The March 2025 ice storm in northeastern Lower Michigan was impactful. Many residents were forced to leave the area until power was restored. Access to properties was hampered for months. Chainsaws and/or generators were started for the first time in years. Past efforts spent in timber or wildlife habitat management were thrown a curveball. Now, with the benefit of time, literature review, and observation, we can start to discuss the ways our forests are responding.

Events that regulate biomass in ecological systems are called disturbances. Fire, insect or mammalian herbivory, timber sales, wind or ice storms, etc. are all disturbances. Disturbances can be relatively specific to a forest type or more general.

Fire, for instance, is an important disturbance in upland pine ecosystems in that it prepares the soil surface for seeds that may fall after the fire. Fire also thins out a forest, reducing the number of smaller diameter trees and/or tree species less fire resistant (e.g., red maple). Red pine, jack pine, and many other associated plants require fire, as do the wildlife of these forests.

Windthrow, on the other hand, is more important in northern hardwoods and in our lowland coniferous swamps. Ice storms impact nearly all forest types.

Plants and animals have evolved a variety of strategies to adapt to different types and severities of disturbances. For instance, while all plants require sunlight to produce their own food via photosynthesis, some species need more sunlight than others. Plant species that require more sunlight are called shade intolerant. Many fire-dependent plants are shade intolerant and need the open canopies created by fire.

Conversely, a different suite of plant species of northern hardwood forests or swamps can exist in more variable light conditions. Yellow birch requires more sunlight than American beech, for instance. And black spruce, balsam fir, and northern white-cedar found in our swamps often exist in very low light conditions.

Assuming the existence of a diversity of seed sources and minimal herbivory (both unlikely in many areas), ice storms can increase natural forest complexity by providing variable light conditions for a broad array of colonizing plant species. Alternatively, individual plants not killed by an ice storm can be freed from competition for light amongst their neighbors and show increased growth across upcoming years. Many deciduous tree species can even survive and resprout if all their limbs are removed as energy stored in their roots can sustain them until new green growth develops.

Ice storms can also theoretically benefit a forest by creating complexity in forest structures. Structures are physical elements in a forest, such as standing dead trees used by woodpeckers and flying squirrels, downed logs used by drumming ruffed grouse or ermine, patches of tree regeneration used by songbirds and snowshoe hares, or openings in which butterflies and bees forage. Forests with more structural complexity tend to be more species rich and store more carbon.

Walk a lowland coniferous swamp dominated by northern white-cedar and the “mess” (as some call it) comprises the important structures that develop from disturbances. These forests, and the shade tolerant plant species that are found in them, require disturbance. In fact, seeds often germinate and grow from the remains of trees that had previously fallen and are decaying. The chaos of a swamp drives the diversity of flora and fauna found in them.

However, forests that lack mature trees, or lack plant diversity in the forest pre-disturbance, or are overrun with white-tailed deer and/or invasive plants face different outcomes. The ice storm may produce openings for plant regeneration, but those plants palatable to deer are eaten and the number of individuals of plant species less palatable to deer increases. Or, invasive species found before the ice storm are provided more sunlight to which they respond by increasing their growth or reproduction rates. In these cases, the ice storm can facilitate more uniformity, not complexity. Much depends on the condition of the forest before the ice storm.

Many scientific studies have illustrated the above points, with a paper in the Journal of Vegetation Science (2021, v.32) being one that showed that the combination of canopy gap size and the control of white-tailed deer browse through exclosures together influenced the composition of plant communities over shorter time frames in central Wisconsin. However, it was deer that impacted the resulting plant community more so over the longer-term.

What should landowners know and do?

Forests with more natural complexity generally respond better to disturbances. Too many forests are uniform and species poor, leaving far fewer adaptation opportunities when unforeseen disturbances occur.

Natural disturbances differ from most traditional forest management techniques that create simplified (homogenized) light conditions and structures. Ecological forestry, on the other hand, aims to produce more natural and complex patterns of disturbances and explicitly uses the natural world as a model for management.

Understanding and planning for opportunities and limitations and the potential tradeoffs in management is a critical first step. Landowners need to know the soils they have, what type(s) of forest grow on them, what type of disturbances shape them, and the natural range of variability they should expect in plant species and structures. Not all forests should look or function the same.

Next, landowners should understand that even in tough situations opportunities exist for managing for a more complex forest in the future (restoration!). For instance, in many forests that are dominated by a few deciduous tree species, such as northern red oak and red maple, canopy gaps created by the ice storm provide opportunities for enhancing the diversity and structure of the forest through planting poorly represented, native tree species such as eastern white pine, white spruce, etc. (see figure).

Above all, consider the range of natural complexity of your forest as a desired future condition and communicate this to the professionals you work with.