Riparian corridors in the California Central Coast Region
Riparian corridors encompass both riparian zones and the adjacent terrestrial ecosystems that protect or influence the riparian zone.
A riparian zone  is a strip of land whose physical and biological character is overwhelmingly determined by its proximity to a body of running water. Riparian zones can exist along perennially and as well as seasonally flowing water-bodies.
Riparian corridors are important in California's Central Coast Region because they serve as wildlife corridors for local fauna, provide flood, erosion and temperature control, and help maintain water quality. The topography and the mixed land use in the region makes riparian corridors crucial for support surrounding ecosystems.
The main issue regarding riparian corridors in the Central California Coast region is that they are threatened by increasing human development which reduces the occurrence of natural riparian zones.
An example of a threatened riparian corridor of local importance is the Salinas river corridor in the Monterey Bay region. The Salinas Valley is a broad alluvial plain of intense agricultural activity defined by three distinct coastal ranges: the Santa Cruz Mountains to the north, the Gabilan Range to the east, and the Santa Lucia Range to the south. Maintaining connectivity between these ranges is seen as an important conservation measure for species with large territorial requirements. Because most land use is agricultural, there is little cover for animals to transverse across the valley, and traveling animals likely utilize waterway channels and riparian habitats.
In 2015, the Monterey County Planning Commission made amendments to the 2010 Monterey County General Plan to establish an ordinance requiring biological studies for developments near riparian corridors and wildlife linkages. A consulting group, Pathways for Wildlife, created a county-wide map of wildlife corridors and linkages (using these methods) to be used as the basis for the ordinance.
Biophysical and Socioeconomic Context
Riparian corridors generally exist as one component, with many features, in a complex landscape and influenced by human interactions with that landscape. Overall, they cannot be thought of in isolation from this landscape and influence; they are comprised of many components, which include:
- Biodiversity In theory, riparian corridors conserve biodiversity by ensuring that species have the ability to migrate, colonize, and interbreed. Migration refers to a species' seasonal movements. Riparian corridors connect habitat utilized by migratory species at different times of the year. Colonization refers to population establishment. Riparian corridors enable species to colonize new areas when local resources have been exhausted. Interbreeding refers to the exchange of genetic information between disparate individuals and populations. Riparian corridors conserve genetic diversity by maintaining access to a larger gene pool. There is a growing body of evidence that riparian corridors facilitate biodiversity .
- Streambank stability Plants found in floodplains thrive those conditions. This vegetation controls erosion and sediment deposits.
- Flood control Riparian vegetation slows the flow of water, allowing more water to percolate into groundwater aquifers and reduce flooding downstream.
- Temperature regulation Riparian corridors provide a buffer of vegetation in the riparian zone that provides shade and facilitates stable stream temperatures.
- Water quality
- Property value
Individuals and organizations that typically have a stake or interest in the management of riparian corridors in the Central Coast Region include:
- California Farm Bureau and Grower-Shipper Association. Many riparian corridors are located on private and/or agricultural land that have navigable waters running through them. Although the government has authority over, and the public has access to, all navigable waters in the state, owners of riparian-adjacent lands are often represented by the California Farm Bureau and/or the Grower-Shipper Association in management decisions.
- State Water Resources Control Board This state agency is concerned with water quality, point and non-point source pollution, of navigable waters in California.
- California Department of Fish and Wildlife (CDFW) and U.S. Forest Service (USFS) As national agencies, the USFS and CDFW are concerned with the management of endangered species, many of which reside in riparian corridors.
- National Park Service and California Department of Parks and Recreation Forest ecosystems in parks can be impacted by management decisions about riparian corridors on adjacent lands.
- Conservation agencies such as The Nature Conservancy
Laws, Policies, & Regulations
California Assembly Bill No. 2785 (approved by Gov. Schwarzenegger Sep 26, 2008) revises the Significant Natural Areas Program "to investigate, study, and identify those areas in the state that are most essential as wildlife corridors and habitat linkages and prioritize vegetative data development in those areas". The funds would be provided by the Wildlife Conservation Board from the monies made available by The Safe Drinking Water, Water Quality and Supply, Flood Control, River and Coastal protection Bond Act of 2006.
The Natural Community Conservation Planning (NCCP) Act of 1991 (AB 2172) provides for multi-species habitat conservation planning (MSHCP), which is recognized as an effective way to preserve the species while minimizing economic disruptions. Several MSHCP’s have been developed in California, with the cooperation of developers, federal and state agencies, and local communities. Different habitats including riparian zones and species can be protected under MSHCPs.
Recent food safety recommendations for agriculture in the Salinas Valley identified riparian habitat as food safety hazards. Vegetable retailers have pressured shippers and processors, which in turn have pressured farm operations to remove riparian vegetation in order to continue contracts. In addition, the practice of installing deer fences has greatly increased along the Salinas river and other areas bordering habitat due to food safety concerns.
The issue deals with the hydrological system, and the riparian ecosystem surrounding it. Specifically it deals with aquatic and terrestrial biota. Ecological sytems on the landscape level are at stake here, as large traveling predators often greatly effect populations of other species.
- Hilty and Merenlender (2004) found that mammalian predators in northern California were 11 times more likely to be found in riparian habitats then in the upland vineyards.
- Crome et al. (1994) demonstrated riparian habitats harbor more bird species then human planted windbreaks.
- Harris et al. (1996) showed that buffered zones around streams facilitate movements of animals such as black bears and forest dependent birds.
- Gennet et al. (2013)  illuminated the elimination of 13.3% of remaining riparian habitat in the Salinas Valley in the name of food safety following and outbreak of E. coli linked to the most productive crop in the region. The study argued that if similar practices were carried out throughout the state, as much as 40% of riparian habitat and 45% of wetlands could be impacted.
It is difficult to conclude from the few studies completed whether all riparian habitats facilitate connectivity. Some suggested topics for future study of riparian corridors include:
- A M.S. thesis on wildlife presence/absence across different habitats/landscapes in the Salinas Valley would shed a light on the degree of connectivity local waterways provide.
- A thorough monitoring program of the California Central Coast waterways would give a good understanding of which characteristics of riparian zones and surrounding landscapes facilitate connectivity. There is a growing concern about maintaining connectivity between the Santa Lucia range and the Gabilan Range across the Salinas valley. It is very likely that waterways are being utilized by wide ranging species to cross the Salinas valley, but there is no documentation to support this theory. Automatic photo-monitoring could establish frequency of use of corridors by different animals. A useful thesis would be an economic cost-feasibility study of different methods to establish connectivity, and easements or lands that might be available for such a purpose.
Several different models are used in establishing corridors and determining connectivity: least cost path modeling, individual based movement models, graph theory, spatially explicit population models, circuit theory, and network flow models.
- USDA Forest Service. Appendix I - Delineation of Riparian Areas, Riparian Corridors and Stream Types
- Wikipedia article on riparian zones http://en.wikipedia.org/wiki/Riparian_zone
- Article on the Watsonville plain http://www.eoearth.org/view/article/157021/
- Peer-reviewed article on corridors http://www.sciencemag.org/content/313/5791/1284.short
- FEMA. 1996. Protecting floodplain resources: a guidebook for communities.
- Sweeny BW, Newbold JD. 2014. Streamside forest buffer width needed to protect stream water quality, habitat, and organisms: a literature review. Journal of the American Water Resources Association 50(3): 560-584.
- Hilty JA, Marenelender AM. 2004. Use of riparian corridors and vineyards by mammalian predators in northern California. Conservation Biology 18:126-135.
- Crome F, Isaacs J, Moore L. 1994. The utility to birds and mammals of remnant riparian vegetation and associated windbreaks in the tropical Quennsland uplands. Pacific Conservation Biology 1:328-343.
- Harris LD, Hoctor T, Maehr D, Sanderson J. 1996. The role of networks and corridors in enhancing the value and protection of parks and equivalent areas. In national parks and protected areas, ed Wright RG, pages 173-197. Cambridge, England: Blackwell Science.
- Gennet S, Howard J, Langholz J, Andrews K, Reynolds MD, Morrison SA. 2013. Farm practices for food safety: an emerging threat to floodplain and riparian systems. Frontiers in Ecology and the Environment 11(5): 236-242.
- Cramer PC, and Portier KM. 1994. Modeling Florida panther movements in response to human attributes of the landscape and ecological settings. Ecological Modeling 140:51-80.
- Simberloff, D., Farr, J.A., Cox, J., Mehlman, D.W. 1992. Movement Corridors: Conservation Bargains or Poor Investments?. Conservation Biology, 6 (4):492-504.
- Thorne JH, Cameron D, Quinn JF. 2006. A conservation design for the central coast of california and evaluation of Mountain Lions as umbrealla species. Natural Areas Journal 26:137-148.
- Steelhead Management in the Monterey Bay Region
- The Carmel River Watershed
- Carmel River Floodplain Restoration and Environmental Enhancement (Carmel River FREE) Project
- Watershed Issues on the Central Coast of California
- Carmel Watershed Issues
- Other Watershed Issues
This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.