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Summary
The effects and impacts of climate change on human health are measured in multiple ways: lives lost, health care systems over-strained, mental and physical well-being, and economies in tatters because of the flow-on effects.
One of the most direct impacts of a steadily warming climate and the weather extremes it amplifies is the general effect on our health. We have recently quantified two aspects of this: rising mortality associated with heat extremes, and mental health crises following devastating storms. – Prof. Noy, Victoria University of Wellington 2026
A clearer picture of the global burden of climate change could encourage policymakers to treat the climate crisis like a public health emergency – Carlson et al 2025
More than 50,000 heat-related deaths estimated in European urban areas during summer 2026. – London School of Hygiene and Tropical Medicine Oct. 2026
High temperature and humidity can degrade the active ingredients in pharmaceutical drugs and change their formulas, potentially making medications less effective and increasing the risk of harmful side effects – Pono & Jones 2026
Increasing atmospheric CO2 changing human blood chemistry and pH
Humans evolved over millions of years in the presence of an atmosphere with far lower concentrations of CO2. Normally, our pH is ~7.35 -7.45. A drop in blood pH (increasing acidity) of 0.2-0.3 can cause seizures, comas, and ultimately, death. This increase in CO2 in our blood, and the concurrent impacts on pH and cellular function should come as no surprise as excess CO2 in the ocean has made the oceans more acidic with concurrent negative impacts on fish and invertebrates already well-documented.
…from 1999 to 2020 as indirect proxies for atmospheric CO2 exposure average bicarbonate levels show an increasing trend which parallels rising atmospheric CO2 concentrations. Both Ca and P (calcium and potassium) have decreased steadily over the same period. If these trends continue, blood bicarbonate values could be at the limit of the accepted healthy range in half a century, and Ca and P will be at the limit of their healthy ranges by the end of this century. – Larcombe & Bierwirth 2026 (Fig. 2)
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Note that in 2026 the level of atmospheric CO2 had risen to 431ppm and is accelerating.
Carbon dioxide overload, detected in human blood, suggests a potentially toxic atmosphere within 50 years – Larcombe & Bierwirth 2026
Increasing food-borne pathogens
Climate change is affecting the distribution and spread of food-borne pathogens, resulting in 600 million food-borne illnesses and 420,000 deaths annually. – Awad et al 2024
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The thickness of the lines is proportional to the number of studies that mention the relationship between climate change and specific foodborne pathogens.
Increasing firestorms leading to toxic smoke & chemical legacy
Public health officials and researchers urge the public to cover up outside and clean carefully indoors, but many low-income and disabled residents, and those lacking air conditioning, have difficulty staying safe in bad air. Incidences of heart attacks and strokes go up right after firestorms. Habre says more research is needed on potential long-term effects, but what’s been proven so far is harrowing. The “chronic” impacts include lower birth weights, enduring lung conditions in children, a variety of cancers in adults and increased cases of dementia. – Inside Climate News 2025
Compared to wildfire smoke, the urban plume was enriched more than 50-fold in lead, 7-fold in halogens, and 3-fold in arsenic, a toxic mixture linked to burning vehicles, electronics, and building materials, a fundamentally different fuel from conventional wildland vegetation. During peak structural burning, we estimate that approximately 7 million residents (range, 4.3 to 8.0 million) experienced 24-hour lead concentrations exceeding 50 nanograms per cubic meter, over 80 times background levels. Unlike wildfire smoke that has been the focus of decades of air quality research, this plume represents an emerging class of urban fire air pollution that demands revised exposure frameworks and emergency response protocols as fires increasingly burn into cities. – Baliaka et al Science Advances 2026
The journal Nature has compiled this open-access (free) series of peer-reviewed paper on wildfires and their impact on ecosystems, contribution to climate change, and damage to human health. The January 2025 Los Angeles fires also highlights additional consequences: toxic chemicals in the air, ground, and groundwater, and the increasing inability get fire insurance.
The important thing here is that the bike [Fig. 3] is gone. Where did it go? I’m not sure vaporized is the right word; aerosolized might be better. Regardless of the word choice, the bike was turned into smoke particles and dispersed across the city. Of course, it wasn’t just this bike. The LA fires burned buildings and everything inside them (furniture, paints, plastics and electronics), and everything on the street (cars, metal tanks, street signs, bicycles, mailboxes, power lines, garbage bins, etc.). Many of these things were also turned into smoke that people then breathed in. – Dessler 2025
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My Co-founder, Josh Weinsch took this photo of his little daughter’s bike, which was in their driveway when they evacuated. Their neighborhood was vaporized. – Seamus Blackey 2025
The article linked above goes on to show evidence from scientists that heavy metals are also are being found in the ash, and yet, the Federal Government (FEMA / US Army Corps of Engineers) will not test for residue in the soil.
IPBES Workshop on Biodiversity and Pandemics
The following is extracted from the 2020 IBES report on the relationship between pandemics, biodiversity, and climate change. The full report is here. Links to more recent research on this topic are at the bottom of this page.
There is no great mystery about the cause of the COVID-19 pandemic—or of any modern pandemic. The same human activities that drive climate change and biodiversity loss also drive pandemic risk through their impacts on our environment. Changes in the way we use land; the expansion and intensification of agriculture; and unsustainable trade, production and consumption disrupt nature and increase contact between wildlife, livestock, pathogens and people. This is the path to pandemics.
The overwhelming scientific evidence points to a very positive conclusion. We have the increasing ability to prevent pandemics—but the way we are tackling them right now largely ignores that ability. Our approach has effectively stagnated—we still rely on attempts to contain and control diseases after they emerge, through vaccines and therapeutics. We can escape the era of pandemics, but this requires a much greater focus on prevention in addition to reaction.
The fact that human activity has been able to so fundamentally change our natural environment need not always be a negative outcome.
It also provides convincing proof of our power to drive the change needed to reduce the risk of future pandemics—while simultaneously benefiting conservation and reducing climate change. – Peter Daszak, President EcoHealth Alliance and IPBES workshop Chair
Pandemics emerge from the microbial diversity found in nature
- The majority (70%) of emerging diseases(e.g. Ebola, Zika, Nipah encephalitis), and almost all known pandemics (e.g. influenza, HIV/AIDS, COVID-19), are zoonoses—i.e. are caused by microbes of animal origin. These microbes ‘spill over’ due to contact among wildlife, livestock, and people.
- An estimated 1.7 million currently undiscovered viruses are thought to exist in mammal and avian hosts. Of these, 540,000-850,000 could have the ability to infect humans.
- The most important reservoirs of pathogens with pandemic potential are mammals (in particular bats, rodents, primates) and some birds (in particular water birds), as well as livestock (e.g. pigs, camels, poultry).
Human ecological disruption, and unsustainable consumption drive pandemic risk
- The risk of pandemics is increasing rapidly, with more than five new diseases emerging in people every year, any one of which has the potential to spread and become pandemic. The risk of a pandemic is driven by exponentially increasing anthropogenic changes. Blaming wildlife for the emergence of diseases is thus erroneous, because emergence is caused by human activities and the impacts of these activities on the environment.
- Unsustainable exploitation of the environment due to land-use change, agricultural expansion and intensification, wildlife trade and consumption, and other drivers, disrupts natural interactions among wildlife and their microbes, increases contact among wildlife, livestock, people, and their pathogens and has led to almost all pandemics.
- Climate change has been implicated in disease emergence (e.g. tick-borne encephalitis in Scandinavia) and will likely cause substantial future pandemic risk by driving movement of people, wildlife, reservoirs, and vectors, and spread of their pathogens, in ways that lead to new contact among species, increased contact among species, or otherwise disrupts natural host-pathogen dynamics.
- Biodiversity loss associated with transformation of landscapes can lead to increased emerging disease risk in some cases, where species that adapt well to human-dominated landscapes are also able to harbour pathogens that pose a high risk of zoonotic transmission.
- Pathogens of wildlife, livestock and people can also directly threaten biodiversity, and emerge via the same activities that drive disease risk in people (e.g. the emergence of chytridiomycosis in amphibians worldwide due to the wildlife trade).
Reducing anthropogenic global environmental change may reduce pandemic risk
- Pandemics and other emerging zoonoses cause widespread human suffering, and likely more than a trillion dollars in economic damages annually. This is in addition to the zoonotic diseases that have emerged historically and create a continued burden on human health. Global strategies to prevent pandemics based on reducing the wildlife trade and land-use change and increasing One Health1 surveillance are estimated to cost between US$22 and 31.2 billion, reduced even further (US$17.7-26.9 billion) if benefits of deforestation on carbon sequestration are calculated—two orders of magnitude less than the damages pandemics produce.
- The true impact of COVID-19 on the global economy can only be accurately assessed once vaccines are fully deployed and transmission among populations is contained. However, its cost has been estimated at US$8-16 trillion globally by July 2020 and may be US$16 trillion in the US alone by the 4th quarter of 2021 (assuming vaccines are effective at controlling it by then).
- Pandemic risk could be significantly lowered by promoting responsible consumption and reducing unsustainable consumption of commodities from emerging disease hotspots, and of wildlife and wildlife-derived products, as well as by reducing excessive consumption of meat from livestock production.
- Conservation of protected areas, and measures that reduce unsustainable exploitation of high biodiversity regions will reduce the wildlife-livestock-human contact interface and help prevent the spillover of novel pathogens
Land-use change, agricultural expansion, and urbanization cause more than 30% of emerging disease events
- Land-use change is a globally significant driver of pandemics and caused the emergence of more than 30% of new diseases reported since 1960.
- Land-use change includes deforestation, human settlement in primarily wildlife habitat, the growth of crop and livestock production, and urbanization.
- Land-use change creates synergistic effects with climate change (forest loss, heat island effects, burning of forest to clear land) and biodiversity loss that in turn has led to important emerging diseases.
- Destruction of habitat and encroachment of humans and livestock into biodiverse habitats provide new pathways for pathogens to spill over and increase transmission rates.
- Human health considerations are largely unaccounted for in land-use planning decisions.
- Ecological restoration, which is critical for conservation, climate adaptation and provision of ecosystem services, should integrate health considerations to avoid potential increased disease risk resulting from increased human-livestock-wildlife contact.
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