California Coastal Commission

PROCEDURAL GUIDANCE FOR THE REVIEW OF WETLAND PROJECTS IN CALIFORNIA'S COASTAL ZONE

I. Introduction:

Wetlands are a significant natural resource within the United States. Only since the late 1960's, however, have wetlands engaged the attention of individuals from a range of disciplines who endeavor to understand their variety and complexity (Williams, 1991). Recent but intense interest in wetlands is due largely to their nature and our changing perceptions of them. We have come to understand how important wetlands are to the existence of numerous plants and animals, as well as the many functions they perform that are important to our quality of life and very existence. Indeed, the scarcity, complexity, and intrinsic value of wetlands has engendered substantial concern and sustained interest.

This chapter presents a review of scientific and technical information relevant to understanding the priority wetland resource concerns for California. Three features of wetlands are discussed: 1) ecology; 2) functions and values; and (3) sources of impacts. A basic understanding of each feature is essential for the intelligent management of this valuable resource. This chapter focuses on those types of wetlands occurring in the California coastal zone. It is not intended to present an exhaustive review, but rather to give the reader a basic level of understanding and a sense of the information available. The subjects covered here are complex and the information base is rapidly expanding. The reader is encouraged to consult the referenced literature for additional information.

II. The Ecology Of Wetlands In Brief:

Wetlands are a transitional landscape occurring within a continuum that begins in aquatic habitats and ends in dry upland habitats. Because of their intermediate location, wetlands contain characteristics of both aquatic and terrestrial environments: they are an ecotone. Thus, a variety of physicochemical processes such as topography, hydrology, sediment dynamics, and water chemistry interact to form the environment that largely determines the flora and fauna found within a wetland. Additionally, biological interactions continually act to further shape the wetland community. In this section some of the major physical (topography and hydrology), chemical (water quality), and biological components affecting the ecology of California's coastal wetlands are described.

A. Topography:

On a geological time scale California's coastal wetlands are relatively recent landscape features resulting from the complex interaction of geological processes and changes in sea level (Bloom, 1983a,b). These geological processes, driven by plate tectonics, resulted in a coastline characterized by a sharp, steeply inclined coast of uplifted marine terraces into which narrow river valleys were cut during the Pleistocene glacial epoch (Bloom, 1983a,b). Coastal wetlands were created during the last 15,000 years when the rapid rise in sea level and the end of the last ice age inundated coastal river valleys resulting in the formation of bays, estuaries, lagoons, and salt marshes³² (Bloom, 1983a,b; Orme, 1991). As a result, the majority of California's coastal wetlands are geographically isolated landscape features and relatively small when compared to the extensive wetlands present in other parts of the United States (NOAA, 1990).

California, however, does have the most extensive wetlands of any west coast state excluding Alaska (NOAA, 1990). Its 110 major coastal wetlands (see Figure 7) represent a diversity of habitat types, ranging from the generally undeveloped estuaries and marshes that border tidal-flushed river mouths in the north, to the highly urbanized saline lagoons, embayments, and salt marshes in the south. This diversity of wetlands is principally due to California's position at the edge of a dynamic continental land mass, where sea level and land elevation are in flux.

FIGURE 7—Map of Major California Coastal Wetlands

Coastal wetlands in the northern region of the State (Del Norte and Humboldt counties) are of four general types: 1) riparian areas surrounding rivers, streams, and other water bodies; 2) relatively isolated fresh- and brackish-water lagoons; 3) estuarine river mouths; and 4) protected bays or coves with little estuarine area. Wetlands in this region have been subjected to relatively little human development, which can have significant impacts on the topography of this landscape.

Some of the State's largest wetlands occur in the central region of California, which extends from Cape Mendocino to Point Conception. Excluding the San Francisco Estuary, many of the wetlands in this region have been subjected to limited human disturbance (with some notable exceptions). Numerous small coastal wetlands, usually at the terminus of coastal streams exist in this region. Freshwater lakes also exist in the coastal zone of several central California counties. Mendocino County contains California's only coastal fen, a relict of the ice age. Vernal pools exist in the coastal terraces of Monterey, San Luis Obispo and Santa Barbara Counties.

The San Francisco Estuary, which includes the San Francisco Bay, the Suisun Marsh, and the Sacramento-San Joaquin Delta, is the largest estuary on the west coast of North and South America (Meiorin, et. al., 1991). Wetlands and related habitats comprise some of the most valuable natural resources of this estuary, but also some of the most adversely affected natural resources. A recent comprehensive study found that only 19% ((44,400 acres) of the original tidal marshes remain in this estuary (Meiorin, et. al., 1991)³³.

At one time, extensive wetland areas occurred in Southern California (Point Conception to Mexico), but only 25% of the total ((13,100 acres) is thought to remain (Septh, 1969a,b). The remaining wetlands are relatively small and discrete, confined by narrow river valleys, and separated by coastal hills and mountains (Zedler, 1982) (Figure 8). Most commonly, wetlands in this region occur along the fringe of bays, as lagoons, river mouth marshes, and salt marshes. Generally, the marshes occur on intertidal slopes or the tops of creek banks that quickly grade from mean sea level to extreme high water (Zedler, 1982). Many of the wetlands in Southern California exist under very disturbed conditions often surrounded by extensive urban development (Zedler, 1982). The primary value of southern California's coastal wetlands is habitat and its role in maintaining biodiversity (Zedler, 1991)

FIGURE 8—Location Map of Southern California Coastal Wetlands and Major Rivers

For California then, large scale evolutionary processes have acted to produce a highly variable coastal zone with numerous relatively isolated and unique wetland landscapes. Humans have also significantly impacted these wetlands resulting in further alterations of the topography as well as the overall ecology.

B. Hydrology:

The hydrology of coastal wetlands is made complex by their location at the interface between terrestrial and marine environments (Orme, 1991). Tides, waves, currents, river discharge, and ground-water seepage are all important, but temporally and spatially variable components of coastal wetland hydrology (Orme, 1991). Yet even with this complex and variable hydrology, coastal wetlands are unified as a system by low gradients, low wave energy, fine-grain sediments and pervasive saltwater influences (Orme, 1991). In California, many coastal wetlands are marine dominated during much of the year, becoming dominated by terrestrial freshwater sources primarily during rainy periods (Josselyn, 1983; Zedler, 1982). In addition, these systems are directly affected by the multi-year drought/flooding events (as is much of California). Thus, for much of the year tidal processes drive coastal wetland hydrology, although seasonally and/or locally important freshwater inputs do occur.

As might be expected, hydrodynamic processes affect many of the environmental and biological processes within wetlands. For example, wetland hydrology affects both the location and rate of sedimentation and erosion, as well as the distribution and concentration of important chemical constituents such as dissolved oxygen, nutrients, and salt (Orme, 1991). In Southern California, tidal processes are extremely important in structuring the salt marsh communities. Sea water provides most of the soil moisture for these intertidal wetlands because of the low precipitation, the limited freshwater runoff, and frequent droughts (Zedler, 1982). The variable tidal regime present in California (i.e., a mixed semidiurnal tidal regime), and the semiarid climate that dominates southern California result in an extremely broad range of wetland soil salinity and long periods of hypersalinity (Zedler, 1982). Soil salinity, in turn, directly affects the distribution of plants within the wetland (Zedler, 1982). In contrast, hydrodynamic processes are affected by the presence or absence of vegetation. Wetland plants such as Spartina foliosa reduce current velocities, dampen waves, discourage erosion, and promote sediment deposition (Orme, 1991).

From this brief discussion it is clear that California's coastal wetlands are strongly affected by hydrologic processes, which are highly variable and complex. Thus, although many wetlands may appear to be in equilibrium with their environment, that equilibrium is neither static nor predictable (Orme, 1991).

C. Water Quality:

Interest in wetland water quality has intensified recently, because of the ability of wetlands to enhance water quality. Through a variety of processes, wetlands are able to remove sediments and both organic and inorganic pollutants from the overlying water (Chan, et al., 1981; Duda, 1992; Sather and Smith, 1984). In addition, however, several water quality constituents have a direct impact on the ecology of coastal wetlands, the most significant of which is probably salt concentration.

Ocean water is the principal source of salts in coastal wetlands, and source inputs are continually renewed by tidal flows. Thus, the tides are not only responsible for physical processes (i.e., hydrology), but chemical processes as well. Through its influence on soil salinity, water salinity has a direct affect on the distribution and abundance of wetland vegetation (Mall, 1969). In southern California where hypersaline soils occur, wetland flora is limited and highly stressed: up to 17 species of halophytes (mostly succulents) are common, and all respond to decreased salinity by becoming taller and more dense (Zedler, 1982). Patterns in primary productivity also show strong correlation with soil salinity (Zedler, 1982). Although the suite of plant species differs among California's coastal wetlands, there is little doubt that salinity is a major limiting factor to vascular plant growth (Josselyn, 1983; Zedler, 1982).

Water turbidity is another water quality constituent that directly affects wetland ecology. Turbidity is caused by the suspension of inorganic sediments and particulate organic matter (POM) derived from sources inside (autochthonous) or outside (allochthonous) the wetland. Autochthonous materials are generated biogenically or chemically, originating either from the accumulation of plant and animal detritus or from the in situ precipitation of evaporate deposits from brines (Orme, 1991). In coastal wetlands, tide and wind resuspension of accumulated sediments are also major causes of turbidity (Orme, 1991) Allochthonous materials arrive via wind, or in suspension with freshwater inflows and tidal waters (Orme, 1991). In California, freshwater inflows can be a major source of suspended material, but are spatially and temporally variable because of the geographical and seasonal variability in precipitation.

Although turbidity directly affects both wetland plants and animals, the impact is mainly confined to the subtidal portion of wetlands. For plants, turbidity affects light penetration, and thus is one factor controlling the lower limit of plant establishment and overall production (Josselyn, 1983). In the intertidal zone, however, turbidity is probably not limiting to plant establishment and growth because these areas are exposed a portion of each day. In the intertidal zone, other factors such as plant shading, desiccation, and temperature increase in importance (Zedler, et al., 1992). For animals, turbidity impacts the effectiveness of visual predators, such as birds and mammals, and the feeding ability of benthic filter feeding organisms (Dickert, et al., 1978; Josselyn, 1983; Nichols and Pamatmat, 1988). Overall, turbidity has limited but important impacts on the distribution of plants and the foraging of some animals.

Nutrients are also water quality constituents of critical importance to the existence of wetland organisms. Nutrients are continually required by all living organisms for growth and reproduction. Although a variety of nutrients are required by plants and animals, most studies focus on the availability of inorganic nitrogen because this constituent is considered most limiting to plants³⁴. Plants, in turn, are the major source of nutrients for animals.

As with turbidity, both allochthonous and autochthonous sources of nutrients are available to wetland organisms. The wetland landscape is an open system with an ongoing exchange of materials among deepwater habitats, uplands, and the atmosphere. The majority of California's coastal wetlands have connections with both the ocean and one or more sources of freshwater. Allochthonous nutrient sources include freshwater inflows and tidal flows, while autochthonous sources include nitrogen fixation, remineraliztion, and animal excretions (Nixon, 1980).

Nutrient dynamics within wetlands are very complex. Both nutrient availability and requirements vary through time and space. Thus, few accurate generalizations regarding nutrient patterns exist. It does appear that coastal wetlands vary in their needs for nitrogen. For example, results from Winfield's (1980) study of the Tijuana Estuary indicate that while both nitrate and nitrite were exported from the estuary in small amounts, overall there was a net import of inorganic nitrogen. Ammonium was usually the most prevalent form of inorganic nitrogen found during the study, with higher concentrations measured on a seasonal basis during the winter and spring, and on a daily basis during flood tide. Thus, while it is clear that nutrients are important to wetlands, much more information is needed (particularly for California's coastal wetlands) before we fully understand the dynamic processes of nutrient sources and sinks.

In summary, like topography and hydrology, water quality also has a direct role in the ecology of wetlands. Evidence to date shows salinity is probably the most important water quality constituent in coastal wetlands, although pollutants, turbidity, nutrients, and a variety of other constituents can also be very important at certain times and locations.

D. Biological Interactions:

The diversity and abundance of organisms in coastal wetlands is remarkable, given the often extreme and variable conditions that can occur. Bacteria, protozoa, algae, vascular plants, invertebrates, amphibians, fish, birds, and mammals can all be found within the wetland, and together comprise the biotic community of the wetland. Many of these organisms are completely dependent on the wetland for their existence, either spending their entire lives in the wetland, or spending a critical portion of their life cycle in the wetland. Still other species receive direct benefit from wetlands but are not dependent upon wetlands for their existence.

The interactions among these organisms are obviously complex and numerous, but basically occur in response to environmental tolerances and resource requirements. For example, vascular plants show strong patterns of distribution within a wetland that are related to their tolerance of specific environmental conditions, such as salinity, soil type, and hydrology, and the competitive interactions that occur among species for limited resources such as recruitment space, nutrients, and light³⁵. The same is generally true for animals, but their mobility affords them the flexibility to seek out more suitable habitat. Additionally, animals consume plants and other animals adding another dimension of interaction, namely predator–prey relationships, which can alter the distribution and abundance patterns of both the predator and the prey25.

Another way to characterize biological interactions is on the basis of energy flow. With the exception of plants, which use sun light as their energy source, all organisms found in wetlands consume plants or animals to meet their energy requirements. This energy in turn, is used by the organism for growth and reproduction.

Diagrams of a food chain or food web (many food chains) are used to conceptualize the flow of energy within an ecosystem. Figure 9 shows a diagram of one such food chain. In general, plants (vascular plants and algae) are termed primary producers and are at the base of the food chain. The next level up the food chain is occupied by herbivores followed by omnivores and carnivores. Energy is lost to respiration at every level of the food chain; thus an enormous amount of plant material is required to provide the energy necessary for the existence of top predators such as carnivorous birds and mammals. Although food chains can be very complex, they do provide a relatively simple way to conceptualize biological interactions. The food chains within many California coastal wetlands are thought to be relatively short (Zedler, 1982). Nonetheless, the wetland food web is complex because of the extensive overlap and shear number of food chains that exist. In general, our knowledge of how food chains are modified as wetland habitat diminishes is not extensive; however, there is little doubt that the native food web is essential to the maintenance of community structure (National Research Council, 1992).

FIGURE 9—Diagram of a Wetland Food Chain

Although a multitude of concepts, principles, and methodologies exist to assist in understanding the biology and ecology of wetlands, our level of knowledge is still relatively rudimentary. This is particularly true for California's wetlands, where ecosystem research lags behind that of Atlantic and Gulf coast efforts by several decades (Williams and Zedler, 1992). We now know that the environment of Pacific coast wetlands differs in fundamental ways (e.g., topography, geology, hydrology, climate, and species composition) from wetlands in other parts of the nation. Thus, information from Atlantic or Gulf coast wetlands does not necessarily apply to Pacific coast wetlands. Additionally, it is difficult to transfer information between coasts on processes such as primary productivity and nutrient cycling because the functions driving these processes are site specific; however, the effects of habitat loss and reduced biodiversity are universal (Williams, et al., 1992). Nevertheless, the task of developing the technical information base necessary for the wise and successful management of California's coastal wetlands is critical.

III. Understanding the Functions and Values of Coastal Wetlands:

Assessing the functions and values of wetlands depends on, and is limited by, information from three fields: science, economics, and politics (Scodari, 1990). For example, scientists have determined that wetlands serve (i.e., function) as critical habitat for a number of threatened and endangered species, while State and federal legislation affords such species higher levels of protection, and therefore increased value. However, because of their limited numbers, threatened and endangered species often contribute little net value to the wetland on an ecological (scientific) or economic basis.

As the above example illustrates, the functions and values of wetlands are often interconnected. In general, wetland functions are those attributes that directly or indirectly benefit humans and other organisms, or provide values perceived by humans as desirable or worthy of protection. However, there is limited agreement on the importance of any one function or value. As Dennis and Marcus (1984) note "[p]resent day land owners, developers, regulatory agencies, and scientists in California are not in agreement on the value of wetlands. A landowner or developer may see a wetland only as flat, developable real estate, made more valuable by its proximity to a waterfront. Traditionally, communities have viewed wetlands as convenient dumping grounds. Engineers acknowledge the functional uses of wetlands for floodwater regulation or shoreline protection... Scientists and educators place a high value on the biological productivity and wildlife habitat of wetlands. A hunter appreciates wetlands for the waterfowl they support, while a farmer may regard a wetland as unproductive unless drained and cultivated."

All of the known functions and values of coastal wetlands are a manifestation of one or more of the physical, chemical, or biological processes inherent to this environment. However, wetland assessments based on functions and values are problematic due to the lack of rigorous and objective assessment criteria. Recent attempts have used economic principles to develop monetary valuations (Allen et al., 1992; Scodari, 1992). Although this is a valid approach, it does not include estimates of intrinsic qualities such as natural beauty, fascination, and peace of mind. Nevertheless, such assessments are important because many of the regulatory decisions regarding wetlands are ultimately decided on the relative importance of these attributes, or the cost to replace them.

Overall, California coastal wetlands have a number of important functions and values³⁶ (Table 3). Although knowledge of most functions and values has existed for some time, their combined importance has increased over time because of the enormous wetland losses California has endured. Thus, the reduction in wetland acreage and function has increased the overall value of this resource regardless of the value of specific attributes (Allen, et al., 1992).

Table 3. KEY FUNCTIONS AND VALUES OF CALIFORNIA'S COASTAL WETLANDS³⁷

IV. Factors Impacting California's Coastal Wetlands:

The major impact suffered by California's wetlands is direct loss attributable to human activities (Dennis and Marcus, 1984). Total wetland loss in California is estimated at 4.6 million acres, which is approximately 91% of the acreage present before European settlement (Dahl, 1990). The majority of this loss (approximately 3.6 million acres) has occurred in the central valley (Dahl, 1990; Dennis and Marcus, 1984). All portions of the coast have suffered losses as well, the largest losses (on a percentage basis) are thought to have occurred in San Francisco Bay and along the south coast (Table 4).

Table 4. SUMMARY OF HISTORIC LOSSES OF CALIFORNIA COASTAL WETLANDS³⁸

A variety of activities are known to have caused the dramatic loss and alterations of wetlands in California. The major activities include:

• Agricultural use and development: This involves the conversion of wetlands to agricultural land. Typically, wetlands are diked or filled, or vegetation is removed in order to expand adjacent crop or grazing lands. Disturbance and degradation can also occur where cattle and other pasture animals are allowed to graze in wetlands, or where nonpoint-source runoff containing pesticides and fertilizers occurs. Agricultural activities are the primary cause of wetland loss in California (Dahl, 1990).

• Residential development: The development and subdivision of land for residential use has resulted in direct wetland loss through filling. Additionally, this development activity has substantially increased sediment discharge into wetlands, through the acceleration of soil erosion. This is especially true in southern California where extensive building has occurred on or near highly erodible soils (Zedler, 1982).

• Commercial and industrial development: Hotels, business parks, and industrial complexes within and adjacent to wetlands can include wetland fill and loss of habitat through encroachment. The release of toxic materials from these forms of development is also a source of wetland degradation.

• Oil and Gas development: Oil and gas wells and the supporting infrastructure have severely impacted several coastal wetlands in Southern California. The deposition of fill for roads and well pads and the unintentional release of pollutants from this form of development results in the fragmentation and degradation of wetland habitat.

• Roads highways and railways: The maintenance and development of transportation corridors has resulted in direct wetland loss through filling. Numerous wetlands have also suffered adverse impacts from the construction of bridges and polluted runoff from these structures.

• Port and marina development: This form of development includes dredging new and expanded channels to increase deepwater area, and the direct filling of wetlands to increase the area of shoreline support facilities.

• Flood control: Development in flood plains and adjacent to wetlands increases the susceptibility of these structures to flooding. Flood control projects result in the dredging, filling, and channelization of wetlands to prevent the natural dissipation of water into low-lying areas.

Many of these activities still occur in California (Dennis, et al., 1984). Yet because of the relatively high social value placed on coastal wetlands, this resource has received greater protection than their inland counterparts (Gosselink, et al., 1991). In California's coastal zone, the Coastal Act does allow certain types of development in wetlands (see chapters one and three), and these activities can result in the loss of wetland habitat. However, wetland alteration in many coastal states of the U.S. —including California— is strictly regulated and generally prohibited. Much of the current loss of wetlands in the coastal states is attributed to either a lingering legacy of past development (e.g., agricultural, urban, and industrial development) or related to secondary or indirect effects of current projects (e.g., point- and nonpoint-source pollution, or changes in the timing and amount of fresh and saltwater inputs) (Gosselink, et al., 1991).

V. Summary:

Wetland resource concerns for California span a variety of complex and sensitive issues. Of paramount concern is the extreme loss of wetlands California has endured, dramatically increasing the intrinsic value of the remaining resource. However, numerous other issues discussed in this chapter also affect the level and focus of concern for this resource. These issues, which are summarized below, generally fall into one of two categories: science and impacts.

1) Science:

• Large scale evolutionary processes have acted to produce a highly variable coastal zone with numerous, relatively isolated and unique wetland landscapes. This fact complicates preservation and restoration activities.

• Wetlands are ecologically complex regions.

• Sound scientific information on California coastal wetlands is lacking, limiting our understanding and predictive ability.

• Rigorous, objective methods to quantify wetland functions and values are generally lacking.

2) Impacts:

• · Human's are responsible for virtually all of the losses and impacts to California's wetlands.

  · Many of the remaining wetlands suffer from chronic disturbance and degradation.

Endnotes

³² For a more detailed discussion of the historical processes that formed California's coastal wetlands, the reader is encouraged to review: Josselyn, M. 1983. The ecology of San Francisco Bay tidal marshes: a community profile. U.S. Fish and Wildlife Service, Division of Biological Services, Washington, D.C. FWS/OBS-83/23. 102 pp.; and Zedler, J.B., C.S. Nordby, and B.E. Kus. 1992. The ecology of the Tijuana Estuary, California: a national estuarine research reserve. NOAA Office of Coastal Resource Management, Sanctuaries and Reserves Division, Washington D.C.; and references cited within.

³³The reader is encouraged to review the cited literature for additional information on the San Francisco Estuary.

³⁴More recently, this view has been challenged. For more information see Smith, S.V. 1984. Phosphorus versus nitrogen limitation in the marine environment. Limnol. Oceanogr. 29:1149–1159; and Howarth, R.W. and J.C. Cole. 1985. Molybdenum availability, nitrogen limitation, and phytoplankton growth in natural waters. Science 229:653–655.

³⁵For detailed examples from California's coastal wetlands see: Zedler, J.B. 1982. The ecology of southern California coastal salt marshes: a community profile. U.S. Fish and Wildlife Service, Biological Services Program, Washington D.C. FWS/OBS-81/54; and Josselyn, M. 1983. The ecology of San Francisco Bay tidal marshes: a community profile. U.S. Fish and Wildlife Service, Division of Biological Services, Washington D.C. FWS/OBS-83/23.

³⁶For a more detailed discussion of wetland functions and values the reader is encouraged to review: Sather, J.H. and R.D. Smith. 1994. An Overview of Major Wetland Functions and Values. U.S. Fish and Wildlife Service. FWS/OBS-84/18; and National Research Council. 1992. Restoration of Aquatic Ecosystems. National Academy Press, Washington D.C.

³⁷Sources: Scodari, 1990; National Research Council, 1992

³⁸Source: Dennis and Marcus, 1984.

³⁹Central Coast numbers exclude San Francisco Bay.

⁴⁰Estimates for S.F. Bay updated from: Meiorion, E.C., M.N. Josselyn, R. Crawford, J. Calloway, K. Miller, R. Pratt, T. Richardson, and R. Leidy. 1991. Status and trends report on wetlands and related habitats in the San Francisco estuary. San Francisco Estuary Project, Oakland, California.

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