Restoring Habitat Impacted by Emerald Ash Borer

Ash trees at Rattray Marsh Conservation Area have been devastated by emerald ash borer (EAB), an invasive insect. We began restoring forests at Rattray Marsh in 2018.

Dead and dying ash trees are unstable and can fall. They pose a safety risk to visitors and staff and are a threat to forest health.

The Restoration Process

There are several stages to restoring habitat affected by emerald ash borer.  We’re working in five priority areas at Rattray Marsh, staggered over six years. Work within each priority area will follow a three-year timeline.

In the fall, we manage and remove invasive trees and shrubs and treat selected invasive with plants with pesticide.

We cut down dead and dying ash impacted by emerald ash borer. We conduct this work in winter to reduce disturbances to wildlife and plants.

In summer and fall, we monitor and continue to treat invasive plant species to ensure they do not outcompete any native species.

When invasive plants have been reduced, we also start to plant native trees and shrubs to increase biodiversity and help establish a future forest.

We continue to monitor and treat invasive species. In spring and fall we finish planting trees and shrubs. We then monitor trees and forest health over time and adjust our management as needed.

Frequently Asked Questions

Reviews answers to frequently asked questions about emerald ash borer restoration.

We completed an assessment on all our properties to identify the location, health and liability risk for ash trees along our trails and property boundaries and for priority sections of unhealthy forest.

The assessment guides:

  • The safe management of ash tree care
  • Ash tree removal
  • Future restoration of our forests

The goal of this restoration is to replace ash trees impacted by emerald ash borer with native trees and shrubs and remove invasive plants so a healthy forest with diverse species can return and thrive.

We’ve prioritized restoration at Rattray Marsh in selected areas because of the combination of ash trees lost and the invasive shrubs that have taken over the understory (the plant life underneath the forest). This created poor value habitat for wildlife. The forest will not recover to its previous habitat value if left on its own.

Our native ash trees are killed by the invasive emerald ash borer beetle, usually within two years of infestation. Ash trees at Rattray Marsh are either dead or dying.

Not all dead or dying ash trees will be cut down. Select trees will continue to provide shelter, food and space for wildlife. This approach is consistent with best practices for forest restoration.

We’re cutting and piling ash trees to create workable areas where our staff can safely treat invasive plant species and plant new trees and shrubs.

We’re also strategically placing cut ash trees in select locations to help restore healthy forest ecosystems. Brush piles and downed logs provide habitat for wildlife such as small mammals, insects, microbes and fungi. As the material breaks down over decades, it provides nutrients for healthy soils and can act as “nurse logs” where seeds from plants and trees such as birch and hemlock can germinate. They also provide a variety of important habitats such as feeding for woodpeckers, nesting sites for birds and snakes, cover for salamanders, escape sites for small mammals and growth sites for fungi, mosses and lichens.

By leaving trees on the ground within the forest, we are mimicking a natural forest disturbance. For example, when there is an insect outbreak, standing dead trees come down in large groups during windstorms, called blowdown. In this case, we’re controlling the blowdown so that we can continue to manage invasive species and plant native trees and shrubs. Disturbances that kill and fall trees are normal. However, we’re dealing with dead ash trees at such a large scale because of the impact of EAB in the watershed, and particularly at Rattray Marsh where there was a very high percentage of ash trees.

If left unmanaged, the dead and dying ash will come down together and on top of each other, creating a tangled maze of downed trees that is difficult to navigate for wildlife such as deer. Areas of blowdown are also unsafe for staff to work around, which would inhibit our ability to restore these degraded forest sites.

Not all dead or dying ash trees will be cut down. Each tree is assessed before being cut for nests or cavities that provide bird habitat. The trees that have these features are left standing to continue to provide habitat. These trees will continue to provide shelter, food and space for wildlife such as woodpeckers. This approach is consistent with forestry science and best practices for ecosystem recovery.

Emerald ash borer kills our native ash trees. The larvae eat the inner bark which prevents the flow of water and nutrients from flowing up and down the tree. This starves the tree. Adult beetles feed on the leaves of the tree.

Since 2014, we’ve injected select ash trees on our properties with TreeAzin, an environmentally safe bio-insecticide treatment. This pesticide helps protect healthy ash trees from becoming infected with emerald ash borer.

We are continuing to treat selected ash trees that remain healthy.

Tree cutting is less disruptive to wildlife and forests. In winter:

  • Plants are dormant
  • The ground is frozen so tree cutting activities are less destructive to soils
  • Reptiles are hibernating underground
  • Migratory birds are not in the area

To date, we’ve cut down almost 13,000 infested ash trees that cannot be saved and that pose a risk to people and infrastructure along trails and property boundaries across all our properties. We continue to monitor hazardous ash trees.

Invasive trees and shrubs such as buckthorn and non-native honeysuckle are already present at Rattray Marsh. When we remove infected ash trees from the forest, it gives invasive plant species the opportunity to take their place.

Removing invasive plants is an important step in the restoration process. Forests with native plants are more resilient to disturbances and provide high quality habitat (food, shelter and space) for wildlife to thrive.

Learn more about the impacts of invasive species.

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