When smoke from Canadian wildfires drifted across much of Michigan in recent days and North America in recent years, the public noticed orange skies, poor air quality, and canceled outdoor events. Less visible was another story unfolding beneath those hazy skies. Fish continued feeding in darkened lakes, migrating birds altered their movements, pollinating insects became less active, and forests hundreds of miles from any flames received measurably less sunlight.
Wildfire smoke is more than suspended ash. It is a complex mixture of fine particulate matter, carbon monoxide, carbon dioxide, nitrogen oxides, volatile organic compounds, ozone precursors, and microscopic particles that influence both living organisms and the physical environment.
The consequences ripple through ecosystems in surprising ways.
Wildlife Breathes the Same Air We Do
Birds are among the most vulnerable because of their highly efficient respiratory systems. Air flows continuously through their lungs and air sacs, making oxygen exchange exceptionally effective—but also exposing them to airborne pollutants. During prolonged smoke events, researchers have documented reduced activity, altered migration timing, and declines in body condition. Migratory birds face an especially difficult challenge. Many depend upon visual landmarks, celestial navigation, and favorable atmospheric conditions. Thick smoke obscures these cues while simultaneously reducing visibility of stopover habitats.
Large mammals such as deer, elk, moose, and bears reduce daytime movement, decrease feeding activity, and shift toward sheltered habitats. While these responses likely reduce smoke exposure, they may also reduce nutritional intake during seasons when animals are building fat reserves. Predators may also hunt less effectively when visibility declines. Wolves, coyotes, hawks, and eagles all rely heavily on vision. Smoke effectively shortens their hunting range.
The Insect Connection
Many ecological effects occur lower in the food web. Bees, butterflies, moths, and numerous flies reduce foraging during heavy smoke. Smoke alters light intensity, masks floral odors, and interferes with insect orientation. Reduced pollination can temporarily decrease seed production and fruit development, particularly if smoke coincides with flowering periods. Dragonflies, mayflies, and caddisflies—the foundation of many freshwater food webs—may experience indirect effects if smoke alters water temperature or chemistry. Since insects support birds, bats, fish, amphibians, and countless other species, even modest reductions in insect activity can cascade through ecosystems.
When Smoke Changes the Sun
One of smoke’s most overlooked effects is its ability to filter sunlight. Heavy smoke reduces the amount of solar radiation reaching Earth’s surface. Lakes remain slightly cooler. Forest floors receive less light. Plant photosynthesis slows.
For aquatic systems, reduced sunlight can suppress growth of algae and aquatic plants. That sounds beneficial where excessive algae occur, but healthy lakes depend upon primary productivity. Less photosynthesis means less oxygen production and fewer food resources for zooplankton and aquatic insects.
Smoke Eventually Falls into Water
What goes up eventually comes down.
Ash, soot, and airborne particles eventually settle onto lakes, streams, wetlands, and forest canopies. Rain accelerates this process by washing particles from the atmosphere. Once deposited, smoke particles introduce nutrients such as nitrogen and phosphorus along with trace metals and organic compounds. Small nutrient inputs can stimulate plankton growth. Larger inputs may contribute to oxygen depletion as algae die and decompose.
Water Chemistry Can Change
Smoke-derived particles may slightly alter pH, dissolved organic carbon, and nutrient concentrations in surface waters. These changes rarely produce fish kills, but they can subtly influence aquatic food webs.
Increased organic matter may reduce water clarity. Less light penetrates deeper waters. Aquatic vegetation may decline while bacterial decomposition increases. In streams already stressed by drought or high temperatures, smoke deposition may compound existing problems.
Habitat Without Fire
Many wildlife habitats experience smoke despite never burning. Prairies hundreds of miles from wildfires receive ash deposition. Wetlands experience reduced sunlight. Forests outside burn zones undergo temporary declines in photosynthesis. Smoke can extend wildfire impacts far beyond mapped fire perimeters and traditional assessments often underestimate the ecological footprint of major wildfire seasons.
Fish Feel Smoke Indirectly
Fish seldom inhale smoke directly. Instead, they experience downstream consequences. Reduced aquatic insect production means less food. Changes in water temperature alter metabolism. Nutrient deposition affects algae and lowers dissolved oxygen following decomposition stresses sensitive species.
Some salmon populations in western North America migrate through rivers affected by ash and smoke deposition, where multiple stressors—including elevated temperatures, sediment, and altered water chemistry—combine to reduce survival.
Behavioral Changes Across Species
Wildlife often responds to smoke before physiological damage occurs. Researchers have documented:
- Reduced bird song.
- Delayed nesting activity.
- Lower pollinator visitation.
- Reduced bat foraging.
- Altered deer movement.
- Changes in predator-prey interactions.
- Delayed migration departures.
These behavioral adjustments represent attempts to minimize exposure but may carry energetic costs if smoke persists.
The Climate Feedback Loop
Wildfire smoke also influences climate. Smoke particles reflect and absorb sunlight, altering local temperatures and atmospheric circulation. Some particles cool Earth’s surface temporarily by reflecting sunlight. Others absorb heat high in the atmosphere. These changes influence cloud formation, rainfall patterns, and even future fire behavior.
Not All Smoke Is Equal
Smoke composition varies dramatically depending on what burns. Grass fires produce different emissions than peatlands and conifer forests release different compounds than hardwood forests. Older, smoldering fires often produce higher concentrations of fine particulates than fast-moving flame fronts. Moisture conditions, fuel type, and combustion temperature all influence ecological effects.
A Growing Conservation Challenge
Climate change, prolonged drought, insect outbreaks, and expanding human development are producing larger, more frequent wildfires across western North America and increasingly in boreal Canada. As these fires grow, so too does the geographic reach of smoke. States like Michigan may escape the flames yet experience weeks of degraded air quality and ecological effects from fires burning thousands of miles away.
Wildlife managers traditionally focus on burned habitat, but future conservation planning may increasingly need to account for smoke as a landscape-scale ecological disturbance.
Looking Beyond the Burn Scar
Wildfire will always be a natural ecological force. Many forests and grasslands evolved with periodic fire, and numerous species depend upon it. Smoke, however, is a different kind of disturbance. It crosses political boundaries, watersheds, and ecosystems, connecting distant landscapes in ways that fire itself cannot. The ecological effects are often subtle rather than catastrophic—a slightly darker lake, fewer pollinating insects on a smoky afternoon, birds delaying migration by a day or two, plants photosynthesizing just a little less efficiently. Yet when smoke blankets millions of acres for weeks at a time, these small changes accumulate. Those invisible impacts remind us that in nature, the reach of a wildfire extends far beyond its flames.
