Insect & Disease Risk Modeling

The Insect and Disease Risk Modeling project was initiated in 1995 with the formation of an interdisciplinary team of specialists to model and predict potential risk of forest mortality due to insect and disease induced tree mortality.  A multi-criterion framework has been established to facilitate a standardized modeling approach across all forest health regions to create a seamless final product.  Model criteria and parameters vary across the landscape for each host type.  Scientific literature, professional knowledge, and statistical data form the basis for the development of the host-specific models.  Input criteria for the models include: stand density index (SDI), basal area (BA), quadratic mean diameter (QMD), precipitation, relative humidity, elevation, percent canopy cover, temperature regime, among others. 

Risk is defined as a 25 percent or more volume loss over the next 15 years including background mortalityNational and Regional risk map products have evolved out of the initial efforts of the Risk Map team.

For the National Risk Map, standardized national data sets have been modeled from Forest Inventory and Analysis (FIA) plots for BA, QMD, SDI, and canopy cover at a spatial resolution of one kilometer. Download the National Insect and Disease Risk Map data at:

While the methodology for the regional risk map is the same as for the national product, the regional product relies on higher resolution datasets for all input data.  The Regional Risk Map uses Existing Vegetation Data (EVEG, USDA Forest Service, Region 5, Remote Sensing Laboratory) and CA-GAP data sets as the vegetation base layers for host type at a spatial resolution of 30 meters.  Other input layers, including SDI and QMD are also generated at a spatial resolution of 30 meters.

The risk models, both regionally and nationally, are constantly evolving as new data becomes available and new scientific literature relating to forest health is published.  The regional map will be updated as regional vegetation data layers are updated.  The planned update schedule for the national map is every 5 years. This approach will help facilitate the prioritization of identifying and protecting biologically significant stands.


Insect and Disease Risk,
Lake Tahoe Basin Management Unit


Click on map for larger view

Insect and Disease Risk by National Forest

Angeles NF (3.52 MB)

Cleveland NF (2.67 MB)

El Dorado NF (3.52 MB)

Inyo NF (3.85 MB)

Klamath NF (3.85 MB)

Lake Tahoe Basin (2.83 MB)

Lassen NF (2.75 MB)

Los Padres NF (3.11 MB)

Mendocino NF (4.51 MB)

Modoc NF (7.12 MB)

Plumas NF (3.6 MB)

San Bernardino NF (4.13 MB)

Sequoia NF (3.43 MB)

Shasta-Trinity NF (3.95 MB)

Sierra NF (3.45 MB)

Six Rivers NF (3.72 MB)

Stanislaus NF (3.57 MB)

Tahoe NF (3.71 MB)


Data available upon request:


Contact Information:

Forest Health Monitoring
1731 Research Park Drive
Davis, CA 95618
(530) 759-1750