How Do We Assess Wetland Health?
Measurement of overall health of wetlands has long been an elusive goal for scientists and wetland managers. Methods of analysis were often restricted to individual agencies or organizations for limited purposes. The ability to compare conditions between places and programs was missing, and so we could not measure or understand trends at the watershed, regional and state level.
Today, we are moving to overcome this by standardization of wetland assessments. One way to measure the overall health of streams in California is to perform assessments using the California Rapid Assessment Method (CRAM). CRAM is a field-based diagnostic tool that, when used as directed, provides rapid, repeatable, and numeric assessment of the overall condition of a wetland.
CRAM assesses four overarching attributes of wetland condition: Buffer and Landscape Context, Hydrologic Regime, Physical Structure, and Biotic Structure. Each attribute is related to several attribute-specific metrics and submetrics that are evaluated in the field for a prescribed assessment area. The attribute scores are averaged to produce an overall index score. Attribute and index scores range from 25 (lowest possible) to a maximum of 100. In the context of CRAM, condition is evaluated based on observations made at the time of the assessment. Higher scores represent better condition and suggest a higher potential to provide the functions and services expected for the wetland site being assessed.
Preliminary studies using CRAM have found that an estimated 60% of the state's remaining riverine wetlands habitat is in "good" or "very good" health. In 2007, 85% of the 44,000 acres of remaining salt marsh in California were found to be in "good" or "very good" condition. Human impacts to salt marshes increase moving from north to south along the coast because of increased urbanization, and as a result, salt marsh health is highest in the north and lowest in the south. Efforts are currently underway to recover many of the State's previously damaged wetlands e (e.g. South Bay Salt Ponds, Malibu Lagoon, etc.), but much more work remains.
The data displayed here represent many wetlands studies around the state including the State of the State's Wetlands, the Perennial Streams Assessment of the Surface Water Ambient Monitoring Program (SWAMP) program. Use of CRAM to get a holistic assessment of wetland condition, in conjunction with probabilistic survey designs allows for a broader perspective on wetland condition. Although rapid methods like CRAM provide a cost-effective means for basic assessment of overall wetland health, they are just one element of a comprehensive regional monitoring plan. In most cases, CRAM will need to be used in conjunction with more intensive methods, rather than as a stand-alone tool, to support management decisions.