Fighting Forest Pests With AI: A Hemlock Success Story

Fairfax County utilized GeoAI and ArcGIS technology to efficiently map and protect its hemlock trees from the invasive woolly adelgid, ensuring targeted pest management and preservation of its evergreen canopy.

2 minute read

January 21, 2025, 5:00 AM PST

By Clement Lau


Looking up at a grove of mature hemlock trees on a sunny day.

pabrady63 / Adobe Stock

Fairfax County, Virginia, faced a significant challenge with the hemlock woolly adelgid, a pest threatening its hemlock trees and evergreen canopy. The county’s Urban Forest Management Division (UFMD), tasked with preserving the urban forest, recognized that mapping hemlocks was critical to combat infestations. Collaborating with the GIS Division, they leveraged geospatial artificial intelligence (GeoAI) using ArcGIS technology to analyze aerial photography. By employing a deep learning model and additional filtering techniques—like analyzing greenness, infrared data, and lidar intensity—UFMD pinpointed evergreen trees requiring treatment, significantly narrowing the target area from 116,521 to 33,110 trees.

The GIS Division’s analysis enabled the Forest Pest Branch to efficiently develop a treatment plan and allocate resources. Utilizing ArcGIS Field Maps, the mobile team located and treated infested trees. This streamlined approach, integrating GIS tools with ground efforts, ensured precise targeting and resource optimization. The collaboration highlighted the effectiveness of automating tree detection, laying the groundwork for future projects aimed at preserving Fairfax County’s tree canopy.

Building on this success, Fairfax County used the evergreen data from the hemlock project to train a new deep learning model to map evergreens across the Mason Neck peninsula. This project covered nearly 9,000 acres and identified over 36,000 evergreen trees. The automated process enabled more efficient planning and monitoring, particularly in areas with dense tree clusters. Fairfax County’s innovative use of GeoAI for forest management demonstrates the transformative potential of technology in addressing environmental challenges.

Monday, January 13, 2025 in ARCNEWS

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Cover CM Credits, Earn Certificates, Push Your Career Forward

Aerial view of town of Wailuku in Maui, Hawaii with mountains in background against cloudy sunset sky.

Maui's Vacation Rental Debate Turns Ugly

Verbal attacks, misinformation campaigns and fistfights plague a high-stakes debate to convert thousands of vacation rentals into long-term housing.

July 1, 2025 - Honolulu Civil Beat

Logo for Planetizen Federal Action Tracker with black and white image of U.S. Capitol with water ripple overlay.

Planetizen Federal Action Tracker

A weekly monitor of how Trump’s orders and actions are impacting planners and planning in America.

July 2, 2025 - Diana Ionescu

White and purple sign for Slow Street in San Francisco, California with people crossing crosswalk.

San Francisco Suspends Traffic Calming Amidst Record Deaths

Citing “a challenging fiscal landscape,” the city will cease the program on the heels of 42 traffic deaths, including 24 pedestrians.

July 1, 2025 - KQED

"Altadena - Not For Sale" yard sign in front of burned down house after Eaton Fire in Altadena, California in January 2025.

Half of Post-Fire Altadena Home Sales Were to Corporations

Large investors are quietly buying up dozens of properties in Altadena, California, where a devastating wildfire destroyed more than 6,000 homes in January.

July 7 - Dwell

Dense multistory residential buildings in hilly San Francisco, California.

Opinion: What San Francisco’s Proposed ‘Family Zoning’ Could Really Mean

Mayor Lurie is using ‘family zoning’ to encourage denser development and upzoning — but could the concept actually foster community and more human-scale public spaces?

July 7 - The San Francisco Standard

Blue self-driving Ford Transit van shuttle in Jacksonville, Florida.

Jacksonville Launches First Autonomous Transit Shuttle in US

A fleet of 14 fully autonomous vehicles will serve a 3.5-mile downtown Jacksonville route with 12 stops.

July 7 - Smart Cities Dive

Urban Design for Planners 1: Software Tools

This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.

Planning for Universal Design

Learn the tools for implementing Universal Design in planning regulations.

Associate/Senior Planner

Gallatin County Department of Planning & Community Development

Senior Planner

Heyer Gruel & Associates PA