By Aleta McKeage
Those of us in Maine often spend time in the woods, and many people in the state steward woodland areas, whether small or large. One of my own passions is hiking in the Maine woods, especially areas with mature forest. Recently, I was out with a friend in one of my favorite areas, the Sheepscot Headwaters Trail Area owned by the Midcoast Conservancy. As we observed beech trees with not one but two deadly disease complexes — a disease that destroys the outer and inner bark, and another newer disease that wilts the leaves of the beech trees — our conversation turned to the many challenges our trees and forests now face.
With this double threat, there seems to be little hope for healthy beech trees in Maine’s woods in the near future, and sadly beeches are not alone. We stopped for a bit in an opening where we could see far into the forest and counted the different tree species we saw — all the typical trees in Midcoast Maine, including red spruce, balsam fir, red maple, red oak, hemlock, ash and a few others, and of course many beech trees.
With a changing climate, these familiar trees face many perils. The cold-climate trees, such as spruce, fir and paper birch, are likely to decline precipitously as the climate warms. There have already been considerable changes in Maine’s climate, not just warming but also the timing and amount of precipitation. Approaching a river, we entered a large grove of hemlocks and checked the trees for an insect pest, the hemlock woolly adelgid, which has already reached our part of Waldo County. Elsewhere, the adelgid has nearly wiped out the tree, although experimental work, including the use of biocontrol insects, is happening now in Maine to try to save hemlocks. The several species of ash trees we saw form an important component of the deciduous (non-evergreen) trees in Maine’s forest. They are facing another pest insect, the emerald ash borer, that has entered Maine and may kill off many of the ash trees. Yet another pest, browntail moth, defoliates oaks and apples in particular and, with drought, even healthy trees can die of this combination of onslaughts.
All of these trees are important to wildlife, with each fulfilling its own role. As the trees die off, food sources and shelter needed by many creatures for their survival are lost. Hemlock, for instance, supports over 400 species, and the nuts from beech trees are a very important wildlife food. The small seeds of ash trees feed many creatures, and the leaf litter from ash trees enriches the forest floor, where countless soil invertebrates depend on the forest for healthy soil. If we look back at history, other trees such as chestnuts and elms have died out due to disease, and their valuable sources of nuts and seeds for wildlife have already been lost, compounding the problem.
Slowly, the Maine forest ecosystem is losing many of the important interrelationships that keep it healthy and resilient. Changes in the climate have many effects on the system, such as allowing pests and diseases to survive a warmer climate. But climate change is really only one aspect of what might be the bigger problem, which is the loss of the rich biodiversity of the north woods. Invasive plants often fill gaps where disturbance and loss of trees occurs in the forest, and native plants cannot compete with aggressive invaders. Insects are often specialized to particular plants and their chemistry, and cannot feed on invasive exotics; and native plants generally furnish more nutritional foods for wildlife. Besides the losses in our ecosystem, the forests of Maine are important for the livelihood of people, with the forests providing sustenance as well as products from lumber to firewood. Indigenous people have long used the brown ash trees to create basketry, an important part of their culture.
It would be easy to despair when you think of Maine losing many of its important trees and the forest losing its insects, birds and other life forms. Though I feel sad that so much is disappearing and changing, I am encouraged by the concerted effort that many people are putting into healing nature and finding ways to adapt to the future. All over Maine, people are working to add ecologically important elements to the land, and to conserve diversity in the landscape, whether it is just a yard or a large farm or forest. Many folks are planting native or naturalized trees that provide strong support for insects and wildlife, such as white oaks, birches, willows, cherries and apples, and even hybrid elms bred to resist disease. People are adding pollinator plants for insects and shrubs that produce food for birds. Many woodland stewards are implementing practices that support wildlife while producing forest products they need.
And, as the climate changes, the idea that we might plant new species of trees to fill the gaps and losses is gaining momentum. Sometimes, when a tree is planted in a new area where it is not native, but may thrive as the climate changes, the process is called “assisted migration.” The idea is that, although birds and other animals may be able to move quickly enough to adapt to a changing climate or other conditions, plants cannot. A tree or shrub may be planted just a short distance from where it is found naturally, or it could be planted in an area far from where it is native. Right now, scientists have looked closely at tree characteristics and different climate scenarios and have listed trees likely to grow in southern and coastal Maine over the coming decades (visit forestadaptation.org for more information). Schools, landowners and communities have begun to plant new tree species that have potential to fill the gaps for losses of wildlife food sources and forest products.
At MOFGA, as part of the low-impact forestry program, such “adaptive” tree species are being planted in forest research plots to study their growth and survival. Trees such as tulip poplar (tulip tree), shagbark hickory, chinkapin oak, spicebush, sassafras, white oak (Quercus alba), black walnut and hackberry are being planted on the MOFGA campus. The trees are protected from deer browse by fencing, as we are studying survival based on climate factors and insectivory, not mortality from deer browse. In the future, MOFGA foresters may study whether these trees continue to grow and even reproduce in the forest. Each has potential to fill a role in nature and human use of the forest. What if the small seeds and lumber from tulip poplar can fill the gap created by the loss of ash trees? Or the shagbark hickory can provide delicious and palatable nuts lost with the decline of beech and chestnut trees? Hickories and white oaks have beautiful, strong wood that is useful for many purposes: They produce great fuelwood, and hickory can be used for smoking. Spicebush and sassafras are smaller plants that create understory layers in the forest and provide wildlife food. White oaks are vital to support our insect populations.
This work allows us as a community to create knowledge and methods that might help us keep our forests healthy in the future. It may be that we need to take a more deliberate approach to forestry by planting new trees and creating a novel ecosystem. MOFGA will continue to install new assisted migration study trees in plots over the next year thanks to a Project Canopy Grant from the Maine Forest Service. Our efforts will create wildlife habitat for the coming century, and also give us a chance to work with hope instead of feeling despair as we move forward with the many changes to the Maine woods.
Aleta McKeage is a conservation biologist who has completed work for local soil and water conservation districts as well as state and national organizations. She specializes in ecological restoration and community science and conservation.
This article was originally published in the winter 2023-24 issue of The Maine Organic Farmer & Gardener.