9.8 BIOLOGICAL RESOURCES
INTRODUCTION
The purpose of this profile report is to summarize available current information on the known biological resources of Sutter County, and to present an evaluation of those resources. This report is not intended to be a list of all plant and animal species occurring in Sutter County, but rather a document to alert the County to unique and valuable areas of biodiversity and habitat value within Sutter County. This is a planning tool. As such a tool, it should not be a static document, but should be periodically updated. Environmental circumstances change rapidly, and this profile represents a snap shot in time of current conditions in Sutter County.
BRIEF HISTORICAL OVERVIEW OF SUTTER COUNTY BIOLOGY
Sutter County, in the flat southern Sacramento Valley, sits on alluvial plain soils deposited by the Sacramento, Feather, and Bear Rivers. Originally, the fertility of these soils was renewed annually with naturally occurring winter floods. Immense wetlands supported vast numbers of waterfowl and other wildlife. A well-known outstanding geologic (and biological) feature of Sutter County is the Sutter Buttes, a system of mountains in the middle of the valley floor that were created by volcanic activity over a million-year-long period starting 2 _ million years ago (Hausback and Nilsen, 1991).
Prior to the arrival of European peoples, Sutter County supported abundant waterfowl, wetland and grassland natural resources. Around 1832, trapping parties arrived to hunt local furbearing species and elk herds. These trappers brought diseases that greatly reduced the local Native American populations.
John Sutter's arrival in 1839 marked the first use of agriculture in Sutter County. He began to graze sheep on the Buttes. This new land use, which continues to the present day, changed the annual plant composition of the Buttes. Sutter and his contemporaries introduced the use of fire to clear valley and Butte areas to renew grazing and for agriculture.
The gold rush brought miners to work the gravels of the Feather River,
followed by a steady stream of cattle drivers, homesteaders and settlers
in the mid to late 1800s. Many of them stayed to cultivate the rich soils
of the valley in Sutter County, and to graze cattle on the grasslands.
The lower areas of the Buttes and its interior valleys became sparsely
inhabited by ranchers, although the interior wild uplands remained unclaimed
until the early 1900s. By 1930 the vast majority of Sutter County land
was under cultivation, most of the ranches on the Buttes were abandoned,
and the valleys of the Buttes were used only for grazing, as they are now,
primarily by cattle.
Currently, most of Sutter County is zoned for agriculture. Generally, agricultural uses effectively limit the natural biodiversity and restrict the value of existing wildlife habitat in any area. However, some agriculture is compatible with some wildlife use, and in fact may become vital to certain wildlife species which have suffered a loss of natural habitat.
Today, although the Valley is still the major wintering area for waterfowl of the Pacific Flyway (Perry 1983), most of the wetlands have been drained for agriculture, the rivers are controlled by dams and levees, and flood waters are channeled into the Sutter Bypass and other artificial waterways. The Buttes remain relatively the same, except for changes caused by livestock grazing. The remaining wildlife habitat in the County has become more necessary to maintaining wildlife populations at existing levels, as the loss of natural areas throughout California have left a small proportion of the original habitat intact.
STUDY ORGANIZATION AND CONTENTS (OVERVIEW)
This section summarizes information on known biological resources throughout Sutter County, as well as the relative biological value of those resources. The results of a literature review are first summarized, followed by a description of the vegetation/habitat associations, including sensitive natural communities of Sutter County and the wildlife associated with the communities. Information on the communities follows the classification system set up by California Department of Fish and Game (Holland, 1986) referred to hereafter as Holland Element Codes. A discussion of special status plant and animal species recorded in or with potential habitat in the County is presented within Tables 9.8-4 and 9.8-5, with specific habitat requirements and location information. A description of the various state and federal classifications that are included under special status species is presented within Table 9.8-3. Finally, an analysis of the sensitivity of the resources is explained. A summary map, Figure 9.8-1, identifies the location and sensitivity of Sutter County biological resources . A larger scale and more detailed map set was also prepared and is available for viewing in the Community Services Department. Also available at the Community Services Department is a set of 1993 California Natural Diversity Data Base (CNDDB) printouts for the County. This data base is maintained and updated by the California Department of Fish and Game Non-Game Natural Heritage Division to provide an inventory and locations of special status species in the state.
STUDY METHODOLOGY
Data Sources
Literature Review and Research
Background research was initiated by conducting a thorough review of the California Department of Fish and Game's Natural Diversity Data Base-RareFind computerized records (CNDDB) and California Native Plant Society (CNPS) publications (CNPS, in press). A list was compiled of special status plant and animal species and sensitive natural communities that have been recorded within Sutter County.
To supplement and expand this information, a review of the following environmental documents was made for information concerning biological resources within the County:
Public and Private Expert Consultation
Consultation with the California Department of Fish and Game (CDFG) Region 2 biologists in Rancho Cordova (Brode, Whitmore, Zezulak, 1993), the CDFG Non-Game Natural Heritage Division in Sacramento (Bittman, 1993), the National Marine Fisheries Service (Lagomarsino, 1993), and the U.S. Fish and Wildlife Service (USFWS) Endangered Species office in Sacramento (White, 1993) was made to obtain additional information on special status species with potential to occur in Sutter County. Local experts were consulted to obtain additional information on local occurrences of sensitive natural communities and special status species, including: local chapters of the Audubon Society (Peacemaker, Manolis, 1993); California Native Plant Society (Skinner, 1993); Sutter National Wildlife Refuge (Mensik, 1993); USFWS National Biological Survey (Miller, 1993); experts on the biology of the Sutter Buttes (Ahart, Anderson, Bills, Heinrich, 1993); and Yuba Community College (Williams, 1993). Through this consultation process, other areas of biological concern were identified, such as wintering waterfowl concentration areas and important fisheries areas.
Aerial Photograph Interpretation
Recent (1992) black-and-white aerial photographs of the entire study area (scale of 1:24,000 [1" = 2,000']) were examined. Based on the scale and quality of the photographs, a classification system was developed for natural communities (based primarily on Holland, 1986) and agricultural and other land uses (based primarily on Mayer and Laudenslayer, 1988) known to occur within Sutter County. These community types include riparian corridors, stream channels (natural and man-made), wetlands (including seasonal marshes and vernal pools), oak woodlands and chaparral, non-native grasslands, rice fields, orchards/vineyards, cropland, irrigated pasture lands, and developed areas. The aerial photographs of the County were photo-interpreted by qualified biologists to identify the geographical extent of each community type. Any areas not identifiable by the aerial photo examination were noted and targeted for later ground-truthing. During the aerial photo-interpretation task, an evaluation was made for the presence or the potential presence of special status plant and animal species known to occur in the region.
Ground-truthing Data (Field Work)
A targeted biological field reconnaissance (on January 13, 14, and 17, 1994) was conducted to assess the type, quality, distribution, and species' composition of existing plant communities by sampling representative areas. Specifically, the areas visited included the Sutter Buttes, Feather River, Sutter Bypass, borders of the Butte Sink, and areas not identifiable in the aerial photos. Existing plant communities were classified as closely as possible, following Holland (1986). Information obtained during the field reconnaissance was registered on the base photos as appropriate. Ground truthing in the field was brief and was conducted outside of the optimal survey period for the majority of special status species (e.g., performed outside of the flowering period of local special status plant species).
DATA SYNTHESIS, ANALYSIS, AND PRESENTATION
Mapping of Existing Data
Pertinent information gathered during ground truthing and expert consultation was mapped. Mapped data includes land use (on the General Land Use map on file with the County), known locations of sensitive natural communities, known records of special status species, and locations of other important biological resource locations.
Biological Resources Sensitivity Analysis and Mapping
Through combining all relevant special status species data and compiled plant community information, a simple three-tiered biological sensitivity classification system was developed for Sutter County lands: High Sensitivity; Moderate Sensitivity; and Low Sensitivity. The basis for ranking the sensitivity and relative importance of an area includes value of an existing resource (e.g., wildlife value of a natural community); legal federal or state status of the resource; location of the resource with respect to other sensitive resources; sensitivity or resiliency of the resource to withstand urban or agricultural development; potential to support special status species; and the potential for/feasibility of mitigation based on current knowledge and practice.
A County-wide Sensitive Biological Resources map was prepared using
the three-tiered system, at an approximate scale of 1 inch = 1 mile. A
reduced copy of this map is included at the end of this report, and the
full-sized map is on file with the County. In mapping biological sensitivities,
consideration was given to interactions between natural communities, including
the values of community complexes/mosaics for common and special status
wildlife species (e.g., foraging habitat adjacent to breeding areas). Explanatory
text is included in later sections of this report.
VEGETATION COMMUNITIES AND ASSOCIATED WILDLIFE
Introduction
Natural vegetation communities, especially riparian corridors and wetlands, provide the primary habitat for most native California special status species. Each natural habitat type in Sutter County, such as live oak woodland or freshwater marsh, has an associated set of plant and animal species that normally occur there. However, in the past 100 years of Central Valley history, these habitats have been drastically reduced by urban development, water projects, and agriculture (CDFG, 1991). When a natural habitat becomes altered, dependent species which are unable to move elsewhere or to adapt to converted areas, such as agricultural lands, decline in number. When this comes to the attention of CDFG, these species are designated as "special status" species, connoting that the species seems to be declining and may eventually require listing as threatened or endangered.
Rapid human population growth and associated development in California is continually shrinking natural habitat into smaller and more isolated "islands," a process known as biological fragmentation. As these islands of natural habitat diminish, some special status species are reduced to occupying only the edges between agricultural lands to survive. While agricultural lands do provide some of the required habitat elements for these species, they cannot provide all of them. For example, grain crops and grazed grassland provide foraging habitat, but not nesting habitat, for the state-listed Swainson's hawk.
The natural communities described in this section are mapped on the General Land Use map that is on file with Sutter County. Urban lands and other developed lands, while included on the General Land Use map, are not classified as vegetation communities. Urban land generally contains a greater amount of construction and paved areas than vegetation. The vegetation present is primarily composed of non-native plant species, including turf grasses, shrubs, and trees commonly used for landscaping. Urban lands provide relatively low habitat value for wildlife and are not discussed in further detail below.
Native and Naturalized Plant Communities of Sutter County
Riparian Corridors
Riparian corridors include primarily remnant forest and scrub communities in Sutter County that occur along the edges of streams and the Sacramento and Feather Rivers.The riparian forest communities generally occur outside of the most active (i.e., most often subject to erosion) portions of stream channels, with scrub communities growing closest to the stream. The riparian forest communities are classified as Great Valley Cottonwood Riparian Forest (Holland Element Code #61410), with examples along the Feather River, and Great Valley Mixed Riparian Forest (Holland Element Code #61420), with examples along the Feather River, particularly near the confluence of the Feather and Bear Rivers (Holland, 1986; California Natural Diversity Data Base (CNDDB), 1993). The dominant tree species found in the cottonwood riparian forest community include Fremont's cottonwood and Goodding's black willow, while the mixed riparian forest community is dominated by a greater variety of species including box elder, sycamore, walnut, Fremont's cottonwood, and several species of willow. Both types of riparian forest often support a lush understory of tree saplings, shrubs and vines such as Oregon ash, California button willow, California grape, blackberry, poison oak, and clematis. In more open portions of the forest, elderberry shrubs may occur.
The CNDDB contains no records of Great Valley Willow Scrub (Holland Element Code #63410), although communities fitting Holland's description are known to grow along streams within the Sutter Buttes area (Anderson, 1983) and likely occur elsewhere along the Sacramento, Feather, and Bear Rivers. Riparian scrub communities are generally dominated by several different willow species, mulefat, small cottonwood seedlings, and sometimes, grasses in the understory (Holland, 1986; Anderson, 1983).
Riparian areas provide some of the highest wildlife habitat value of any community type in Sutter County. Throughout the Central Valley, riparian corridors contrast with the surrounding dry, open grassland and agricultural habitats, providing a sheltered area for wildlife with an abundant food and water supply. Conversion of nearly 99 percent of pre-European settlement riparian habitats in California has severely limited the extent of these habitats (Faber and Holland, 1988). As a result, many riparian-dependent wildlife species that are unable to adapt to alternative habitats are now declining.
Riparian areas support seasonal foliage, emergent vegetation, and invertebrates that provide forage for a large number of migratory birds using the Pacific Flyway. The Central Valley portion of the Pacific Flyway supports the largest single concentration of wintering waterfowl in North America, approximately 20 percent (Heitmeyer, 1989). Riparian woodlands provide nesting and roosting sites for waterfowl, such as wood ducks, and courtship and pairing areas for mallards and wood ducks. Nesting riparian birds use these areas because of the diverse forage opportunities on foliage, bark, seeds, and insects. Amphibians, reptiles, and mammals also use riparian areas for water, forage, cover (from predators and for thermal relief), and corridors for movement through otherwise open areas.
Because of the loss of most of the riparian habitat in California, some mammals and waterfowl species have adapted to agricultural habitats. Wintering waterfowl, including mallards and other ducks, geese, swans, and cranes, are now highly dependent on harvested grain fields, foraging on waste grains in croplands during mid-winter and on invertebrates in remnant riparian areas, seasonally flooded marshes, and rice fields. Other agricultural fields, such as wheat, hay, and set-aside lands provide nesting sites for resident waterfowl species in the summer. Waterfowl and other wildlife use of agricultural communities is discussed further in this report.
Many special status species that are known to occur or have potential to occur in Sutter County are dependent on riparian habitat. Neo-tropical birds (species that migrate to Central and South America in winter) that may breed in riparian areas of Sutter County include willow flycatcher, yellow-billed cuckoo, yellow warbler, yellow-breasted chat, purple martin, bank swallow and Swainson's hawk. Resident bird species that breed and/or forage in this community include Cooper's hawk, sharp-shinned hawk, tricolored blackbird, great blue heron, long-eared owl, great egret, black-shouldered kite, bald eagle, black-crowned night heron, osprey, double-crested cormorant, and American white pelican. The ringtail is a special status mammal species known to occur in riparian areas of the County; the northwestern pond turtle and giant garter snake use the riparian habitats; and the valley elderberry longhorn beetle completes its entire life cycle in and on elderberry shrubs, which are frequently associated with open areas of riparian woodlands.
Natural Rivers or Stream Channels and Man-made Channels
Sutter County, located within the Sutter and Butte drainage basins, contains both natural and man-made waterways. Natural waterways include the Sacramento and Feather Rivers that define much of the County's boundary and smaller streams and sloughs that are most common in the northwest and southeast areas of the County. A Holland Element Code cannot be included for waterways themselves because aquatic communities are not included in Holland's classification system. The banks of some natural waterways support riparian communities, as described above, and others support marshy areas of emergent vegetation (Coastal and Valley Freshwater Marsh, Holland Element Code #52410). The dominant vegetation found in these emergent wetlands include cattail, tule bulrush, nutsedge, sedge, and arrowhead. Emergent wetlands provide valuable wildlife habitat distinct from the riparian forest. Mammals use emergent vegetation areas for cover and resting. The marshes also provide foraging and nesting habitat for birds.
Special status bird species that nest near freshwater marshes and stream channels in Sutter County include tricolored blackbird, northern harrier, snowy egret, and least bittern. Other special status birds forage in these areas, including short-eared owl, great blue heron, great egret, prairie falcon, California gull, greater sandhill crane, black-crowned night heron, and white-faced ibis. California tiger salamander, northwestern pond turtle, and giant garter snake are special status animals that may occur in stream channel and freshwater marsh habitats of Sutter County. Special status plants with potential to occur in freshwater marshes along stream channels include Ferris's milk-vetch, which has been recently rediscovered in the Butte Sink (CNPS, in press), rose mallow (California hibiscus), and trichocoronis. Palmate bird's beak is a special status plant that potentially occurs in alkaline emergent wetlands in Sutter County.
Man-made waterways in Sutter County convey irrigation water and provide drainage channels for the croplands. They form an extensive network throughout the County, much of which is relatively unvegetated, and provide low quality wildlife habitat. Some irrigation channels, however, support areas of vegetation similar to that found along the natural waterways, providing the same type of habitat for wildlife. These areas provide some of the most important remaining habitat in California for the state-listed giant garter snake. Recent surveys of the southern end of the County bordered by the Sacramento River, Natomas Cross Canal, and Natomas East Main Drainage Canal identified the presence of giant garter snake and its habitat within irrigation canals, ditches, and rice fields (Brode and Hansen, 1992). Previous surveys also identified giant garter snake habitat and potential habitat within the Butte Sink, East Butte Road north of Nuestro Road, Sutter Bypass, west of the Bypass north of Gilsizer Slough, and the area between the Sacramento River and the Sutter Bypass in the vicinity of Robbins (Beak Consultants, Inc., 1992; Hansen, 1988).
Off-channel Wetlands
This habitat category is similar to the emergent wetland described above, but these wetlands are relatively unconnected to a stream channel. Also known as seasonal wetlands, these areas include freshwater marsh, vernal swales, vernal seeps, and vernal pools. As with the stream channels, some of the seasonal wetlands in Sutter County are natural and others have been created by excavation for crop irrigation, livestock watering, or other purposes. Coastal and Valley Freshwater Marsh (Holland Element Code #52410) is recorded in the Butte Sink and Sutter Bypass (CNDDB, 1993) and generally resembles the marsh community described above in the preceding section, with similar dominant vegetation and special status species habitat.
The natural seasonal wetland communities in Sutter County also include vernal pools, specifically the Northern Hardpan Vernal Pool (Holland Element Code #44110). Vernal pools occur in small depressions within non-native grasslands, described below, and fill with water during winter rains, gradually drying as the rainy season ends. The CNDDB contains recorded occurrences of this community at the north end of the Sutter Bypass and along the northern side of the Sutter Buttes (CNDDB, 1993). The vernal pool community provides potential habitat for an assemblage of endemic plant and animal species. Waterfowl and shorebirds forage in vernal pools when water is present, and amphibians such as the California tiger salamander, a special status species, breed in vernal pools. Other wildlife such as rodents and rabbits may use the pools as temporary water sources. Vernal pool habitats may support one or more special status invertebrates (e.g., fairy shrimp), and special status plant species including dwarf downingia, Bogg's Lake hedge-hyssop, toad rush, valley meadowfoam, and trichocoronis.