Alaska's Aerial Detection Survey

2023 Aerial Detection Survey Map

Forest damage mapped during the 2023 aerial detection survey in Alaska.

Forest Health Protection and the Alaska Division of Forestry & Fire Protection conduct annual aerial detection surveys of forest damage across Alaska from June to August. Learn more below about how to request surveys and obtain survey data. Click here to view the 2023 aerial detection survey overview map as a pdf.

2023 Survey Snapshot

Interior Alaska

Aspen leafminer-caused defoliation continues to be widespread across the region, though the activity was less pronounced from around Dot Lake east.
Willow leafblotch miner-caused defoliation was also widespread and was observed in a variety of willow species, from very small shrubs to mid-story willow species. The damage signature for this species, what it looks like from the air, varies substantially depending on the willow species in which it is occurring.

Small pockets of tree mortality associated with flooding were observed at several locations along or near the Tanana River and were scattered along other rivers and streams in the region.

Alaska Range Transition Zone

In the northern portion of the spruce beetle outbreak, activity is still being observed within the Alaska Range.

The outbreak continues to be active along the Denali Highway.
Damage in the Yanert Fork valley and surrounding drainages has become more expansive.
Damage was observed as far north as the Healy Creek drainage.

Southcentral Alaska

The spruce beetle outbreak continued across the region.

The outbreak continues to be active in the upper Susitna River valley.
Scattered spruce beetle activity was also observed from about Sheep Mountain northeast to around Lake Louise.
Activity on the Kenai Peninsula was observed in many valleys of the Kenai Mountains and on the south shore of Kenai Lake as well as between Skilak and Tustumena Lake. Some light beetle activity was also observed in previously impacted stands in the northeastern Kenai National Wildlife Refuge. Light scattered activity was visible on the west side of Cook Inlet from about the Chakachatna River valley south to near Big River Lakes.

An outbreak of spruce needle rust was occurring east of the Copper River and north of the Chitina River near their confluence. High levels of spruce needle rust were also observed along the upper Matanuska River and scattered on the southern Kenai Peninsula. Subsequent ground observations from local land managers confirmed extensive spruce needle rust on the western Kenai Peninsula.
Much of the southwestern shore of Kachemak Bay was obscured by a heavy cloud bank, limiting survey coverage in this area where extensive defoliation of alder and other hardwoods was observed in 2022. Observations along the few unobscured inlets that were flown in that area this season suggest that the defoliation event continues. The insect causing this damage has not been confirmed but is presumed to be a generalist-feeding moth species.

Southeast Alaska

Light western blackheaded budworm activity was recorded south of Juneau near Holkham Bay and north to Skagway. There was active defoliation also recorded near Hoonah and Excursion Inlet. The defoliation impacts diminished north and stopped more abruptly to the south. Hemlock mortality from past defoliation was minimal in most areas, but very high in some pockets on Admiralty and Chichagof Islands and along Excursion Inlet. Previously damaged areas were dominated by top-killed trees with some trees showing needle regeneration that cast a subtle green shade to gray trees.
Moderate levels of mortality from yellow-cedar decline were aerially mapped in Southeast Alaska in 2023. Over the past several years, decline detection was hindered by widespread defoliation damage from western blackheaded budworm, which also causes tree crowns to appear reddish-brown. In particular, Kupreanof Island had a high concentration of yellow-cedar decline in new areas. For the third consecutive year we documented scattered pockets of yellow-cedar mortality in Glacier Bay National Park near Finger and La Perouse Glaciers. Yellow-cedar forests in this area have been considered healthy and incidence of cedar mortality will be closely tracked.

We encourage interested parties to request areas of interest for survey. These requests and other information are used to determine survey routes. Aerial survey requests should include specific location information (waypoints of distinct landmarks) and any observations about the type, extent and severity of the damage, the host/s affected, and when the damage was first noted. For aerial survey requests or Alaska aerial detection survey data, contact Karen Hutten at karen.hutten@usda.gov or Garret Dubois at garret.d.dubois@usda.gov. Alaska Region Forest Health Protection can also produce customized pest maps and analyses tailored to projects conducted by partners.

2023

Damage AGOL feature layer Flightlines AGOL feature layer

Damage feature server url Flightlines feature server url

2022

AGOL feature layer Feature server url

2021

AGOL feature layer Feature server url

Aerial survey data 2015-2020 is available through Alaska Department of Natural Resources Open Data Portal: Alaska Insect and Disease Damage Public View

2020*

2020 Damage Polygons 2020 Survey Area 2020 Imagery Footprint

2019

2019 Damage Polygons 2019 Flightlines

2018

2018 Damage Polygons 2018 Flightlines

2017

2017 Damage Polygons 2017 Flightlines

2016

2016 Damage Polygons 2016 Flightlines

2015

2015 Damage Polygons 2015 Flightlines

*Aerial surveys were cancelled in 2020 due to COVID-19. Damage was mapped through a combination of ground-based surveys and a remote sensing approach using high-resolution satellite imagery. The imagery footprint is the area for which imagery was obtained and surveyed.

Forest insect and disease data can also be downloaded from the Forest Health Assessment and Applied Sciences Team (FHAAST) website:

FHAAST- Homepage
FHAAST- Mapping, Reporting & Aerial Survey Data Download

Prior to each annual aerial survey, we plan tentative survey dates and routes. These plans sometimes change to accommodate survey requests and damage observed during the survey, and also due to weather conditions and other constraints. Contact our team to request locations for survey or to report recent forest damage. Karen Hutten is the Aerial Survey Program Manager for Alaska (karen.hutten@usda.gov).

Aerial surveys are an effective and economical means of monitoring and mapping insect, disease and other forest disturbance at a coarse scale. In Alaska, Forest Health Protection (FHP) and the Alaska Division of Forestry & Fire Protection, monitor approximately 15% of Alaska’s 126 million acres of forest annually at a cost of less than a penny per acre. Much of the damage acreage referenced in annual Forest Health Conditions of Alaska reports is generated from aerial detection surveys, so it is important to understand how these data are collected and the data’s inherent strengths and weaknesses.

No two observers will interpret and record an outbreak or damage signature in exactly the same way, but the essence of the event should be captured. While some observations are ground checked, most are not. Many times, the single opportunity to verify the data on the ground by examining affected trees and shrubs is during the survey mission, and this can only be done when the terrain will allow the plane to land and take off safely. The data provides estimates of the location and intensity of damage, but only for damage agents with signatures that can be detected from the air during the survey period. Many root diseases, dwarf mistletoe, stem decays and other destructive pathogens are not represented in aerial survey data because these agents are not detectable from an aerial view or signs and symptoms do not coincide with the timing of the survey.

Surveys provide a non-systematic sampling of forest damage via flight transects. Due to survey priorities, client requests, known outbreaks, and several logistical considerations, some areas are rarely or never surveyed, while other areas are surveyed annually. The reported data is an indicator of insect and disease activity for a given year and maps with survey flightlines show where the data was collected. Although general trends in non-surveyed areas could be similar to those in surveyed areas, this is not always the case. Establishing trends from aerial survey data is possible, but care must be taken to ensure that multi-year projections compare the same areas, and that sources of variability are considered.

Aerial detection surveys employ a method known as aerial sketch-mapping to observe and document forest damage from an aircraft. When an observer identifies an area of forest damage, a polygon or point is drawn on a computer touch screen. The touch screen displays the plane's location over a topographic map with a variety of features and layers that can improve mapping accuracy. Trained observers have learned to recognize and associate damage patterns, discoloration, tree species, and other clues to distinguish specific types of forest damage from surrounding undamaged forest. Damage attributable to a known agent is a “damage signature” and is often pest-specific. Only actively occurring, recent damage is mapped; old damage or mortality is not mapped during the aerial detection survey unless there are specific extenuating circumstances.

Knowledge of these damage signatures allows trained surveyors to not only identify damage caused by known pests, but also to be alerted to new or unusual signatures, such as those that may be caused by uncommon or invasive species. Detection of novel damage signatures caused by newly invasive species is an important component of early detection rapid response monitoring.

Aerial sketch-mapping offers the added benefit of allowing the observer to adjust their perspective to study a damage signature from multiple angles and altitudes, but is challenged by time limitations, fuel availability and other factors. Survey aircraft typically fly at about 100 knots (115 mph) and 1,000-1,500 feet above ground level with variable atmospheric conditions. Low clouds, high winds, precipitation, smoke, and poor light conditions can inhibit the detection of damage signatures. Terrain, distance, and weather conditions prevent some areas from being surveyed altogether.

Prior to 1999, sketch-mapping was done on 1:250,000 (1 inch = 4 miles) USGS quadrangle maps. Today, forest damage information is sketched on 1:63,000 scale (1 inch = 1 mile) digital USGS quadrangle maps or imagery on a digital sketch-mapping system. This system displays the plane’s location via GPS and has many advantages over paper maps including greater accuracy and resolution in polygon placement and shorter turnaround time for processing and reporting data. The sketch-map information is then entered into a computerized Geographic Information System (GIS) for more permanent storage and retrieval by users. Over 40 years of aerial survey data has been collected in Alaska, giving a unique perspective of Alaska’s dynamic and changing forests.

Citing Maps and Survey Data: Please cite “USDA Forest Service, Forest Health Protection and its partners” as the source of this data in maps and publications.

Aerial Detection Survey Data Disclaimer: Forest Health Protection and its partners strive to maintain an accurate Aerial Detection Survey (ADS) dataset, but due to the conditions under which the data are collected, FHP and its partners shall not be held responsible for missing or inaccurate data. ADS data are not intended to replace more specific information. An accuracy assessment has not been done for this dataset; however, ground checks are completed in accordance with local and national guidelines. Maps and data may be updated without notice.

The USDA Forest Service makes no warranty, expressed or implied, including the warranties of merchantability and fitness for a particular purpose, and assumes no legal liability or responsibility for the accuracy, reliability, completeness, or utility of these geospatial data, or for the improper or incorrect use of these geospatial data. These geospatial data and related maps or graphics are not legal documents and are not intended to be used as such. The data and maps may not be used to determine title, ownership, legal descriptions or boundaries, legal jurisdiction, or restrictions that may be in place on either public or private land. Natural hazards may or may not be depicted on the data and maps, and land users should exercise due caution. The data are dynamic and may change over time. The user is responsible to verify the limitations of the geospatial data and to use the data accordingly.

Content prepared by Robin Mulvey and Karen Hutten, Forest Health Protection, Juneau, AK.