in 1992 (Fig. 4b). About 52.4 percent (1,741,981
acres) was farmed wetlands. This acreage was dominated by
rice growing operations, but also included some natural
wetlands that are farmed when dry enough. Forested wetlands
made up 23.8 percent (789,808 acres) of the total. Emergents
made up 17.2 percent (571,867 acres) of the total, and
scrub-shrub wetlands and ponds made up 5.2 percent (171,295
acres) and 1.1 percent (37,621 acres), respectively. Other
palustrine wetlands (unvegetated shore and aquatic beds) made
up only about 0.3 percent of the total. Palustrine wetlands were
most common in Jefferson, Chambers, Liberty, Orange, Hardin,
Brazoria, Wharton, Jackson, Matagorda, and Calhoun Counties
(Fig. 12). Palustrine emergents were most prevalent in
Jefferson, Chambers, Brazoria, Calhoun, Refugio, Aransas,
Kleberg, Kenedy, and Cameron Counties (Fig. 13). Palustrine
forested wetlands were found mostly on the northern half of the
coastal plain (Fig. 14). Newton, Jasper, Orange, Hardin,
Liberty, Harris, and Brazoria Counties had significant forested
wetland acreage; Jefferson, Chambers, and Matagorda Counties
supported some acreage. Palustrine scrub-shrub occurred
mostly in the upper coast counties of Newton, Jasper, Orange,
Hardin, Liberty, and Harris, although some concentrations of
shrub wetlands were found in Jefferson, Victoria, and Cameron
Counties (Fig. 15).
Figure 8.
Estuarine wetland
distribution in 1992
Figure 9.
Estuarine emergent
wetland distribution in
1992
Figure 10.
Estuarine
unvegetated wetland
distribution in 1992
Figure 11.
Estuarine scrub-shrub
wetland distribution in
1992
Figure 12.
Distribution of
palustrine wetlands in
1992
Figure 13.
Distribution of
palustrine emergent
wetlands in 1992
Figure 14.
Distribution of
palustrine forested
wetlands in 1992
Figure 15.
Distribution of
palustrine scrub-shrub
wetlands in 1992
Results and Discussion
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REGIONAL TRENDS
Overall, coastal Texas wetlands sustained an estimated net loss
of 210,590 acres from 1955 to 1992 (Table 3). This was an
average annual net loss of about 5,700 acres of wetlands. This
compares with 259,000 acres average annual net loss observed
for the other 10 states of the southeastern U.S. (Hefner et al.
1994). Deepwater habitats gained an estimated 96,203 net
acres. Upland categories had an estimated net gain of 114,387
acres.
Estuarine wetlands
Overall, estuarine intertidal wetlands sustained a net loss of
about 59,618 acres (a 9.5 percent decrease); an average annual
net loss of about 1,600 acres over the 37 years. Figure 16
summarizes the dynamics of net acreage changes for estuarine
wetlands and deepwater habitats.
Estuarine intertidal emergents decreased from 387,211 acres in
1955 to 355,632 acres in 1992. The net loss of 31,579 acres (an
8.2 percent decrease) resulted primarily from loss or conversion
to: estuarine subtidal bays (19,931 acres); palustrine emergents
(9,238 acres); lacustrine reservoirs (7,023 acres); and, upland
categories other than agriculture (6,291 acres).
The loss of estuarine marsh to open subtidal bay occurred
primarily between Freeport and Port Arthur and was associated
with the submergence (drowning) and erosion of wetlands
probably due to faulting and land subsidence resulting from the
withdrawal of underground water and oil and gas as described
by White and Tremblay (1995).
Figure 16.
Net acreage changes
for estuarine wetlands
and deepwater
habitats of coastal
Texas, 1955 to 1992
Village Creek,
Hardin County
RIVERINE &
PALUSTRINE
FORESTED
JIM DICK
Estuarine intertidal unconsolidated (unvegetated) shore
decreased from 236,414 acres in 1955 to 205,972 acres in 1992.
This net loss of 30,442 acres (a 12.9 percent decrease) resulted
primarily from loss or conversion to: upland "other" (15,805
acres); estuarine emergents (14,376 acres); rural development
(4,079 acres); and, palustrine emergents (3,686 acres).
Loss of estuarine intertidal wetlands to upland "other" and
conversion to palustrine emergents resulted partly from the
construction of dredge spoil compartments along the Gulf
Intracoastal Waterway and other ship channels, and also from
construction of roads, levees, etc. that altered original tidal
hydrologic characteristics.
Estuarine intertidal scrub-shrub increased from 2,563 acres in
Results and Discussion
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1955 to 4,966 acres in 1992. This net gain of 2,403 acres (a
93.8 percent increase) resulted primarily from conversion of
estuarine emergents (2,226 acres) to estuarine scrub-shrub.
Palustrine wetlands
Overall, palustrine wetlands decreased by 151,048 acres (a 4.3
percent loss) from 3,474,330 acres in 1955 to 3,323,282 acres
in 1992. Figure 17 summarizes the dynamics of net acreage
changes for palustrine wetlands.
Palustrine emergents decreased from 806,996 acres in 1955 to
571,867 acres in 1992. This net loss of 235,129 acres (a 29
percent decrease) resulted primarily from loss or conversion to:
agriculture (67,745 acres); the other upland categories (37,183
acres), especially urban and rural development; palustrine
farmed (62,830 acres); palustrine scrub-shrub (42,198 acres);
palustrine forested (13,072 acres); ponds (5,171 acres); and,
lacustrine reservoirs (20,470 acres).
Palustrine emergents sustained an average annual net loss of
6,355 acres. This was the largest acreage change for any
wetland category studied (Fig. 18). On the upper and mid-coast,
part of the conversion of emergents to scrub-shrub resulted
from invasion by the introduced Chinese Tallow-tree (White et
al. 1993). The 20,470-acre loss of emergents to lacustrine was
due to reservoir construction.
The 67,745-acre loss of emergents to agriculture occurred
despite the 618,313-acre net loss for the agriculture category.
The loss of palustrine wetlands to agriculture was widespread
along the coast and was greatest in Chambers, Harris, Brazoria,
Fort Bend, Wharton, Matagorda, and Refugio Counties (Fig.
19).
Palustrine forested wetlands decreased from 886,285 acres in
1955 to 789,808 acres in 1992. This net loss of 96,477 acres (a
10.9 percent decrease) resulted primarily from loss or
conversion to: palustrine scrub-shrub (29,573 acres); palustrine
farmed (12,252 acres); ponds (2,910 acres); agriculture (26,818
acres); forested plantation (14,232 acres); rural development
(13,112 acres); urban (9,563 acres); and, lacustrine reservoirs
(15,436 acres). Loss of forested wetlands to forested plantation
was confined to the upper coast, with Newton, Hardin, and
Jefferson Counties showing the greatest losses (Fig. 20).
Timber Harvest by
Barge
RIVERINE &
PALUSTRINE
FORESTED
TEXAS PARKS & WILDLIFE
DEPARTMENT
Figure 17.
Net acreage changes
for palustrine
wetlands of coastal
Texas, 1955 to 1992
Figure 18.
Changes in coastal
Texas wetland
acreages, 1955 to
1992
Figure 19.
Loss of coastal Texas
wetlands to
agriculture, 1955 to
1992
Figure 20.
Loss of coastal Texas
wetlands to
silviculture, 1955 to
1992
Results and Discussion
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Palustrine scrub-shrub wetlands increased from 107,951 acres
in 1955 to 171,295 acres in 1992. This net gain of 63,344 acres
(a 58.7 percent increase) resulted primarily from conversion of:
palustrine emergents (42,197 acres); palustrine forested (29,573
acres); and, palustrine farmed (2,138 acres) to scrub-shrub
wetlands.
Palustrine unconsolidated bottom, mostly man-made ponds,
increased from 15,872 acres in 1955 to 37,621 acres in 1992.
This net gain of 21,749 acres (a 137 percent increase) consisted
primarily of gain from or conversion of: agriculture (7,759
acres); upland "other" (2,337 acres); palustrine emergents
(5,171 acres); palustrine farmed (2,985 acres); and, palustrine
forested (2,910 acres) to ponds. A loss of natural prairie
potholes was masked by the proliferation of man-made stock
tanks and other ponds.
Palustrine farmed wetlands increased from 1,645,492 acres in
1955 to 1,741,981 acres in 1992. This net gain of 96,489 acres
(a 5.9 percent increase) consisted primarily of gain from or
conversion of: agriculture (140,865 acres); palustrine emergents
(62,830 acres); and, palustrine forested (12,252 acres) to farmed
wetlands.
Most of the palustrine farmed wetlands acreage is in some type
of rice production rotation, primarily in Wharton, Colorado,
Brazoria, Matagorda, Jackson, Jefferson, Chambers, Liberty,
and Fort Bend counties. Texas ranks fourth among all states in
rice production, with an average annual value in the early 1990s
of about $150 million (Texas Agricultural Statistics Service
1994).
There were losses of palustrine wetlands, particularly palustrine
farmed (96,500 acres) and palustrine emergents (29,100 acres),
to urban and rural development. Loss to urban land use was
greatest in the Houston and Beaumont-Port Arthur areas (Fig.
21). Loss to rural development was greatest in Orange,
Jefferson, Chambers, Galveston, Harris, Brazoria, and Nueces
Counties (Fig. 22).
Figure 21.
Loss of coastal Texas
wetlands to urban,
1955 to 1992
Figure 22.
Loss of coastal Texas
wetlands to rural
development, 1955 to
1992
Results and Discussion
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Deepwater habitats
Overall, deepwater habitats increased by 96,203 acres (a 5.8
percent gain), from 1,668,233 acres in 1955 to 1,764,436 acres
in 1992.
Estuarine subtidal unconsolidated bottom, i.e., open water of
bays and lagoons, increased from 1,537,851 acres in 1955 to
1,550,073 acres in 1992 (Fig. 16). This net gain of 12,222 acres
(a 0.8 percent increase) resulted primarily from conversion of:
estuarine emergents (19,931 acres); upland "other" (3,875
acres); and, agriculture (2,461 acres) to subtidal bays. These
conversions resulted from the submergence and erosion of tidal
marshes and bay shorelines mostly along the upper and
mid-coast.
Lacustrine acreage increased from 67,544 acres in 1955 to
147,363 acres in 1992. This net gain of 79,819 acres (a 118
percent increase) resulted primarily from conversion of:
palustrine emergents (20,470 acres); palustrine forested (15,436
acres); palustrine farmed (11,110 acres); upland "other" (11,791
acres); agriculture (6,409 acres); and, estuarine intertidal
wetlands (8,100 acres), mostly emergents, to lacustrine. The
expansion of the lacustrine category resulted from reservoir
construction.
Marine subtidal habitats, i.e., open Gulf water, were included in
this study only insofar as they relate to losses or gains of the
other measured habitat categories. For example, the erosion of
Gulf beaches would create a loss of marine intertidal shore to
marine subtidal; or, the accretion of sand on a barrier island
beach would create a loss of marine subtidal to marine
intertidal. In that regard, marine subtidal acreage increased
from 3,535 in 1955 to 6,841 in 1992. This net gain of 3,306
acres (a 93.5 percent increase) resulted primarily from
conversion of: marine intertidal beaches (2,044 acres); and
upland "other" (1,627 acres) to marine subtidal.
Upland categories
Overall, upland categories increased by 114,387 acres (a 1.6
percent gain) from 7,044,569 acres in 1955 to 7,158,956 acres
in 1992.
Upland agriculture decreased from 5,315,561 acres in 1955 to
4,697,248 acres in 1992. This net loss of 618,313 acres (a 11.6
percent decrease) resulted primarily from loss or conversion to:
urban (323,706 acres); rural development (184,633 acres);
Results and Discussion
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forested plantation (58,891 acres); palustrine farmed (140,865
acres); ponds (7,759 acres); and, lacustrine reservoirs (6,409
acres).
Agriculture, the largest land-use category, experienced a
618,313-acre net loss even though 98,000 acres of palustrine
vegetated wetlands, mostly emergent and forested, were lost to
agriculture, as were 12,000 acres of upland "other."
Bird Watching,
Mid-coast
ESTUARINE
SCRUB/SHRUB
TEXAS PARKS & WILDLIFE
DEPARTMENT
Upland urban increased from 329,790 acres in 1955 to 858,490
acres in 1992. This gain of 528,700 acres (a 160 percent
increase) resulted primarily from conversion of: agriculture
(323,706 acres); upland "other" (72,271 acres); rural
development (64,252 acres); palustrine farmed (36,628 acres);
palustrine emergents (15,966 acres); palustrine forested (9,563
acres); and, palustrine scrub-shrub (2,425 acres) to urban.
Upland "other," primarily unmanaged or nonpatterned forest
and rangelands, and barren land, decreased from 1,178,802
acres in 1955 to 788,186 acres in 1992. This net loss of 390,616
acres (a 33 percent decrease) resulted primarily from loss or
conversion to: forested plantation (244,900 acres); urban
(72,271 acres); rural development (53,507 acres); agriculture
(11,960 acres); palustrine forested (14,570 acres); ponds (2,337
acres); lacustrine reservoirs (11,791 acres); and, estuarine
subtidal bays (3,875 acres). Much of the upland "other" acreage
that was converted to forested plantation was originally native
hardwood and pine-hardwood forest.
Upland forested plantation (silviculture), primarily planted and
managed pine plantations, clear cuts, and other intensively
managed forest stands, increased from 82,302 acres in 1955 to
404,284 acres in 1992. This net gain of 321,982 acres (a 391
percent increase) resulted primarily from conversion of: upland
"other" (244,900 acres); agriculture (58,891 acres); palustrine
forested (14,232 acres); palustrine emergents (4,588 acres);
and, palustrine farmed (1,774 acres) to forested plantation.
Commercial timber operations in southeast Texas have
emphasized the growing of Loblolly and nonnative Slash Pine
for production of pulp for paper, lumber and plyboard for
building, and pressure-treated fenceposts, pilings, landscape
timbers, etc. (G. Spencer pers. comm.). There is a growing
export market, particularly to Japan, for hardwood chips used in
the production of high quality papers.
Upland rural development, i.e., low-intensity, often isolated
development outside distinct cities or towns, increased from
Results and Discussion
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138,114 acres in 1955 to 410,748 acres in 1992. This net gain
of 272,634 acres (a 197 percent increase) resulted primarily
from conversion of: agriculture (184,633 acres); upland "other"
(53,507 acres); palustrine farmed (59,838 acres); palustrine
forested (13,112 acres); and, palustrine emergents (13,062
acres) to rural development.
Results and Discussion
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Table 3.
Coastal Texas wetland, deepwater habitat, and upland
trends (acres), 1955 to 1992. Standard error, in percent,
shown below acreage estimates; percentage of total
acreage for each category included for comparison.
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Figures 3a-6b.
Change from 1955 to 1992 by type of wetlands
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Figures 3a-6b
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Figures 7a-b.
Distribution of all coastal Texas wetlands in 1955 (a) and
1992 (b)
Note: the "pixels" shown on these graphics represent
USGS 7.5 minute quadrangles
Figures 7a-b
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Figures 7a-b
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Figure 8.
Estuarine wetland distribution in 1992
Figure 8
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Figure 9.
Estuarine emergent wetland distribution in 1992
Figure 9
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Figure 10.
Estuarine unvegetated wetland distribution in 1992
Figure 10
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Figure 11.
Estuarine scrub-shrub wetland distribution in 1992
Figure 11
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Figure 12.
Distribution of palustrine wetlands in 1992
Figure 12
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Figure 13.
Distribution of palustrine emergent wetlands in 1992
Figure 13
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Figure 14.
Distribution of palustrine forested wetlands in 1992
Figure 14
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Figure 15.
Distribution of palustrine scrub-shrub wetlands in 1992
Figure 15
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Figure 16.
Net acreage changes for estuarine wetlands and
deepwater habitats of coastal Texas, 1955 to 1992
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Figure 16
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Village Creek, Hardin County
RIVERINE & PALUSTRINE FORESTED
JIM DICK
Photo
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Timber Harvest by Barge
RIVERINE & PALUSTRINE FORESTED
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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Figure 17.
Net acreage changes for palustrine wetlands of coastal
Texas, 1955 to 1992
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Figure 17
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Figure 18.
Changes in coastal Texas wetland acreages, 1955 to
1992
Figure 18
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Figure 19.
Loss of coastal Texas wetlands to agriculture, 1955 to
1992
Figure 19
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Figure 20.
Loss of coastal Texas wetlands to silviculture, 1955 to
1992
Figure 20
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Figure 21.
Loss of coastal Texas wetlands to urban, 1955 to 1992
Figure 21
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Figure 22.
Loss of coastal Texas wetlands to rural development,
1955 to 1992
Figure 22
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Bird Watching, Mid-coast
ESTUARINE SCRUB/SHRUB
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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We examined the status of coastal Texas wetlands at two points
in time -- the mid-1950s and the early 1990s. The average
annual net loss of all vegetated wetlands for that period was
5,400 acres. However, federal and state legislation such as the
1948 "Clean Water Act" as amended, the 1969 National
Environmental Policy Act, the 1985 and 1990 "Farm Bills," the
1986 Emergency Wetlands Resources Act, the 1989 North
American Wetlands Conservation Act, the 1981 Texas
Waterfowl Stamp Act, the 1991 Texas Coastal Coordination
Act, and others, have had a positive influence on wetlands
conservation and management in Texas. For example, in the
Galveston Bay area, the average rate of loss of vegetated
wetlands decreased from about 1,000 acres per year from
1953­1979
to about 500 acres per year from 1979­1989
(White
et al. 1993).
Mid-coast Salt
Marsh
ESTUARINE
INTERTIDAL
EMERGENT
ROSE SULLIVAN
Nevertheless, our results indicate that vegetated wetlands,
particularly freshwater emergent and forested wetlands, are
resources that need additional conservation efforts. The acreage
losses within the upland agriculture and upland "other"
categories also give cause for concern. The upland "other"
category consists mostly of nonpatterned native forests,
grasslands, and brush lands. As these habitats, as well as
agricultural lands, undergo urban, rural, and silvicultural
development, pressure to make up losses of farm and range
lands at the expense of wetlands may intensify.
In 1992, palustrine farmed wetlands comprised 52 percent of all
palustrine wetlands and 45 percent of total wetlands for coastal
Texas. The predominance of this wetland type commands
attention from coastal resource managers; and also indicates
great potential for the conservation of wildlife and other
resources.
The Gulf Coast Joint Venture of the North American Waterfowl
Management Plan and the Texas Wetlands Conservation Plan
(Texas Parks and Wildlife Dept. 1997) have led the way in
Texas regarding private lands incentive programs for wetlands
conservation and management. The role of private landowners
in wetlands conservation is crucial, and efforts to provide
incentives and assistance must be redoubled. The great potential
of coastal Texas for wetlands restoration on upland agricultural
lands is, as yet, largely unrealized.
Conclusions
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Conclusions
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Mid-coast Salt Marsh
ESTUARINE INTERTIDAL EMERGENT
ROSE SULLIVAN
Photo
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Anderson, J.R., E.E. Hardy, J.T. Roach, and R.E. Witner. 1976.
A land use and land cover classification system for use with
remote sensor data. U.S. Geological Survey Professional Paper
964, U.S. Geological Survey, Washington, D.C.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979.
Classification of wetlands and deepwater habitats of the United
States. U.S. Fish and Wildlife Service, FWS/OBS - 79/31,
Washington, D.C.
Dahl, T.E. and C.E. Johnson. 1991. Status and trends of
wetlands in the conterminous United States, mid-1970's to
mid-1980's. U.S. Dept. of Interior, Fish and Wildlife Service,
Washington, D.C.
Eubanks, T.L., P. Kerlinger, and R.H. Payne. 1993. High
Island: a case study in avitourism. Birding 25:415-420.
Frayer, W.E. and J.M. Hefner. 1991. Florida wetlands: status
and trends, 1970's to 1980's. U.S. Dept. of Interior, Fish and
Wildlife Service, Atlanta, GA.
Frayer, W.E., T.J. Monahan, D.C. Bowden, and F.A. Graybill.
1983. Status and trends of wetlands and deepwater habitats in
the conterminous United States, 1950's to 1970's. Colorado
State Univ., Fort Collins, CO.
Frayer, W.E., D.E. Peters, and H.R. Pywell. 1989. Wetlands of
the California Central Valley: status and trends, 1939 to
mid-1980's. U.S. Dept. of Interior, Fish and Wildlife Service,
Portland, OR.
Hammond, E.H. 1970. Physical subdivisions of the United
States of America. In: National Atlas of the United States of
America. U.S. Geological Survey, Washington, D.C.
Hefner, J.M., B.O. Wilen, T.E. Dahl, and W.E. Frayer. 1994.
Southeast wetlands; status and trends, mid-1970's to
mid-1980's. U.S. Dept. of Interior, Fish and Wildlife Service,
Atlanta, GA.
Robinson, L., P. Campbell, and L. Butler. 1994. Trends in
Texas commercial fishery landings, 1972-1993. Management
Data Series No. 111, Texas Parks and Wildlife Dept., Coastal
Fisheries Branch, Austin, TX.
Literature Cited
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Teisl, M.F. and R. Southwick. 1995. The economic
contributions of bird and waterfowl recreation in the United
States during 1991. Southwick Assocs., Arlington, VA.
Texas Agricultural Statistics Service. 1994. 1993 Texas Crop
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Texas General Land Office. 1995. Texas coastal management
program. Austin, TX.
Texas Parks and Wildlife Department. 1993. Saltwater finfish
research and management in Texas: a report to the Governor
and the 73rd Legislature. Coastal Fisheries Branch, Austin, TX.
Texas Parks and Wildlife Department. 1997. Texas wetlands
conservation plan. Austin, TX.
Texas Parks and Wildlife Dept. and Texas Dept. of Commerce.
No date. Nature tourism in the Lone Star State; economic
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Tiner, R.W., Jr. 1984. Wetlands of the United States: current
status and recent trends. U.S. Dept. of Interior, Fish and
Wildlife Service, Washington, D.C.
U.S. Fish and Wildlife Service. 1990a. Cartographic
conventions for the National Wetlands Inventory. St.
Petersburg, FL.
U.S. Fish and Wildlife Service. 1990b. Photo interpretation
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Petersburg, FL.
U.S. Fish and Wildlife Service. 1993. 1991 national survey of
fishing, hunting, and wildlife-associated recreation: Texas. U.S.
Dept. of Interior and U.S. Dept. of Commerce, U.S.
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White, W.A. and T.A. Tremblay. 1995. Submergence of
wetlands as a result of human-induced subsidence and faulting
along the upper Texas Gulf Coast. J. Coastal Res. 11:788-807.
White, W.A., T.A. Tremblay, E.G. Wermund, Jr., and L.R.
Handley. 1993. Trends and status of wetland and aquatic
habitats in the Galveston Bay system, Texas. Galveston Bay
National Estuary Prog. Publ. GBNEP-31, Webster, TX.
Whittington, D., G. Cassidy, D. Amaral, E. McClelland, H.
Wang, and C. Poulos. 1994. The economic value of improving
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the environmental quality of Galveston Bay. Galveston Bay
National Estuary Prog. Publ. GBNEP-38, Webster, TX.
Literature Cited
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Wetland and deepwater habitat categories used in this report
were adapted from Cowardin et al. (1979). In general terms,
wetlands are lands where saturation with water is the dominant
factor determining the nature of soil development and the types
of plant and animal assemblages living in the soil and on its
surface. Wetlands are lands transitional between terrestrial and
aquatic ecosystems where the water table usually is at or near
the surface or the land is covered by shallow water. The
classification system requires that wetlands have one or more of
the following attributes: 1) at least periodically, the land
supports predominantly hydrophytes (water-loving plants); 2)
the substrate is predominantly undrained hydric (water-logged)
soil; and, 3) the substrate is nonsoil and is saturated with water
or covered by shallow water at some time during the growing
season of each year.
Deepwater habitats consist of certain permanently flooded
lands. The separation between wetland and deepwater habitat in
tidal areas coincides with the elevation of the extreme low
water of spring tide. In other areas, the separation is at a depth
of 2 meters (6.6 feet) below low water. This is the maximum
depth in which emergent plants normally grow.
Galveston Island
Salt Marsh
ESTUARINE
INTERTIDAL
EMERGENT
JIM DICK
Within the classification hierarchy, wetlands and deepwater
habitats are grouped according to five major systems: Marine,
Estuarine, Palustrine, Riverine, and Lacustrine. Systems consist
of environments of similar hydrologic, geomorphological,
chemical, and biological characteristics. Each system is further
divided by the predominant ecological influence, such as the
ebb and flow of the tide, and by substrate material and flooding
regimes, or by vegetative life form. Groupings of habitat
categories were made to accommodate the special interests of
the study and the detail to which aerial photography could be
interpreted.
An overview of the Cowardin et al. classification system and
general descriptions of category types can be found in Dahl and
Johnson (1991). The following descriptions are specific
examples of the most common coastal Texas wetland habitats
included within the study categories.
Appendix A -- Habitat Categories
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Marine Wetlands
The marine intertidal unconsolidated shore category includes
beaches, bars, and flats alternately exposed and flooded by tidal
action, including the splash zone, of the open Gulf of Mexico.
Estuarine Wetlands
The estuarine intertidal emergent category includes coastal
marshes which are flooded periodically by tidal waters with
salinity of at least 0.5 parts per thousand. The three types of
estuarine marshes that occur along the Gulf of Mexico are
commonly called salt marsh, brackish marsh, and intermediate
marsh. These types can be separated based on salinity, as
reflected by the dominant plant assemblages. Some common
plants of the estuarine marshes include Smooth Cordgrass
(Spartina alterniflora), Saltwort (Batis maritima), Seashore
Saltgrass (Distichlis spicata), and Seashore Dropseed
(Sporobolus virginicus) in salt marshes; Black Needlerush
(Juncus roemerianus), Marshhay Cordgrass (Spartina patens),
and Olney's Bulrush (Scirpus americanus) in brackish marshes;
and California Bulrush (Scirpus californicus), Southern Cattail
(Typha domingensis), and Seashore Paspalum (Paspalum
vaginatum) in intermediate marshes.
The estuarine intertidal scrub-shrub category describes
wetlands dominated by woody vegetation and periodically
flooded by tidal waters with salinity of at least 0.5 parts per
thousand. On the Texas coast, this category includes wetlands
dominated by the evergreen shrubs Eastern Baccharis
(Baccharis halimifolia), Marshelder (Iva frutescens), and on the
mid- and lower coast, Black Mangrove (Avicennia germinans).
Sea Oxeye (Borrichia frutescens), although a shrub, does not
appear as such on aerial photos probably because it often occurs
in low, dense stands of unbranched plants.
The estuarine intertidal unconsolidated shore category includes
wetlands with less than 30 percent areal coverage by vegetation
and periodically flooded by tidal waters with salinity of at least
0.5 parts per thousand. This category includes sandbars,
mudflats, and other nonvegetated or sparsely vegetated habitats
called saltflats. Saltflats are hypersaline environments that
generally occur near the interface of salt marsh and upland
habitats. Sparse vegetation of saltflats may include glassworts
(Salicorniaspp.), Saltwort, and Shoregrass (Monanthochloe
littoralis). Wetlands consisting mostly of sand flats dominated
by algal beds or blue-green algal mats and periodically flooded
Appendix A -- Habitat Categories
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by astronomic or wind tides were also included in this category.
These habitats occur extensively on the lower Texas coast along
the Laguna Madre.
This study did not include estuarine subtidal aquatic beds
(seagrasses) or oyster reefs because these habitats cannot
always be accurately delineated on color infrared aerial photos.
Palustrine Wetlands
The palustrine forested category includes all freshwater (less
than 0.5 parts per thousand ocean-derived salinity) wetlands
dominated by woody vegetation greater than 6 meters (20 feet)
in height. Floodplain wetlands called hardwood bottomlands
are the predominant habitat of this category. Water regimes
range from brief periodic flooding to near permanent
inundation. For example, assemblages dominated by oaks such
as Overcup Oak (Quercus lyrata), Water Oak (Q. nigra), and
Willow Oak (Q. phellos) along with Green Ash (Fraxinus
pennsylvanica), Sweetgum (Liquidambar styraciflua), and
Black Willow (Salix nigra) are subject to seasonal flooding.
Old river channels and oxbows may support swamps vegetated
predominantly by Bald Cypress (Taxodium distichum) and
Water-Tupelo (Nyssa aquatica) and may be flooded almost
continuously. Forested wetlands with intermediate degrees of
flooding are an extensive component of the hardwood
bottomland spectrum. Some common trees of the intermediate
zones include elms (Ulmusspp.), Red Maple (Acer rubrum),
Water Hickory (Carya aquatica), and Hackberry/Sugar-Berry
(Celtisspp.). In addition to hardwood bottomlands, interfluvial
forested wetlands such as wet pine flatwoods dominated by
Loblolly Pine (Pinus taeda) cover large acreages on the upper
Texas coast.
Cypress Swamp,
Orange County
PALUSTRINE
FORESTED
TEXAS PARKS & WILDLIFE
DEPARTMENT
The palustrine scrub-shrub category includes all freshwater
wetlands dominated by woody vegetation less than 20 feet in
height. These habitats include formerly forested wetlands
experiencing regrowth or invasion by species such as Green
Ash or the introduced Chinese Tallow-tree (Sapium sebiferum).
This category includes shrub-dominated floodplain depressions,
beaver ponds, gravel pits, river point-bars, and backwaters of
ponds and reservoirs vegetated by species such as Swamp
Privet (Forestiera acuminata), Brook-side Alder (Alnus
serrulata), Black Willow, ash (Fraxinus caroliniana, F.
pennsylvanica), Buttonbush (Cephalanthusspp.), and
Planer-tree (Planera aquatica). Chinese Tallow-tree is rapidly
invading palustrine emergent wetlands, including rice fields, on
Appendix A -- Habitat Categories
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the upper and mid-coast. Rattlebush (Sesbaniaspp.) and
Saltcedar (Tamarix ramosissima) are common in depressions
and along drainages throughout the coastal plain.
The palustrine emergent category includes all freshwater
wetlands dominated by rooted herbaceous (nonwoody) plants.
Most habitats in this category are freshwater marshes
dominated by plants such as cattails (Typhaspp.), spikerushes
(Eleocharisspp.), smartweeds (Polygonumspp.), arrowheads
(Sagittariaspp.), etc. Also included are wet prairies and
meadows vegetated by species such as Gulf Cordgrass
(Spartina spartinae), sedges (Carexspp.), Bushy Bluestem
(Andropogon glomeratus), Switchgrass (Panicum virgatum),
Seacoast Bluestem (Schizachyrium scoparium var. littoralis),
Giant Bristle Grass (Setaria magna), and other grasses.
The palustrine farmed category consists primarily of actively
farmed rice (Oryza sativa) fields, but also includes some natural
wetlands which are farmed when dry enough.
The palustrine aquatic bed category includes shallow freshwater
wetlands dominated by floating or submerged vegetation.
Typical species are floating vascular plants such as duckweed
(Lemnaspp.), and Common Water-Hyacinth (Eichhornia
crassipes); and rooted vascular plants such as water-lilies
(Nymphaeaspp.), pondweeds (Potamogetonspp.), and Hydrilla
(Hydrilla verticillata).
Redhead Pond,
Corpus Christi
PALUSTRINE
UNCONSOLIDATED
BOTTOM
BRIAN BENEDICT
Two palustrine nonvegetated (less than 30 percent areal
coverage by vegetation) categories were evaluated. These are
palustrine unconsolidated bottom, which includes all ponds and
other permanently flooded open freshwater bodies less than 20
acres in size; and palustrine unconsolidated shore, which
includes periodically flooded freshwater beaches, bars, and
flats, as well as palustrine wetlands temporarily devoid of
vegetation.
Deepwater Habitats
Several deepwater habitat categories were included as they are
the aquatic end of the continuum for which wetlands function
as transitional zones. These categories are: marine subtidal,
where the substrate is permanently submerged by the open Gulf
of Mexico; estuarine subtidal, which includes the permanently
submerged areas of bays, lagoons, and lakes where
ocean-derived salinity exceeds 0.5 parts per thousand, where
there is at least partial obstruction (barrier islands or peninsulas)
Appendix A -- Habitat Categories
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from the open Gulf of Mexico, and there is occasional dilution
by freshwater runoff from the land; riverine, which includes all
flooded unvegetated freshwater habitats found within a channel;
and lacustrine, which includes all flooded unvegetated
freshwater areas of lakes and reservoirs larger than 20 acres.
Upland Categories
All areas not identified as wetlands or deepwater habitats were
placed in five upland categories. The agriculture category
consists of cropland, pasture, and managed range. The urban
category consists of cities, towns, and other intensively built-up
areas. The "other" uplands category was adapted from
Anderson et al. (1976). "Other" includes unmanaged or
nonpatterned forest land and rangeland, and barren land, as well
as lands that have been drained and cleared but not put to
identifiable use. The forested plantation category includes
planted and managed pine plantations, clear cuts, and other
intensively managed forests. The rural development category
includes low-density, often isolated development outside
distinct cities and towns. Rural infrastructure including major
roads, other transportation, power, and communications
facilities, mines and quarries, and golf courses and other
recreational areas were included.
Houston Ship
Channel, San
Jacinto River
RIVERINE
TEXAS PARKS & WILDLIFE
DEPARTMENT
Appendix A -- Habitat Categories
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Galveston Island Salt Marsh
ESTUARINE INTERTIDAL EMERGENT
JIM DICK
Photo
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Cypress Swamp, Orange County
PALUSTRINE FORESTED
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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Redhead Pond, Corpus Christi
PALUSTRINE UNCONSOLIDATED BOTTOM
BRIAN BENEDICT
Photo
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Houston Ship Channel, San Jacinto River
RIVERINE
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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Estimates produced include acreages with associated standard
errors. Some estimates are not considered reliable enough to
recommend their use for making decisions. An indication of the
statistical reliability of each acreage estimate is given in the
summary tables included in this appendix. The standard error of
each entry expressed as a percentage of the entry (SE %) is
below each acreage estimate. Reliability can be stated generally
as: "we are 68 percent confident that the true value is within the
interval constructed by adding to and subtracting from the
estimate the SE%/100 times the estimate." For example, if an
estimate is one million acres and the SE% is 20, then we are 68
percent confident that the true value is between 800,000 and
1,200,000 acres. An equivalent statement for 95 percent
confidence can be made by adding and subtracting twice the
amount to and from the estimate. Therefore, a large SE%
indicates that the estimate has little, if any, reliability. If the
SE% is 100 or greater, we can not state that we are 68 percent
confident that the true value is not zero.
This discussion of reliability is meant to aid in interpretation of
the study results. It was expected that only certain estimates
would be precise enough to be meaningful. However, all
estimates are included in the summary tables for additivity and
ease of comparison.
Estimates for 1955, 1992, and change over that period were
produced for the categories described in Appendix A. These
estimates are summarized in Table 1 of Appendix B. Table 2
summarizes estimates by selected surface area groups. Totals
for columns are estimates of total acreage by category for 1992.
Row totals (the column on the extreme right) are estimates of
total acreage by category for 1955. Table entries are interpreted
as in the following examples (all from the seventh row or
column of Table 1):
Table 1.
Area, in thousands of
acres, by surface area
classification.
Table 2.
Area, in thousands of
acres, by selected
surface area groups.
447,293 acres classified as palustrine emergent in 1955 were
again classified as palustrine emergent in 1992;
Impounded Farm
Pond
PALUSTRINE
UNCONSOLIDATED
92,562 acres classified as palustrine emergent in 1955 had
changed to agriculture by 1992;
Appendix B -- Data Tables
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BOTTOM
TEXAS PARKS & WILDLIFE
DEPARTMENT
Duck Hunting
PALUSTRINE
EMERGENT
TEXAS PARKS & WILDLIFE
DEPARTMENT
15,523 acres classified as palustrine emergent in 1955 had
changed to upland "other" by 1992;
12,692 acres classified as palustrine scrub-shrub in 1955 had
changed to palustrine emergent by 1992;
70,886 acres classified as palustrine emergent in 1955 had
changed to palustrine farmed by 1992;
The estimate of palustrine emergent area in 1955 is 806,996
acres;
The estimate of palustrine emergent area in 1992 is 571,867
acres;
The estimate of net change in palustrine emergent area from
1955 to 1992 is ­235,129
acres.
Appendix B -- Data Tables
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Appendix B: Table 1.
Area, in thousands of acres, by surface area
classification.
This table is provided in Adobe Acrobat (PDF) format. You
will need the free reader application from Adobe to view this
file.
Click here for the file. (42K)
Appendix B: Table 1
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Embedded Secure Document
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secure document that has been embedded in this document. Double click the pushpin to view
datab01.pdf.
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Appendix B: Table 2.
Area, in thousands of acres, by selected surface area
groups.
This table is provided in Adobe Acrobat (PDF) format. You
will need the free reader application from Adobe to view this
file.
Click here for the file. (43K)
Appendix B: Table 2
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Embedded Secure Document
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secure document that has been embedded in this document. Double click the pushpin to view
datab02.pdf.
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Impounded Farm Pond
PALUSTRINE UNCONSOLIDATED BOTTOM
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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Duck Hunting
PALUSTRINE EMERGENT
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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Many individuals within the U.S. Fish and Wildlife Service and
others contributed to this report. The authors especially thank
W. W. Hagenbuck, National Wetlands Inventory Regional
Coordinator, Albuquerque, NM; D. W. Woodard, NWI Group
Leader, St. Petersburg, FL; B.O. Wilen, NWI Project Leader,
Arlington, VA; K.E. Cathey, J.A. Dick, R.E. Sullivan, and S.J.
Vosler, NWI Group, Austin, TX; M. Newcastle, Office of
Public Affairs--Printing, Washington, DC; K. Patterson and
staff at Geonex, Inc. in St. Petersburg.
Special recognition is due the staff of the Wetlands Status and
Trends Unit, St. Petersburg, which includes Richard D. Young,
who performed the GIS data analysis, and Martha C. Caldwell,
who was responsible for the statistical outputs.
The authors also express their appreciation to Dr. Kenneth P.
Burnham, Colorado State University, for providing statistical
programming support and oversight; and to Thomas Gale, Gale
Communications, St. Paul, MN, for editing, layout, and
graphics.
We thank the Texas Parks and Wildlife Department for photos.
This report should be cited as:
Moulton, D.W., T.E. Dahl, and D.M. Dall. 1997. Texas Coastal
Wetlands; Status and Trends, mid-1950s to early 1990s. U.S.
Department of the Interior, Fish and Wildlife Service,
Albuquerque, New Mexico. 32 pages.
Oyster Harvest
ESTUARINE
SUBTIDAL
TEXAS PARKS & WILDLIFE
DEPARTMENT
Acknowledgments
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Oyster Harvest
ESTUARINE SUBTIDAL
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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1. Texas Physiographic Regions and Coastal Texas Study
Area
2. Distribution of 754 sample plots within study area
3. Total wetlands of coastal Texas in 1955 (a) and 1992 (b)
4. Palustrine wetlands of coastal Texas in 1955 (a) and 1992
(b)
5. Estuarine wetlands of Texas in 1955 (a) and 1992 (b)
6. Estuarine wetlands and deepwater habitats of Texas in
1955 (a) and 1992 (b)
7. Distribution of all coastal Texas wetlands in 1955 (a) and
1992 (b)
8. Distribution of Texas estuarine wetlands in 1992
9. Distribution of Texas estuarine emergent wetlands in
1992
10. Distribution of Texas estuarine unvegetated wetlands in
1992
11. Distribution of Texas estuarine scrub-shrub wetlands in
1992
12. Distribution of coastal Texas palustrine wetlands in 1992
13. Distribution of coastal Texas palustrine emergent
wetlands in 1992
14. Distribution of coastal Texas palustrine forested wetlands
in 1992
15. Distribution of coastal Texas palustrine scrub-shrub
wetlands in 1992
16. Net acreage changes for estuarine wetlands and
deepwater habitats of Texas, 1955 to 1992
17. Net acreage changes for palustrine wetlands of coastal
Texas, 1955 to 1992
List of Figures
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18. Net changes in coastal Texas wetland acreages, 1955 to
1992
19. Loss of coastal Texas wetlands to agriculture, 1955 to
1992
20. Loss of coastal Texas wetlands to silviculture, 1955 to
1992
21. Loss of coastal Texas wetlands to urban, 1955 to 1992
22. Loss of coastal Texas wetlands to rural development,
1955 to 1992
List of Figures
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1. Some valuable goods and services produced by coastal
Texas wetlands; environmental quality functions and
socioeconomic values
2. Wetland, deepwater, and upland habitat categories used
in this study
3. Coastal Texas wetland, deepwater habitat, and upland
trends (acres), 1955 to 1992
List of Tables
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Cultivated Rice
PALUSTRINE FARMED
Texas Parks and Wildlife Department
Photo
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Shrimp Harvest
ESTUARINE SYSTEM
TEXAS PARKS & WILDLIFE DEPARTMENT
Photo
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