S & S Decoded: The Health Effects of Climate Change

At A Glance – Connecting the Climate Emergency with Earth Systems and Human Health

The global health agenda has never been more in focus. A myopic lens has prioritised the coronavirus over pre-existing conditions and diseases which will have repercussions in due course.

Connecting the effects of the climate emergency in terms of rising sea levels, higher temperatures, atmospheric carbon dioxide as well as floods and droughts with the impact on the health and wellbeing of the global population has been somewhat neglected.

This is a health and humanitarian crisis of unrivalled scale and we all have an obligation to address it.

Having recently completed the Harvard course on this exact topic, I wanted to share some key takeaways that further prompt the sense of urgency we must adopt to negate and mitigate the fall-out from global warming.

This S & S decoded provides learnings on how mechanisms like fires, water shortages, ozone depletion, pollution ­and mass migration are exacerbating health conditions and diseases. It clarifies who the most vulnerable will be and evaluates the impact of the shocking of earth systems on nutrition, environmental allergies, heart and respiratory illnesses as well as waterborne and vector borne diseases. This is supplemented of course by the less tangible conditions linked to mental health and trauma, a seismic and mounting challenge in society.

Supported by extensive academic research, it is clear improving climate resilience, achieving carbon neutrality and vehemently pursuing the UN’s Sustainable Development Goals with a 1.5-degree temperature rise has never been more urgent. It will be critical to provide the health infrastructure necessary to alleviate the effects of the planet’s warming by the end of the century.  

In Focus – Exacerbating the Health Crisis

To contextualise, there are six main components of climate change to consider:

-Temperature increase

-Altered rainfall patterns

-Sea-level rise

-Ocean Acidification

-Extreme weather events

-Climate-active pollutants

The table below depicts the link between effects of climate change and specific health conditions experienced by citizens.

Source: Sustainable & Social

The concept of co-benefits is crucial to this field of research. It refers specifically to additional benefits to human health that arise from working to reduce climate change.

How Can We Reduce the Effects of Climate Change on Human Life?

There are 3 main methods to mitigate the disease burden of the climate emergency:

1. Adaptation policies and actions that look to reduce greenhouse gas emissions and increase carbon sequestration

2. Mitigation i.e. reducing emissions

3. Health co-benefits. This looks at health gains, climate friendly policies and a shift in individual behaviour. For example, public transportation, cycling, investing in electric vehicles etc.  

Academic research pertaining to health and climate change is roughly half of that in other sectors impacted by climate change. This includes agriculture, forestry, industry, economics and energy, to name but a few.

Heat related illnesses will be exacerbated

Remember the hottest day in London in 2019 which reached 38 degrees? We were all encouraged to work from home and avoid the saunas of city public transport. If you’ve read my decoded on climate science, you will be aware that the frequency of higher temperatures is only set to increase. Uncomfortable heat levels create organ failures and put vulnerable populations at risk. This includes, in tropical regions, the elderly and those forced to work outside through manual labour. Obese members of the population will be the first to feel the effects as they are prone to strokes and heart attacks which will increase the strain on health services.

Ozone depletion, particular matter and pollution

Exposure to air pollution is the fourth highest ranking risk factor for death in the world. According to a study conducted by Environmental Epidemiology, this type of pollution associated with reliance on fossil fuels leads to roughly one in eight, or 6.8 million deaths a year. The root cause of this is the toxic substances in smoke, with elements such as acolein, formaldehyde, benzene and carbon monoxide which all are cancerous. Yet, how much media attention does this receive? Effects of particulate matter are outlined in the table above but their prevalence in causing heart attacks, strokes, lung cancer and preterm births should worry legislators. It is worth noting the effects are disproportionality likely to affect African and Asian countries.

Algal blooms

These traditionally absorb carbon and release oxygen. However, harmful algal blooms have become more prominent and occur when algae or cyanobacteria grow out of control and produce toxins. This growth is exacerbated by nitrogen found in the atmosphere from fertilizers of food. Toxic algal blooms are predominantly found where agriculture and rivers co-exist, making populations that dwell in such places increasingly vulnerable. If ingested, these toxins can cause headaches, vomiting, diarrhea as well as numbness. Ocean acidification and warming sea levels have expanded the range in water sources where this occurs.

Waterborne diseases

These are catalysed by the intensification of greenhouse gas emissions. Warming temperatures and intense precipitation with prolonged periods of rainfall may favour waterborne disease outbreaks. Regions with traditionally heavy rainfall in the tropics will be impacted to varying degrees depending on their sewage systems. On the flipside, as droughts occur more regularly, infectious pathogens are more likely to contaminate freshwater supplies.

Vector borne diseases

Transmission rates will surge in frequency. Increasing temperatures and challenges surrounding flooding will impact the spread of the zika virus, malaria and dengue fever. For those that are immunocompromised and live near to these endemic diseases in Africa, South America and Asia, demographics including children, the elderly and pregnant women are likely to suffer the most.


The heightened spread of vector borne diseases is best understood by tracing the impact of changing climate on mosquitos. This relationship is not entirely linear due to the complexity of ecological systems and numerous factors like density dependence, competition and development rates. These parasites are temperature sensitive, and to a certain degree, biting rates will increase thus propelling the rates of transmission in warmer climates which promote faster reproductive cycles. Poignantly, areas historically too cool for the disease to spread like cities in mountainous regions will become warm enough to accommodate higher levels of transmission. This will be problematic as populations look to habit spaces on higher ground to escape rising sea levels. Forecasting for the spread of these vector borne diseases is especially tricky as it must be measured at a local level, not at a country or regional level.

Nutrition and crop yields

The impact of climate change on nutrition and crop yields is the bulkiest topic to grapple with. Its many tangents require urgen addressing as ecosystems are destroyed through deforestation, irresponsive hunting/fishing as well as coral bleaching and population migration. All of these integrated issues will pose downstream effects on food security. Additionally, higher carbon dioxide concentrations will substantially reduce nutrients found in crops such as protein, Vitamin A, folate and zinc. One of latest global burdens of disease, is the inadequate growth of fruit, vegetables, nuts and seeds which are ranked 4th, 12th and 17th, respectively as largest risk factors for global burden of disease. Below I have delved into a little more detail:

  • The health crisis cannot ignore the fundamental challenge of obesity. Nearly every single nation across the world has had a substantial increase in adult and child hood body mass index (BMI). Globally, 18% of children are overweight and nearly 7% of all children are obese. Shockingly, over 40% of adults are overweight with 13% considered obese. Refer back to the table to correlate the intrinsic link between obesity and further health conditions.
  • Rising temperatures will drive additional ground level ozone production and this will impact plant growth and damage leaves. Extensive research by Ghude (2014) and Fujin (2008) have found that ozone toxicity has been estimated to kill enough crops in India which could feed close to 94 million people. Additionally, in China, the loss of agricultural productivity costs $250 billion per year which is close to 20% of the total agricultural revenue for the nation.  Below you can see the predicted yield changes between 2000 and 2050 due to the various impacts of climate change.
  • The impact of floods and droughts on agriculture is not to be ignored. Using the United States as a case study, the likelihood of their experience of extreme rainfall events may increase by up to four times in certain regions. By 2100, such events may increase by as much as 70%, so that a 2-inch rainfall today would be 3.5. Rising sea levels also exert forces on groundwater which accelerates land flooding, ruining harvests.
  • Simultaneously, droughts will challenge food security. An analysis conducted by Nature found that between 1964 and 2007 droughts contributed to a 10% loss of agricultural output globally but with 8-11% more damage in developing countries than in developed ones. You don’t have to be a scientist to grasp that climate change will increase demand for clean groundwater as it increasingly evaporates. Reports by SciencesAdvances relay that two out of 3 people on earth live in areas where water consumption is twice as great as availability – half of these being in China and India. Shockingly, half a billion people face the extent of scarcity every month of the year, fuelling the fact that future wars are likely to be started over water related issues. Touching on the water effects of wasted food – this stands at 45 trillion gallons of water, which is nearly 25% of all the water used for agriculture globally each year. (For more on food waste click here.)
Credit: ScienceAdvances
  • As outlined earlier, rising reproductive rates of pests and pathogens, stimulated by warmer temperatures will prolong their active ability to ruin crops. For example, codling moths, which feed on apples, as well as other fruits and nuts, are expected to have two reproductive cycles every warm season towards the end of the century in climates where they today typically only reproduce once in that given season. Another interesting case is the impact of warmer temperatures in accelerating the breeding of bark beetles. These creatures infest forests which creates vast amounts of dead wood and increases wooden areas prone to fire. In early 2020, in Kenya experienced a locust plague which is another example of a unprecedented threat to food security. A swarm of only one square kilometre of locusts will eat as much as 35,000 people consume in one day. Desert locusts can spread across 29 million square kilometres or more than 20% of the total land surface of the planet. Across the horn of Africa and parts of India, locust swarms are destroying food sources.
  • Crops and carbon dioxide. Anthropogenic carbon dioxide emissions threaten the adequacy of protein intake. Elevated levels will widen the disparity in protein intake within countries where populations following plant-based diets will become most suseptible. Why is this important? Currently over 1.4 billion children aged between 1-5 and women of childbearing age live in countries where protein and iron deficiency prevalence is over 20%. In these countries, the iron supply could fall by 3.8% based upon the foods consumed in their current diets and the detrimental effects of higher carbon dioxide levels on iron content of crops.
  • The implications of the decline in fisheries for seafood and nutrition.  Approximately 3 billion people get 20% of their animal protein intake from seafood. In coastal regions of developing nations and small island states, up to 50% of their animal protein originates from fish. This is why monitoring the earth’s fisheries is so crucial, especially as 90% of the excess heat trapped by greenhouse gas emissions is being absorbed into the world’s oceans.
  • The value of coral reefs must be highlighted. Coral reefs supply over 500 million people with food, income, coastal protection and a range of other services.
  • Up to two thirds of a population of 400 million who live within 100 kilometres proximity of coral reefs live on less than $500 a year and are likely to depend heavily on the reefs for sustenance. This is another illustration of how those that live below the poverty line are likely to suffer most.
  • This makes combatting coral bleaching imperative to protect populations’ source of nutrients. Coral bleaching takes place when the ocean temperatures rise to a point that stresses the algae and forces them to migrate. In turn, this deprives the coral of basic sustenance that the algae help to provide. Once bleached, the reefs are then at higher risk from infection from opportunistic pathogens. To put this into perspective, major reef ecosystems can bleach as often as every 6 years yet recovery can take 10-15 years.
  • According to America’s National Oceanic and Atmospheric Administration, between 2014-2017, over 70% of the world’s reefs endured temperatures high enough to bleach them for pro longed periods. This is important for human health as reefs serve as habitats for fish throughout their life cycle.

Mass migration

The effect of climate change on mass migration is undeniable. Nations can become destabilised by extreme weather events such as droughts. ach year, since 2008, over 20 million people have been forced to migrate due to extreme weather. Improving climate resilience with critical infrastructure will increase people’s ability to stay put. As it stands, the World Bank estimated 143 million people may become internally displaced by 2050 yet international humanitarian law doesn’t provide clear protections for this displacement due to climate change, whether that’s within their own country or in another nation.

For climate refugees forced to flee, access to health care is rare. Consider those populations constantly on the move, living in less than sanitary conditions within refugee camps, deprived of access to basic clean water for washing and forced to cohabit in densely populated spaces where contagion of disease is rife. The post-traumatic stress and mental health implications for those denied the ability to live in their homes cannot be put into words. This therefore, solidifies the need for institutional change and transformation of building design and cities to enable a certain degree of mitigation.  For more information relating to climate refugees, click here.   

Final Thoughts  – A Moral Imperative to Protect the Future of Human Health  

The facts are startling. As we edge closer to crossing further planetary boundaries, causing irreversible damage to the earth’s eco systems, the implications for human health are salient.

As over 7 million deaths annually are created by particulate matter that arises during the production of fossil fuels, this can no longer be ignored or overshadowed by statistics on coronavirus.

It must act as a call to action for those in power whether that be that development banks, business leaders, health industries, governments or citizens to demand the deconstruction of fossil fuel industries and implementation of appropriate economic measures.  

The horrendous statistics surrounding obesity and preventable or reversable conditions like type 2 diabetes must be combatted both by individual citizens and by increasing accountability of the food industry through sugar levy’s and responsible marketing. This will decrease the strain on our health services throughout the course of the next century.

As the world becomes increasingly urbanised, and populations of cities rise, the adoption of biophilic design will prove invaluable to increase climate resilience and enable dwellers to remain in their chosen habitats.

At an academic research level, attention must be prioritised  as to the impact of climate change on health to prevent extreme crises. Applying research with appropriate climate forecasting must be done both at a global and local level to achieve optimum accuracy.

Adopting a longer-term strategy through adoption policies, mitigation and altering individual behaviours to subvert the insidious implications on human health cannot be stressed enough. For months we have been told to stay home to protect our national health service, but when the time comes, we won’t be able to socially distance ourselves by two metres from the onslaught of rising temperatures, flooding and food scarcity.

No one is immune to the health effects of climate change, and that means we all have a moral imperative to address this before it’s too late.

If this topic was of interest, be sure to read my decoded features on the science behind climate change and the importance of the sustainable development goals.

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