Where There's Smoke There's Potential Losses in Agriculture.

Like many people across central North America, I've spent much of the past week looking out at a hazy sky and checking air quality alerts. Before going any further, it's important to acknowledge that for many northern communities—particularly First Nations communities located near active fires—wildfire season is far more than an inconvenience or a source of smoky skies. Many families have faced evacuations, disruptions to daily life, threats to homes and traditional territories, and prolonged exposure to unhealthy air. The human impacts of these fires are profound and should remain at the centre of the conversation.

Even for those of us hundreds or thousands of kilometres from the fires themselves, the health implications of wildfire smoke have been widely discussed—and for good reason. Poor air quality affects respiratory health, limits outdoor activities, and creates concerns for vulnerable populations. But I found myself wondering about another question: what happens to agriculture when smoke lingers for days or even weeks? I found that where there is smoke, there is potential for losses in Agriculture.

Smoke over a farm

Wildfire smoke is increasingly becoming another factor to consider. While smoke is often most visible in cities and towns, it also hangs over fields, pastures, and barns.

Farmers spend much of their year managing risks that come from weather. Drought, excessive rainfall, hail, heat, frost, and wind can all affect crop and livestock production. Wildfire smoke is increasingly becoming another factor to consider. While smoke is often most visible in cities and towns, it also hangs over fields, pastures, and barns.

I'm not a crop scientist or an animal scientist, but I was curious enough to do some reading. After working through research papers, extension publications, and industry summaries, I found that smoke can affect both crops and livestock. Some effects are relatively well understood, while others remain difficult to quantify. One thing is clear: wildfire smoke is not just an air quality or community threat issue. It is also an agricultural issue.

Why This Matters Now

This year's smoke event is unusual even in a period when wildfires seem to be occurring more frequently and over longer periods. Much of central North America has experienced significant smoke coverage, including areas that produce a substantial share of Canada's and the United States' food. In recent days, smoke has not simply been a high-altitude haze. In many locations it has settled closer to the ground, creating dramatically reduced visibility and much higher concentrations of pollutants. Timing matters in agriculture. Many crops across Ontario and the U.S. Midwest are currently in key stages of development. Corn is approaching or entering pollination, one of the most yield-sensitive periods in the entire production cycle. Stress during this period can have measurable effects on productivity. Soybeans are also actively growing and entering important reproductive stages.

When a major environmental event coincides with these critical growth periods, it naturally raises questions about potential impacts.

Smoke Can Affect Crops in Several Different Ways

One of the challenges in studying wildfire smoke is that it is difficult to isolate its effects. Researchers cannot easily create controlled field experiments where one half of a commercial field experiences smoke while the other does not. As a result, much of our understanding comes from observational studies, smaller-scale experiments, and our understanding of plant physiology. One particularly useful summary came from Dr. Mark Jeschke, Agronomy Manager with Pioneer, who outlines several competing effects that smoke can have on crops.

The first is straightforward: smoke can reduce the amount of sunlight reaching plants.

Plants rely on sunlight to power photosynthesis. If smoke reflects or blocks incoming solar radiation, less energy is available to drive plant growth. Less photosynthesis generally means less plant productivity. This is especially important for crops such as corn during pollination and grain fill. During these stages the plant is directing energy toward producing kernels. Reduced sunlight during this period has the potential to reduce yield. The effect is not uniform across all fields. Factors such as hybrid selection, planting dates, crop health, and plant populations all influence how crops respond. Fields with very high plant populations may be especially sensitive because plants are already competing intensely for available light.

Not All Smoke Effects Are Negative

Interestingly, the story does not end there. Smoke particles also scatter sunlight, creating what agronomists refer to as diffuse light. Instead of sunlight arriving primarily in a direct beam from above, it becomes more evenly distributed throughout the plant canopy.

This can actually provide an advantage under certain conditions. In a dense corn canopy, upper leaves often receive more sunlight than they can effectively use while lower leaves operate in relative shade. Diffuse light penetrates deeper into the canopy, allowing lower leaves to contribute more to photosynthesis. In some situations this improved light distribution can partially offset the reduction in total sunlight. Some researchers have even observed productivity benefits from diffuse light under the right conditions. This helps explain why the impact of smoke is not always obvious. The same smoke layer that reduces overall sunlight may simultaneously improve light distribution within the crop canopy.

The net result depends on the balance between those opposing forces.

Ozone May Be the Biggest Concern

A third effect receives less public attention but may be one of the most important.

Smoke and hot weather can contribute to the formation of ground-level ozone.

Unlike the protective ozone layer high in the atmosphere, ground-level ozone damages plant tissue. It interferes with photosynthesis, accelerates plant stress, and can reduce yields.

The scientific literature is remarkably consistent on this point: ozone is bad for crops.

Soybeans appear particularly sensitive because of their physiology and their exposure within the lower atmosphere. Other crops can also be affected. This issue becomes especially relevant during hot summer weather, which often accompanies major smoke events. In other words, the same environmental conditions that help create heavy smoke impacts can also increase the risks associated with ozone formation.

The Type of Smoke Matters

One of the more interesting insights from agronomists is that not all smoke events are equal.

Earlier in the recent smoke episode, much of Southern Ontario experienced a high, thin haze. While visually striking, those conditions may have promoted greater light diffusion without dramatically reducing available sunlight. More recently, smoke has shifted closer to the ground and become significantly denser. This "thick plume" scenario is different. Less sunlight reaches crops, ozone concerns become more pronounced, and air quality deteriorates significantly. Many agronomists view sustained low-level smoke during pollination and grain fill as a genuine risk factor. The challenge is that quantifying the exact impact remains difficult. We are unlikely to be able to point to a specific percentage yield reduction attributable solely to smoke. That uncertainty should not be confused with an absence of risk.

Livestock Impacts Are Easier to Measure

While crop impacts are difficult to isolate, livestock responses are somewhat easier to study because animal performance can be measured directly. The strongest evidence comes from dairy cattle. Research has shown that wildfire smoke exposure can reduce milk production and decrease milk protein concentrations. Both outcomes have economic consequences for dairy farmers. Milk protein, in particular, is an important driver of farm revenue and remains in strong demand. Some studies suggest these impacts can persist for up to a week after air quality improves.That means a smoke event does not necessarily end when the skies clear.

Why Cattle Are Particularly Vulnerable

Cattle appear especially susceptible to smoke-related respiratory issues. Both dairy and beef cattle have relatively small lung capacity relative to their body size. They also lack the extensive collateral ventilation pathways found in some other species. As a result, damage or infection in one part of the lung is more difficult to compensate for. Prolonged exposure to smoke can therefore create challenges that extend beyond immediate discomfort.

Research on beef cattle is more limited than the dairy literature, but the available evidence raises concern. Producer surveys in western U.S. states have reported increased pneumonia, lower conception rates, reduced weight gains, and lower birth weights following significant smoke events. One Australian postmortem study found substantially higher rates of pneumonia among cattle exposed to wildfire smoke for extended periods. Young calves appear especially vulnerable. This is worth noting because many calves across North America are currently spending their days on pasture alongside their mothers and are directly exposed to outdoor conditions.

What About Pigs and Poultry?

Interestingly, there is very little research examining wildfire smoke impacts on pigs or poultry.

The most likely reason is that these animals are typically housed in enclosed barns equipped with ventilation systems that provide at least some degree of protection from outdoor air conditions. The lack of research should not be interpreted as evidence that smoke has no impact. It simply means we have not done enough work to understand those impacts fully.

That distinction is important.

Another Climate Risk for Food Production

The bottom line is that wildfire smoke is more than a visibility or air quality issue. It has the potential to affect crop yields, livestock productivity, and ultimately food production. The exact magnitude of those impacts remains difficult to quantify, especially for crops. But as smoke events become more frequent and more intense, they represent another way climate-related disruptions can ripple through our food system.

That observation should not distract from the immediate reality that many northern and Indigenous communities are living with the direct consequences of these fires in ways that most of us are not. Rather, it highlights how extensive the effects of major wildfire events can be. From evacuations and health impacts to agricultural productivity and food systems, the consequences extend far beyond the fire line itself.

The haze hanging over our cities may be the most visible sign of wildfire season. The impacts on people, communities, agriculture, and food systems are less visible—but they may linger long after the smoke clears.

Recommended citation format: von Massow, M, "Where There's Smoke There's Potential Losses." Food Focus Guelph (148) , Department of Food, Agricultural and Resource Economics, University of Guelph, July 20, 2026

Keywords: Smoke, wildfires, agriculture, crops, livestock, beef, dairy