Evaluation of CRAM performance for assessing wetland stress, small wetlands, and wetland habitat development
Caltrans funded this wetlands research to fill important gaps in knowledge about the ability of the California Rapid Assessment Method (CRAM) to assess small wetlands, wetlands stress, and the rate at which wetland restoration projects develop into mature habitats. Caltrans proposed specific tasks based on the research priorities provided by the CRAM Commitee of the statewide California Wetlands Monitoring Workgroup. This research focused on wetlands that exist in natural or manmade topographic depressions referred to as palustrine or depressional wetlands. To fill the knowledge gaps, SFEI developed and analyzed datasets for natural and restored depressional wetlands throughout California.
Task 1: CRAM Fieldwork 2015 to Support Tasks 2 & 3 (memo)
SFEI conducted this research using nearly 400 existing and new depressional wetland assessments from accross California collected between 2007 and 2015. During the spring and summer of 2015, SFEI conducted 83 new CRAM assessments that targeted different ages of wetlands or landscape settings to fill gaps in the existing dataset. Assessments were conducted across six ecoregions, including sites in central and northern California, as well as in the Sierra. The new assessments occurred in a variety of types of depressional wetlands, including stockponds, water management ponds (e.g. detention basins, reservoirs, pump station ponds), stormwater basins, and depressions created/managed for habitat (e.g. restoration or mitigation sites). The sites also covered a wide variety of landscape settings, including urban, sub-urban, industrial, parks, grazing lands, agricultural lands, and open space. Many sites were in mitigation banks, or other types of wetland projects that are managed for diverse habitat functions. The new assessments were added to the existing depressional dataset to support tasks 2 and 3. The depressional wetland condition data (CRAM data) are available online though EcoAtlas.
Task 2: Relationship between wetland size and CRAM scores for small depressional wetlands (memo)
Small depressional wetlands are often integral elements of Caltrans projects. These wetlands are expected to provide a variety of ecosystem services. However, one assumption of CRAM is that larger, more complex wetlands receive higher CRAM scores. Caltrans would like to know if even small depressional wetlands can be in good condition and provide the variety of ecosystem services, as reflected by high CRAM scores. This is the first study to investigate the relationship between wetland size and CRAM scores for any wetland type.
Task 3: Develop a depressional wetland habitat development curve (memo)
CRAM data from wetland restoration and mitigation projects have shown that the condition of projects improves with their age. Regulatory permits typically identify performance criteria based on assumptions of how fast the improvements in condition will occur, and they usually stipulate monitoring to demonstrate either progress toward the criteria or their attainment.
However, the general relationship between project age (or time since construction) and condition is not known for depressional wetlands. The permitting agencies and permittees, such as Caltrans, need information about the habitat development trajectory of projects, such that realistic expectations and requirements for their performance can be set.
Task 4: Relationship between wetland condition, stress, and buffer (memo)
According to CRAM, a stressor is an unnatural (i.e., anthropogenic) event or process that negatively effects the condition of a wetland. The number, proximity, intensity, and duration of stressors can all affect wetland performance.
The current version of CRAM captures information about stressors for each wetland assessment via the standardized Stressor Checklist, a qualitative documentation of the presence/absence and likely severity of commonly recognized stressors. The checklist does not have any effect on CRAM scores, but can be used to hypothesize reasons for low scores and to suggest management actions to improve scores.
As currently configured, the Stressor Checklist does not meet some well-defined needs of the wetland management community. Recent analysis of completed checklists suggests that the assessments of stressor severity are often too subjective to inform management actions. Furthermore, since the Checklist does not provide a numerical assessment of stress, relationships between stress and wetland condition or performance cannot be quantified. More specifically, there is a need to evaluate to what degree wetland buffers mediate the effects of stress on wetland condition, such that buffers can be properly considered in wetland projects to reduce the risk of project failure. Such evaluation requires statistical tests of how stress influences the correlation between wetland condition and buffer condition, and such tests require a numerical value for stress.
Task 5: Effects of aquatic area abundance, buffer, and hydrology on depressional wetland condition based on CRAM (memo)
CRAM assumes that the kinds and levels of ecosystem services that a wetland provides increases with the support of its surrounding landscape. This support is assessed as landscape connectivity using the Aquatic Area Abundance Metric, resistance to landscape stressors using the Buffer Metric, and naturalness of hydrological sources and processes using the Hydrology Attribute.
CRAM practitioners have especially questioned the usefulness of the Aquatic Area Abundance Metric for assessing the conditions of restored, enhanced, or created wetland projects. It is the only CRAM Metric that is intended to assess connectivity between projects and their surrounding landscape. One concern is that project sponsors usually lack control over these conditions. Another concern is that the landscape surrounding the project may not support the abundance of aquatic areas necessary for high Condition Index scores, due to natural constraints, such as aridity or topographic steepness, or land use. These concerns have led to the consideration that the Aquatic Area Abundance Metric may be biased against projects. To a much lesser degree, there is a concern that the Buffer Metric and Hydrology Attribute might also be biased against projects, since their scores sometimes reflect conditions outside project boundaries. This task investigated several null hypotheses based on those concerns.
Task 6: Enhancements to EcoAtlas’ CRAM analysis tools: Habitat Development Curves and Ecoregional Cumulative Distribution Function plots (memo)
Caltrans funded SFEI to enhance EcoAtlas’ wetland project analysis features to allow users to compare project assessments to Habitat Development Curves (HDCs) for estuarine and depressional wetlands, and to compare both project and non-project assessments to the ecoregional Riverine Cumulative Distribution Function plots (CDFs) for six ecoregions across the state.
2014 to 2016
Rebecca Payne (Caltrans)
Jelica Arsenijevic (HDR)
Programs and Focus Areas:
Information Technology Systems
Resilient Landscapes Program
Wetland Monitoring & Assessment