TEXAS GEMS -Clive Runnells Family Mad Island Marsh Preserve

Site Description

In 1987 Clive Runnells and The Nature Conservancy of Texas established a relationship that began the conservation efforts in the Mad Island Marsh area. Through a land swap with Clive Runnells, the Conservancy acquired 2,307 ha. (5,700 ac.) of wetlands and coastal prairies in and around the Freshwater Lake and Crab Lake areas. This land was turned over to the Texas Parks and Wildlife Department and became part of the Mad Island Wildlife Management Area, a 2,946-ha. (7,281-ac.) public hunting area. Mad Island Marsh Preserve was created in 1989 when Clive Runnells generously donated 1,273 ha. (3,148 ac.) of coastal wetlands and upland prairies adjacent to the wildlife management area to the conservancy. Two additional acquisitions were made in 1993 and 2000 through partnerships with several corporations, other non-profit organizations, and a grant from the North American Wetlands Conservation Council. These brought the total Nature Conservancy preserve to 2,858 ha. (7,063 ac.).

Mad Island Marsh Preserve is part of an expansive coastal wetland system which, until perhaps 60 years ago, stretched nearly unbroken along the mid- and upper-Gulf Coast of Texas. The conservation area is comprised of palustrine emergent wetlands (freshwater wetlands), farmed wetlands (rice fields), coastal prairie and cordgrass (Spartina spp.) meadows, estuarine intertidal emergent and aquatic bed wetlands (intertidal marshes), and unvegetated intertidal flats. The southern boundary of the preserve is adjacent to West Matagorda Bay. Characteristic fauna of the preserve include American alligators (Alligator mississippiensis), western diamondback rattlesnakes (Crotalus atrox), bobcats (Lynx rufus), nine-banded armadillos (Dasypus novemcinctus), white-tailed deer (Odocoileus virginianus), river otters (Lutra canadensis), Texas horned lizard (Phrynosoma cornutum), raccoon (Procyon lotor), and coyote (Canis latrans). Plant communities represented on the preserve include the Gulf Cordgrass Series (Spartina spartinae), Marsh-hay Cordgrass Series (Spartina patens), Rush-Sedge Series (Juncus spp.), Saltgrass-Cordgrass Series (Distichlis spicata - Spartina spp.), Seacoast Bluestem-Gulfdune Paspalum Series (Schizachyrium scoparium var. littoralis - Paspalum monostachyum), Glasswort-Saltwort Series (Salicornia bigelovii/S. virginica-Batis maritima), Mesquite-Huisache Series (Proposis glandulosa-Acacia smallii), and Sugarberry-Elm Series (Celtis laevigata/C. reticulata-Ulmus spp.) (Texas Conservation Data Center 2002).

Area of Influence:

West – Cities of Collegeport and Palacios, Texas
East – City of Matagorda, Texas and South Texas Power Plant
North – City of Bay City, Texas
South – West Matagorda Bay

Ecological and Cultural Characteristics

Habitat Types:

The preserve consists of coastal prairie, freshwater wetlands (farmed, artificial, and natural), intertidal wetlands, and open water habitats.
Coastal prairie: There are approximately 3500 acres of native coastal prairie on the preserve, most of which have never been plowed. The prairie portions of the preserve are either salty prairie, gulf cordgrass (Spartina spartinae) dominated, or more upland prairies, little bluestem-brownseed paspalum (Schizachyrium scoparium – Paspalum plicatulum) dominated. These habitat types are crucial in the life cycle of many grassland dependant birds and small mammals. Prescribed fire is an important ecological tool employed in preserve management and plays an integral role in maintaining the function and diversity in coastal prairies and is a key ecological process. Fire also rejuvenates grass and forb growth, removes standing biomass and accumulated litter, supports nutrient cycling, retards brush encroachment, and assists in exotic/invasive species control programs. Without fire at regular intervals, every 3-5 yrs., grasslands become homogenous and less productive and brushy species tend to increase.

Freshwater wetland (palustrine marsh): The preserve has approximately 2400 acres of freshwater wetlands. Of these freshwater wetlands, 1200 acres are ricefield, 134 acres are moist soil units, and the remaining 1,123 acres are natural freshwater wetlands. Approximately 100 acres of the ricefield wetlands and all of the moist soil units are flooded each fall to provide critical migrating and wintering habitat for a variety of waterfowl, waterbirds, and shorebirds. Various species of rushes (Juncus spp.), sedges (Carex spp.), and smartweeds (Polygonum spp.) occur in these wetlands.

Intertidal wetland (estuarine marsh): There are approximately 680 acres of intertidal wetlands on the preserve. These wetlands border the intracoastal waterway, Mad Island Lake, and several areas along the dredge spoil islands. Common plant species found here include marsh-hay cordgrass (Spartina patens) and smooth cordgrass (Spartina alterniflora). There are also beds of submerged widgeon grass (Ruppia maritima) in various portions of Mad Island Lake.

Open water: There are approximately 300 acres of open water habitats on the preserve. Fresh open water habitats are dominated by white water lily, various species of pondweed (Potomogeton spp.), duckweed (Lemna sp.) common duckmeat (Spirodela polyrhiza) and provide habitat for a multitude of freshwater fish and clam species. The open brackish water provides habitat for many species of commercially and recreationally important species including red drum (Sciaenops ocellatus), southern flounder (Paralichthys lethostigma), blue crab (Callinectes sapidus), brown shrimp (Penaeus aztecus), white shrimp (Penaeus setiferus), and oyster (Crassostrea virginica). Both open water types provide loafing, feeding, and roost habitats for waterfowl and shorebirds.

Rare/Endangered Species:

Endangered and threatened bird species observed on the preserve include the brown pelican (Pelecanus occidentalus), reddish egret (Egretta rufescens), wood stork (Mycteria americana), white-tailed hawk (Buteo albicaudatus), arctic peregrine falcon (Falco peregrinus tundrius), Aplomado falcon (F. femoralis), burrowing owl (Athene cunicularia), and piping plover (Charadrius melodus). There are also two rare plant species known to occur on the preserve. These are coastal gay-feather (Liatris bracteata) and threeflower broomweed (Thurovia triflora), both of which are endemic to coastal prairies in south Texas. Texas horned lizards (Phrynosoma cornutum) have been observed on the dry prairie portions of the preserve and fingerling tarpon (Megalops atlanticus) have been observed in the estuaries of the preserve.

Breeding/Nursery Area:

Mad Island Lake and its surrounding intertidal wetlands provide nursery habitat for numerous marine species from adjacent Matagorda Bay and the Gulf of Mexico. Such species include the red drum (Sciaenops ocellatus), southern flounder (Paralichthys lethostigma), blue crab (Callinectes sapidus), brown shrimp (Penaeus aztecus), white shrimp (Penaeus setiferus), and oyster (Crassostrea virginica), all of which are recreationally and/or commercially important species to local communities. The coastal prairie habitats provide nesting and breeding habitat for a multitude of grassland dependant bird species including the northern bobwhite (Colinus virginianus), loggerhead shrike (Lanius ludovicianus), and seaside and grasshopper sparrows (Ammodramus maritimus and A. savannarum). Mottled ducks (Anus fulvigula), white-tailed hawks (Buteo albicaudatus), and white-tailed kites (Elanus leucrus) have also been observed nesting in the upland prairie portions of the preserve. The intertidal marsh habitats provide nesting and brooding habitat for a variety of birds , including the king and clapper rails (Rallus elegans and R. longirostris), and the black rail (Laterallus jamaicensis).

Forage Area:

The coastal prairies, marshes, and open water of the preserve provide foraging habitat for many species of birds, mammals, and fish. The aggressive prescribed burning and invasive/exotic species control programs maintain the prairie portions of the preserve in high quality habitat with various successional stages thus optimizing mast and invertebrate production.

Migratory Species:

Mad Island Marsh Preserve is situated at the terminus of the Central Flyway, thus it sees considerable use by migrating birds every year. The preserve provides critical migration and over wintering habitat for a multitude of waterfowl, waterbirds, shorebirds, raptors, and songbirds. There is a unique south Texas thornscrub community along the southern portion of the preserve, directly adjacent to the Gulf Intracoastal Waterway (GIWW). This thornscrub community provides critically important fallout/stopover habitat for neotropical migrants during their migrations. The annual Audubon-sponsored Mad Island Marsh Christmas Bird Count has ranked number one in North America for the most number of species from 1998 to 2002.

Uniqueness of Natural Community:

There is a geologically and vegetationally unique Paleo Beach Ridge along the GIWW that is comprised of shell substrate. This ridge supports an unusual assemblage of Tamaulipan thornscrub vegetation interspersed with other Texas vegetation such as mountain laurel (Sophora secundiflora). This is the most northern extent of this community.

Ecosystem Function:

While the diverse habitats at Mad Island provide breeding, nesting, foraging, and loafing habitat for a variety of important species, these habitats also serve several other important ecological functions. The marsh systems at Mad Island perform the basic intrinsic functions of all wetlands (i.e., flood control, water purification, sediment retention), they also provide a buffer against saltwater intrusion into other more sensitive freshwater habitats.

Uniqueness of Natural Community:

The coastal habitats found on the preserve are intact remnants of once-vast communities that are now largely fragmented elsewhere on the Texas coast.

Archaeological and Cultural Significance:

A few native American shell middens have been identified at various locations surrounding the Mad Island Lake area.

Current and Potential Use of the Site

Existing or Potential Educational Use:

Habitat conservation and enhancement is the primary purpose of the preserve, however, education has become a significant aspect of the conservation effort as well. In 1994, the Coastal Conservation Education Program was established at the preserve. The primary purpose of this program is to share ecological information with surrounding communities to foster support for conservation efforts at the preserve and in surrounding areas. Each year over 1,000 students from kindergarten to college-age visit the preserve and are taught, hands-on in the field, subject matter ranging from wetland and prairie ecology to entomology and marine biology. In addition, Conservancy staff routinely travel to schools and community facilities to conduct education programs.

Recreational Use:

Recreational activities occurring on the site include birding and other wildlife viewing. The preserve is not open to the general public on an ad libitum basis, but guided trips and conservation education activities are supported as well as regularly scheduled volunteer events.

Commercial Use:

None

Private Use:

The preserve is owned and managed by The Nature Conservancy, a non-profit international wildlife conservation organization, as a venue to raise awareness and support for coastal conservation along the entire Texas coast. The preserve is managed as an important wildlife conservation area with special emphasis given to increasing the diversity of species endemic to the area. The site also provides opportunities for effective outreach and conservation education with local and regional communities. Through the Nature Conservancy’s Ecoregional Planning Process, this preserve was identified as an “action site” henceforth designating the preserve and surrounding area as a model for conservation action in conjunction with other conservation agencies.

Management Status

Land Ownership:

Mad Island Marsh Preserve is owned and operated by The Nature Conservancy of Texas; Headquarters in San Antonio, Texas

Existing Designations:

The preserve is a national demonstration site for the USA Rice foundation, and is designated a Category 6 Wetland of Special Significance by the United States Fish and Wildlife Service. The preserve and adjacent coastal habitats are also considered an “action site” through the Nature Conservancy’s Gulf Coast Prairies and Marshes Ecoregional planning process.

Management Status:

The site is currently managed by the owners and is managed for native and natural habitats. It is also a demonstration site for the compatibility of sustainable agriculture (rice farming and cattle grazing) and wildlife/habitat conservation . Management on the preserve is proactive wherein prescribed fire is used in combination with a planned livestock grazing rotation to promote healthy coastal prairie systems and provide for the greatest biodiversity on the site. There is also an aggressive invasive/exotic species control program in which several species are targeted for control. Such species include Chinese tallowtree (Sapium sebiferum), salt cedar (Tamarix spp.) narrowleaf cattail (Typha angustifolia), alligator weed (Alternanthera philoxeroides), common reed (Phragmities australis), MacCartney rose (Rosa bracteata), mesquite (Prosopis glandulosa), and feral hogs (Sus scrofa).

Existing Monitoring Activities:

There currently are several on-going monitoring projects in place on the preserve. There is a long-term project dealing with monitoring of water quality parameters in and around the Mad Island Slough complex, and there have been various studies conducted on the small mammal communities and fish communities of the preserve. In addition, there have been studies addressing the effects of ricefield tailwaters.

Management Needs:

The preserve is currently evaluating different methods of monitoring the prescribed fire program and its impacts on local ecological communities. There are proposed studies to further improve our understanding of the ecological role rice tailwater plays for increasing freshwater inflows into coastal estuaries. There is always the need for continuing/increasing the invasive/exotic species control program.

Site Viability

Threats to Ecological Integrity:

Freshwater Inflows: Because hydrology, and freshwater inflows in particular, control the viability of the conservation area, maintaining freshwater inputs are a critical ecological issue. Therefore, the most important goal for the Mad Island Marsh preserve is to maintain or increase freshwater inputs required for key hydrological processes in area wetlands, marshes, and open water estuaries. Successfully abating this threat will serve to provide no net loss of intertidal marsh and unvegetated flats while increasing the extent of oligohaline marsh within the area.

Shoreline Erosion: On-going shoreline erosion along the entire stretch of the GIWW is a concern across the coast. Likewise, the Nature Conservancy’s portion of the Gulf Intracoastal Waterway is receding at alarming rates and threatens important neotropical songbird habitats as well as the hydrology and salinity of Mad Island Bayou. Loss of the hydrological integrity of Mad Island Bayou will eventually lead to saltwater intrusion and the loss of important oligohaline marsh habitats.

Invasive and Exotic Species: Encroachment of non-endemic and invasive species in the area will lead to loss of biodiversity and reduced ecological health and function.|

Management Potential:

On site management actions are critical to maintaining the preserves ecological function. Lack of prescribed fire in the prairies leads to brush encroachment and decreased productivity of these areas. Likewise, ceasing or reducing the invasive/exotic species control program would cause shifts to non-desirable communities, resulting in area-wide reduction in productivity and function. Ever decreasing freshwater inflows are an ongoing problem in many coastal bays and estuaries. The same is true of this site, therefore it is critical to maintain inflows via rice tailwater and restoration of hydrological function to more closely mimic that of natural levels.

Source of Information

The Nature Conservancy of Texas, Mad Island-Oyster Lake Conservation Area Plan
The Nature Conservancy, Gulf Coast Prairies and Marshes Ecoregional Plan