Difference between revisions of "Riparian corridors in the California Central Coast Region"

Revision as of 16:14, 25 March 2014

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

Summary

A riparian zone or riparian area is the ecological interface between land and a stream or river. Riparian areas are significant in ecology, environmental management and civil engineering due to their influence on biodiversity, soil conservation and ecological aquatic processes. Riparian zones dissipate stream energy and facilitate the meandering curves of a river. These curves trap sediment, which builds river banks, replenishes soil, filters pollutants from runoff and reduces turbidity, erosion and flood damage. In addition riparian areas provide native landscape irrigation by extending seasonal or perennial flows of water. Nutrients from terrestrial vegetation (e.g. plant litter and insect drop) is transferred to aquatic food web. The vegetation surrounding the stream helps to shade the water, mitigating water temperature changes and also contributes wood debris to streams which is important to geomorphology. Riparian habitats support a large number of species when compared to other landscapes. They are often utilized by wildlife for movement, and buffered stream zones have been documented to facilitate dispersal of animals. Designating protected buffer zones around streams and rivers is an important tool toward preserving connectivity in a region, particularly in a fragmented landscape.

A wildlife corridor or habitat corridor is a generally defined as a relatively narrow area/strip of land that acts as a link between larger habitat areas that have been fragmented by human activity. The linkage between larger habitat areas allows for an exchange of individuals between populations and thus increases the opportunity for gene flow between the habitats and improves biodiversity. Corridors may also help facilitate colonization and migration to habitats that have recently experienced disturbance events. Although corridors have been implemented with the assumption that they will increase biodiversity, not enough research has been done to come to a definitive conclusion. The case for corridors has been built more on intuition and much less on empirical evidence (Tewksbury et al. 2002). In addition corridors are species specific, not every kind of animal will utilize every kind of corridor, and a corridor for one species could act as a barrier for another species.

Corridors can also be quite costly to develop and implement. For example, Daniel Simberloff et al. states that “a bridge that would maintain a riparian corridor costs about 13 times as much per lane-mile as would a road that would sever the corridor.” Corridors are also more costly to maintain than simple ecological refuges as it would be logistically easier and more cost effective to manually transport animals between different refuges than to buy land, install a corridor and keep it properly maintained.However, if the goal is to protect biodiversity among all plants and animals, and not to just preserve a few large species, then habitat corridors may be the only option. Corridors are going to be expensive to implement no matter what, but it does depend on the type, location, and size, which can all vary to a great degree. With the lack of field data on the effectiveness, many management agencies are tentative to turn to wildlife corridors as the 'solution' to their ecological 'issues'.

The main issue in the Central California Coast region is that increasing human development is reducing the occurrence of natural Riparian Zone, which threatens the impedes the overall utility of the watershed and its various ecological processes.

Location

Riparian corridors occur most watersheds to some degree, but is particularly interesting when it occurs in fragmented landscapes. It is an especially important in California's Central Coast Region due to the topography and the mixed land uses in the area. The Coastal Mountain Ranges of Santa Cruz Mts. to the north, and the Santa Lucia range to the south, are separated from each other and the Gabilan range to the east by Salinas Valley. Maintaining connectivity between the those ranges is seen as an important conservation measure for wide ranging species such as mountain lions, especially for the Santa Cruz Mts. population, as it is believed the area is too small to support a viable population. 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 agriculture, 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
  • Primary resource at stake is biodiversity, but other benefits from buffering riparian zones exist:
    • Streamside vegetation slows the runoff into waterways, and increases the infiltration of water by soil.
    • Vegetation also serves to significantly reduce contamination of waterways by chemical pollutants in runoff water.[1]
    • Floodplain forests and riparian wetlands minimize the effects of floods by storing the flood water.
    • Streamside vegetation stabilizes stream banks and beds, as well as traps and filters pollutants and sediments entering the waterways.
    • Riparian vegetation also serves as a water temperature regulator by shading the stream surface.
• Private land use
  • Agricultural land....<Need more text here>
  • Residential land...<Need more text here>

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[2]
• U.S. Forest Service[3]
• National Parks Service[4]
• California State Parks[5]
• Conservation agencies such as The Nature Conservancy[6]
• Agricultural interest groups such as the California Farm Bureau[7].

Laws, policies, & regulations

California Assembly Bill No. 2785 [8](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.

Science

• 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.

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.

Future research

• It is difficult to conclude from the few studies on the subject whether all riparian habitats facilitate connectivity.
• 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.

References

• 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._orig=search&_sort=d&view=c&_acct=C000059570&_version=1&_urlVersion=0&_userid=521395&md5=61517c180a6a26f587c2bc95590bc89e
• 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 th evalue and protection of parks and equivalent areas. In national parks and protected areas, ed Wright RG, pages 173-197. Cambridge, England: Blackwell Science.
• Hilty JA, Marenelender AM. 2004. Use of riparian corridors and vineyards by mammalian predators in northern California. Conservation Biology 18:126-135.[9]
• Simberloff, D., Farr, J.A., Cox, J., Mehlman, D.W. 1992. Movement Corridors: Conservation Bargains or Poor Investments?. Conservation Biology, 6 (4):492-504.
• Tewksbury, J.J., Levey, D.J., Haddad, N.M., Sargent, S., Orrock, J.L., Weldon, A., Danielson, B.J., Brinkerhoff, J., Damschen, E.I., Townsend, P. 2002. Corridors Affect Plants, Animals, and Their Interactions in Fragmented Landscapes. Ecology, 99 (20):1223-1226.
• 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. [10]

Links

• Other Watershed Issues

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.