Chapter 2. Climate Change and Its Health Impacts

Climate change is often thought of in terms of weather and the environment, but it is fundamentally a health issue. Around the world and here in Canada, we are already seeing climate-driven events affect people’s bodies and minds. From heatwaves to wildfires and floods, these events pose direct physical dangers and also take a profound mental health toll. For health and social care providers – physicians, nurses, social workers, therapists, community workers, and others – understanding these impacts is critical. We know from experience that after a disaster strikes, people face not only immediate injuries but also emotional and psychological trauma that can last long after the event (1). This chapter explores how different climate-related impacts – extreme heat, wildfires, flooding, drought, displacement, and ecosystem change – affect health. We pay special attention to mental health and trauma, which are too often overlooked in climate discussions. Throughout, we’ll highlight how vulnerable populations are disproportionately affected, and we’ll take an inclusive, trauma-informed perspective. By the end, it will be clear that climate change is everyone’s problem in health care. Chapter 3 will then delve even deeper into the psychological consequences and what we can do about them.

Extreme Heat

When extreme heat waves hit, the health impacts are immediate – and deadly. In late June 2021, British Columbia experienced an unprecedented heatwave or “heat dome.” Temperatures soared above 40°C in many communities, shattering records (2). Over the course of one week, more than 800 sudden deaths were reported, and 619 were ultimately confirmed as heat-related (2). Most who died were older adults or people with chronic illnesses who lived alone in homes without air conditioning (2). This tragic event brought home the reality that heat can kill. Heatstroke and dehydration are the most obvious risks, but extreme heat also exacerbates heart and lung conditions and even affects kidney function. For instance, on hot days we see more patients with asthma flare-ups (due to ozone and wildfire smoke), more cardiac arrests, and more complications in people with diabetes whose medications or equipment fail in the heat (3).

What’s equally concerning – and less visible – are the mental health impacts of extreme heat. As temperatures climb, people often feel irritable, anxious, or unable to sleep. During the 2021 heat dome, many British Columbians genuinely feared for their lives in the stifling heat (4). Those with pre-existing mental health conditions were especially vulnerable. A study by the BC Centre for Disease Control found that people with serious mental illnesses (like schizophrenia) had a risk of dying three times higher than expected during the heat dome (3). Why? Some psychiatric medications interfere with heat regulation, and cognitive challenges can make it harder to escape the heat. The heat dome also struck during the COVID-19 pandemic, isolating many people who might otherwise have had someone to check on them (4). Social isolation and poverty compounded the risk – most deaths occurred in low-income urban areas where people lived alone in poorly ventilated apartments (4).

Beyond the physical dangers, there is a psychological side to heat waves. Surviving a life-threatening heat event can leave emotional scars – anxiety whenever the forecast calls for high temperatures, or trauma for those who lost loved ones. Many British Columbians reported a spike in climate change anxiety after living through the 2021 heat dome (5). Front-line workers also felt the strain. Paramedics and emergency staff were inundated with 911 calls (which doubled during the peak of the heat dome) and described their shifts as “taking an emotional toll” while being physically exhausting (6). First responders experienced moral distress arriving too late to help some patients, and some needed time off for mental health afterward (7). These experiences underscore that extreme heat is not just an environmental problem – it is a public health crisis that tests our health systems and our resilience (1).

Looking ahead, climate change means Canada will face more frequent and severe heatwaves. Health providers should recognize that heat emergencies can present with both physical symptoms (heat exhaustion, fainting, organ failure) and psychological distress (anxiety, confusion, even delirium). Simple steps like ensuring patients have access to cooling, hydration, and a support network during heat alerts can save lives. And as we’ll explore further in the next chapter, we must be prepared to support the mental health needs that follow in the wake of extreme heat.

Wildfires

In recent years, Canada’s wildfire seasons have been record-breaking – and communities have felt the impact in body and mind. Wildfire smoke has blanketed towns and cities, turning skies an eerie orange-grey and prompting air quality warnings. Breathing in heavy smoke can irritate the lungs, trigger asthma attacks, and even increase the risk of heart attacks and strokes (8). During bad wildfire smoke days, hospitals see more patients with breathing difficulties and chest pain. But the damage isn’t only physical. There is growing evidence that wildfire smoke exposure can affect mental health too, contributing to anxiety and a sense of dread (8). When the air is thick with smoke for days, people describe feeling “on edge” or trapped inside, especially if they know a fire is raging nearby.

The most acute impacts, however, hit those in the path of the flames. Wildfires force mass evacuations, destroy homes, and can devastate entire communities. The trauma of fleeing a wildfire can linger for a long time. In 2016, a ferocious wildfire in Fort McMurray, Alberta forced 80,000 people to evacuate. Even 18 months after the fire, local teens had markedly higher rates of depression, suicidal thoughts, and substance use than peers elsewhere. Disturbingly, three and a half years after the fire their mental health had declined even further, indicating prolonged trauma. This Canadian example shows how post-traumatic stress disorder (PTSD) and other issues can persist and even worsen over time after a disaster. Studies of other wildfires echo this pattern – more anxiety, depression, and PTSD in affected communities, especially among those who directly witnessed destruction or lost their homes (8). Children are particularly vulnerable; kids who live through wildfires may become fearful of any sign of smoke or fire, have nightmares, or develop behavioral changes that last for years (5).

During the 2023 wildfire season in B.C., which saw thousands evacuated from the Okanagan and Shuswap regions, mental health workers reported a rollercoaster of emotions in evacuees: anxiety, fear, sadness, numbness, anger (1). It’s normal to feel relief when the fire is contained, followed by guilt that others are still in danger (1). People can experience “survivor’s guilt” if their home was spared while a neighbour’s burned. The loss of one’s home or community in a fire is more than just losing property – it means losing memories, stability, and even a sense of identity. As one B.C. resident put it, “It was just so traumatic… you didn’t think anything was going to survive” (5).

For Indigenous communities, wildfires can also mean loss of traditional lands and disruption of cultural practices (for example, loss of hunting grounds or medicinal plants), adding layers of grief. And for first responders and firefighters, repeated exposure to life-threatening situations and witnessing devastation can lead to burnout, PTSD, or moral injury. In fact, first responders are one of the groups at higher risk of mental health challenges from climate disasters (5).

Wildfires also bring a slower-burning mental health strain: during the summer of 2017, vast parts of interior B.C. were shrouded in smoke for weeks even in areas not under immediate threat. Many people described a creeping anxiety – Will we have to evacuate next? – and a sense of claustrophobia from being indoors to avoid the smoke. Eco-anxiety can be heightened when each summer seems to bring more burning forests. Health providers in affected regions should be attentive not only to respiratory symptoms in patients, but also signs of stress and trauma related to wildfires. The good news is that with support, individuals and communities can be resilient. Talking about fears, accessing counselling (including culturally safe services for Indigenous evacuees), and community gatherings for mutual support have all helped people recover after wildfires. Still, as climate change makes fire seasons longer and more intense, we need to prepare for a continued mental health aftershock long after the flames are doused (1).

Floods and Storms

From catastrophic river floods in Western Canada to powerful hurricanes lashing Atlantic Canada, extreme weather events linked to climate change are becoming more frequent. These events pose immediate physical dangers: injuries from debris or rushing water, hypothermia from exposure, drownings, and exposure to contaminated water. Floodwaters can carry sewage or toxic materials, leading to infections or gastrointestinal illnesses. In the aftermath, mold growth in water-damaged homes can cause respiratory problems if not properly cleaned. For example, after severe flooding in a Nova Scotia community, improperly refilling a dry well led to an outbreak of gastrointestinal illness in dozens of residents (9) – a reminder that water quality issues often follow floods. And we shouldn’t overlook that power outages often accompany storms, which can be life-threatening for people on medical devices or who rely on refrigerated medications.

As with heat and fire, however, the mental health impacts of floods and storms can be far-reaching. Being caught in a flood or hunkering down through a ferocious storm is terrifying. In Eastern Canada, residents who lived through post-tropical storm Fiona in 2022 described the ordeal – hearing the wind rattle their homes, seeing storm surges carry away roads and houses – and the shock that set in afterward. People often experience acute stress reactions: disorientation, nightmares, or a sense of disbelief that their neighborhood is underwater. And when the waters recede, survivors may face months of displacement and rebuilding, which takes a psychological toll. It is common for flood survivors to report anxiety every time it rains, flinching at any heavy downpour, much like how some wildfire survivors become jumpy at whiffs of smoke. This kind of conditioned fear is a hallmark of trauma. Studies globally have found high rates of PTSD and depression in communities hit by major floods. For instance, after severe flooding in Southern Alberta in 2013, many residents showed signs of PTSD in the year following, especially those who had to be rescued or suffered extensive home damage.

Floods and storms also uproot the social fabric. Families might be living in temporary accommodations for long periods, communities can be split apart, and the usual support networks (neighbors, local clinics, community centers) are disrupted. The stress of navigating insurance claims and rebuilding can lead to anger and frustration, sometimes straining relationships. In some cases, there’s an element of grief – grief for lost possessions that were heirlooms, or grief for the loss of a sense of safety. After a disaster, it’s not uncommon for people to say they no longer feel safe in their own home if that home has been damaged by flood or storm. This can manifest as chronic anxiety or insomnia.

Healthcare and social service providers may see an uptick in conditions like insomnia, substance use, or family violence in the aftermath of a disaster, all of which can be exacerbated by the stress and financial strain. One B.C. clinician noted that after the 2021 floods that washed out highways and isolated entire towns, some patients exhibited signs of acute stress and panic – for example, truck drivers stranded by road closures who were running out of necessary medications, or parents separated from their children due to evacuation orders. These indirect effects illustrate how care delivery itself can be challenged: patients and providers might literally be cut off from one another, or health facilities might be flooded and closed. Community workers recall how volunteer and mental health supports poured in after the Fort McMurray fires and the Calgary floods – showing the importance of mobilizing resources quickly to support psychological recovery.

The silver lining is that communities often come together after floods and storms. Neighbors help neighbors, volunteers show up with food and supplies, and this social solidarity can buffer mental health impacts. However, we must remember that some individuals – especially those with fewer resources or who were vulnerable beforehand – may struggle to recover. Providers should be aware of resources for trauma counselling or peer support groups for disaster survivors. Simple interventions, like teaching grounding techniques for anxiety or offering referrals for counselling, can make a big difference. And as a system, integrating mental health services into disaster response (for example, having counsellors at evacuation centres) is now recognized as a best practice in Canada.

Droughts and Water Insecurity

Droughts do not strike with the drama of a wildfire or hurricane, but they represent a slow-burning crisis that can deeply affect health. In the Canadian Prairies and interior British Columbia, climate change is bringing hotter, drier summers with more frequent drought conditions (9). For farmers and ranchers, drought can mean crop failures, poor harvests, or having to cull livestock – an economic and emotional disaster. Repeated bad years create a crushing sense of helplessness. One Saskatchewan farmer described the 2021 drought as “watching your livelihood wither away, day after day, under a relentless sun,” noting how it led to sleepless nights and constant worry about the future of the family farm. This kind of stress adds up: research shows that farmers experience high levels of stress, depression, and anxiety, in part due to uncontrollable factors like weather (10, 11). In bad drought years, crisis lines see more calls from farmers in distress (12). Tragically, severe droughts have been associated with increased suicide risk in farming communities (9). It’s a stark reminder that mental health in rural areas is tightly linked to the climate and the land.

Beyond farmers, drought affects entire communities. When water levels drop, towns may impose water-use restrictions, wells may run dry, and wild animals may encroach on settlements in search of water. These changes can cause friction and anxiety. For example, if a community’s reservoir runs low, people might worry whether their tap will run tomorrow – that uncertainty is stressful. Droughts also raise the risk of other hazards: extremely dry conditions set the stage for wildfires (as witnessed in 2023 when a spring drought primed Alberta’s worst wildfire season on record; 9). And when rains finally return after a drought, the hardened ground can lead to flash floods – a cruel whiplash effect that has its own dangers (9). So communities in drought can feel they’re in a constant state of alert.

Physical health can suffer in less obvious ways. Drought can compromise water quality (concentrating pollutants or causing saltwater intrusion in coastal wells) and reduce food availability. In remote or northern areas, if traditional food sources like fish or game decline due to changing habitats, communities may face food insecurity and poorer nutrition. This can lead to knock-on health effects like higher rates of chronic illness over time. For Indigenous peoples, the loss of traditional foods and clean water isn’t just a nutritional issue – it’s deeply psychological and spiritual. It represents an erosion of culture and identity, leading to feelings of grief. Elders in one First Nation community in the B.C. interior shared that seeing the once-abundant salmon runs dwindle in drought years brought immense sadness, as salmon are integral to their way of life.

Even in urban settings, drought can affect mental health. Think of a city under water restrictions during a long summer drought – lawns turn brown, parks get dusty, and there’s a sense of tension in the air. People might start arguing over water use or feeling guilty about that long shower. While Canadians are not as accustomed to thinking about water scarcity, other parts of the world have shown how drought can cause collective anxiety and even conflict. It’s not far-fetched that as our climate warms, Canadians too may experience a psychological strain from periods of prolonged dryness and heat.

For healthcare providers, some drought impacts will appear indirectly. You might see increased mental health issues tied to financial stress (e.g., farmers facing bankruptcy), or respiratory issues if dust and wildfires increase. Substance use might rise as a coping mechanism in struggling rural towns. It’s important to connect the dots: asking patients about their work and environment can reveal if climate stressors like drought are contributors to their anxiety or depression. On the flip side, community-based interventions – such as farm peer support programs or phone lines for those in the agriculture sector – have proven helpful. (In fact, provinces like Saskatchewan have farm stress lines that have been lifesaving during drought crises (9).) Building these support systems and letting people know about them is key as we navigate an era of increased climate uncertainty.

Food Insecurity and Agriculture

Climate change poses a serious threat to food security and nutrition. Warming temperatures, shifting precipitation, and more frequent extreme weather disrupt all stages of food production – from crop growth to livestock health and even food storage and transport (1). In Canada, a country often viewed as a breadbasket, these disruptions have tangible impacts. The 2021 extreme heat and drought in Western Canada, for example, caused national wheat yields to plummet to their lowest in over a decade – a nearly 40% drop in production compared to the previous year (2). Such steep losses illustrate how climate extremes can reduce the availability of staple foods, drive up prices, and threaten livelihoods in farming communities. Less obvious, but equally important, is the decline in nutritional quality of some crops under climate stress, which can mean fewer nutrients in the food that reaches Canadian tables (1). All of these changes have direct consequences for physical health: reduced food availability and rising costs increase the risk of hunger and malnutrition, especially among those who already struggle to afford healthy food.

Agricultural regions across Canada are experiencing new challenges that affect food safety as well. Warmer weather and humidity enable food-borne pathogens to thrive, increasing the risk of contamination and illness. For instance, higher summer temperatures can accelerate the growth of Salmonella bacteria and even heighten the chance of toxins like botulism forming in improperly stored foods (3). Meanwhile, heavy rainfall and flooding – expected to worsen with climate change – can spread agricultural pollutants and sewage into fields and water supplies, tainting crops and leading to boil-water advisories. Coastal fisheries and aquaculture are also feeling the strain: warming oceans and changing salinity have been linked to outbreaks of Vibrio bacteria in shellfish, a cause of serious food poisoning (1). These food safety issues mean that climate change not only threatens how much food is available, but also whether that food is safe to eat. Outbreaks of food-borne illness can cause dehydration, organ damage, or worse, especially in young children and seniors. Public health agencies warn that without adaptation, Canadians could see more frequent cases of gastrointestinal infections and other illnesses tied to spoiled or contaminated food (1).

The health impacts of climate-induced food insecurity are far-reaching. A lack of reliable access to nutritious food is linked to higher rates of chronic illnesses like heart disease and diabetes, as well as developmental problems in children (1). In the most extreme cases, malnutrition can weaken the immune system and leave people more susceptible to disease, creating a vicious cycle where poor health makes it even harder to obtain or prepare food (1). Healthcare providers in Canada have observed that adults in food-insecure households are more likely to require hospital care and become high-cost health system users (1). Additionally, the stress and anxiety of not knowing if one can feed one’s family is a heavy burden. Research shows that household food insecurity often leads to mental health challenges, including elevated risks of depression and distress (1). While this chapter centers on physical health, it is important to note that the emotional toll of food insecurity – the worry, sense of helplessness, and trauma of going hungry – is very real for many Canadians, foreshadowing some of the mental health impacts explored in the next chapter.

Importantly, climate change does not affect all communities equally. Northern and Indigenous populations in Canada are among the most vulnerable to climate-related food insecurity (1). These communities already face high rates of food insecurity due to systemic inequities and the erosion of traditional food systems. In fact, Inuit adults in Nunavut experience food insecurity at 3.7 times the rate of non-Indigenous Canadians – the highest documented in any high-income country (1). Climate change is compounding this crisis. Thawing ice and unpredictable seasons are making it dangerous or impossible to hunt, fish, and forage in some areas, cutting off access to traditional foods like caribou, seal, and wild plants (1). With permafrost warming, even historic ways of preserving food are under threat; for example, in-ground ice cellars used for meat storage in Arctic communities are becoming unreliable as the ground warms and shifts (1). These changes force greater reliance on store-bought foods that are often exorbitantly expensive in remote regions, further straining family budgets and diets. The loss of traditional foods also has cultural and emotional repercussions: it weakens the transmission of knowledge and identity across generations, and diminishes the sense of security and pride that comes from living off the land. In this way, climate change’s impact on food and agriculture is not just an environmental or economic issue – it is fundamentally a public health issue. Ensuring equitable access to sufficient, safe, and culturally appropriate food in a changing climate will be critical to protecting Canadians’ health and well-being in the years ahead (1).

Sea Level Rise and Coastal Erosion

Around the world and in Canada, sea levels are steadily rising, and the rate is expected to accelerate through this century. As oceans warm and land ice melts, higher seas are magnifying coastal hazards that were once only seen in rare storms. In Atlantic Canada – where the land is slowly sinking – relative sea levels could climb by up to 1.75 metres by 2100 under high-emission scenarios (4). Even on British Columbia’s Pacific coast, where fewer extreme rises are projected, rising seas threaten large urban populations. Canada boasts the longest coastline in the world, and an estimated 600,000 Canadians are already exposed to coastal flooding, a number projected to swell to 850,000 by 2100 as sea levels continue to creep higher (4). This slow-moving change often goes unnoticed day-to-day, but its effects are becoming alarmingly clear during high tides and storms. What used to be “once in a century” flood levels are occurring more frequently, turning seasonal king tides or windy days into flood events for low-lying neighborhoods (4). Coastal communities in Nova Scotia, Prince Edward Island, and Newfoundland have seen roads and wharves regularly inundated by tides that now reach farther inland. On the West Coast, First Nation villages and cities alike watch the tides warily, knowing the Salish Sea and Fraser River are inching closer to their doorsteps each year (4).

The immediate physical impacts of sea level rise and coastal erosion on health can be devastating. Floodwaters can inundate homes and hospitals, cut off roads, and overload sewage and drainage systems, leading to contamination and disease outbreaks. Coastal flooding often brings saltwater into freshwater aquifers and wells (4), jeopardizing drinking water supplies with salinity and pollutants. Communities in Atlantic Canada have reported saltwater intrusion in their wells after storm surges, leaving residents without safe water for days. Consuming water with high salt content can cause dehydration and hypertension over time, while exposure to bacteria-laden floodwater can result in gastrointestinal illnesses or skin infections. There is also a risk of physical injuries or fatalities from these events: drowning in severe floods, or trauma from collapsing structures and storm debris. For instance, during Hurricane Fiona in 2022 – one of the most intense post-tropical cyclones to ever hit Atlantic Canada – storm surge flooding and coastal erosion swept houses out to sea and caused multiple deaths and injuries. Such disasters underscore how rising seas turn up the dial on storm impacts, transforming what would have been dangerous storms into outright catastrophes for health and safety.

In many places, erosion of shorelines is an equally urgent concern, albeit a slower one. Gradually, coastal land is crumbling away – cliffs collapsing, beaches narrowing, entire stretches of shoreline retreating. Prince Edward Island has been losing roughly 28 cm of coastline per year in some areas due to erosion, a rate expected to increase with higher seas and more powerful waves. Homes and critical facilities near the edge are at risk of being literally undermined. In Canada’s North, the village of Tuktoyaktuk (NT) sits on a low-lying spit that has been eroding at an alarming pace as permafrost thaws and Arctic sea ice (which once buffered the shore from waves) diminishes (4). Several families in Tuktoyaktuk have already had to relocate as their houses teeter on the eroding coast, and the entire community is considering plans to move inland – a drastic and costly step that exemplifies climate-forced displacement. On the Pacific coast, the City of Delta (south of Vancouver) illustrates a different dilemma: about half its land lies below 1.5 m above sea level, protected only by an aging dike network (4). If those dikes were to fail under rising seas and a one-in-100-year storm, it’s estimated that over 300,000 people in the Lower Mainland could be displaced (4). The scale of such an evacuation would strain emergency services and health care systems, as seen in past mass evacuations. Even short of that worst-case scenario, recurrent flooding and creeping erosion impose chronic health stresses on coastal residents – from mold infestations in constantly damp homes to the loss of arable land, which can reduce local food supply and economic security.

The human toll of sea level rise goes beyond the physical damage. Living under the constant threat of losing one’s home, land, or community takes a heavy psychological toll. Indigenous communities on all three coasts are particularly vulnerable to these impacts (4), as they often inhabit low-lying delta lands or small islands and have deep cultural ties to their coastal homelands. For these communities, the erasure of ancestral shorelines is not only a property loss but a loss of heritage, sense of place, and even sacred sites. This slow-onset disaster can cause profound grief, eco-anxiety, and feelings of helplessness as familiar landscapes literally vanish. Studies have found significantly higher levels of anxiety, depression, and trauma in people whose communities are at high risk from sea level rise and erosion, compared to those in safer areas (5). The process of relocation – should it become unavoidable – can itself be traumatic, particularly for elders and those with strong attachments to place. Uprooting an entire community means disrupting social networks, cultural practices, and access to services like schools and hospitals, all of which can negatively affect health. Moreover, not everyone has the resources to adapt or move; low-income families and isolated settlements may lack the funding for sea walls or the option to simply relocate to safer ground. This raises issues of climate justice: those with the fewest resources often face the greatest risks. Addressing sea level rise, therefore, is not just a matter of building seawalls but also safeguarding the health and dignity of coastal peoples. Ensuring access to mental health support, safe housing, and clean water for affected communities is essential as Canada confronts this rising tide.

Infectious Diseases and Illness

Climate change is altering the landscape of infectious diseases in Canada, influencing where and when pathogens spread. Many diseases are climate-sensitive, meaning their incidence can rise or fall with shifts in temperature, precipitation, and other environmental conditions. In recent years, public health experts have observed troubling changes: illnesses once thought to be tropical or rare in Canada are appearing more frequently and further north. For example, Lyme disease, a tick-borne illness, was virtually unheard of in most of Canada a few decades ago; today, it’s an emerging public health concern in numerous provinces. There is strong evidence that Lyme disease’s northward emergence has been driven by climate warming, which makes more of Canada hospitable to the blacklegged ticks that carry the disease (6). Warmer winters allow ticks to survive in greater numbers and expand their range, while hotter, longer summers boost their breeding season. The result has been a dramatic increase in reported Lyme cases – a rise from only a handful of cases in the early 2000s to well over a thousand per year by the late 2010s. Victims of Lyme disease can suffer serious physical health effects, from fevers and severe joint pain to long-term neurological complications if the infection goes untreated. Beyond Lyme, other tick-borne diseases like anaplasmosis and Powassan virus are also projected to spread into Canadian regions where they were previously absent. Each of these infections brings its own health risks, such as organ damage or brain inflammation, posing new challenges for healthcare providers and communities.

Mosquito-borne diseases are also on the move. Canada has historically had limited exposure to diseases carried by mosquitoes, but that is changing as the climate warms. West Nile virus, transmitted by certain mosquito species, provides a cautionary tale. In the early 2000s, West Nile virus became established in Canada, with periodic outbreaks causing cases of encephalitis (brain inflammation) and even deaths. Research suggests that weather extremes – hot, dry spells followed by rainfall – create ideal conditions for West Nile virus outbreaks, and climate change is making such weather patterns more common (6). Meanwhile, the range of mosquitoes themselves is shifting. The Aedes mosquitoes capable of carrying dengue, Zika, or chikungunya viruses struggle to survive Canada’s cold winters, but warmer temperatures are improving their odds of establishment should they be introduced. Just as ticks marched north, there is concern that mosquito vectors from the southern United States could gradually move into southern Canada given milder conditions and longer warm seasons. Already, viruses like the Eastern equine encephalitis (EEE) virus have been detected in Canada, and scientists believe that the emergence of EEE here “could have been facilitated by a changing climate”. Though still relatively rare, EEE has a high fatality rate in humans, so its presence is closely monitored. Additionally, Canada has several homegrown mosquito-borne viruses (such as Snowshoe Hare virus and Jamestown Canyon virus) that may see changes in incidence as the climate shifts. Warmer, wetter summers and flooded habitats can boost mosquito populations, increasing the bite risk for people and potentially raising infection rates during the summer months. The health effects of these diseases range from mild flu-like symptoms to severe neurological damage or death, underscoring why the spread of vectors is a serious public health issue.

Beyond ticks and mosquitoes, climate change influences many other infectious disease pathways. Water-borne illnesses can surge with heavy rainfall and flooding, when runoff can contaminate drinking water with pathogens like Giardia or E. coli. In 2000, a catastrophic water contamination event in Walkerton, Ontario (though not directly caused by climate change), tragically demonstrated how fecal bacteria in water can lead to widespread illness and even loss of life. Now, with climate projections of more intense downpours, rural and urban communities alike face higher risks of sewage overflow and well contamination. Harmful algal blooms in warming lakes – such as the blue-green algae that increasingly foul Lake Winnipeg – produce toxins that can sicken people, causing rashes, gastrointestinal illness, or liver damage if contaminated water is consumed (7). In coastal areas, warming seas have led to more cases of vibriosis (infection by Vibrio bacteria) from eating raw oysters, something virtually unheard of in Canada decades ago. Climate change is also affecting diseases transmitted directly from animals to humans (zoonoses). In the Arctic, for instance, rabies in wildlife like foxes is a growing concern as changing habitat conditions alter animal behavior and bring them into closer contact with communities. Scientists worry that melting permafrost could even revive dormant pathogens or expand the range of diseases like anthrax (spores of which triggered a deadly outbreak among Siberian reindeer and a child in 2016 after a heatwave thawed old carcasses). While such scenarios are speculative, they highlight the unpredictable ways climate shifts can introduce novel health threats. More immediately, fungal infections that thrive in certain climates – such as Coccidioides (valley fever) or Cryptococcus – may expand in Canada, as has already happened on Vancouver Island where Cryptococcus gattii caused a cluster of pulmonary infections after establishing in the milder, moister environment. Even seasonal flu patterns could be affected: warmer winters tend to reduce influenza transmission in winter, but paradoxically can lead to a larger susceptible population and more widespread flu outbreaks in the subsequent year. In short, the map of infectious disease risk in Canada is being redrawn by climate change, demanding vigilance and adaptability from health systems.

As with other climate health impacts, not everyone faces equal risk from infectious diseases. Factors like geography, income, housing quality, and pre-existing health all influence who is most exposed and most vulnerable. Outdoor workers (such as farmers, construction workers, park rangers) and those who spend a lot of time hiking or camping may have greater exposure to ticks and mosquitoes, putting them on the front lines of vector-borne disease risk. People living in substandard housing or without air conditioning might be more inclined to open windows or lack window screens, increasing the likelihood of mosquito bites indoors. Low-income neighborhoods sometimes have more standing water or inadequate pest control, which can create local breeding grounds for disease vectors. Additionally, individuals with weaker immune systems or chronic illnesses are at higher risk of severe outcomes if they do become infected – for example, an elderly person is more likely to suffer life-threatening encephalitis from West Nile virus than a younger adult. Health inequities play a big role: those with fewer resources to protect themselves (like buying insect repellent, installing home water filters, or accessing timely medical care) bear a disproportionate burden of climate-sensitive infections. For instance, an unhoused person or a remote northern resident might have difficulty getting prompt treatment for a tick bite, raising the risk of chronic Lyme disease complications. First Nations, Inuit, and Métis Peoples may also face unique exposures. Many Indigenous communities rely on land-based activities – hunting, fishing, harvesting traditional foods – which means more direct contact with wildlife and insects that can carry disease. The warming climate has already been linked to unusual outbreaks in the North, such as a surge in invasive Giardia infections in Nunavik linked to changing snowmelt patterns, and increased concerns about food-borne botulism in fermented foods as permafrost cellars warm (3). Culturally, there is also concern that fear of disease could undermine traditional practices (e.g. avoiding the land due to tick worries), which in turn impacts physical fitness and mental well-being.

Finally, the psychological dimension of infectious disease risk should not be overlooked. The COVID-19 pandemic demonstrated how profoundly an infectious threat can affect mental health through stress and isolation. In the context of climate change, the gradual spread of diseases like Lyme or West Nile can create a persistent undercurrent of anxiety in affected regions. Parents might worry about letting children play in tick-infested woods; communities may experience stress during every mosquito season, wondering if this year will bring an outbreak. Those who do fall ill can endure not just physical symptoms but also mental health struggles – for example, patients with long-term Lyme disease often report depression, cognitive difficulties, and a feeling of being misunderstood or dismissed. Trauma can also stem from surviving a serious illness like encephalitis or from losing a loved one to an infection. In this way, the expansion of infectious diseases due to climate change is not only a biomedical issue but a social one. It challenges how we design our cities (to control mosquitoes), how we educate the public (to check for ticks, boil water, etc.), and how we support one another in the face of new health fears. While the next chapter will delve deeper into mental health, it is clear that every fever, bite, and infection tied to our changing climate carries with it a human story – one of adaptation, resilience, but also grief and concern. Protecting Canadians from these burgeoning infectious diseases will require an equitable public health approach, early warning systems, and support for the most vulnerable, ensuring that as our environment changes, our wellbeing does not have to deteriorate in tandem.

Displacement

Displacement is a common thread through all the climate hazards discussed above. Whether it’s a wildfire evacuation, a flood that forces people from their homes, or coastal erosion slowly eating away at a village, climate change is causing people to be uprooted. The health impacts of displacement are profound. Being forced from your home – suddenly or gradually – is traumatic. People often describe a sense of unmooring: loss of stability, loss of community, and a fear of the unknown. Even when evacuation is “just temporary,” the disruption can cause acute stress. Families may be living in an evacuation centre or with relatives, unsure when (or if) they can return. Normal routines collapse – kids are out of school, work is interrupted, medications or health records might have been left behind – adding to chaos and anxiety.

We have seen this in British Columbia repeatedly. In 2021, the entire town of Lytton, B.C., was destroyed by a wildfire in a matter of minutes. Its residents, including members of the Lytton First Nation, dispersed to surrounding communities. Years later, most have not been able to return as the town rebuilds from scratch. The prolonged displacement has had cascading effects: increased mental health issues like depression and PTSD, difficulties accessing healthcare and medications, and strain on social ties as the community is scattered. One father from Lytton described how even a prescribed burn (intentional fire set to manage forest fuels) months later triggered panic in his children – they thought another wildfire was coming for them (5). This illustrates how trauma and displacement go hand in hand: the body remembers the fleeing and fear, and even a whiff of smoke can bring it all back.

It’s crucial to note that climate displacement doesn’t affect everyone equally. Those with financial means might have insurance or second homes to go to, whereas low-income families could lose everything and have nowhere to land. After major evacuations, studies found that racialized evacuees were less likely to access mental health services or support (8), due to barriers like systemic inequities or lack of culturally appropriate care. People with disabilities or chronic illnesses often struggle during displacement – for example, someone who uses a wheelchair may find an evacuation center lacks appropriate facilities, or an individual with schizophrenia may find the crowded, chaotic environment highly destabilizing. These stressors can lead to worsening health. On the flip side, not everyone can evacuate easily; some seniors or folks without vehicles may end up trapped in dangerous situations. All of these scenarios create moral distress for communities and responders.

Indigenous communities face particular challenges with climate-related displacement. Many First Nations, Métis, and Inuit communities have deep spiritual and cultural connections to their land. Losing one’s land – even temporarily – can be experienced as a form of cultural loss or bereavement. Furthermore, due to historical injustices, Indigenous peoples have already endured forced relocations in the past, so climate displacement can retraumatize and compound historical trauma (13).

Sadly, we’ve seen examples in Canada’s North where entire hamlets are planning relocations because melting permafrost or rising seas are making their location uninhabitable. The mental health fallout includes grief, anger, and anxiety about the future, as well as very practical stress about how and where to move.

Conclusion

In all the ways discussed above and more, it is clear that climate change poses a major threat to our individual and collective wellbeing. As health and social care providers, we can play a role in supporting our communities as they navigate these challenging threats. Through collective efforts and collaboration the great health and social burdens posed by climate change can be partially mitigated even if we can’t stop the climate from changing. Building resilience in individuals and communities before these impacts are realized is the best way to ensure we are able to survive what lies ahead.