Riparian corridors in the California Central Coast Region

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A watershed-related issue examined by the ENVS 560/L Watershed Systems class at CSUMB.


Summary

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 maintain water quality. The topography and the mixed land use in the region makes riparian corridors crucial for support surrounding ecosystems.

A riparian zone [1] 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 perrenially and as well as seasonally flowing water-bodies. A wildlife corridor [2] or habitat corridor is generally defined as a relatively narrow strip of land that acts as a link between larger habitat areas that have otherwise been fragmented by human activity.

The main issue regarding riparian corridors in the Central California Coast region is the increase of human development reducing the occurrence of natural riparian zones that threatens and impedes the overall utility of the watershed and its various ecological processes.

Location

Monterey Bay is hemmed 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. These ranges are separated from one another by the broad alluvial plain of the Salinas Valley [3], an area of intense agricultural activity. Maintaining connectivity between these ranges is seen as an important conservation measure for species with large territorial requirements. The Santa Cruz Mountains, for example, are believed to be too small to support a viable population of mountain lions. Corridors connecting those ranges have been identified, but no studies have been done to prove or disprove their utility. In Salinas Valley, where most land use is agricultural, there is little cover for animals to transverse across the valley, and waterway channels and riparian habitats are likely being utilized by traveling animals.

Resources at stake

Ecological and geomorphological

  • 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 [4].
  • Streambank stability
  • Flood control
  • Temperature regulation

Agricultural and Residential

  • Water quality
  • Property value

Stakeholders

In the central coast region stakeholders include:

  • Private and public land owners whose lands border or contain riparian habitats
  • U.S. Fish and Wildlife service[1]
  • U.S. Forest Service[2]
  • National Parks Service[3]
  • California State Parks[4]
  • Conservation agencies such as The Nature Conservancy[5]
  • Agricultural interest groups such as the California Farm Bureau[6].

Laws, policies, & regulations

California Assembly Bill No. 2785 [7](approved by Gov. 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 moneys 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.

Systems

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.

Research

To Date

  • 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.

Future

It is difficult to conclude from the few studies completed whether all riparian habitats facilitate connectivity. Future studies needed on raparian corridors include:

  • A MS 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.

Tools

Several different models are used in establishing corridors and determining connectivity. Those are least cost path modeling, individual based movement models, graph theory, spatially explicit population models, circuit theory, and network flow models.

References

  1. ↑ Article on riparian zones http://en.wikipedia.org/wiki/Riparian_zone
  2. ↑ Article on wildlife corridors http://en.wikipedia.org/wiki/Wildlife_corridor
  3. ↑ Article on the Watsonville plain http://www.eoearth.org/view/article/157021/
  4. ↑ Peer-reviewed article on corridors http://www.sciencemag.org/content/313/5791/1284.short


Links

Disclaimer

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.

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