Mar 5, 2016

How do you know whether your project assessment, conducted by the California Rapid Assessment Method, reflects an improvement that is aligned with ecosystem goals? Habitat Development Curves (HDCs) help to visualize and measure the performance of on-the-ground projects relative to ecosystem goals.

Wetland Habitat Development Curves (HDCs) are used to evaluate the rate of habitat development  for restoration and mitigation projects, and how they compare to other projects of the same age and habitat type, based on CRAM. HDCs have recently been developed for three CARI wetland types (riverine, estuarine, and depressional) using existing CRAM assessments from wetlands across California.  Each curve represents the average rate of development bounded by its 95% Confidence Interval (CI), plus the average condition and 95% CI for the reference sites. Projects that are well-designed for their location and setting, and well-managed tend to be on or above the curve.  In general, as projects age, their habitats should mature, gaining similarity to the reference sites, such that the project’s CRAM scores increase. HDCs for the CRAM Attributes and Metrics can be used to understand and correct habitat developmental problems.

Each Habitat Development Curve (HDC) is based on assessments of habitat condition for different age areas of one habitat type that in aggregate represent the full spectrum of habitat development. The assessments of condition are provided by expert applications of the California Rapid Assessment Method (CRAM). Reference condition is represented by areas of a habitat that consistently get very high CRAM scores, have not been subject to disruptive management practices, and exist within landscapes that are protected and managed for their natural conditions. Visit the CRAM website for more information about CRAM.

The age of a project is estimated as the elapsed time in years between the groundwork end date for the project and the date of the CRAM assessment. The minimum age in years of a non-project area, including any natural reference area, is estimated from all available local information, including historical maps and imagery, historical written accounts, and place-specific scientific studies of habitat development. 

An HDC can be used to help address the following questions:

  • At what time in the future will the area of assessed habitat achieve the reference condition or other milestones in habitat development? 

The HDC can answer this question if the CRAM score for the assessed area is within the confidence interval of the HDC. The answer is the time in years along the HDC between the current age of the assessed area and the future date corresponding to the intersection of the HDC and the reference condition or other milestone. 

  • Is the area of assessed habitat likely to develop faster, slower, or at the same pace as most other areas of the same habitat type?  

The habitat area is likely to develop faster, slower, or at the same pace if the CRAM score for the area is above, below, or within the confidence interval of the HDC, respectively. 

  • What can be done to improve the condition of the habitat area or to increase its rate of development?

HDCs by themselves cannot answer this question, but possible answers can be inferred by analysis that involves HDCs.

The HDC is available as a separate tab in the Project Information Page and is only visible when a project has a recorded construction end date (groundwork end date), and there are existing CRAM assessments for the project boundaries in the statewide CRAM database. 

Cristina Grosso
Programs and Focus Areas: 
Resilient Landscapes Program
Wetland Science