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* Metric Name: Current Fire Return Interval Departure, Since 1970  

* Tier: 2  

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

* Unit Of Measure: Average Years  

* Metric Definition and Relevance: The fire return interval departure (FRID) analysis quantifies the difference between current and pre-settlement fire frequencies, allowing managers to target areas at high risk of threshold-type responses owing to altered fire regimes and interactions with other factors. This is a measure of the extent to which contemporary fires (i.e. since 1970) are burning at frequencies similar to the frequencies that occurred prior to Euro-American settlement, with the mean reference FRI as the basis for comparison. With this metric, mPFRID_1970, the same formulas are used as with meanPFRID but with 1970 as the baseline rather than 1908. Important note: because 1970 is the baseline for this measure, no fires before 1970 are taken into account and all PFRs start at a PFRID of zero beginning in 1970.

* Creation Method: Current fire return interval 1908 is calculated by dividing the number of years in the fire record by the number of fires occurring between 1908 and the current year in a given polygon plus one.

CurrentFRI = Number of years/Number of Fires +1

  

* 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