Forest Health Advisory
Background
America’s forests provide ecological, social, and economic services to our Nation. An important aspect of maintaining and enhancing a healthy forest is to protect and restore forests from insects and diseases that cause high levels of tree decline and mortality.
The US Forest Service conducted the 2013-2027 National Insect and Disease Forest Risk Assessment to provide a nationwide summary of the potential susceptibility to tree mortality caused by major forest pests. Results for Hawaii are presented below to inform assessments of natural ecosystems and prioritize potential management for pest prevention, suppression, and restoration.
Since 2012, major tree mortality events from forest pest outbreaks, fire, and broad scale forest harvesting operations have reduced or in some cases eliminated risk*. To account for this, areas where significant tree mortality events have occurred have been removed. These areas are represented in the map below as ‘Disturbances/treatments in risk areas’. However, many areas still remain highly susceptible to future mortality - ‘Remaining Risk’ in the map below. A major tree mortality event was defined as one or more of the following:
- Areas depicted as forest cover loss in the University of Maryland Global Forest Change dataset.
- Three or more years of mortality mapped in aerial detection surveys (ADS; Insect and Disease Survey database).
- In the Eastern U.S. only, three or more consecutive years of defoliation mapped in ADS.
Note: The 2018 update does not account for increases in risk due to recent tree growth and density, which can make additional trees susceptible and vulnerable to new forest pest attacks.
This advisory is designed to raise awareness about forest health concerns and provide common ground for consultation between resource managers and forest health specialists. Impacts summarized below assume no active management during a 15-year (2013-2027) time frame.
*Risk, or more appropriately termed hazard, is defined as the expectation that, without remediation, at least 25% of standing live basal area greater than one inch in diameter will die over a 15-year time frame (2013 to 2027) due to insects and diseases.
What is at Risk and What are the Threats for Hawaii?
Within Hawaii, 76,514 acres are susceptible to high levels (≥25%) of overall tree mortality, and N/A of the tree biomass is at risk to forest pests. Accounting for major forest disturbances, such as insect and disease outbreaks, fires, and treatments, the number of susceptible acres has not significantly changed.
| Host Tree Species | Loss, % of Host | Loss, % of All Trees |
|---|---|---|
| Naio | 86% | N/A |
| Wiliwili | 26% | N/A |
| Koa | 25% | N/A |
| Ohia | 1% | N/A |
| Forest Pest | Loss, % of Host | Loss, % of All Trees |
|---|---|---|
| Myoporum Thrips | 86% | N/A |
| Erythrina Gall Wasp | 26% | N/A |
| Koa Wilt | 25% | N/A |
| Ohia Rust | 1% | N/A |
| ALL FOREST PESTS | N/A |
| Forest Pest | Host Tree Species |
|---|
Interactive Maps
Potential Management Strategies & Key Contacts
| STRATEGY | Erythrina Gall Wasp | Koa Wilt | Myoporum Thrips | Ohia Rust |
|---|---|---|---|---|
| Detection & Monitoring - Can prevent a pest from increasing to damaging levels and reduce tree mortality, when early detection is followed by a rapid response | ||||
| Monitor for population fluctuation, establishment, range expansion - traps, aerial/ground survey | x | x | x | x |
| Restoration - Re-establishing processes necessary to facilitate forest sustainability, resilience, and health | ||||
| Reforestation - replant existing or alternative native species or silvicultural systems that promote natural regeneration | x | x | ||
| Salvage and dead (hazard) tree removal | x | x | x | x |
| Genetic improvement and conservation | x | |||
| Suppression - Reduce the overall damage to forest resources from outbreaks of insect and disease-causing pests | ||||
| Pesticide and biocontrol application | x | |||