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1For a complete characterization of the meaning of the term bioregion, see M.V. McGinnis. Bioregionalism (New York and London: Routledge, 1999).2http://www.ceres.ca.gov/ocean/geo_area/bioregions/bioregion_index.html.

Southern California is considered a distinct bioregion1 of California that extends from Point Conception (in Santa Barbara County) to Punta Banda, south of Ensenada,

Baja Mexico. The bioregion is part of the marine-coastal interface of the Southern California Bight, a recognized ecosystem that includes the Channel Islands and the Santa Barbara Channel2. This bioregion extends inland to encompass the coastal wetlands and watersheds of southern California.The Bight’s embayments, marshes and estuaries are among the most densely populated and productive habitats on the Pacific coast. Within the coastal zone of the Bight, over 60 species of fishes are known to frequent bays and estuaries while no less than 195 species of birds have been identified (Dailey et al. 1993).Coastal wetlands are transitional ecosystems that are influenced and affected by dynamic ecological connections and linkages between watersheds, coastal and marine systems. Wetlands are constantly changing in response to the relationship that exists between terrestrial and aquatic ecosystems. For example, the daily intrusion of tidal water is an essential component of the fragile coastal salt marsh community. Tidal currents shape the wetland’s channels and the shoreline, and bring in sea water that is needed to maintain the function and structure of wetland habitat. Sediments and nutrients that were received from the rivers, creeks and streams are carried out to sea by the tide. These nutrients are also important for the nearshore marine system. During the summer months, sand bars may form berms that close wetlands to these tidal influences.Tidal circulation is important to the biodiversity that is associated with marsh habitats. Coastal wetlands are nursery areas for juvenile fish, such as halibut. Many of these fish species are of commercial and recreational value. Other animals, such as the endangered Light-footed Clapper Rail, depend on healthy marsh habitats for nesting while sea birds such as the California Brown Pelican use lagoons and river mouths as roosting areas. se

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Existing and Historical Conditions in Coastal Wetlands and Coastal

Watersheds of the South Coast

Michael Vincent McGinnis, Christina McGinnis and William Groves

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3For a general profile and characterization of southern California’s wetlands, see Wayne R. Ferren, Jr. Peggy L. Fiedler, Robert A. Leidy, Kevin D. Lafferty, and Leal A. K. Mertes. Madroño: The West American Journal of Botany. 105-233 and J.B. Zedler. 1982. The ecology of southern California coastal salt marshes: a community profile. US Fish and Wildlife Service. Biological Services Program. Washington, D.C. FWS/OBS-81/54.

Migrating birds also use south coast wetlands. For example, the Artic Tern travels thousands of miles to nest in the Bolsa Chica wetlands. Rare and colorful songbirds migrate from the south to nesting areas, such as Goleta Slough. In addition to the importance of the tidal influence, coastal watersheds and their run-off patterns, hydrological and sedimentation cycles affect wetland habitats and biodiversity. Streams and creeks contribute important nutrients needed for healthy wetlands. The remnants of riparian woodland and forest habitats along Santa Clara and Santa Margarita Rivers support many rare bird species. The riparian habitats within these two watersheds remain one of the last refuges for the endangered Least Bell’s vireo. Waterfowl depend on the riparian habitats that may exist upriver or along a creek’s bank. Foothill riparian and canyon woodland are dominated by Back Cottonwoods, Western Sycamores, Coastal Live Oaks and willows. Rare woodland and riparian forests exist in a few creeks that flow onto the coastal plain between Goleta and the Ventura County line, the Santa Monica Mountains, and the southern part of coastal Orange County. A number of species of concern depend on these riparian forests and canyon woodland areas.During the last 150 years, coastal wetlands and watersheds have been dramatically altered or destroyed by human activities. Most of the riparian areas of the coastal rivers and streams of the region have been lost. Rivers have been rerouted and dammed. Creeks have been paved and channelized. Wetlands have been filled. Important fresh-water and salt water inputs to coastal wetlands have been altered. Few estuaries are open to the necessary tidal influence. The overall general health and integrity of the region’s watersheds and wetland habitats has declined.One sign of this decline is plight of the southern steelhead trout. The number of southern steelhead has been reduced to about 200 to 300 (Pacific Marine Fisheries Council 2000) in the region. In addition, a significant decline in the abundance of several species of fishes, shorebirds, seabirds, kelp habitats, plankton, and the supply of food produced in the Southern California Bight has occurred since 1950 (McGowan et al. 1998). In the US, California ranks second in the number of aquatic species that are endangered (Allendorf 1982).The decline in healthy aquatic ecosystems in southern California is a result of both human activity (such as suburban sprawl) and natural events (such as changing oceanographic patterns and increasing sea surface temperatures). The south coast has been subjected to intense coastal development pressures. In addition, natural threats, such as erosion, subsid-ence, sea level rise, droughts, and El Niño/La Niña events can significantly change watersheds and wetlands.This chapter provides a general overview of the ecology of coastal wet-lands, and describes the relationship between climate, hydrology, geology, and topography that shape coastal wetlands. Next, the interconnected-ness and active relationship between watersheds, coastal wetlands, and marine systems is described. The historic and current extent of wetlands within each of the SCWRP subregions is included, along with an overview of human threats and impacts on these watersheds and wetlands. The chapter concludes with a brief summary of subregional conditions for San Diego County, Southern Orange County, the Los Angeles Basin, Ventura County Basin, and Southern Santa Barbara County.

Introduction3

Prior to the 1800’s, southern California contained rivers with wide, unobstructed floodplains that were fed by numerous tributaries and creeks. These rivers flowed freely to the sea. A total of twenty-eight estuaries and wetlands occurred along the south coast in 1850 prior to development (Office of Technology Assessment [OTA] 1982). These wetlands were discontinuous in distribution. The size and character of the wetland was a product of its particular hydrologic regime, degree of protection, and location on the south coast.The appearance of wetlands along the Pacific coastline coincided with sea level rise following the last ice age. About 18,000 years ago, sea level was some 400 feet

lower than current conditions, and the shoreline lay miles to the west. Over thousands of years, rivers and creeks cut canyons and hollowed wide valleys. These “drowned” valleys became the bays and lagoons of today. Eventually, sea level rise slowed enough to equal the geologic uplift of the continent. The shoreline took on a contour similar to that existing today. Landward, sediment flowing down creeks slowly created mudflats and marshes communities.Historically, all of the river systems in southern California had large estuaries at their mouths, such as the Tijuana River, San Diego River, Santa Ana River, San Gabriel River, Los Angeles River, and the Santa Clara River. These systems contained an “ecological staircase” that was composed of salt marsh habitat that transitioned from brackish to freshwater to riparian habitat. Riparian vegetation consisting of cottonwood, alder, willow and freshwater marsh species lined most of the coastal rivers and creeks. The width of riparian vegetation was a reflection of the summer water levels of the watercourse rather than flood flows (Zedler 1982). The wide floodplains of rivers held relatively narrow strips of riparian vegetation and woodland.This rich landscape mosaic of marsh and riparian habitats existed for thousands of years. These coastal wetlands remained in a dynamic equilibrium between terrestrial and marine influences. Several diverse indigenous tribes lived along the coast. Excavation of middens (garbage heaps) from areas they occupied

included numerous shells of estuarine mussels and clams. Since these animals only occur in tidal embayments, they indicate that several lagoons were fully tidal systems prior to European settlement. In addition, a series of vernal pools were found in scattered locations throughout the region. Today, vernal pools are found only in San Diego and Santa Barbara Counties.Each wetland system has suffered some level of degradation from urbanization and land-use development. Rapid population growth in the Santa Barbara, Los Angeles, and Ventura Counties began in the early 1900’s, and Orange and San Diego Counties followed in the 1940s and 1950s. Along with this rapid growth came many alterations to the delicate and fragile ecological relationships that shape coastal wetland processes, structures and functions.

The Physical LandscapeClimate, Hydrology, Geology and Topography

Coastal wetlands in the region vary widely depending on the climate, topographic set-ting, hydrologic regime, and geologic substrate. The effects of climate and topography have contributed to the historic erosion patterns of the region, which in turn have

Historical Conditions

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helped form the region’s wetlands. Each wetland has a unique evolutionary character.Overall, southern California’s coastal wetlands are small and discrete (Zedler 1982). The wetlands are confined to narrow river valleys, and are separated by coastal hills and mountains. The marshes within these wetlands are not identical to one another – they should be considered unique ecosystems because of their distinct physiographic settings and ecological characteristics (Ferren et al. 1996).The transitional character of coastal southern California creates many contrasts that affect wetlands. In particular, wetlands are shaped by climate, elevation, location, chem-icals within habitats (salt, alkali, sulfur, petroleum), geologic, oceanic, and terrestrial processes, intermittent and perennial water bodies, organisms, land use practices (current and historic), natural and artificial landforms, and habitat quality.

Climate

Southern California is noted for its mild temperatures, short wet winters, and long dry summers characteristic of a Medi-terranean climate. California has a greater climatic diversity than any other state, and its vegetational diversity is reflective of this varied climate. Although in many regions, latitude is a major factor in determining climate, the physiography of the south coast is the major determinant of climate. The region includes various types of both Mediterranean and desert climates. Important climatic variants that affect the development of wetland types include:

• Mediterranean warm (hot) summer -- found in the interior foothills of southern California

• Mediterranean cool (warm) summer -- characterizes the high elevations in the mountains and the maritime regions immediately along the coast

• Mediterranean cool (warm) summer with fog -- distinguished from the others by the presence of dense fog for more than 30 days of the year.

Mean annual air temperatures are similar from north (Santa Barbara County) to south (San Diego County). They vary only from 17.8º C in Los Angeles to 15ºC and 16.7º C in Santa Barbara and San Diego, respectively (Dailey et al. 1993). Temperatures throughout the area are generally mild due to the proximity of the Pacific Ocean. Most precipitation falls during the 6-month winter period, and is produced mostly by frontal systems transiting the area. Little rainfall occurs from May to October (see Hydrology section below for precipitation estimates).Natural weather fluctuations caused by La Niña and El Niño conditions also affect the region’s precipitation (see Hydrology section below for a more detailed discussion of El Niño/La Niña).

parallels the coastline from Santa Barbara to Ventura. The San Gabriel Range forms the dominant backdrop on the north side of the Los Angeles Basin.The Transverse Ranges geomorphic province is characterized by east-west trending faulting and folding and geomorphic features (mountain ranges and valleys). Tertiary marine and non-marine sedimentary rocks are exposed in the western Transverse Ranges, including the Santa Ynez Mountains. Teritiary volcanic rocks, Mesozoic meta-morphic rocks, and Tertiary sedimentary rocks are exposed in the Santa Monica Moun-tains. Precambrian to Mesozoic age granitic rocks overlain by metamorphic rocks are

exposed in the San Gabriel and San Bernardino Mountains of the eastern Transverse Ranges.The coastal portion of the Peninsular Ranges, which form the northern end of the long peninsula known as Baja California, includes the Los Angeles Basin. From north to south, along the main ridge of the Peninsular Ranges, are the San Jacinto Mountains, Santa Rosa Mountains, and Laguna Mountains. These mountains are separated from the Santa Ana Range, to the west, by a broad plain that includes the Hemet and Elsinore valleys. The Santa Ana Range is located between Orange and Riverside counties. The Los Angeles Basin is considered part of the Peninsular Range Province, although the basin itself is a lowland filled with sediments which were deposited by runoff from the Transverse and Peninsular Ranges.The Peninsular Ranges are characterized by northwest-southeast trending faulting and folding and geomorphic features (mountain ranges and val-leys). The granitic rocks of the Southern California Batholith form the core of the Peninsular Ranges and are exposed in the inland areas. Mesozoic and Tertiary sedimentary rocks outcrop along the coastal areas of Los Angeles, Orange, and San Diego Counties to the west of the Southern California Batholith.The shoreline features of the Transverse and Peninsular Ranges include rocky headlands and cliffs where the hills and mountain ranges approach the coastline, and sandy beaches and sand dune fields where valleys or basins

such as the Oxnard Plain and Los Angeles Basin intersect the coastline. In some areas, marine terraces have been formed by sea cliff erosion. In some areas, including the San Onofre and Oceanside, the Palos Verdes Peninsula and the southern flank of the Santa Ynez Mountains, uplift of the shoreline has elevated these wave-cut benches into a series of terraces.Coastal estuaries form at the mouths of the rivers and major streams of the Tranverse and Peninsular Ranges. Where rivers and streams empty into the ocean within valleys or basins, sloughs and marsh areas are formed. In the coastal hills of the Peninsular Ranges of San Diego County, lagoons have formed where stream valleys have been submerged by rise in sea level since the Pleistocene. The various cliffs are broken by river mouths, which are usually blocked by a sand bar or spit during the summer months.

Hydrology

Rainfall amounts vary slightly from the northern portion of the region (Santa Barbara County) to the southernmost portion (San Diego County). Rainfall amounts for the southern portion of the region (San Diego County) aver-age about 8-10 inches, occurring mostly from November through March. Evaporation exceeds rainfall throughout most of the year in this area. The regional climate is classified as semiarid Mediterranean. In the central and northern portions of the region (LA/Ventura County and northern Santa Barbara County), average annual precipita-tion is from 11 to 13 inches, with slightly higher amounts falling in mountainous and vegetated areas, such as the Santa Monica Mountains. Most precipitation falls during the 6-month winter period, and is produced mostly by frontal systems transiting the area. Little rainfall occurs from May to October.

Geology and Topography

Several topographic and geologic features make the southern California region unique. The shape of California’s coastline is a product of geologic activity and erosion. Coastal mountain ranges include two geomorphic provinces, the Transverse Ranges (so named because unlike most mountain ranges along the Pacific coast of North America they trend east-west as opposed to north-south) and the Peninsular Ranges (so named because this province includes the Baja California peninsula). These ranges form a natural “amphitheater” to the coastline, and provide a unique setting for watersheds and wetlands.The Transverse Ranges form the northern border of the Los Angeles Basin. Active faults separate the ranges. From east to west, the prominent ranges visible from the Los Angeles Basin are the Santa Monica, San Gabriel, and San Bernadino mountains. Another prominent feature of the south coast landscape is the Santa Ynez Range, which

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Floods and drought cycles occur regularly in the southern California area, and are influenced by La Niña versus El Niño events, which occur on a cyclic basis. El Niño events are characterized by a large scale weakening of the trade winds and warming of the surface layers in the eastern and central equatorial Pacific Ocean. El Niño events occur irregularly at intervals of 2-7 years, although the average is about once every 3-4 years. They typically last 12-18 months, and create a large amount of rainfall that enters watersheds and associated wetlands. During El Niño, unusually high atmospheric sea level pressures develop in the western tropical Pacific and Indian Ocean regions, and unusually low sea level pressures develop in the southeastern tropical Pacific. Conversely, unusually low pressures west of the date line and high pressures east of the date line have also been linked to periods of anomalously cold equatorial Pacific sea surface temperatures (SSTs) sometimes referred to as La Niña, which typically produces less rainfall in a given year.

The Biological Landscape -- Wetlands of the Region

Wetlands are transitional lands between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is often covered by shallow water during some parts of the year. Wetlands can be categorized according to specific habitat and type of vegetation. Wetlands in southern California occur in various ecosystem contexts (e.g., lagoons, rivers, lakes, ponds), but have origins related to the region’s major physical processes. There are numerous methods for classifying wetlands. The following broad categories cover the four main types of wetlands found in the region.

• Tidal wetlands• Riparian wetlands• Freshwater marshes (seasonal and perennial)• Vernal pools

Tidal Wetlands

Most of California’s coastal wetlands are estuarine salt marshes with associ-ated tidal channels and mudflats. An estuary is a semi-enclosed body of water that receives both fresh water and seawater and includes the bays, lagoons, rivers and creek mouths of the coast. Along the shores of these estuaries are salt and brackish (somewhat salty) marshes, mudflats, and tidal channels. Marshes usually begin at the mean lower high tide level, and are covered by the highest tide of the day. Tidal flats are intermediate between the open water of bay or lagoon or surrounding marshes. They extend down from mean lower high water to extreme low water and are submerged and exposed twice a day.The size of tidal wetlands is dependent on a number of factors, including topography, geology, and hydrology. As described above (see historical conditions), the size and productivity of tidal wetlands has been drastically reduced in the last 200 years or so. The large estuaries that formerly received flows from both the ocean and the upper water shed have been gradually reduced in both health and size due to habitat destruction and urbanization. The remaining large river systems that remain relatively unobstructed in the region include the Santa Margarita and Santa Clara Rivers, although issues such as sedimentation, urbanization, and pollution have also affected the health of these rivers and their associated wetlands. Tidal wetlands are highly impacted by sediment flows because small changes in marsh topography can have large impacts on marsh habitats. The following descriptions of estuary and vernal pool types are after Ferren, et al. (1996):Canyon Mouth Estuaries. Emergent portions of the southern California coastline are characterized by a series of incised, parallel canyons, arroyos or barrancas, and valleys that drain watersheds in mountain, foothill, coastal plain, and coastal mesa landscapes. These various “canyons” empty into the ocean through small estuaries that is quite

variable in size, frequency of tidal flushing, salinity regimes, and biota. Arroyo Burro Estuary in Santa Barbara County is one type of canyon-mouth estuary with mixohaline water because of perennial runoff.Lagoonal Estuaries. Lagoonal estuaries are primarily found in San Diego County in wetlands where river mouths are closed by sand bars most of the year. Lagoonal estuaries are generally characterized by brackish fringe-marshes rather than vegetated flats, often have salinities that can approach those of fresh water, and support fauna typical of brackish to fresh water conditions. Buena Vista Lagoon is a lagoonal estuary in an urban setting.Coastal Dune-Creek Estuaries. Although they are often similar in size to canyon mouth estuaries and with seasonal sand bar impoundments, coastal dune estuaries are characterized by having a perennial source of fresh water from adjacent dunes, and are generally slightly brackish most of the year.Bay Estuaries. Bay estuaries contain large areas of subtidal habitat (bays) and low

elevation salt marsh on the bay margins. Bolsa Chica, Anaheim Bay, Upper Newport Bay, Mission Bay, Kendall-Frost Reserve, and San Diego Bay are examples of bay estuaries. There is a strong marine influence in bay estuar-ies because there is: (1) a consistently open and generally wide mouth; (2) a large body of marine water that floods wetland habitats; and (3) the low elevation of adjacent marshes that results in diurnal (twice daily) tidal flooding of these marshes.Structural Basin Estuaries. In subregions characterized by considerable tectonic activity such as coastal Santa Barbara County, down-faulted and down-folded geologic structures may support estuaries of moderate size (200-300 ac). Structural basin estuaries are found along the south side of the Santa Ynez Mountains, such Goleta

Slough or in down-folded (synclinal) basins, such as Carpinteria Salt Marsh. These structural basins have steep but short watersheds rising to approximately 1130 m (3500 ft) in elevation, and are characterized by occasional catastrophic flooding and sedimentation, particularly from large storms that may occur after chaparral fires in the adjacent foothills and mountains.Artificial Drain Estuaries. Agricultural and urban drains along the south coast may form small, narrow estuaries. Some of these exist in the form of small wetlands on sandy beaches at the mouths of culverts and storm drains. Others reach the coast as canals and have tidal channels with fringe marshes on their margins. Many urban drains are the downstream limit of coastal streams that have their headwaters in the adjacent mountains beyond the urban boundary. Depending on the type of agricultural or urban runoff, these small estuaries may be extremely polluted. Some estuaries are characterized by a combination of features from different estuary types. The Tijuana Estuary occurs at the mouth of the Tijuana River and is a bay-type estuary. Unlike various other river-mouth estuaries (e.g., Ventura and Santa Clara rivers), the estuary is influenced more by the extent of deepwater habitats, adjacent low marshes and flats, and oceanic water than by the runoff of the river, except during catastophic flooding events.

Riparian Wetlands

Riparian wetlands are dependent on a healthy floodplain and a regime of periodic flooding and regrowth. They form as a result of fluvial processes in floodplains and along river and stream corridors. There are a number of watersheds associated with river systems in the region that support many types of riparian wetlands. Urban developments are located along river and stream corridors and flood plains. In the urban environment, several river and stream corridors have been channelized and rerouted, such as the San Diego River, which has been rerouted twice in the past 100 years. Without input from a floodplain that contributes freshwater and nutrients,

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