Climate change impact on human health part2

In part 1 we described the mechanism of climate change in general and derived out of this some impacts to human health. With this article we would like to somehow complete the picture and to draw out a conclusions about human health, derived from the climate change. The part1 we closed with the description of waterborne diseases, which will grow with further climate change. Let us now go to a subject, which is also water related.

Causes of Algal and Cyanobacterial Blooms

Algae and cyanobacteria behave like plants: they absorb carbon dioxide and release the oxygen that we need to survive on Earth. However, they can also produce toxins that are dangerous to wildlife and swimmers. Warmer ocean temperatures and heavier precipitation, which increases the delivery of nutrients such as nitrogen and phosphorous to coastal waters and lakes, can promote the growth of algae and cyanobacteria. When conditions are right, algal blooms occur.

One of the key ingredients for a harmful algal bloom is nitrogen. The map below shows where nitrogen is deposited across the Mississippi river basin in the United States. The heavy use of nitrogen-based fertilizer to grow food, as well as highly concentrated livestock operations in the upper Midwest, deliver nitrogen into the Mississippi river. There, it ultimately reaches the Gulf of Mexico, where it can fuel harmful algal blooms. This scenario occurs wherever agriculture and rivers co-exist, which means it can – and does – occur on every continent except Antarctica.

The Mississippi River watershed covers nearly half of the United States, including substantial amounts of farmland that contribute large amounts of nitrogen from fertilizer. Agricultural runoff flowing into river basins and ultimately to the sea and fuelling harmful algal blooms is occurring around the world.

A very popular example is the damage of the Great Barrier Reef near Australia. It is the biggest reef we know on earth and contributes to a diverse population on fish. It is a fact almost beyond comprehension: In the summer of 2015, more than 2 billion corals lived in the Great Barrier Reef. Half of them are now dead.

Algal and cyanobacterial toxins cause a range of illness in humans and wildlife. Toxins can cause disease when swallowed or when they touch the skin. If ingested, these toxins most often cause headaches, vomiting, diarrhoea, and numbness or tingling. They are also toxic to wildlife.

What are conditions, which make Algal Bloom developing? Recent research has found that warming oceans have expanded the range of the northern Atlantic and Pacific oceans in which harmful algal blooms can occur.

Recent research has also shown that ocean acidification may promote even more abundant and toxic algal blooms.

Malaria’s Impact

Ever been bitten by a mosquito? Depending on where you were when that happened the bite could have been merely an itchy nuisance or the beginnings of a life-threatening disease. Malaria, a parasitic disease transmitted through the bite of a mosquito, is a major global health challenge. Each year, more than 200 million people – mostly in lowland tropical areas – are estimated to contract malaria and more than 400,000 people, mostly children younger than 5, die. Almost half of the Earth’s population currently live in areas where malaria can be transmitted.

The impact of many diseases is measured in DALYs: Disability-Adjusted Life-Years. The greater the DALYs, the worse things are. The map below shows the DALYs associated with malaria round the world.

Map: Malaria DALYs per 100,000 pop

The impact of the climate change of the life cycle of mosquitos and Malaria, we explain in the following part.

Mosquito life cycle

The reproduction of malarial parasites involves stages in mosquitoes and in humans (including periods of time in liver cells and blood cells). You can see quick overviews of the mosquito life cycle above and malaria life cycle below. Note that the mosquitoes lay their eggs in water. The parasites have a lifecycle that includes time inside the human body and inside a mosquito. The time the parasite spends developing in the mosquito, where it is exposed to outdoor temperatures, is known as the extrinsic incubation period.

The following diagrams show the ideal temperatures for the life of mosquitos. This gives an indication, how and where Malaria can spread out with increasing temperatures on earth.

The optimal development temperature for mosquitos and malaria will spread out with rising earth temperature to high land regions and regions, in which mosquitos cannot live today due to the lower temperature.

Malaria transmission factors


Greenhouse gases will affect crop yields through several pathways as illustrated in the diagram below. The extensive connections between crop yields and greenhouse gas emissions make nutritional outcomes a key to understanding the health effects of climate change. Lower Crop Yields Flowchart

Heat, Ozone, and Crops

More heat also will drive additional ground level ozone production, and ozone can impair plant growth and damage leaves.

The bar graphs below show estimated yield changes between 2000 and 2050 due to warming temperatures with climate change and/or ground level ozone.

The pie graphs show the percent of the world total production by country or region of each of major food crops.

Change in crop yield

The above picture shows, the crop yield will become strongly reduced, in the tropic regions, were today we have a dense population. This will provoke that people have the need to move to other regions. These changes will have health impact due to the movements. migration and due to change of nutrition.     

Salinization of Coastal Groundwater

Sea level rise makes salinization of coastal groundwater more likely. As sea level rises, the pressure of salt water to intrude through rock and earth into aquifers rises, which drives salty water into fresh water.

How sea water rise salinizes ground water!

CO2 and Crops

Experiments have demonstrated that exposure to elevated carbon dioxide levels can substantially decrease the nutrient content of staple crops.

1.4 billion children aged 1-5 and women of childbearing age live in countries where iron deficiency prevalence is >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, as illustrated below.

Percent Change in Plant Nutrition between 380ppm CO2 and 550ppm CO2

Fishes disappear due to overfishing but also due to acid and to hot water. They are going to colder regions.

All the above shown changes in the diet of people can provoke nutritional diseases.

Nutritional diseases are conditions that effect the human body due to its food intake. Their strongest and most widespread effects are on children, the elderly and women of child bearing age. Each nutrient has a different set of diseases that can be induced by over- or under-consumption.

Nutritional diseases are sometimes referred to as nutritional deficiencies or malnutrition, but this overlooks the (comparatively new) issue of overnutrition, which can lead to obesity.

Macronutrients include carbohydrates, fiber, fat, essential fatty acids and protein. Protein deficiencies can lead to a variety of issues, from kwashiorkor to birth defects. An excess of protein may lead to increased kidney stone formation.

Micronutrients are primarily vitamins and minerals. Many have well documented and specific effects caused by deficiency: low vitamin C causes scurvy; low calcium causes osteoporosis. Others have broader effects: low zinc intake can result in a broad variety of issues from depressed growth to skin lesions to diarrhoea. There are often connections between various nutrients: for instance, it is difficult for the human body to absorb calcium without vitamin D.

Some micronutrients (like vitamin C) can be tolerated in doses much larger than what is needed by the body. Others (like iron) can cause severe issues in overdose, especially in children. Taking in more micronutrients than the minimum the body needs does generally not show any health benefits. The following diagram shows the connections which provoked migration and the health impact

The United Nations estimates that an unprecedented number of people – more than 65 million – have currently had to move against their will from their homes. About 22 million have moved outside their home countries and are refugees and the vast majority are hosted in developing nations. About 40 million are internally displaced within their home countries and are so called “internally displaced persons” or IDPs.

Each year since 2008, more than 20 million people have been forced to migrate due to extreme weather.


The already visible effects of climate change impacts the health of a lot of population already. Infection, migration,  impact on crop yields, water shortages and wildfires are jeopardising the health of more and more people and we come closer to the point that we have not any more enough healthy food for the world population.

What is most importand: the climate change and the increasing impact of CO2, ozone and particulate matter has already influenced our living conditions a lot. It is mandatory, to react now consequently. We anyhow will only be able to slow down the climate change. It is hard for me to believe we can stop it completely. Nevertheless, we are talking about, to assure several 100 years live for humans on earth. But with every degree temperature rise and rising CO2 emissions, the living conditions are becoming more and more challanging.

To show these interactions was the intention of the two articles.

Leave a Reply

Your email address will not be published. Required fields are marked *