Effects of global warming on human health

The effects of global warming include effects on human health. This article describes some of those effects on individuals and populations. The observed and projected increased frequency and severity of climate related impacts will further exacerbate the effects on human health.

Impact on infectious diseases

Warming oceans and a changing climate are resulting in extreme weather patterns which have brought about an increase of infectious diseases—both new and re-emerging.^[1][2] These extreme weather patterns are creating extended rainy seasons in some areas,^[3] and extended periods of drought in others,^[4] as well as introducing new climates to different regions.^[4] These extended seasons are creating climates that are able to sustain vectors for longer periods of time, allowing them to multiply rapidly, and also creating climates that are allowing the introduction and survival of new vectors.^[1]

Impact of extreme weather

“The rise of extreme weather is itself a symptom of an unstable climate. Moreover, the variance around the long-term warming trend has begun to influence biological systems, Indeed, two main effects of climate change—warming and greater weather variability-mean that millions of people worldwide face a higher risk of infectious disease”.^[3] El Nino is an extreme weather pattern that is often responsible for increased precipitation, resulting in increased flooding, creating a more promising breeding ground for a plethora of vectors that both carry and cause infectious diseases.^[5]

Another result of the warming oceans are stronger hurricanes, which will wreck more havoc on land, and in the oceans,^[5] and create more opportunities for vectors to breed and infectious diseases to flourish.^[1][3] Extreme weather also means stronger winds. These winds can carry vectors tens of thousands of kilometers, resulting in an introduction of new infectious agents to regions that have never seen them before, making the humans in these regions even more susceptible.^[1]

Impact of warmer and wetter climates

Mosquito-borne diseases are probably the greatest threat to humans as they include malaria, elephantiasis, Rift Valley fever, yellow fever, and dengue fever.^[6][7][8] Studies are showing higher prevalence of these diseases in areas that have experienced extreme flooding and drought.^[6][7] Flooding creates more standing water for mosquitoes to breed; as well, shown that these vectors are able to feed more and grow faster in warmer climates.^[1] As the climate warms over the oceans and coastal regions, warmer temperatures are also creeping up to higher elevations allowing mosquitoes to survive in areas they had never been able to before.^[1] As the climate continues to warm there is a risk that malaria will make a return to the developed world.^[1]

Ticks are also thriving in the warmer temperatures allowing them to feed and grow at a faster rate.^[9] The black legged tick, a carrier of Lyme disease, when not feeding, spends its time burrowed in soil absorbing moisture.^[3][10] Ticks die when the climate either becomes too cold or when the climate becomes too dry, causing the ticks to dry out.^[3][10] The natural environmental controls that used to keep the tick populations in check are disappearing, and warmer and wetter climates are allowing the ticks to breed and grow at an alarming rate, resulting in an increase in Lyme disease, both in existing areas and in areas where it has not been seen before.^[3][9]

Other diseases on the rise due to extreme weather include: hantavirus,^[11] schistosomiasis,^[7][8] onchocerciasis (river blindness),^[8] and tuberculosis.^[2]

Impact of warmer oceans

The warming oceans are becoming a breeding ground for toxic algae blooms (also known as red tides) and cholera.^[1][8][12] As the nitrogen and phosphorus levels in the oceans increase, the cholera bacteria that lives within zooplankton emerge from their dormant state.^[12] The changing winds and changing ocean currents push the zooplankton toward the coastline, carrying the cholera bacteria, which then contaminate drinking water, causing cholera outbreaks.^[12] As flooding increases there is also in increase in cholera epidemics as the flood waters that are carrying the bacteria are infiltrating the drinking water supply.^[13] El Nino has also been linked with cholera outbreaks because this weather pattern warms the shoreline waters, causing the cholera bacteria to multiply rapidly.^[12][13]

Toxic algae blooms (red tides) are the result of a changing and warming climate.^[14] El Nino events precipitation resulting in flooding, which causes the coastal seawater to be infiltrated with runoff from the flooding land resulting in increased nitrogen and phosphorus which feed the algae and spur their growth.^[15] These toxic blooms in turn infect shellfish, which threatens the health of the millions of people who depend on shellfish for protein.^[15] Paralytic shellfish poisoning is the most common result of red tides, as was seen in the 1987 outbreak in Prince Edward Island.^[15] Ciguatera fish poisoning is also a result of red tides.^[16] Humans that ingest these infected reef dwelling fish become ill.^[16] Further, red tides are so powerful that they also cause respiratory illness simply by breathing the air near them.^[15]

Malaria

Malaria is a mosquito-borne parasitic disease that infects humans and other animals caused by microorganisms in the Plasmodium family. It begins with a bite from an infected female mosquito, which introduces the parasite through its saliva and into the infected host’s circulatory system. It then travels through the bloodstream into the liver where it can mature and reproduce.^[17] The disease causes symptoms that typically include fever, headache, shaking chills, anemia, and in severe cases can progress to coma or death.

Climate is an influential driving force of vector-borne diseases such as malaria. Malaria is especially susceptible to the effects of climate change because mosquitoes lack the mechanisms to regulate their internal temperature. This implies that there is a limited range of climatic conditions within which the pathogen (malaria) and vector (a mosquito) can survive, reproduce and infect hosts.^[18] Vector-borne diseases, such as malaria, have distinctive characteristics that determine pathogenicity. These include: the survival and reproduction rate of the vector, the level of vector activity (i.e. the biting or feeding rate), and the development and reproduction rate of the pathogen within the vector or host.^[18] Changes in climate factors substantially affect reproduction, development, distribution and seasonal transmissions of malaria.

Mosquitoes have a small window for preferential conditions for breeding and maturation. The ultimate breeding and maturing temperature for mosquitoes range from sixteen to eighteen degrees Celsius.^[19] If the temperature is decreased by two degrees, most of the insects will succumb to death. This is why malaria is unsustainable in places with cool winters. If a climate with an average of approximately 16 degrees Celsius experiences an increase of about two degrees, the mature bugs and the larvae flourish.^[1] Female mosquitoes will need more food (human/animal blood) to sustain life and to stimulate production of eggs. This increases the chance of spread of malaria due to more human contact and a higher number of the blood sucking insects surviving and living longer. Mosquitoes are also highly sensitive to changes in precipitation and humidity. Increased precipitation can increase mosquito population indirectly by expanding larval habitat and food supply.^[18] These prime temperatures are creating large breeding grounds for the insects and places for the larvae to mature. Increased temperature is causing snow to melt and stagnant pools of water to become more common.^[1] Bugs that are already carrying the disease are more likely to multiply and infect other mosquitoes causing a dangerous spread of the deadly disease.

Climate change has a direct impact on people’s health in places where Malaria is not prevalent. In communities of higher altitudes in Africa and South America, people are at higher risk for developing malaria in recent years because of an increase temperature. A fluctuation of two or three degrees is creating exceptional breeding grounds for mosquitoes, for larvae to grow and mature mosquitoes carrying the virus to infect people that have never been exposed before.^[1] This is a severe problem because people in these communities have never been exposed to this disease causing an increased risk for complications from malaria such as cerebral malaria (a type of malaria that causes mental disability, paralysis and has a high mortality rate) and death by the disease.^[1] Residents of these communities are being hit hard by malaria because they are unfamiliar with it; they do not know the signs and symptoms and have little to no immunity.

The population at risk of malaria in the absence of climate change is projected to double between 1990 and 2080 to 8820 million, however; unmitigated climate change would, by the 2080s, further increase the population at risk of malaria by another 257 to 323 million.^[20] Therefore, reducing the effects of climate change in the present would reduce the total by about 3.5%, saving tens of thousands of lives worldwide.

If there is a slight discrepancy in the normal temperature, the perfect conditions for the insects to multiply are created. People that have never been infected before are unknowingly at risk for this deadly disease and do not have the immunity to combat it.^[1] An increase in temperature has the potential to cause a widespread epidemic of the disease that has the capacity to wipe out entire populations of people. It is important to track the prevalence, species and number of insects carrying the disease as well as the amount of humans infected in countries and places that have never seen malaria before. It is simple for the slightest of fluctuation in temperature to cause a catastrophic epidemic that has the possibility to end the lives of many innocent and unsuspecting people.^[19]

Dengue fever

Background

Dengue fever is an infectious disease caused by dengue viruses known to be in the tropical regions.^[21] It is transmitted by mosquito Aedes, or A. aegypti.^[22]

The cases of Dengue fever have increased dramatically since the 1970s and it continues to become more prevalent.^[23] The greater incidence of this disease is believed to be due to a combination of urbanization, population growth, increased international travel, and global warming.^[24] The same trends also led to the spread of different serotypes of the disease to new areas, and to the emergence of dengue hemorrhagic fever. There are four different types of viruses in dengue fever. If someone is infected with one type of dengue virus, he or she will have permanent immunity to that type of dengue virus, but will have short term immunity to the other type of dengue fever.^[21] Some of the symptoms of dengue fever are fever, headache, muscle and joint pains and skin rash.^[25] There is no vaccine for Dengue fever right now and there is no true treatment to get rid of it, but there are treatments to assist with some of the symptoms of dengue, such as the use of oral or intravenous fluids for rehydration.^[25]

Climate change impacts

Dengue fever used to be considered a tropical disease, but climate change is causing dengue fever to spread. Dengue fever is transmitted by certain types of mosquitos, which have been spreading further and further north. This is because some of the climate changes that are occurring are increased heat, precipitation and humidity which create prime breeding grounds for mosquitos.^[26] The hotter and wetter a climate is the faster the mosquitos can mature and the faster the disease can develop. Another influence is the changing El Nino effects that are affecting the climate to change in different areas of the world, causing dengue fever to be able to spread.^[27]

What can be done?

There are many things that can be done, both on a governmental level and on an individual basis. 1.) Have a better system of detecting when dengue outbreaks may happen. This can be done by monitoring environments, such as temperatures, rainfall and humidity that would be attractive for these types of mosquitos to flourish. 2.) Educating the public: Letting the public know when a dengue outbreak is occurring and what they can do to protect themselves. For example, people should create a living environment that is not attractive to mosquitos (no sitting water), dress in appropriate clothing (light colours, long sleeves)and wear insect repellant.

HIV/AIDS

HIV AIDS and Climate Change are both long wave issues that cause fear and uncertainty in the population. One of the main reasons why climate change appears to have such an impact on HIV/AIDS seems to be related to food shortage. “In the fight against hunger we could now be facing a perfect storm of challenges, including climate change and increasingly severe droughts and floods, soaring food prices and the tightest supplies in recent history, declining levels of food aid, and HIV/AIDS, which also aggravates food insecurity” says Sheeran.^[28] The lack of food security, due to climate change, in South Africa has been affected by HIV/AIDS. In Sub-Saharan Africa over 70% of the population are farmers and human capital has decreased due to HIV/AIDS.^[29] “This reduction in the household labour capabilities severely decreases agricultural output. The source of nourishment and income for the bulk of Sub-Saharan Africa’s population, agricultural output, is further hurt by a loss in the transfer of intergenerational knowledge, as the productive adult population with experience in agricultural labour is the most severely affected by AIDS”.^[29] This has been made worse as 90% of the people infected with HIV/AIDS in sub-Saharan Africa are adults. This not only greatly reduces human capital, but it leaves many children to tend to themselves. Malnutrition, brought about by food security in Sub-Saharan Africa, exacerbates the effects of HIV/AIDS.^[29] A study done in Ethiopia showed that chronic malnutrition was a predictor of first line antiretroviral therapy failure.^[30] This has the potential to create more HIV deaths each year, as immune capabilities are further weakened by Malnutrition. Another important factor about food insecurity is that it could increase the spread of HIV AIDS from the use of Transactional sex. Women who are desperate and suffer malnutrition are more likely to sell their bodies in order to support themselves. Also food insecurity and poverty may prevent people from seeking a diagnosis or prevent them from having the ability to afford treatment.

Secondly the spread of Malaria due to climate change will also be degrading to the burden of disease of HIV/AIDS.^[31] As people become infected by HIV/AIDS and are then exposed to Malaria, it will create an even more substantial loss of life because AIDS victims will be less likely to be able to fight the Malaria infection. Climate change may also increase the spread of HIV/AIDS. As climate change disasters sweep the globe, more people will become displaced, and be forced to live in close quarters to one another. There is evidence to suggest that this could “aggravate gender inequalities"^[31] that have the potential to raise the possibility of transmission of the disease. Migrants often have poor living conditions, are separated from their spouses and families, perform demanding and dangerous jobs and have limited access to health care.^[32] This can all lead to an increased risk of contracting HIV/AIDS.

Lastly climate Change will reduce the funds available to mitigate HIV/AIDS. As more money is spent on repairing infrastructure due the increasing nature of extreme weather, less money will be available for programs to prevent HIV/AIDS and to look after those that are already infected.^[33] This is especially true in underdeveloped countries where they are least able to cope. The governments in these countries are less able to provide for their populations, and will even more under strain from the climate change related costs. This raises the possibility of bankrupt countries that may leed to the Failed state phenomenon. The twin effects of HIV/AIDS and Climate Change therefore will be degrading to human health.

Mental health

While the physical health impacts of climate change are well known, the impact on mental health has only begun to be recognized in the last decade.^[34] According to 2011 in American Psychologist Clayton & Doherty, concluded that global climate change is bound to have substantial negative impacts on mental health and well-being, effects which will primarily be felt by vulnerable populations and those with pre-existing serious mental illness.^[35]

They identified three classes of psychological impacts from global climate change:^[36]

• Direct - "Acute or traumatic effects of extreme weather events and a changed environment"
• Indirect - "Threats to emotional well-being based on observation of impacts and concern or uncertainty about future risks"
• Psychosocial - "Chronic social and community effects of heat, drought, migrations, and climate-related conflicts, and postdisaster adjustment"

In order to appreciate the impacts on psychological well-being an understanding and recognition of the multiple meanings and cultural narratives associated with climate change and the interrelatedness of climate change and other global phenomena, like increased population, is required.^[35] The psychological impacts of climate change can be divided into three classes; direct, indirect, and psychosocial. Direct impacts refer to the immediate or localized consequences of an environmental change or disaster, such as stress or injury. Indirect impacts are more gradual and cumulative and are experienced through the media and social interaction and communication. Psychosocial impacts are large-scale community and social effects, like conflicts related to migration and subsequent shortages or adjustment after a disaster. Climate change does not impact everyone equally; those of lower economic and social status are at greater risk and experience more devastating impacts.^[35]

Direct impacts on mental health, such as landscape changes, impaired place attachment, and psychological trauma are all immediate and localized problems resulting from extreme weather events and environmental changes.^[35] Research has shown that extreme weather events lead to a variety of mental health disorders from the impacts of loss, social disruption, and displacement.^[37] Further reinforced by Clayton & Doherty (2011), “[a]cute and direct impacts include mental health injuries associated with more frequent and powerful weather events, natural disasters, and adjustment to degraded or disrupted physical environments”.^[35]:265 For example, events such as wildfires and hurricanes can lead to anxiety and emotional stress, further exacerbated in already vulnerable populations with current mental health issues ^[37]

On the other hand, indirect impacts pertaining to mental health are more gradual and cumulative and are experienced through the media and social interaction and communication.^[35] For example, extreme weather events can pose indirect impacts through the migration of large communities due to stressors upon already limited resources.^[37] Some examples of common mental health conditions associated indirectly from these extreme weather events include: acute traumatic stress, post-traumatic stress disorder, depression, complicated grief, anxiety disorders, sleep difficulties, sexual dysfunction, and drug or alcohol abuse.^[37] Similarly, the devastating effects of the extreme weather event of Hurricane Katrina lead to a variety of mental health problems due to the destruction of resources.^[38] Many people impacted by Hurricane Katrina were left homeless, disenfranchised, stressed, and suffering physical illness.^[38] This strain on the public health system decreased access and availability of medical resources.^[38] Some climate change adaptation measures may prevent the need for displacement; however, some communities may be unable to implement adaptation strategies, and this will create added stress, further exacerbating already existing mental health issues.^[37] Extreme weather events and population displacement lead to limited availability of medications, one of the primary resources required to meet psychological and physical needs of those affected by such events.^[37]

Furthermore, one of the more devastating indirect impacts of climate change on mental health is the increased risk in suicide. Studies show that suicide rates increase after extreme weather events.^[38] This has been demonstrated in Australia, where drought has resulted in crop failures and despair to the Australian countryside.^[38] Farmers were left with nothing, forced to sell everything, reduce their stock, and borrow large sums to plant crops at the start of the season.^[38] The indirect consequences have caused a growing increase in depression, domestic violence, and most alarmingly, suicide.^[38] More than one hundred farmers in the countryside had committed suicide by 2007.^[38]

Psychosocial impacts are indirect impacts on social and community relationships. While some impacts result directly from an event caused by climate change, most are indirect results of changes in how people use and occupy territory.^[35] Extreme weather events can lead to the migration of large communities due to stressors upon already limited resources.^[37] Climate change affects the suitability of territory for agriculture, aquaculture, and habitation, which means that the experiences of people in particular geographical locations, as well as the geographical distribution of populations, will be altered.^[35]

Consequences of psychosocial impacts caused by climate change include: increase in violence, intergroup conflict, displacement and relocation and socioeconomic disparities. Based on research, there is a causal relationship between heat and violence and that any increase in average global temperature is likely to be accompanied by an increase in violent aggression.^[39] Diminished resources leads to conflict between two groups over remaining natural resources or the migration of one group to another group’s territory leading to conflict over rights and ownership of space.^[35] Furthermore, this can lead to civil unrest when governments fail to adequately protect against natural disasters or respond to their effects, causing people to lose confidence and trust in their government leading to backlash.^[40] Forced relocations and displacement, result in disruptions of geographic and social connections which can lead to grief, anxiety, and a sense of loss.^[41] Another consequence of psychosocial impacts is an increase in the disparity between those countries and people with adequate economic resources and those with fewer or in need of. Those nations and people with fewer resources will feel the impacts more strongly, as they have less ability to afford the technologies that would mitigate the financial and medical effects of climate change.^[35] Within nations, these individuals of lower socioeconomic status are more likely to become ethnic minorities, increasing ethnic tensions and inter group hostility. An example of such tension and hostility occurred in the aftermath of Hurricane Katrina where African Americans interpreted the government’s response to the disaster as indicating racism.^[35]

Climate change and permafrost

Permafrost is an important part of our environment and plays an important role in maintaining the stability of many ecosystems around the world. Below are a few brief descriptions of how climate change has contributed to the melting of permafrost and the associated impacts on different aspects of ecosystems.

Fresh water supplies

Permafrost plays and integral role in the regulation of fresh water supplies in the arctic and high alpine regions.^[42] Three general ground water systems found in permafrost regions include: Supra-permafrost, intra-permafrost and sub-permafrost.^[42] Supra-permafrost system involves the water that is present above the frozen ground layer.^[42] Intra-permafrost water system involves the water present within channels or holes that run through the frozen ground layer.^[42] Supra-permafrost water systems exist below the frozen layer of earth.^[42] Together, these systems regulate and support aquifer water supply as well as above ground fresh water sources such as lakes and streams.^[42] When permafrost melts many freshwater lakes drain into the newly exposed soil below.^[42] The surrounding ecosystems are affected as arctic lakes provide important habitat for migratory waterfowl, ungulates such as moose and many aquatic species.^[43] Fresh water evaporation also occurs as permafrost melts.^[42] When the frozen ground disappears, associated surface air temperatures increase causing increased evaporation of fresh water supplies. Increased ground surface temperature also increases the rate of spring glacier melt.^[42] This associated increase in freshet causes water to run over soil and into muskeg areas where the water stagnates and becomes acidic.^[42] Once the acidified water enters into aquatic systems, it impacts the associated ecosystem.^[42]

Plants

There is a trong interdependence between permafrost and vegetation in permafrost regions.^[44] The melting of permafrost has a significant effect on soils, such as the moisture content and the availability of nutrients. Permafrost functions to serve terrestrial ecosystems; when permafrost thaws it decreases the amount of species that can grow in the low temperatures and high moisture soils.^[44] The effects that thawing permafrost has on vegetation greatly depends on the depth of the regions active layer.^[44] In some regions the thawing of permafrost leads to increased soil drainage and in others it leads to increased soil moisture; both causing changes to the dominant species in an area.^[44] In areas where the thawing permafrost causes increased soil drainage, wet plant species like Kobresia tibetica and Kobresia humilis decrease and drought plants such as Poa annua and Agropyron cristatum begin to take over.^[44] Unfortunately the decreased soil moisture leads to the disappearance of Alpine meadows and creates Alpine deserts.^[44] As Ice-rich permafrost regions begin to thaw the terrestrial ecosystems turn to aquatic or wetland ecosystems.^[44] Due to this process “wet sedge meadows, bogs, thermokarst ponds and lakes are replacing forests”.^[44] In Alaska the permafrost degradation has caused a decrease in birch forests by 25%.^[44] Permafrost degradation in the lowlands of Alaska has caused tussock (grass)-tundra communities to turn into shrub-tundra communities.^[44] Shrubs and woody plants are extending their northern ecological range and encroaching on lichen-dominated ecosystems.^[43]

As a result, the amount of lichens found in the affected areas decrease.^[43] This affects the entire ecosystem, as lichens are a vital food source for caribou that are commonly found in arctic regions.^[43] The degradation of permafrost and its effects on vegetation is a complex and intricate cycle; thus far the thawing permafrost has two major effects on vegetation: 1. Permafrost thaw in ice-rich soils equates to a loss of terrestrial ecosystems and an increase in aquatic or wetland ecosystems. 2. Permafrost thawing in the upland regions results in improved soil drainage leading to the alpine meadows undergoing a transformation to either shrub communities or drought communities.^[44]

Soil sustainability

Permafrost is integral to soil stability in arctic regions.^[45] Melting permafrost causes the surrounding soil to become unstable and settle.^[45] As permafrost melts, surrounding lakeshore destabilization takes place.^[46] Consequently, bank materials slump into the lakes decreasing oxygen concentration.^[42] As a result, water temperature increases which allows bacteria to flourish.^[42] The abundant bacteria produce carbon dioxide and methane gas causing the lakes and ponds to produce a significant source of greenhouse gas.^[42] This increased methane release is further amplified as melting permafrost exposes previously buried soil. Methane and carbon dioxide stored in the organic matter seep into the atmosphere and contribute further to the climate change problem.^[42] Similar to lake shore destabilization, melting permafrost causes bank materials to slump into river water which causes sedimentation of fish bearing streams and adversely effects habitat and health of salmon and other aquatic species.^[47] Settlement of surface soil associated with melting permafrost leads to significant infrastructure instability and damage to roads, bridges, buildings, homes, pipelines and airstrips in affected areas.^[45]

Impact on natural resources

Drinking water

In rural Africa and the Middle East, when droughts dry up the regular water supply, rural and impoverished families are forced to resort to drinking the dirty, sediment-and-parasite-laden water that sits in puddles and small pools on the surface of the earth. Many are aware of the presence of contamination, but will drink from these sources nonetheless in order to avoid dying of dehydration. It has been estimated that up to 80% of human illness in the world can be attributed to contaminated water.^[48]

When there is an adequate amount of drinking water, humans drink from different sources than their livestock. However, when drought occurs and drinking water slowly disappears, catchment areas such as streams and depressions in the ground where water gathers are often shared between people and the livestock they depend on for financial and nutritional support, and this is when humans can fall seriously ill. Although some diseases that are transferred to humans can be prevented by boiling the water, many people, living on just a litre or two of water per day, refuse to boil, as it loses a certain percentage of the water to steam.^[49]

The sharing of water between livestock and humans is one of the most common factors in the transmission of non-tuberulosis mycobacteria (NTM). NTM is carried in cattle and pig feces, and if this contaminates the drinking water supply, it can result in pulmonary disease, disseminated disease or localized lesions in humans with both compromised and competent immune systems.^[50] During drought, water supplies are even more susceptible to harmful algal blooms and microorganisms.^[51] Algal blooms increase water turbidity, suffocating aquatic plants, and can deplete oxygen, killing fish. Some kinds of blue-green algae create neurotoxins, hepatoxins, cytotoxins or endotoxins that can cause serious and sometimes fatal neurological, liver and digestive diseases in humans. Cyanobacteria grow best in warmer temperatures (especially above 25 degrees Celsius), and so areas of the world that are experiencing general warming as a result of climate change are also experiencing harmful algal blooms more frequently and for longer periods of time. During times of intense precipitation (such as during the “wet season” in much of the tropical and sub-tropical world, including Australia and Panama, nutrients that cyanobacteria depend on are carried from groundwater and the earth’s surface into bodies of water. As drought begins and these bodies gradually dry up, the nutrients are concentrated, providing the perfect opportunity for algal blooms.^[52][53][54]

Fresh water

As the climate warms, it changes the nature of global rainfall, evaporation, snow, stream flow and other factors that affect water supply and quality. Freshwater resources are highly sensitive to variations in weather and climate. Climate change is projected to affect water availability. In areas where the amount of water in rivers and streams depends on snow melting, warmer temperatures increase the fraction of precipitation falling as rain rather than as snow, causing the annual spring peak in water runoff to occur earlier in the year. This can lead to an increased likelihood of winter flooding and reduced late summer river flows. Rising sea levels cause saltwater to enter into fresh underground water and freshwater streams. This reduces the amount of freshwater available for drinking and farming. Warmer water temperatures also affect water quality and accelerate water pollution.^[55]

Impact on livestock

Climate change is beginning to lead the global population into a food shortage, greatly affecting our livestock supply. Although the change in our climate is causing us to lose food, these sources are also contributing to climate change, essentially, creating a feedback loop. Greenhouse gases, specifically from livestock, are one of the leading sources furthering global warming; these emissions, which drastically effect climatic change, are also beginning to harm our livestock in ways we could never imagine.

Greenhouse gas effects

Our agricultural food system is responsible for a significant amount of the greenhouse-gas emissions that are produced.^[56][57]

According to the IPCC, it makes up between, at least, 10-12% of the emissions, and when there are changes in land due to the agriculture, it can even rise as high as 17%. More specifically, emissions from farms, such as nitrous oxide, methane and carbon dioxide, are the main culprits, and can be held accountable for up to half of the greenhouse-gases produced by the overall food industry, or 80% of all emissions just within agriculture.^[57]

The types of farm animals, as well as the food they supply can be put into two categories: monogastric and ruminant. Typically, beef and dairy, in other words, ruminant products, rank high in greenhouse-gas emissions; monogastric, or pigs and poultry-related foods, are low. The consumption of the monogastric types, therefore, yield less emissions. This is due to the fact that these types of animals have a higher feed-conversion efficiency, and also do not produce any methane.^[57]

As lower-income countries begin, and continue, to develop, the necessity for a consistent meat supply will increase.^[57][58] This means the cattle population will be required to grow in order to keep up with the demand, producing the highest possible rate of greenhouse-gas emissions.^[57]

There are some strategies that can be used to help soften the effects, and the further production of greenhouse-gas emissions. Although there are many, some of them include: a higher efficiency in livestock farming, which includes management, as well as technology; a more effective process of managing manure; a lower dependence upon fossil-fuels and nonrenewable resources; a variation in the animals’ eating and drinking duration, time and location; and a cutback in, both, the production and consumption of animal-sourced foods.^{[57][58][59][60]}

Heat stress

Heat stress on livestock has a devastating effect on not only their growth and reproduction, but their food intake and production of dairy and meat. Cattle require a temperature range of 5-15 degrees Celsius, but upwards to 25 °C, to live comfortably, and once climate change increases the temperature, the chance of these changes occurring increases.^[58] Once the high temperatures hit, the livestock struggle to keep up their metabolism, resulting in decreased food intake, lowered activity rate, and a drop in weight. This causes a decline in livestock productivity and can be detrimental to the farmers and consumers. Obviously, the location and species of the livestock varies and therefore the effects of heat vary between them. This is noted in livestock at a higher elevation and in the tropics, of which have a generally increased effect from climate change. Livestock in a higher elevation are very vulnerable to high heat and are not well adapted to those changes.

Impact on plant based food

Climate change has many potential impacts on the production of food crops—from food scarcity and nutrient deficiency to possible increased food production because of elevated carbon dioxide (CO₂) levels—all of which directly affect human health. Part of this variability in possible outcomes is from the various climate change models used to project potential impacts; each model takes into account different factors and so come out with a slightly different result.^[61] A second problem comes from the fact that projections are made based on historical data which is not necessarily helpful in accurate forecasting as changes are occurring exponentially.^[62][63] As such, there are many different possible impacts—both positive and negative—that may result from climate change affecting global regions in different ways.^[63][64]

Food scarcity

Food scarcity is a major concern for many populations and is one of the prominent concerns with the changing climate. Currently, 1/6 of the global population are without adequate food supply.^[65] By 2050, the global population is projected to reach 9 billion requiring global food productions to increase by 50% to meet population demand.^[65][66] In short, food scarcity is a growing concern that, according to many researchers, is projected to worsen with climate change because of a number of factors including extreme weather events and an increase in pests and pathogens.

Extreme weather

Rising temperatures

As the temperature changes and weather patterns become more extreme, areas which were historically good for farmland will no longer be as amicable.^[67][68] The current prediction is for temperature increase and precipitation decrease for major arid and semi-arid regions (Middle East, Africa, Australia, Southwest United States, and Southern Europe).^[67][69] In addition, crop yields in tropical regions will be negatively affected by the projected moderate increase in temperature (1-2 °C) expected to occur during the first half of the century.^[70] During the second half of the century, further warming is projected to decrease crop yields in all regions including Canada and Northern United States.^[69] Many staple crops are extremely sensitive to heat and when temperatures rise over 36 °C, soybean seedlings are killed and corn pollen loses its vitality.^[62][71] Scientists project that an annual increase of 1 °C will in turn decrease wheat, rice and corn yields by 10%.^[69][72]

There are, however, some positive possible aspects to climate change as well. The projected increase in temperature during the first half of the century (1-3 °C) is expected to benefit crop and pasture yields in the temperate regions.^[61][62][73] This will lead to higher winter temperatures and more frost-free days in these regions; resulting in a longer growing season, increased thermal resources and accelerated maturation.^[63][64] If the climate scenario results in mild and wet weather, some areas and crops will suffer, but many may benefit from this.^[61]

Drought and flood

Extreme weather conditions continue to decrease crop yields in the form of droughts and floods. While these weather events are becoming more common, there is still uncertainty and therefore a lack of preparedness as to when and where they will take place.^[64][74] In extreme cases, floods destroy crops, disrupting agricultural activities and rendering workers jobless and eliminating food supply. On the opposite end of the spectrum, droughts can also wipe out crops. It is estimated that 35-50% of the world’s crops are at risk of drought.^[62] Australia has been experiencing severe, recurrent droughts for a number of years, bringing serious despair to its farmers. The country’s rates of depression and domestic violence are increasing and as of 2007, more than one hundred farmers had committed suicide as their thirsty crops slipped away.^[62] Drought is even more disastrous in the developing world, exacerbating the pre-existing poverty and fostering famine and malnutrition.^[61][62]

Droughts can cause farmers to rely more heavily on irrigation; this has downsides for both the individual farmers and the consumers. The equipment is expensive to install and some farmers may not have the financial ability to purchase it.^[67] The water itself must come from somewhere and if the area has been in a drought for any length of time, the rivers may be dry and the water must be transported from further distances. With 70% of “blue water” currently being used for global agriculture, any need over and above this could potentiate a water crisis.^[61][65] In Sub-Saharan Africa, water is used to flood rice fields to control the weed population; with the projection of less precipitation for this area, this historical method of weed control will no longer be possible.^[75]

With more costs to the farmer, some will no longer find it financially feasible to farm. Agriculture employs the majority of the population in most low-income countries and increased costs can result in worker layoffs or pay cuts.^[61] Other farmers will respond by raising their food prices; a cost which is directly passed on to the consumer and impacts the affordability of food. Some farms do not export their goods and their function is to feed a direct family or community; without that food, people will not have enough to eat. This results in decreased production, increased food prices, and potential starvation in parts of the world.^[65]

Financial

Some research suggests that initially climate change will help developing nations because some regions will be experiencing more negative climate change effects which will result in increased demand for food leading to higher prices and increased wages.^[61] However, many of the projected climate scenarios suggest a huge financial burden. For example, the heat wave that passed through Europe in 2003 cost 13 billion euros in uninsured agriculture losses.^[70] In addition, during El Nino weather conditions, the chance of the Australian farmer’s income falling below average increased by 75%, greatly impacting the country’s GDP.^[70] The agriculture industry in India makes up 52% of their employment and the Canadian Prairies supply 51% of Canadian agriculture; any changes in the production of food crops from these areas could have profound effects on the economy.^[63][68] This could negatively affect the affordability of food and the subsequent health of the population.

Pests and pathogens

Currently, CO₂ levels are 40% higher than they were in pre-industrial times.^[62] This diminishes nutritional content for both human and insect consumption. Studies have shown that when CO₂ levels rise, soybean leaves are less nutritious; therefore plant-eating beetles have to eat more to get their required nutrients.^[62] In addition, soybeans are less capable of defending themselves against the predatory insects under high CO₂. The CO₂ diminishes the plant’s jasmonic acid production, an insect-killing poison that is excreted when the plant senses it’s being attacked. Without this protection, beetles are able to eat the soybean leaves freely, resulting in a lower crop yield.^[62] This is not a problem unique to soybeans, and many plant species’ defense mechanisms are impaired in a high CO₂ environment.^[66]

Currently, pathogens take 10-16% of the global harvest and this level is likely to rise as plants are at an ever-increasing risk of exposure to pests and pathogens.^[66] Historically, cold temperatures at night and in the winter months would kill off insects, bacteria and fungi. The warmer, wetter winters are promoting fungal plant diseases like soybean rust to travel northward. Soybean rust is a vicious plant pathogen that can kill off entire fields in a matter of days, devastating farmers and costing billions in agricultural losses. Another example is the Mountain Pine Beetle epidemic in BC, Canada which killed millions of pine trees because the winters were not cold enough to slow or kill the growing beetle larvae.^[62] The increasing incidence of flooding and heavy rains also promotes the growth of various other plant pests and diseases.^[76] On the opposite end of the spectrum, drought conditions favour different kinds of pests like aphids, whiteflies and locusts.^[62]

The competitive balance between plants and pests has been relatively stable for the past century, but with the rapidly shifting climate, there is a change in this balance which often favours the more biologically diverse weeds over the monocrops most farms consist of.^[76] Currently, weeds claim about one tenth of global crop yields annually as there are about eight to ten weed species in a field competing with crops.^[62] Characteristics of weeds such as their genetic diversity, cross-breeding ability, and fast-growth rates put them at an advantage in changing climates as these characteristics allow them to adapt readily in comparison to most farm's uniform crops, and give them a biological advantage.^[62] There is also a shift in the distribution of pests as the altered climate makes areas previously uninhabitable more uninviting.^[71] Finally, with the increased CO₂ levels, herbicides will lose their efficiency which in turn increases the tolerance of weeds to herbicides.^[76]

Impact on nutrition

Another area of concern is the effect of climate change on the nutritional content of food for human consumption. Studies show that increasing atmospheric levels of CO₂ have an unfavourable effect on the nutrients in plants. As the carbon concentration in the plant’s tissues increase, there is a corresponding decrease in the concentration of elements such as nitrogen, phosphorus, zinc and iodine. Of significant concern is the protein content of plants, which also decreases in relation to elevating carbon content.^[63][66][77]

Irakli Loladze explains that the lack of essential nutrients in crops contributes the problem of micronutrient malnutrition in society, commonly known as “hidden hunger”; despite adequate caloric intake, the body still is not nutritionally satisfied and therefore continues to be “hungry”.^[78] This problem is aggravated by the rising cost of food, resulting in a global shift towards diets which are less expensive, but high in calories, fats, and animal products. This results in undernutrition and an increase in obesity and diet-related chronic diseases.^[65][78]

Countries worldwide are already impacted by deficiencies in micronutrients and are seeing the effects in the health of their populations. Iron deficiency affects more than 3.5 billion people; increasing maternal mortality and hindering cognitive development in children, leading to education losses. Iodine deficiency leads to ailments like goitre, brain damage and cretinism and is a problem in at least 130 different countries.^[78] Even though these deficiencies are invisible, they have great potential to impact human health on a global scale.

It must also be noted that small increases in CO₂ levels can cause a CO₂ fertilization effect where the growth and reproduction abilities of C₃ plants such as soybeans and rice are actually enhanced by 10-20% in laboratory experiments. This does not take into account, however, the additional burden of pests, pathogens, nutrients and water affecting the crop yield.^[77][79]

Adaptation and mitigation strategies

While researchers acknowledge there are possible benefits, most agree that the negative consequences of climate change will outweigh any potential benefits and instead the shifting climate will result in more benefits to developed countries and more detriments to developing countries; exacerbating the discrepancy between wealthy and impoverished nations.^[66][72][79] By thoughtful and proactive efforts, climate change can be mitigated by addressing these issues with a multidisciplinary approach that works on a global, national and community basis that recognizes the uniqueness of each country’s situation.^[65][68]

According to a study of East Africa’s smallholder farms, impacts of climate change on agriculture are already being seen there resulting in changes to farming practices such as intercropping, crop, soil, land, water and livestock management systems, and introduction of new technologies and seed varieties by some of the farmers.^[74] Some other suggestions such as eliminating supply chain and household food waste, encouraging diverse and vegetable-rich diets, and providing global access to foods (food aid programs) have been suggested as ways to adapt.^[61][65][66] Many researchers agree that agricultural innovation is essential to addressing the potential issues of climate change. This includes better management of soil, water-saving technology, matching crops to environments, introducing different crop varieties, crop rotations, appropriate fertilization use, and supporting community-based adaptation strategies.^{[63][65][68][76][80]} On a government and global level, research and investments into agricultural productivity and infrastructure must be done to get a better picture of the issues involved and the best methods to address them. Government policies and programs must provide environmentally sensitive government subsidies, educational campaigns and economic incentives as well as funds, insurance and safety nets for vulnerable populations.^{[61][65][66][68][80]} In addition, providing early warning systems, and accurate weather forecasts to poor or remote areas will allow for better preparation; by using and sharing the available technology, the global issue of climate change can be addressed and mitigated by the global community.^[65]

Ocean acidification and human health

Overview

Perhaps one of the most recent adverse effects of climate change to be explored is that of ocean acidification. Our oceans cover approximately 71 percent of the Earth's surface and support a diverse range of ecosystems, which are home to over 50 percent of all the species on the planet.^[81] Oceans regulate climate and weather as well as providing nutrition for a vast variety of species, humans included.^[81] Covering such an extensive part of the planet has allowed the oceans to absorb a large portion of the carbon dioxide (CO₂) from the atmosphere.^[82] This process is part of the carbon cycle in which the fluxes of carbon dioxide (CO₂) in Earth's atmosphere, biosphere and lithosphere are described.^[83] Humans have drastically added to the amount of carbon dioxide (CO₂) in the atmosphere through the burning of fossil fuels and the process of deforestation. Oceans work as a sink absorbing excess anthropogenic carbon dioxide (CO₂). As the oceans absorb anthropogenic carbon dioxide (CO₂) it breaks down into carbonic acid, a mild acid, this neutralizes the normally alkaline ocean water. As a result the pH in the oceans is declining. In the research surrounding global climate change we are only just beginning to realize that our oceans can sequester a finite amount of CO₂ before we start seeing impacts on marine life that could lead to devastating losses. Acidification of our oceans has the potential to drastically alter life as we know it - from extreme weather patterns and food scarcity to a loss of millions of species from the planet - all of these consequences hold the potential to directly affect human health.

Chemistry

The mechanism by which CO₂ is absorbed into the ocean is basic chemistry. CO₂ combines with water H₂O to form carbonic acid (H
2CO
3) then eventually dissociates into carbonate (CO2−
3) and hydrogen ions (H+
). The free hydrogen ions (H+
) lower the pH of the surrounding waters making it acidic. The mechanism is shown here

CO_{2 (aq)} + H₂O H₂CO₃ HCO₃⁻ + H⁺ CO₃²⁻ + 2 H⁺.

According to our records since the pre-industrial age pH has already dropped approximately 0.1 pH unit, or 30 percent because the pH scale is logarithmic.^[84] If we continue with business as usual it is expected that by mid-century pH could drop another o.3 pH units - at this rate our oceans would be two and a half times as acidic then previous levels.^[84]

Temperature

Decreasing pH and rising water temperatures due to global warming and increased greenhouse gas emissions work synergistically. When the temperature rises, the chemical reaction above proceeds at a faster rate therefore, the water becomes more acidic as it warms. Conversely, warmer water is unable to hold as much CO₂ therefore, it releases more into the atmosphere, in turn, making the atmosphere warmer further warming the oceans water.^[85]

Impacts on marine life

Acidification has multiple implications on marine life such as physiological sensitivities, reduced metabolism, decreased oxygen uptake and reproductive success.^[86] Looking at it from a bottom up approach, the simpler organisms are considered first moving up the food chain culminating with the ultimate apex predator, man.

Coral

Coral reefs appear to be both negatively and positively affected by pH and temperature changes. Corals in currently warmer waters appear to break down and die off as a consequence of lower pH and higher water temperatures, whereas corals in cooler waters appear to become hardier and grow faster due to pH changes and temperatures rising.^[87] This change in coral community composition will allow formerly cold water corals to slowly move into areas previously occupied by warm water species.^[87] This shift in regional locality will likely be a slow, laborious process and the mean time could actually lead to more pronounced ‘dead zones’ throughout the oceans. Acidification and temperature increase leads to ‘dead zones’, because it allows for eutrophication to occur. Blooms of algae and phytoplankton explode removing oxygen during their eventual death and decomposition.^[88] The Southern Ocean is an area of particular high risk.^[88] A decrease in coral reef cover leads to less viable fish habitat and a breakdown in the food chain, further exacerbating ‘dead zones’.^[87] In 2008, it was estimated that global fisheries dependent upon species associated with coral reefs topped US$5.7 billion annually.^[88]

Oceanic calcifying organisms

Ocean acidification also leads to a reduction in the ability for calcareous organisms to build and maintain their shells, skeletons and other structures.^{[88][89][90][91]} The decreased pH renders them unable to fix calcium Ca₂ to carbonate (CO2−
3) for production of calcium-based protection, and they become easy prey for predators, if they are able to survive the more acidic conditions in the first place.^[90] Many island states and developing nations depend upon such organisms (like mussels and oysters) for sustenance and income since they may occupy land that has little terrestrial agricultural value.^[88] The decrease in native species allows for non-native, invasive species to take hold and a shift from calcareous species to soft-bodied inverts takes place.^[89] This also affects the food chain from a bottom-up perspective.^[89]

Fish

Fish are not immune to ocean acidification either. Not only does the lower pH affect their food availability, it has also been shown to impair their senses. It affects their sense of smell, hearing, balance and ability to sense predators.^[88] Further, studies have shown that acidification has positive and negative impacts on fecundity, distribution range, growth and seasonal movements.^[87][91][92] Some fish, like the anemone fish, have been able survive the pH shifts and live to reproduce, provided the parents existed in the same conditions prior to offspring being born.^[87] More studies need to be conducted with a wider range of species to determine the full scope of implications associated with this phenomenon. In one study from Southeastern Australia, ocean acidification had the largest negative impact on total fish biomass, more so than either fishing or ocean warming alone.^[92] Overall, ocean acidification had the single largest negative effect on total biomass (top predators, fishes, benthic invertebrates, plankton, and primary producers).^[92] Taken together, the additive effects of more than one stressor at the community level resulted in decreased biomass in majority of the marine communities.

Human health

The health of our oceans has a direct effect on the health humans. According to Small and Nicholls, they estimated that 1.2 billion people worldwide, lived in the near-coastal region (within 100 km and 100m of the shoreline).^[93] This data was collected in 1990 and therefore is a conservative estimate in modern terms. In the U.S. alone 53% of the population lives within 50 miles of the coastal shoreline.^[94] Humans rely heavily on oceans for food, employment, recreation, weather patterns and transportation.^[95] In the U.S. alone the lands adjacent to the oceans contribute over $1 trillion annually through these various activities not to mention pharmaceutical and medicinal discoveries.^[95] In all, the oceans are very important for our survival as a species.

Infiltrating fresh water and extreme weather

With degradation of protective coral reefs through acidic erosion, bleaching and death, salt water is able to infiltrate fresh ground water supplies that large populations depend on.^[96][97] Nowhere is this more evident than atoll islands. These islands possess limited freshwater supplies, namely ground water lenses and rain fall. When the protective coral reefs surrounding them erodes due to higher temperatures and acidic water chemistry, salt water is able to infiltrate the lens and contaminate the drinking water supply.^[96] In coastal Bangladesh it has been demonstrated that seasonal hypertension in pregnant women is connected with such phenomenon due to high sodium intake from drinking water.^[97] Reef erosion, coupled with sea level rise, tends to flood low lying areas more frequently during storm surges and weather events. Warming ocean waters generate larger and more devastating weather events that can decimate coastal populations especially without the protection of coral reefs.

Food safety

Our insatiable appetite for seafood of all types has led to overfishing and has already significantly strained marine food stocks to the point of collapse in many cases. With seafood being a major protein source for so much of the population, there are inherent health risks associated with global warming. As mentioned above increased agricultural runoff and warmer water temperature allows for eutrophication of ocean waters. This increased growth of algae and phytoplankton in turn can have dire consequences. These algal blooms can emit toxic substances that can be harmful to humans if consumed. Organisms, such as shellfish, marine crustaceans and even fish, feed on or near these infected blooms, ingest the toxins and can be consumed unknowingly by humans. One of these toxin producing algae is Pseudo-nitzschia fraudulenta. This species produces a substance called domoic acid which is responsible for amnesic shellfish poisoning.^[98] The toxicity of this species has been shown to increase with greater CO2 concentrations associated with ocean acidification.^[98] Some of the more common illnesses reported from harmful algal blooms include; Ciguatera fish poisoning, paralytic shellfish poisoning, azaspiracid shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning and the above-mentioned amnesic shellfish poisoning.^[98]

Extreme weather events

Infectious disease often accompanies extreme weather events, such as floods, earthquakes and drought. These local epidemics occur due to loss of infrastructure, such as hospitals and sanitation services, but also because of changes in local ecology and environment. For example, malaria outbreaks have been strongly associated with the El Niño cycles of a number of countries (India and Venezuela, for example). El Niño can lead to drastic, though temporary, changes in the environment such as temperature fluctuations and flash floods.^[99] Because of global warming there has been a marked trend towards more variable and anomalous weather. This has led to an increase in the number and severity of extreme weather events. This trend towards more variability and fluctuation is perhaps more important, in terms of its impact on human health, than that of a gradual and long-term trend towards higher average temperature.^[99]

Drought

Arguably one of the worst effects that drought has directly on human health is the destruction of food supply. Farmers who depend on weather to water their crops lose tons of crops per year due to drought. Plant growth is severely stunted without adequate water, and plant resistance mechanisms to fungi and insects weaken like human immune systems. The expression of genes is altered by increased temperatures, which can also affect a plant’s resistance mechanisms. One example is wheat, which has the ability to express genes that make it resistant to leaf and stem rusts, and to the Hessian fly; its resistance declines with increasing temperatures. A number of other factors associated with lack of water may actually attract pestilent insects, as well- some studies have shown that many insects are attracted to yellow hues, including the yellowing leaves of drought-stressed plants. During times of mild drought is when conditions are most suitable to insect infestation in crops; once the plants become too weakened, they lack the nutrients necessary to keep the insects healthy. This means that even a relatively short, mild drought may cause enormous damage- even though the drought on its own may not be enough to kill a significant portion of the crops, once the plants become weakened, they are at higher risk of becoming infested.^[100]

The results of the loss of crop yields affect everyone, but they can be felt most by the poorest people in the world. As supplies of corn, flour and vegetables decline, world food prices are driven up. Malnutrition rates in poor areas of the world skyrocket, and with this, dozens of associated diseases and health problems. Immune function decreases, so mortality rates due to infectious and other diseases climb. For those whose incomes were affected by droughts (namely agriculturalists and pastoralists), and for those who can barely afford the increased food prices, the cost to see a doctor or visit a clinic can simply be out of reach. Without treatment, some of these diseases can hinder one’s ability to work, decreasing future opportunities for income and perpetuating the vicious cycle of poverty.^[101]

Floods

Health concerns around the world can be linked to floods. With the increase in temperatures world wide due to climate change the increase in flooding is unavoidable.^[102] Floods have short and long term negative implications to peoples' health and well being. Short term implications include mortalities, injuries and diseases, while long term implications include non-communicable diseases and psychosocial health aspects.^[103]

Moralities are not uncommon when it comes to floods. The Countries with lower incomes are more likely to have more fatalities, because of the lack of resources they have and the supplies to prepare for a flood. This does depend on the type and properties of the flood. For example if there is a flash flood it would not matter how prepared you are. Fatalities connected directly to floods are usually caused by drowning; the waters in a flood are very deep and have strong currents.^[103] Deaths do not just occur from drowning, deaths are connected with dehydration, heat stroke, heart attack and any other illness that needs medical supplies that cannot be delivered.^[103]

Injuries can lead to an excessive amount of morbidity when a flood occurs. Victims who already have a chronic illness and then sustain a non-fatal injury are put at a higher risk for that non-fatal injury to become fatal. Injuries are not isolated to just those who were directly in the flood, rescue teams and even people delivering supplies can sustain an injury. Injuries can occur anytime during the flood process; before, during and after.^[103] Before the flood people are trying to evacuate as fast as they can, motor vehicle accidents, in this case, are a primary source of injuries obtained post flood. During floods accidents occur with falling debris or any of the many fast moving objects in the water. After the flood rescue attempts are where large amounts of injuries can occur.^[103]

Communicable diseases are increased due to many pathogens and bacteria that are being transported by the water. In floods where there are many fatalities in the water there is a hygienic problem with the handling of bodies, due to the panic stricken mode that comes over a town in distress.^[103] There are many water contaminated diseases such as cholera, hepatitis A, hepatitis E and diarrheal diseases, to mention a few. There are certain diseases that are directly correlated with floods they include any dermatitis and any wound, nose, throat or ear infection. Gastrointestinal disease and diarrheal diseases are very common due to a lack of clean water during a flood. Most of clean water supplies are contaminated when flooding occurs. Hepatitis A and E are common because of the lack of sanitation in the water and in living quarters depending on where the flood is and how prepared the community is for a flood.^[103]

Respiratory diseases are a common after the disaster has occurred. This depends on the amount of water damage and mold that grows after an incident. Vector borne diseases increase as well due to the increase in still water after the floods have settled. The diseases that are vector borne are as follows: malaria, dengue, West Nile, yellow fever.^[103]

Non-communicable diseases are a long-term effect of floods. They are either caused by a flood or they are worsened by a flood; they include cancer, lung disease and diabetes. Floods have a huge impact on victims psychosocial integrity. People suffer from a wide variety of losses and stress. One of the most treated illness in long-term health problems are depression caused by the flood and all the tragedy that flows with one.^[103]

Glacial melting

A glacier is a mass of ice that has originated from snow that has been compacted via pressure and have definite lateral limits and movements in definite directions.^[104] They are found in areas where the temperatures do not get warm enough to melt annual snow accumulation, thus resulting in many layers of snow piling up over many years, creating the pressure needed to make a glacier. Global climate change and fluctuation is causing an increasingly exponential melting of Earth’s glaciers. These melting glaciers have many social and ecological consequences that directly or indirectly impact the health and well-being of humans.^[105] The recession of glaciers change sea salt, sediment, and temperature ratios in the ocean which changes currents, weather patterns, and marine life.^[99] The melt also increases ocean levels and decreases the availability of water for human consumption, agriculture, and hydroelectricity. This aggravates and increases the likelihood of issues such as sanitation, world hunger, population shifts, and catastrophic weather such as flooding, drought, and world-wide temperature fluctuations.^[99]

“Glacier mass-balances show consistent decreases over the last century in most regions of the world and retreat may be accelerating in many locations" ^[106] with an average loss of ten meters per year,^[105] nearly twice as fast as ten years ago.^[107] Glaciers currently cover ~10% of the Earth’s surface, or ~15 million km² and holds ~75% of Earth’s fresh water supply. Glacial retreat first gained the attention of alpinists and the tourist industry shortly after 1940 – when the globe warmed ~0.5 °C.^[104] Even with 62 years of awareness, climate change is just becoming an issue for some parts of society. Over this time period the cirque and steep alpine glaciers were able to acclimatize to the new temperatures posed by climate change; large valley glaciers have not yet made this adjustment. This means the large valley glaciers are rapidly retreating, as their mass is attempting to achieve equilibrium with the current climate. If regional snow lines stay constant, then the glaciers remain constant.^[104] Today this is clearly not the case as global warming is causing mountain snow lines to rapidly retreat. Even the United States’ famous Glacier National Park is receding. More than two-thirds of its glaciers have disappeared and it is expected for them to be nonexistent in the park by the year 2030.^[108]

Glacial melt will affect low lying coastal wetlands via sea level rise, change key drivers of fresh-water ecosystems, shift the timing of snow packs, and alter the unique character of associated fresh water streams off of snow pack.^[109] It has also been stated that the sea level will rise 28–43 cm by 2100;^[109] if all the ice on Earth melts, it is predicted that the ocean level will increase 75 meters, destroying many coastal cities.^[99] In addition, the freshwater swaps in northern areas are already affected by the intrusion of salt water. “Sea level rise will cause a change of state from freshwater to marine or estuarine ecosystems, radically altering the composition of biotic communities".^[109]

Not only are glaciers causing a rise in sea level, they are causing an increase in El Niño Southern Oscillation (ESNO) and global temperature itself.^[104] Glacier loss adds to global heat rise through a decrease in what is called ice-albedo feedback. As more ice melts, there is less solar reflectivity and less heat is reflected away from the Earth, causing more heat to be absorbed, and retained in the atmosphere and soil ^[99] In addition to the El Niño events, glacial melt is contributing to the rapid turnover of sea surface temperatures ^[104] and ocean salt content by diluting the ocean water and slowing the Atlantic conveyor belt's usually swift dive because of a top layer of buoyant, cold, fresh water that slows the flow of warm water to the north.^[99]

Fifty percent of the world’s fresh water consumption is dependent glacial runoff.^[108] Earth's glaciers are expected to melt within the next forty years, greatly decreasing fresh water flow in the hotter times of the year, causing everyone to depend on rainwater, resulting in large shortages and fluctuations in fresh water availability which largely effects agriculture, power supply, and human health and well-being.^[99] Many power sources and a large portion of agriculture rely on glacial runoff in the late summer. “In many parts of the world, disappearing mountain glaciers and droughts will make fresh, clean water for drinking, bathing, and other necessary human (and livestock) uses scarce" and a valuable commodity.^[99]

Heat stress

The upper limit for heat stress humans can adapt to is called into question with a 7 °C temperature rise, quantified by the wet-bulb temperature, regions of Earth would lose their habitability.^[110]

Deforestation

Forests account for approximately 30% of the Earth’s land surface.^[111] The soils and ecosystems that exist within these forests store around 1200 gigatonnes of carbon. With the earth’s atmospheric concentration of carbon dioxide (CO2) recently reaching 391 ppm (parts per million) in October 2012,^[112][113] more than a 100 ppm increase from the pure-industrial era^[114] it is clear that the relationship between the Earth’s forests and atmosphere is critically important.^[111] During the 1980s it became increasingly clear that the terrestrial biosphere played an important part in terms of the global atmospheric carbon balance. It became apparent that the conversion of land, most notably deforestation in the tropics, caused large terrestrial carbon losses into the atmosphere forcing other carbon sinks to compensate.^[111]

Tropical forests

Tropical Forests account for just under 50% of the world's forests, however they contain as much carbon in their vegetation and soils as boreal and temperate type forests combined.^[115] With trees in the tropics holding in general approximately 50% more carbon per hector than trees outside of the tropics, deforestation in these areas is more likely to lead to higher levels of carbon release.^[115]

Amazon rainforest

Forests currently play a major role in carbon uptake in the global carbon cycle.^[116] The Amazon rain forest plays an important role by sequestering carbon under stable climatic conditions.^[117] Forest fires are often not assigned a net emission of carbon as they are viewed as a bi-product of forest conversion for agriculture use, however accidental spread of fires beyond agriculture areas may contribute to increased carbon emissions.^[118] If the carbon emissions from forest fires are due to a natural cycle of burning and regrowth, the net carbon balance is nearly zero.^[118] However current forest-fire models suggest that forest fragmentation and climate change could shift the Amazon forest from a carbon sink to a source of atmospheric CO2.^[117] Recurrent fires increase pyrophytic vegetation, such as bamboos and grasses which also increase forest flammability thus increasing potential emissions.^[117] In 1997 and 1998 forest fires during the El Niño drought affected at least 20,000 km² in the Amazon leading to large smoke episodes which halted air traffic in the area and caused ships to collide at sea.^[119] The short-term effects on human health effects were irritations of the respiratory tract, skin and eyes, bronchitis, conjuctivitis as well as increased asthma attacks.^[119]

The major drivers of deforestation and degradation in the Amazon are, forest conversions for shifting cultivation, croplands, pastures as well as industrial and fuel wood harvest.^[118] When forests are converted to croplands all initial vegetation is replaced by crops causing a change in the carbon density.^[118] Cropland conversion also causes a 25-30% soil carbon reduction.^[118] Forest conversion to pastures for cattle is a major cause of deforestation in the Amazon, and although it does not cause the reduced soil carbon seen with croplands, it is still significant primarily due to its sheer magnitude.^[118] The harvest of both industrial wood and fuel wood causes increased carbon emissions due to burning and decay of wood products as well as reduced carbon density of forests.^[118] Tree plantations result in a carbon sink reducing atmospheric carbon dioxide in participating areas. However within tropical forests worldwide tree plantations have only accounted for an approximately 4% decrease in net carbon emissions.^[118]

Southeast Asia

By World War II approximately one-third of the tropical forests in Southeast Asia had been cleared, with declines continuing past the mid-century mark.^[120] Over the past thirty years commercial logging for export has caused significant forest loss.^[120] In the forested uplands of Indonesia, in order to extract timber, large forestry corporations constructed road systems to allow access to previously inaccessible areas. After having logged a given area the loggers moved on and small farmers settled along the roads and cleared additional forests.^[120] Logging companies shifted from one concession to another, moving from country to country.^[120] Increased market expansion for tropical timber along with inferior law enforcement, vested interests, and corruption, allowed for illegal logging operations to exist.^[120] The lowland forests of Laos and Cambodia have been subjected to increasingly intense swidden cultivation and the majority of old-growth forests have ceased to exist in these areas.^[120] Forests generally hold 20 to 50 times more carbon than the ecosystem which replaces them,^[115] thus leading to a net increase of atmospheric C02.

Mangroves

Mangroves are the salt-tolerant evergreen forests, found in the intertidal zones of sheltered shores, estuaries, tidal creeks, backwaters, lagoons, marches and mudflats of the tropical and subtropical latitudes. Mangrove systems are in continuous jeopardy, facing threats from human interventions. Human interference in mangrove forests has caused the system to shrink in an alarming way and at a faster rate than inland tropical forests and coral reefs.^[121] It is predicted that small rise in sea level would be the greatest threat to the existing mangroves.^[122] The mangrove forests are likely to be totally lost in the next 100 years, if current trends continues.^[121] A healthy mangrove ecosystem provides vast benefits to the adjoining systems and mankind. Mangroves and associated soils can sequester 22.8 million metric tons of carbon each year, which is 11% of the total input of terrestrial carbon into oceans ^[123] and provides more than 10% of essential organic carbon to the global oceans.^[124]Carbon sequestration potential of mangroves is 50 times greater than many other tropical forests. This is due to the high levels of below ground biomass and also the considerable storage of organic carbon in mangrove sediment soils. Failing to preserve mangrove forests may cause considerable carbon emissions and thus accelerate global warming.^[125] The restoration of mangroves can be an ideal and natural counter-measure to global warming, and mangroves also play a key role in environmental security. This consists of mitigating the effects of tsunami, cyclones, floods and green house gas. In general, every ecosystem provides life supporting functions as well as other valuable services, many of which are interlaced with human welfare ^[126] Mangroves have a medicinal value as well. Coastal ecosystems such as mangroves are as a potential site for new drugs.^[127] Drug research groups have pointed out that mangroves possess an untapped source of new medicines and in the future this ecosystem will be the new frontiers for drug discoveries.^[127]

Effects of deforestation in the African Highlands

Environmental changes such as deforestation could increase local temperatures in the highlands thus could enhance the vectorial capacity of the anopheles.^[128] Anopheles mosquitos are responsible for the transmission of a number of diseases in the world, such as, malaria, lymphatic filariasis and viruses that can cause such ailments like O'nyong'nyong virus.^[128] Environmental changes, climate variability, and climate change are such factors that could affect biology and ecology of Anophelse vectors and their disease transmission potential.^[128] Climate change is expected to lead to latitudinal and altitudinal temperature increases. Global warming projections indicate that the best estimate of surface air warming for a “high scenario” is 4 C, with a likely range of 2.4-6.4 C by 2100.^[129] A temperature increase of this size would alter the biology and the ecology of many mosquito vectors and the dynamics of the diseases they transmit such as Malaria. Arthropods critically depend on ambient temperature for survival and development,^[130] and their distribution range is limited by the temperature. Climate warming or any factor that alters the microclimate conditions of Anopheles mosquitos (e.g., Deforestation) in the highlands may facilitate the persistence of the mosquito population.^[131] Climate warming can mediate mosquito physiology and metabolic rate because metabolic rate increases exponentially rather than linearly with temperature ectotherms.^[132] Anopheles mosquitoes in highland areas are to experience a larger shift in their metabolic rate due to the climate change. This climate change is due to the deforestation in the highland areas where these mosquitos dwell. When temperature rises, the larvae take a shorter time to mature ^[133] and, consequently, there is a greater capacity to produce more offspring. Microclimatic changes in human homes caused by the effects of deforestation can also significantly shorten the duration of the mosquitoes' gonotrophic cycle by 1.7 days (4.6 vs 2.9 days)^[134] The gonotrophic cycle is the period between the taking of a blood meal by a mosquito, including the digestion of the blood meal, until oviposition or egg laying.^[135] The decrease of the gonotrophic cycles implies an increase of the biting frequency from an average of once every five days to once every three days. In turn this could potentially lead to an increase in malaria transmission when infected humans are available.

Deforestation for the purpose of logging and self-subsistence agriculture is a serious problem in the tropical regions of Africa. For Example, Malava forest, a tropical rainforest in kakamega district, Kenya, shrank from 150 km² in 1965 to 86 km² in 1997. In East African highlands, 2.9 million hectares of forest were cleared between 1981 and 1990, representing an 8% reduction in forest cover in one decade.^[136] Land use and land cover changes may modify the temperature and relative humidity of malaria vector habitats in the highlands. For instance, deforestation in Cameroon caused the introduction of A. gambiae into the habitat that was previously dominated by A. moucheti.^[137]

Biodiversity

Deforestation is directly linked with a decrease in plant biodiversity.^[138] This decrease in biodiversity has several implications for human health. One such implication is the loss of medicinal plants. The use of plants for medicinal purposes is extensive, with ~70 to 80% of individuals worldwide relying solely on plant-based medicine as their primary source of healthcare.^[139] This dependency on plants for medicinal purposes is especially rife in developing countries that only consume 15% of manufactured pharmaceutical drugs, many of which are fake.^[139] Local knowledge surrounding medicinal plants is useful for screening for new herbal medicines that may be useful for treating disease.^[140] Villages and communities which reside continually in a single geographic area over time, create, transmit and apply widespread information surrounding the medicinal resources in the area.^[140] Formal scientific methods have been useful in identifying the active ingredients used in ethnopharmacy and applying them to modern medicines. However, it is important that medicinal resources are managed appropriately as they become globally traded in order to prevent species endangerment.^[140]

Extinction of indigenous groups

Deforestation is also a primary cause of dislocation and in some cases, extinction of indigenous people.^[141] The Malaysian state Sarawak is an example where rampant deforestation has overrun many Dayak groups.^[141] The indigenous Sarawakians relied on shifting agriculture, hunting and gathering in order to sustain their relatively low population density.^[142] With the advent of modern logging technology the Sarawak forests entered 'mainstream' economic development.^[141] This has led to massive forced evacuations and relocation of the Dayak people causing a loss of their traditions and culture.^[143]

Mountain pine beetle, forest ecosystems and forest fires

Climate change and the associated changing weather patterns occurring world-wide have a direct effect on biology, population ecology, and the population of eruptive insects, such as the mountain pine beetle (MPB). This is because temperature is a factor which determines insect development and population success.^[144] Mountain Pine Beetle are a species native to Western North America.^[145] Prior to climatic and temperature changes, the mountain pine beetle predominately lived and attacked lodgepole and ponderosa pine trees at lower elevations, as the higher elevation Rocky Mountains and Cascades were too cold for their survival.^[146] Under normal seasonal freezing weather conditions in the lower elevations, the forest ecosystems that pine beetles inhabit are kept in a balance by factors such as tree defense mechanisms, beetle defense mechanisms, and freezing temperatures. It is a simple relationship between a host (the forest), an agent (the beetle) and the environment (the weather & temperature).^[145] However, as climate change causes mountain areas to become warmer and drier, pine beetles have more power to infest and destroy the forest ecosystems, such as the whitebark pine forests of the Rockies.^[145] This is a forest so important to forest ecosystems that it is called the “rooftop of the rockies”. Climate change has led to a threatening pine beetle pandemic, causing them to spread far beyond their native habitat. This leads to ecosystem changes, forest fires, floods and hazards to human health.^[145]

The whitebark pine ecosystem in these high elevations plays many essential roles, providing support to plant and animal life.^[145] They provide food for grizzly bears and squirrels, as well as shelter and breeding grounds for elk and deer; protects watersheds by sending water to parched foothills and plains; serves as a reservoir by dispensing supplies of water from melted snowpacks that are trapped beneath the shaded areas; and creates new soil which allows for growth of other trees and plant species.^[145] Without these pines, animals do not have adequate food, water, or shelter, and the reproductive life cycle, as well as quality of life, is affected as a consequence.^[145] Normally, the pine beetle cannot survive in these frigid temperatures and high elevation of the Rocky Mountains.^[145] However, warmer temperatures means that the pine beetle can now survive and attack these forests, as it no longer is cold enough to freeze and kill the beetle at such elevations.^[145] Increased temperatures also allow the pine beetle to increase their life cycle by 100%: it only takes a single year instead of two for the pine beetle to develop. As the Rockies have not adapted to deal with pine beetle infestations, they lack the defenses to fight the beetles.^[145] Warmer weather patterns, drought, and beetle defense mechanisms together dries out sap in pine trees, which is the main mechanism of defense that trees have against the beetle, as it drowns the beetles and their eggs.^[145] This makes it easier for the beetle to infest and release chemicals into the tree, luring other beetles in an attempt to overcome the weakened defense system of the pine tree. As a consequence, the host (forest) becomes more vulnerable to the disease-causing agent (the beetle).^[145]

The whitebark forests of the Rockies are not the only forests that have been affected by the mountain pine beetle. Due to temperature changes and wind patterns, the pine beetle has now spread through the Continental Divide of the Rockies and has invaded the fragile boreal forests of Alberta, known as the “lungs of the Earth”.^[145] These forests are imperative for producing oxygen through photosynthesis and removing carbon in the atmosphere. But as the forests become infested and die, carbon dioxide is released into the environment, and contributes even more to a warming climate. Ecosystems and humans rely on the supply of oxygen in the environment, and threats to this boreal forest results in severe consequences to our planet and human health.^[145] In a forest ravaged by pine beetle, the dead logs and kindle which can easily be ignited by lightning. Forest fires present dangers to the environment, human health and the economy.^[145] They are detrimental to air quality and vegetation, releasing toxic and carcinogenic compounds as they burn.^[145] Due to human induced deforestation and climate change, along with the pine beetle pandemic, the strength of forest ecosystems decrease. The infestations and resulting diseases can indirectly, but seriously, effect human health. As droughts and temperature increases continue, so does the frequency of devastating forest fires, insect infestations, forest diebacks, acid rain, habitat loss, animal endangerment and threats to safe drinking water.^[145]

Smoke from wildfires

Climate change increases wildfire potential and activity.^[147] Climate change leads to a warmer ground temperature and its effects include: earlier snowmelt dates, drier than expected vegetation, increased number of potential fire days, increased occurrence of summer droughts, and a prolonged dry season.^[148]

Warming spring and summer temperatures increase flammability of materials that make up the forest floors.^[148] Warmer temperatures cause dehydration of these materials, which prevents rain from soaking up and dampening fires. Furthermore, pollution from wildfires can exacerbate climate change by releasing atmospheric aerosols, which modify cloud and precipitation patterns .

Wood smoke from wildfires produces particulate matter that has damaging effects to human health.^[149] The primary pollutants in wood smoke are carbon monoxide and nitric oxide.^[148] Through the destruction of forests and human-designed infrastructure, wildfire smoke releases other toxic and carcinogenic compounds, such as formaldehyde and hydrocarbons.^[150] These pollutants damage human health by evading the mucociliary clearance system and depositing in the upper respiratory tract, where they exert toxic effects.^[148] Research by Naeher and colleagues.^[149] found that physician visits for respiratory diseases increased by 45-80% during wildfire activity in urban British Columbia.

The health effects of wildfire smoke exposure include: exacerbations and development of respiratory illness such as asthma and chronic obstructive pulmonary disorder; increased risk of lung cancer, mesothelioma and tuberculosis; increased airway hyper-responsiveness; changes in levels of inflammatory mediators and coafulation factors; and respiratory tract infection .^[149] It may also have intrauterine effects on fetal development, resulting in low birth weight newborns.^[151] Because wildfire smoke travels and is often not isolated to a single geographic region, the health effects are widespread among populations.^[150] The suppression of wild fires also takes up a large amount of a country’s gross domestic product which directly affects the country’s economy.^[152] In the United States, it was reported that approximately $6 million was spent between 2004-2008 to suppress wildfires in the country.^[152]

Displacement/migration

Climate change causes displacement of people in several ways, the most obvious—and dramatic—being through the increased number and severity of weather-related disasters which destroy homes and habitats causing people to seek shelter or livelihoods elsewhere. Slow onset phenomena, including effects of climate change such as desertification and rising sea levels gradually erode livelihoods and force communities to abandon traditional homelands for more accommodating environments. This is currently happening in areas of Africa’s Sahel, the semi-arid belt that spans the continent just below its northern deserts. Deteriorating environments triggered by climate change can also lead to increased conflict over resources which in turn can displace people.^[153]

Extreme environmental events are increasingly recognized as a key driver of migration across the world. According to the Internal Displacement Monitoring Centre, more than 42 million people were displaced in Asia and the Pacific during 2010 and 2011, more than twice the population of Sri Lanka. This figure includes those displaced by storms, floods, and heat and cold waves. Still others were displaced drought and sea-level rise. Most of those compelled to leave their homes eventually returned when conditions improved, but an undetermined number became migrants, usually within their country, but also across national borders.^[154]

Asia and the Pacific is the global area most prone to natural disasters, both in terms of the absolute number of disasters and of populations affected. It is highly exposed to climate impacts, and is home to highly vulnerable population groups, who are disproportionately poor and marginalized. A recent Asian Development Bank report highlights “environmental hot spots” that are particular risk of flooding, cyclones, typhoons, and water stress.^[155]

To reduce migration compelled by worsening environmental conditions, and to strengthen resilience of at-risk communities, governments should adopt polices and commit financing to social protection, livelihoods development, basic urban infrastructure development, and disaster risk management. Though every effort should be made to ensure that people can stay where they live, it is also important to recognize that migration can also be a way for people to cope with environmental changes. If properly managed, and efforts made to protect the rights of migrants, migration can provide substantial benefits to both origin and destination areas, as well as to the migrants themselves. However, migrants – particularly low-skilled ones – are among the most vulnerable people in society and are often denied basic protections and access to services.^[155]

The links between the gradual environmental degradation of climate change and displacement are complex: as the decision to migrate is taken at the household level, it is difficult to measure the respective influence of climate change in these decisions with regard to other influencing factors, such as poverty, population growth or employment options.^[154] This situates the debate on environmental migration in a highly contested field: the use of the term 'environmental refugee', although commonly used in some contexts, is disrecommended by agencies such as the UNHCR who argue that the term 'refugee' has a strict legal definition which does not apply to environmental migrants.^[156] Neither the UN Framework Convention on Climate Change nor the Kyoto Protocol, an international agreement on climate change, includes any provisions concerning specific assistance or protection for those who will be directly affected by climate change.^[157]

See also

• Arctic methane release
• Effects of global warming
• Environmental Security and Peace
• Food security
• Long-term effects of global warming

References

External links

• Human Rights and climate change
• Intergovernmental Panel on Climate Change