We examined a place near Santa Ysabel, off Highway 78 in San Diego County that we know well. What we found was disturbing.
1. Much of the area designated as having 40 – 15 dead trees per acre is either California sage scrub or chaparral (where there are no trees), or non-native grassland with a few scattered oaks. The white square in the first image represents one square acre for reference. The X on the second Google Image and the corresponding Tree Mortality Viewer map marks the approximate location of the square.
2. In oak woodland areas where there are actually trees, the estimate of tree mortality doesn’t seem to come close to what is actually on the ground.
3. We question the likelihood of having 40 – 15 dead, mature oaks on a single acre, especially in the upper range.
Whatever measurements the state is using, they appear to be based on crowded mixed-conifer forests. Where there are no conifers, the program seems to have a major hiccup.
We have discussed the inaccuracy of the maps with others in the field and they have confirmed the problems are statewide. This is an important issue because land and fire management decisions are likely being made based on these maps.
The state needs to conduct ground-truthing of their computer generated data if they intend to develop policy that reflects what is actually occurring.
The Tree Mortality Viewer can be seen here:
Above: The area in which Cal Fire indicates there are 40 – 15 dead trees per acre. Most of the area in view is California sage scrub, chaparral, or non-native grassland with a few oaks. White square represents one square acre for reference.
Above: Much of the terrain to the right of Highway 79 is not forested, but rather California sage scrub and chaparral. X marks the approximate location of the square acre in the previous photo.
Above: The state’s Tree Mortality Viewer map. The X marks the approximate spot for the square acre in the above photo. Red designates areas that supposedly have 40 – 15 dead, mature trees (oaks) per acre. Other colors: Orange (15-5 dead trees per acre), Yellow (5 or less dead trees per acre).