Dune Restoration

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Coastal dunes are a natural feature of sandy shorelines and are present in most temperate regions. They are among the most dynamic landforms, shifting with the winds and storm tides. Dunes are part of the near-shore environment that change seasonally and with episodic storms. They serve as reservoirs of sand to re-nourish the beach during storms as erosion of sand transports it offshore where it is deposited on sand bars to be returned gradually by the tides. Formation of dunes requires a source of sand, usually carried from the beach by onshore winds, and vegetation to catch sand and stabilize it.

Dunes are stressful environments characterized by blowing sand that abrades vegetation, salt spray, high soil temperatures, low water holding capacity and low nutrients, especially nitrogen (N). Historically, many dunes were deforested for timber then used for grazing. Today, they are under stress from shoreline development and overbuilding of the coastal fringe. Development of the shore often leaves no room for dunes to migrate inland, as occurs when sea level rises. The combination of ever-changing environmental conditions and urban encroachment makes coastal dunes a globally endangered ecosystem.

The Dune Community

Dune vegetation consists of distinct plant communities, pioneer, scrub, and forest zones, that occur along a gradient of increasing distance from the sea and increasing age (Figure 1). The pioneer zone occurs on the upper beach or foredune area, closest to the sea. Vegetation consists of a few species of grasses, sedges, and forbs that are able to withstand salt spray, sandblast, burial by sand, temperature extremes, drought, episodic flooding with salt water and low nutrient (N) availability (Table 1). Pioneer species include dune initiators and dune builders. Dune initiators are annuals such as sea rocket, Cakile maritima, which is widely distributed throughout the world, sea purslane (Sesuvium spp.), and other species. Dune initiators are important for trapping seeds of dune builders. Dune builders consist of perennials such as American beach grass (Ammophila breviligulata), European beach grass or marram grass (A. arenaria), European dunegrass (Elymus arenarius), and American dunegrass (Elymus mollis) in cool climates, and sea oats (Uniola paniculata) and bitter panicum (Panicum amarum) in warm climates. Saltmeadow cordgrass, Spartina patens, also is common in

Sea (Swale)

Forest zone

Sea (Swale)

Figure 1 Vegetation of the coastal dunes from the sea inland to the forest.

Forest zone

Table 1 Environmental constraints on establishment of coastal dune and tidal wetland vegetation

Constraints

Dune

Tidal marsh/mangrove

Physical

Inadequate water/drought Salt spray

Wind/sand abrasion Excessive soil temperature

Excess water/anoxia Salinity

Excess wave action Excessive soil temperature

Nutritional

Inadequate N, (P)

Inadequate N, (P) Acid sulfate soils

Disturbance

Foot/vehicular traffic Grazing/herbivory

Grazing/herbivory

Colonization

Excessive tidal energy

Disease

Fungal pathogens, scale insects

See text for an explanation of the various constraints.

See text for an explanation of the various constraints.

the foredune zone where it is found on low, moist sites where exposure to salt is greater. Once dune initiators and dune builders become established, secondary invaders such as Abrona, Ambrosia, Artemesia, Croton, Carex, Carpobrotus, Euphorbia, Erigeron, Festuca, Fimibristylis, Hydrocotyle, Ipomoea, Lathyrus, Lupinus, Schizachyrium, Solidago, Spartina, and Sporobolus colonize the pioneer zone.

The shrub zone lies immediately behind the foredune zone and consists of secondary dunes and low-lying areas, swales, and flats, between them. In addition to pioneer species, the shrub zone is colonized by woody vegetation that stabilizes dunes. The shrub zone receives less salt spray and fresh sand relative to the foredune zone. Nitrogen supply also is low. In the shrub zone, woody shrubs and trees are stunted by salt spray and wind. Along the US Atlantic coast, seashore elder, Iva imbricata, is important in the shrub zone. It is highly adaptable and tolerates saltwater, salt spray, sandblast, and sand accumulation. Seashore elder grows in foredunes, swales, maritime forests, and upper fringes of the salt marsh. Growth of pioneer species is poor in the shrub zone relative to the foredune zone. Shrub species do well though and they are important in stabilizing sand and initiating soil development. The decline of vigor and growth of pioneer species in the shrub zone is thought to be linked to reduced sand accumulation that supplies mineral nutrients, especially phosphorus (P).

The forest zone is the oldest and most stable dune community. It forms only after substantial time passes and soil formation begins. Considerable protection from salt spray and flooding is needed for the forest zone to develop. Once dunes are stabilized and pioneer and shrub communities develop, trees may be planted to accelerate succession. However, trees are not planted in the fore-dune or shrub zones near the sea because salt spray inhibits their growth. Also, trees shade out pioneer and shrub species and inhibit regeneration of these species following a severe disturbance such as disease outbreak, insect outbreak, or fire.

Limiting Factors for Establishment

Establishment of dunes requires a supply of sand and vegetation to catch and stabilize it. Sand is supplied by onshore winds that pick it up from the beach and carry it inland where it is intercepted by vegetation. Sand is transported mostly by saltation, bounced along as the impact of moving grains dislodges other grains, and by surface creep. Sand fences often are erected to trap sand and initiate dune building. Fences may be built using wooden pickets, boards, bamboo, reeds, fabric, or other materials such as branches that deflect and slow the wind. Guidelines for using fences include (1) use fences of 40-50% porosity as they are most efficient in trapping sand, (2) install fences parallel to the shoreline, and (3) a single row of fence is suitable at lower wind speed but double fences may be needed at higher wind speed. As the dune builds, continued sand trapping and dune growth is facilitated by installing additional fences atop the original fence as it becomes buried. Other sources of sand for dune building include dredged material pumped onto the beach and sand pushed up by bulldozers.

The dune environment is harsh. The sandy soils hold little water and are low in nutrients, especially N. Dune vegetation responds favorably to fertilizer additions, especially N with a lesser response to P. Because of its fragile nature, it is essential to keep existing dunes and dune plantings free of vehicular and foot traffic (Table 1). In some regions, grazers, rabbits in Europe, nutria in Louisiana (USA), may graze on dune vegetation, reducing plant cover (Table 1). In Europe, where dunes were afforested centuries ago, grazers such as sheep and rabbits are important for maintaining early-successional vegetation.

Restoration and Ecosystem Development

Restoration of coastal dunes has been widely used around the world, including Europe, North America, South Africa, New Zealand, and elsewhere to help stabilize beaches and barrier islands.

In Europe, coastal dunes have been used for centuries for low-intensity agriculture (e.g., grazing). In the nineteenth-century pine trees, Pinus maritima, P. mugo, and other trees were planted along the coast of France for dune stabilization and silviculture. With increasing urban encroachment and fragmentation in the twentieth century, public awareness of the importance of dunes for shoreline defense, habitat for nature and esthetics led to interest in restoring these ecosystems.

In Europe, where trees were planted for silviculture, early dune restoration efforts involved cutting down the trees and shrubs to promote conditions favorable for pioneer vegetation. The first, scientifically based restoration efforts involved planting European beach grass, American beach grass, and other pioneer vegetation to identify suitable species for use in dune plantings. In the 1960s, experimental plantings were established along the US Atlantic coast. Different sources of sand were tested and different species, including American beach grass, were planted to determine their geographic range and environmental requirements. On the Pacific coast, similar experiments were underway evaluating European beach grass.

Frequently, dunes are established too close to the beach which does not allow for the natural ebb and flow of sand between the dune, beach, and offshore sand bar. Along the US Atlantic coast, it is recommended that dunes be placed at least 100 m from mean high water to avoid dune erosion during storms. Once a site is selected,

Sand Dune Fence
Figure 2 (a) Installation of a sand fence for dune restoration in January 1978. (b) The same site in October 1981.

a sand fence is installed to catch and perennial vegetation is planted to stabilize and hold the sand in place (Figure 2a). Plant stems and leaves increase surface roughness that decreases wind velocity near the ground and interferes with sand movement, and roots that hold sand in place. Over time, a healthy dune community develops (Figure 2b). Vegetation is planted early in the growing season to avoid high soil temperatures that occur later and to give plants the full growing season to colonize the site.

Dune vegetation is N-limited and sometimes P-limited. N-P-K fertilizer (30-10-0) is applied at the rate of 23 kg ha 1 (50 lb acre ) 2-3 months after planting to promote plant growth. Do not fertilize at the time of planting as the fertilizer will leach from the soil. Rather, once the root system begins to develop, fertilizer is applied in three applications (69kgha_1 total) spread out over the growing season.

Several pioneer species should be planted as multi-species plantings generally outperform monoculture plantings. Beach grass traps sand and accumulates it faster than other species. Beach grass also migrates faster toward the ocean than other species such as sea oats and bitter panicum, but it is susceptible to disease and insect problems (Table 1). Infestations by insects and pathogens are less of a problem in cool temperate climates as opposed to warm climates. In North Carolina (USA) American beach grass is attacked by a scale insect (Eriococcus carolinae) and a fungal pathogen (Marasmius). Woody vegetation, which is common on older dunes, is not planted in the foredune area because it does not grow well. Rather, shrubs and trees will colonize the site as succession proceeds, assuming environmental conditions are stable (i.e., the sea is not encroaching).

Monitoring studies indicate that multispecies plantings are most successful in accumulating sand, building dunes, and providing good plant cover. On Ocracoke Island (North Carolina, USA), 10 years after planting a mixture of American beach grass and sea oats, sea oats dominated the zone where sand was no longer accumulating. On the active sand-accumulating zone toward the beach, beach grass was dominant. Long-term monitoring of restored dunes on the Brittany Coast of France revealed that, after 10 years, fixed (nonmigrating) dunes had been reestablished but plant species diversity was lower than in mature dunes. In North Carolina, 20 years after installing a sand fence and planting with American beach grass, a 3 m high dune developed that had built 30-40 m seaward (Figure 3). After 10 years, species richness averaged three species m"2 with a total of nine species observed on the planted site. After 20 years, species richness doubled to 6.2 species m" and 15 species were counted. Over time, American beach grass decreased in importance as it was replaced by later-successional vegetation, S. patens, and woody vegetation, red cedar (Juniperus virginiana), wax myrtle (Myrica cerifera), and silverling (Baccharis halimifolia).

Population Dynamics Ecology

Figure 3 Change in dune profile characteristics and plant species composition 4, 10, and 20 years after dune restoration along the North Carolina (USA) coast.

Figure 3 Change in dune profile characteristics and plant species composition 4, 10, and 20 years after dune restoration along the North Carolina (USA) coast.

Tidal Wetland Restoration

Tidal wetlands consist of salt marshes, found mostly in temperate regions, and mangroves, found in tropical and subtropical regions. Marshes are dominated by grasses, notably the genus Spartina, rushes (Juncus, Schoenoplectus), sedges, forbs, and shrubs. Mangroves, salt- and flood-tolerant trees, and shrubs that inhabit the intertidal zone, are dominated by the genera Rhizophora, Avicennia, Laguncularia, Conocarpus, Sonneratia, and others. Similar to dunes, tidal marshes were used for centuries for grazing and for mangroves, for silviculture, and for gathering firewood. In Europe, the United States, and elsewhere, levees were constructed around tidal marshes to isolate them from the sea for agriculture. Like dunes, today tidal marshes and mangroves exist in a fragile environment squeezed by human encroachment.

Tidal Marsh and Mangrove Communities

Vegetation of tidal wetlands often grows in distinct zones determined by tidal inundation and salinity. Marsh vegetation often is separated into 'low' and 'high' marsh based on the frequency of tidal inundation. Smooth cordgrass, Spartina alterniflora, of the US Atlantic coast, forms mono-typic stands in the low marsh, where inundation by the astronomical tides occurs twice daily. Other species of Spartina (i.e., S. foliosa on the US Pacific coast, S. townsendii in Europe, S. anglica (the fertile form of S. townsendii) in China) and some forbs (e.g., Halimioneportulacoides) dominate the low marsh in other parts of the world. A different assemblage of species grows at higher elevations, in the high marsh. In the US, needlerush (Juncus roemerianus), saltmeadow cordgrass (S. patens), and salt grass (Distichlis spicata) grow in the high marsh. Puccinellia maritima is common in the high marshes of Western Europe.

Tidal wetland vegetation varies with the salinity of tidal floodwaters. Salinity, mostly sodium chloride, stresses plants by altering osmotic potential that interferes with water and nutrient (N) uptake. High marsh vegetation generally is less tolerant of salinity than Spartina and grows better at higher elevations in the marsh and in areas farther away from the ocean, where salinity is diluted by freshwater. In arid and semiarid regions where precipitation is low and evaporation is high, salinity of floodwaters may exceed that of seawater, which is 35 parts per thousand (ppt). In these regions, salt-tolerant halophytes such as glasswort (Salicornia spp.), saltwort (Batis spp.), and others (Borrichia, Suaeda, Distichlis) dominate. Vegetation grows slowly and cover is sparse in these salt-stressed tidal wetlands.

Similar to marshes, mangrove vegetation grows in zones related to hydroperiod and salinity. In the Western Hemisphere, red mangrove (Rhizophora mangle)

grows closest to the water's edge while black mangrove (Avicennia germinans), white mangrove (Laguncularia race-mosa), and buttonwood (Conocarpus erectus) grow further inland. Salt marsh vegetation, including Spartina, Distichlis, Batis maritima, Sporobolus virginicus, and others, often is found growing with mangroves.

Limiting Factors for Establishment

Successful establishment of tidal wetland vegetation requires recreating or restoring hydrology and salinity, as well as other factors (soils, nutrients) that favor marsh and mangrove vegetation (Table 1). Reestablishing the appropriate hydroperiod, the depth, duration and frequency of inundation, is critical for successful establishment of vegetation. Restoring hydroperiod is easier in tidal wetlands than in inland wetlands because the astronomical tides provide for predictable and frequent inundation. In the intertidal zone, a narrow elevation range exists where vegetation can be successfully established and the width of this zone will depend on slope of the land and tide range. A large tidal range and gentle slope (1-3%) will produce the maximum amount of potentially restorable marsh area (Figure 4a). Low marsh vegetation such as Spartina alterniflora grows at elevations between mean sea level and mean high water. Above mean high water, inundation is less frequent and 'high' marsh vegetation such as S. patens, Distichlis spicata, and Juncus roemerianus grow between mean high water and the mean spring high tide line. Where tidal inundation is less predictable or where tide range is small, small differences in elevation produce distinctly different plant communities. In North Carolina (USA), four different species grew in distinct zones, all within an elevation range of less than 30 cm. Thus, it is critical to understand the hydroperiod requirements of different species so they can be planted in the appropriate elevation zones.

Determining the appropriate salinity regime also is critical for successful establishment of tidal wetland vegetation. Smooth cordgrass and red mangrove grow well in areas regularly inundated by a mixture of freshwater and seawater, in the range of 20-30 ppt. Other species are less tolerant of salinity and should be established in areas where salinity is lower, from fresh (0 ppt) to brackish (15-20 ppt) salinities.

Soil properties also determine whether tidal marsh vegetation becomes established or not. Nitrogen, in particular, limits growth of Spartina and other vegetation so N additions usually are needed to jumpstart the plant community. On sites that are planted, success is best achieved when N is added in slow-release form directly into the planting hole. Sufficient phosphorus (P) is brought in by tidal inundation so that P additions usually are not necessary.

Wetlands created on upland or terrestrial soils pose significant problems. Grading the site to intertidal

Upland MarshSoil Spoil

Figure 4 Tidal marsh restoration on (a) dredge spoil and (b) graded upland soil, (c) the redge spoil marsh, and (d) the graded upland marsh 7 years after restoration.

Figure 4 Tidal marsh restoration on (a) dredge spoil and (b) graded upland soil, (c) the redge spoil marsh, and (d) the graded upland marsh 7 years after restoration.

elevations exposes subsurface soils (Figure 4b) with high bulk density that impedes rooting. Subsoils also contain essentially no organic matter and N. In some situations, grading exposes acid sulfate soils (Table 1 ) with low pH (2-3) and high ferrous iron (Fe2+) concentrations that kill vegetation. In addition to N, establishment of vegetation on graded upland soils requires additions of lime to raise the pH and P to counteract the high Fe content that immobilizes P. Because of the problems involved with creating wetlands on upland soils, emphasis today is on restoring degraded wetlands back to health rather than creating entirely new ones. Other advantages of restoring tidal wetlands, rather than creating entirely new ones, is that restored sites contained wetland vegetation and soils in the past so the restoration effort begins with soils that contain some relic organic matter, N and, possibly, viable seeds.

On sites such as dredge spoil, where no vegetation existed and no seed bank is present, vegetation needs to be planted. Similar to dune vegetation, marsh and mangrove vegetation should be planted early in the growing season, before soil temperatures get too high. Seeding or sowing rhizome fragments usually is ineffective because tidal inundation disperses the seeds and fragments from the site. This is especially problematic on sites with a long fetch that enables large wind-generated waves whose energy translates onto the site and may uproot even planted vegetation (Table 1). Herbivory by geese, nutria (Myocastor coypus), and muskrats (Ondatra zybethicus) that graze on aboveground biomass also may hinder establishment of vegetation in tidal wetlands.

Restoration and Ecosystem Development

Large-scale efforts to restore tidal wetlands began in the last century as marsh and mangrove vegetation was planted throughout the world to control coastal erosion and reclaim land. Documented accounts of large (9000 ha) mangrove plantings date from the late 1800s. Cordgrass, Spartina townsendii, was transplanted extensively in Europe in the 1920s and 1930s to slow coastal erosion, reduce channel siltation, and to reclaim land for agriculture. From the 1930s to the 1960s, S. townsendii and smooth cordgrass, Spartina alterniflora, were planted in Australia, New Zealand, the United States, and China for the same reasons.

One of the first systematic efforts to create and restore tidal wetlands was initiated by the United States Army Corps of Engineers (COE) in the 1960s and it was focused on creating salt marshes using dredged material. The COE began planting smooth cordgrass on material dredged from navigable waterways to stabilize dredged material by establishing vegetation (Figure 4c). The technique proved successful and, in the 1970s, S. alterni-flora was successfully used to stabilize eroding estuarine shorelines. In the 1980s, salt and brackish water were created and restored to mitigate or replace wetlands lost to mineral extraction, highway and pipeline construction, dredging activities, oil spills, and coastal development (Figure 4d). Most of these wetlands were created using dredged material or graded upland sites or by restoring hydrology to diked marshes. Restoration usually involves removing dikes, levees, or tide gates to restore tidal inundation to promote growth of marsh vegetation and initiate wetland soil formation. In the northeastern US, restoration frequently involves removing tidal gates that were installed, in some cases 100 years ago, to exclude tidal inundation and reduce flooding of coastal communities. Once the tide gates are removed, tidal inundation and salinity are reintroduced and S. alterniflora gradually replaced freshwater wetland vegetation.

Successful restoration of hydroperiod and vegetation does not ensure immediate recreation of wetland functions on the site though. Created and restored tidal wetlands are young relative to older, mature, wetlands and some time must pass before ecological functions such as productivity, biogeochemical cycles, and habitat develop to levels found in older natural wetlands. Many wetland functions depend on establishment of a productive plant community with good spatial coverage. Emergent vegetation is important for dissipating energy from waves and for stabilizing sediments, and good coverage usually develops within 3-5 years following planting (Table 2, Figures 5a and 5b). Woody vegetation such as mangroves takes longer to form good coverage. Also, mangroves are susceptible to attack by fungal pathogens and the isopod, Sphaeroma, which may slow the restoration effort.

Table 2 Estimated rate of development of wetland-dependent functions following saltwater marsh creation

Time required to achieve equivalence to natural marshes

Hydrologie functions

Energy dissipation

1-3 years

Sediment stabilization

3-5 years

Biogeoehemieal functions

Sediment, P retention

1-3 years

Carbon, N sequestration

3-5 years

Microbial processes

5-15 years

Soil formation

10'sto 100's of years

Ecological functions

Primary production

3-5 years

Secondary production

Benthic invertebrates

10-20 years

Finfish, shellfish

2-15 years

Waterfowl and wading birds

1-3 years

Songbirds

10-15 years

Spartina Alterniflora Loisel
Year after establishment

Figure 5 Development of above- and belowground biomass stocks over time on a constructed Spartina alterniflora marsh in North Carolina (USA). Reprinted from Craft C, Reader J, Sacco JN, and Broome SW (1999) Twenty-five years of ecosystem development of constructed Spartina alterniflora (Loisel) marshes. Ecological Applications 9: 1405-1419, with permission from the Ecological Society of America.

Year after establishment

Figure 5 Development of above- and belowground biomass stocks over time on a constructed Spartina alterniflora marsh in North Carolina (USA). Reprinted from Craft C, Reader J, Sacco JN, and Broome SW (1999) Twenty-five years of ecosystem development of constructed Spartina alterniflora (Loisel) marshes. Ecological Applications 9: 1405-1419, with permission from the Ecological Society of America.

Biogeochemical functions such as sediment deposition, carbon sequestration, N and P accumulation in soil, and microbial N fixation also develop within 3-5 years. Heterotrophic microbial processes (decomposition, methanogenesis, and denitrification) and soil invertebrates are strongly linked to soil organic matter so sufficient organic matter must accumulate to support these processes, usually about 5-15 years (Table 2). Soil formation takes longer to develop, on the order of tens to hundreds of years.

Animal use of created and restored wetlands depends on their ability to disperse to and colonize the site. Invertebrates with planktonic (free-swimming) larvae readily disperse to the site whereas invertebrates that lack planktonic larvae take much longer to colonize. Oligochaetes, a major component of the salt marsh benthic invertebrate community, lack planktonic larvae and several decades elapsed before these organisms colonize the site. Fish and birds readily use created and restored wetlands once hydrology is restored and vegetation covers the site (Table 2). Fish use is enhanced by maximizing the amount of edge between vegetation and open water. Waterfowl use of created and restored wetlands is enhanced by increasing the proportion of open water, up to about 50% of the area. Songbird use increases with amount of woody shrubs which takes longer to develop than herbaceous vegetation.

Ecosystem development of tidal wetlands is accelerated by addition of fertilizer N and seasoned organic matter that jumpstart plant growth and heterotrophic activity. Amending soils with organic matter, however, is costly and time consuming and generally is not employed for most projects.

In recent years, large-scale restoration of tidal marshes has been undertaken for mitigation of natural resource damages. In Delaware Bay (USA), Public Service Electric and Gas developed a large-scale estuarine enhancement project to mitigate for loss of finfish caused by entrain-ment in power plant cooling water. As part of the enhancement effort, tidal inundation was restored to 1800 ha of diked salt hay (Spartina patens) marsh to create new habitat to enhance fisheries production in the estuary.

In the Mississippi River delta (USA), tidal wetlands are restored to combat wetland loss attributed to natural subsidence and anthropogenic factors that exacerbate it. Enacted by the US Congress in 1990, the Coastal Wetland Planning, Protection, and Restoration Act (CWPPRA) was designed to protect, restore, and create tidal wetlands by freshwater and sediment diversion from the Mississippi River and by beneficial use of dredged material. CWPPRA spends about 40 million USD annually to support wetland restoration in the delta. In 1997, a long-term plan, Coast 2050, was developed to combat wetland loss in the region. The goal of Coast 2050, which has yet to be implemented, is to restore more than 10 000 km2 of coastal wetlands over the next 50 years, with a price tag of 14 billion USD.

See also: Dunes; Mangrove Wetlands; Wetland Models. Further Reading

Broome SW (1988) Tidal salt marsh restoration. Aquatic Botany 32: 1-22.

Craft C, Reader J, Sacco JN, and Broome SW (1999) Twenty-five years of ecosystem development of constructed Spartina alterniflora (Loisel) marshes. Ecological Applications 9: 1405-1419. Craft CB, Megonigal JP, Broome SW, et al. (2003) The pace of ecosystem development of constructed Spartina alterniflora marshes. Ecological Applications 13: 1417-1432. Houston JA, Edmonson SE, and Rooney PJ (eds.) (2001) Coastal Dune Management: Shared Experience of European Conservation Practice. Liverpool, UK: Liverpool University Press.

Kaly UL and Jones GP (1998) Mangrove restoration: A potential tool for coastal management in tropical developing countries. Ambio 27: 656-661.

Leatherman SP (1982) Barrier Island Handbook. College Park, MD: University of Maryland.

Lewis RR (1982) Creation and Restoration of Coastal Plant Communities. Boca Raton, FL: CRC Press.

Minello TJ and Webb JW, Jr. (1997) Use of natural and created Spartina alterniflora salt marshes by fishery species and other aquatic fauna in Galveston Bay, Texas, USA. Marine Ecology - Progress Series 151: 165-179.

Mitsch WJ and Gosselink JG (2000) Wetlands. New York: Wiley.

Roze F and Lemauviel S (2004) Sand dune restoration in North Brittany, France: A 10-year monitoring study. Restoration Ecology 12: 29-35.

Thayer GW (ed.) (1992) Restoring the Nation's Marine Environments. College Park, MD: Maryland Sea Grant.

Van der Muelen F, Junerius PD, and Visser JH (eds.) (1980) Perspectives in Coastal Dune Management. The Hague: SPB Academic Publishing.

Weinstein MP and Kreeger DA (eds.) (2000) Concepts and

Controversies in Tidal Marsh Ecology. Dordrecht: Kluwer Academic Publishers.

Woodhouse WW, Jr. (1978) Dune Building and Stabilization with Vegetation. Special Report 3. Fort Belvoir, Virginia: US Army Corps of Engineers, Coastal Engineering Research Center.

Zedler JB (ed.) (2001) Handbook for Restoring Tidal Wetlands. Boca Raton, FL: CRC Press.

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Renewable Energy 101

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