A New Monitoring Challenge: Protecting Forests from Pests

Every fall, one of the planet’s most extraordinary natural spectacles occurs amid the fir forests of central Mexico: Millions of monarch butterflies land here to find respite from the cooling winter temperatures in northeastern U.S. and Canada for their annual hibernation. It is a phenomenon that the Monarch Butterfly Fund affectionately refers to as “the arrival of the sun’s daughters.” The sight is both visually splendid and culturally important to the people of Mexico. Several myths surround this phenomenon, such as beliefs that monarch butterflies are returning souls of loved ones.  

This incredible event, a critical part of the monarchs’ life cycle, depends on Mexico’s forests. However, these forests are feeling the effects of global climate change. One of the effects is the rise of pests; a problem that is not unique to Mexico, forests pests are a growing threat in many other countries (for example, in 2024, WRI reported that forest pests are a growing threat to Europe’s forests).  

To help tackle this issue in Mexico’s Monarch Butterfly Biosphere Reserve, Global Forest Watch (GFW) Small Grants Fund recipient Neovolcanic Axis Conservation Fund (FOCEN) has developed a novel approach, combining alerts on GFW’s Forest Watcher app and complementary technology like drones to monitor pests and inform actions to eradicate them.

A new challenge for monarchs and monitoring: Forest pests

FOCEN works regionally to create alliances for the conservation, restoration and responsible use of natural resources in central Mexico. Since 2000, FOCEN has worked to conserve the valuable forests in Mexico’s Monarch Butterfly Biosphere Reserve (MBBR), a UNESCO World Heritage Site. Through the Monarch Butterfly Conservation Fund (Monarch Fund), FOCEN has facilitated a scheme that provides economic incentives for the payment of ecosystem services to forest owners (ejidos — small landowners and Indigenous communities) across 12,367 hectares of forests, 91% of which are within MBBR’s core zone.

In 2021, after receiving a grant from GFW’s Small Grants Fund, FOCEN set out to address forest disturbance in the MBBR.

While conducting initial field investigations using Forest Watcher to identify areas of degradation and create reports on their findings, they quickly discovered that the primary cause of forest degradation in the Reserve is forest pests, specifically bark beetles, which attack weakened trees. Worse, they discovered that the beetles are continuing to spread as temperatures and drought increase, threatening forest habitat that is critical for monarch butterfly migration and overwintering.

A new way to use Forest Watcher and monitoring tools

FOCEN worked quickly to mobilize on this new finding. Teaming up with technical monitoring partner Ambiomas Acciones y Respuestas Adaptativas (Ambiomas), they adapted their project and set out to create an early warning system for monitoring forest pests and to develop capacity for using the system and monitoring the forest in a new way.  

As a first step, FOCEN and Ambiomas recognized that engaging forest owners and community members living in and around the Reserve was essential. They created a comprehensive course with a corresponding manual and led a two-day intensive training event for 14 people on using Forest Watcher. Over the course of six months, community technicians from the participating ejidos and communities, with the support of Ambiomas and FOCEN, conducted more than 100 field visits and produced more than 1,000 reports on observations of forest degradation in the field. This provided the data needed to inform FOCEN’s development of an early warning system.  

Next, FOCEN and Ambiomas, with support from GFW and the Monarch Butterfly Fund, took a multi-pronged approach to creating the early warning system. Realizing the time commitment of ground patrols and the limitations of satellite imagery, they incorporated multispectral drone technology that can capture data in multiple wavelengths beyond the visible spectrum (red, green, blue) to complement field visits and provide high-resolution imagery of forest degradation that satellites cannot always capture.

They selected five watersheds to assess that had historical records of monarch butterfly hibernation and that are critical to communities. After conducting drone flights, they used a Tree Density Calculator algorithm (available as a QGIS plugin) that provides an estimate of the number of trees present in the study area and shows the coordinates of each tree, creating a forest inventory that includes each tree’s precise location. They then assessed vegetation health using a platform to interpret the multispectral drone imagery and by assessing high-resolution images.

Using the forest inventory, they performed a visual interpretation for each tree determined by the algorithm to have signs of disease, such as standing dead or dry trees and trees with dry tops. The identification criteria were based on the color and appearance of the tree.

They compared this information with the reports generated during monitoring trips using Forest Watcher and found that the reports aligned with the visual interpretation of the images identified by the algorithm.

FOCEN and Ambiomas have now conducted multispectral drone flights for two consecutive years during the pre- and post-rainy season and at times of the year when monarchs are not present to determine the vitality of the fir trees and in order to have timely information on the possible presence of forest pests.

Outcomes for improved pest monitoring and response

Thanks to the early warning system, FOCEN, Ambiomas and communities have been able to take targeted action in controlling bark beetles — namely, removing infected trees and wood debris, in accordance with Mexican regulations for controlling and preventing beetle outbreaks. More monitoring is needed to determine whether the bark beetles are now contained, and local communities are currently conducting pest and forest disease monitoring surveys as part of FOCEN’s Best Management Practices Programs within their payment for ecosystem services program.

The combination of tools and practices used in the early warning system provides an important complement to field monitoring. It has helped ejidatarios (community landowners), community members and field technicians monitor larger areas and less accessible places faster and has allowed them to better understand their territory. Using the information collected, they have been able to implement conservation and restoration activities that are helping counteract the effects caused by forest pests.

Additionally, FOCEN and Ambiomas have developed a MapBuilder and Story Map for each of the five watersheds crucial to monarch hibernation that they monitored throughout the project to aggregate and represent all the data generated, making it possible to conduct spatial analyses with this information.

FOCEN and Ambiomas also worked with the team at GFW to make several improvements to Forest Watcher such as improving the location accuracy of reports and the ability to directly link reports to MapBuilder, which will help others interested in monitoring for pests or using these tools for other applications in the future.

Adapting lessons for tackling forest pests around the world

In October 2022, FOCEN convened a workshop with the Reserve’s community technicians, technical advisors and researchers from the Colegio de Geografía de la Universidad Nacional Autónoma de México to discuss the impact of climate change on forest degradation. As a next step for FOCEN and Ambiomas, greater funding is needed to allow the continuation of monitoring larger areas and to more accurately assess levels of forest degradation in the forests that monarchs depend on.

These impacts to forests and lessons learned are relevant for many geographies that are confronted with similar issues. FOCEN and Ambiomas found that, in addition to an early warning system to reduce response time to forest damage, early detection and monitoring activities are essential to prevent forest degradation from pests. This requires long-term aerial monitoring and strengthening the local capacities of forest owners, in coordination with the various stakeholders involved in the area.

As climate change continues to wreak havoc, less visible but damaging effects like forest pests are becoming more apparent. The issue of pests causing degradation is not isolated to Mexico, and others can learn from the technologies and approaches developed by FOCEN and Ambiomas and implement similar strategies in the areas that are experiencing similar challenges.

To learn more about FOCEN and Ambiomas’s work and their early warning system for forest pests, please contact eligio.garcia@focenmexico.org or ambiomasorg@gmail.com.