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* Metric Name: Mean Percent FRI Departure, Since 1970 

* Tier: 2  

* Data Vintage: 2022. Includes disturbances through the end of 2022.  

* Unit Of Measure: Percent  

* Metric Definition and Relevance: Mean Percent FRID (meanPFRID_1970) quantifies the extent in percentage to which recent fires (i.e., since 1970) are burning at frequencies similar to those that occurred prior to Euro-American settlement, with the mean reference FRI as the basis for comparison. Mean PFRID measures the departure of current FRI from reference mean FRI in percent

* Creation Method: The current FRI is calculated by dividing the number of years in the fire record (e.g., 2019-1970 equals 49 years inclusive) by the number of fires occurring between 1970 and the current year in a given polygon plus one (CurrentFRI = Number of years/Number of fires +1). The mean reference FRI is an approximation of how often, on average, a given PFR likely burned in the three or four centuries prior to significant Euro-American settlement. This measure does not return to zero when a fire occurs, unlike FRID values used in some other analyses ( for example NPS FRID Index).

  

* Credits: Fire History (2022), CAL FIRE \--Department of Forestry and Fire Protection Existing Vegetation (CALVEG 2011), USDA Forest Service, Region 5, MARS Team \--Region 5 - Pacific Southwest Region