Category: Health

Extreme heat in South Asia threatens millions of people

Extreme heat in South Asia threatens millions of people

By Gracie Pearsall

Pervasive climate-based heat affects all corners of the globe, even places that normally have hot, tropical climates. One place already experiencing some of the devastating effects of rising temperatures and heatwaves is South Asia. The region’s rapid urbanisation and poverty rates are among the most important factors when it comes to heat, and general climate, vulnerability. However, solutions like green and reflective roofs are emerging as heat adaptation measures.

Heat-related illness

South Asia is already a hot and humid region and it’s getting even hotter. The average temperature there is rapidly approaching 37° C, which is the operating temperature of the human body. When the apparent temperature approaches body temperature, the body’s capacity to function properly is greatly diminished. This type of heat-stress leads to heat-related illnesses such as heat-stroke, exhaustion, and dehydration.

In the Ganga Plains, there are regularly days where the temperature exceeds 37° C, which puts residents highly at risk for heat-related illness. Climate projections for this area suggest that by 2050 there will be 152 out of 200 days between April and October where temperatures exceed 37° C. Because of these extended periods of extreme heat, the residents of the Ganga Plains will experience even more heat-related illnesses.

Heat stress in rural areas

Millions of families in rural South Asia depend on livelihoods that expose them to extreme heat, such as farming. These families are usually low-income and do not have access to cooling systems that offer relief from the heat. Extended periods of manual labor in the heat make farmers and other manual laborers distinctly vulnerable to heat-related illnesses.

The heat also decreases agricultural productivity because the heat harms crops and livestock. For example, Terai, Nepal’s most productive agricultural region, is in jeopardy because projections show temperatures increasing by 2.8° C by 2060. This heat will likely reduce the arability of the land, limit water for irrigation, and pose a deadly threat to the farmers’ health.

Urban heat island effect

The Urban Heat Island effect caused by the rapid urbanization and population growth in South Asia is adding heat to the already warming climate. Urbanization modifies land cover and replaces natural heat sinks, such as trees, lakes, and wetlands, with pavement and buildings that absorb a lot more heat. Because of this phenomenon urban areas in South Asia are significantly warmer than their rural counterparts.

This phenomenon is even present in typically cooler hill cities such as Kathmandu. As of 2016, a study estimated that the Kathmandu’s average heat index per month is 20 percent higher than that of each corresponding month 30 years ago. Currently, Kathmandu’s metropolitan center is 1° C warmer than the outskirts. The increased heat makes city residents vulnerable to heat-related illnesses and exposes them to respiratory harm from the high concentrations of air pollutants that usually accompany urban heat islands.

Beating the heat

To cope with the heat, South Asian communities use a variety of cooling techniques. The most popular technique is to install reflective material or vegetation on roofs to minimize heat absorption. Reflective roofs are especially critical in combating heat in urban areas where roofs make up the majority of surfaces hit by solar radiation. In Pakistan, a National Center for Atmospheric Research and Institute for Social and Environmental Transition study found that at night houses with reflective roofs were 3° C cooler inside than outside. Furthermore, in Bangladesh reflective roofs have been shown to reduce the indoor heat index by 77 percent during peak heat times.

South Asia’s overall ability to limit heat stress depends on reliable delivery of basic services such as clean water, sanitation, healthcare, and energy to run cooling technology. These services will help communities stay cool and treat heat-related illnesses. However, to provide these services, there must be significant investment in infrastructure. South Asian governments must also implement policy measures to preserve natural heat sinks, such as parks and lakes, and limit human activities that contribute to climate change, in order to brace for rising temperatures.


Cover photo by Barun Khanal/Wikimedia (CC BY-SA 3.0): Aerial view of field in the Madhesh region of Nepal.
Iranian city experiences scorching heat close to 54 degrees Celcius

Iranian city experiences scorching heat close to 54 degrees Celcius

By Elisa Jiménez Alonso

In late June the Iranian city of Ahwaz, home to over 1 million people, registered scorching 53.7°C. This falls short of the hottest temperatures to ever be reliably measured by just 0.3°C. Météo France meteorologist Etienne Kapikian reported the temperature on 29 June. However, hours later, the website Weather Underground reported 54°C air temperature, tying it with two heat records measured in Kuwait in 2016 and Death Valley in 2013, if verified.

Air temperature vs Heat Index

Verified or not, we can probably all agree that temperatures above 40 and, even worse, 50 degrees are unbearable. However, air temperature, which is what thermometers usually measure, is only one part of the equation. In order to calculate the “felt air temperature” or Heat Index, relative humidity needs to be considered as well. Taking into account the 17% relative humidity measured in Ahwaz on 29 June, the “felt air temperature” that day was a staggering 61°C. To put that into perspective: Egg whites cook at 65°C.

The heat index was developed because relative humidity affects how the body cools itself. The human body cools down by sweating. As the sweat evaporates, heat is removed from our bodies. If there is high relative humidity, however, the sweat cannot evaporate anymore leading to a sense of overheating. The degree to which this affects people often depends on their physical disposition like e.g. being pregnant or having metabolic differences. Thus, the index contains many assumptions that might not apply to everyone. Most importantly, however, the Heat Index is based on temperatures in the shade, meaning that actual conditions, especially when being exposed to direct sunlight can be even worse than the index states. One can only guess what this meant for the people of Ahwaz in late June this year.

Temperature records in line with scientists’ expectations

The high temperatures of Ahwaz come just a month after several places in the Middle East experienced their highest temperatures ever recorded. A bit further, the Pakistani town of Turbat recorded 53.5°C on 28 May, a world record for the month.

All of these readings are consistent with scientists’ expectations of extreme temperatures in a warming world. A 2016 report by the National Academy of Sciences stated that hotter and more frequent heatwaves are among the weather events that are most easily connected to human-made climate change. A study published in late 2015 found that future heatwaves in the Gulf might push the region’s temperatures beyond anything humans can adapt to or endure. They likened the future climate of certain Middle Eastern regions to that current one of Northern Afar, Africa, which has no human settlements and an average annual temperature of 34.4°C.

Tackling extreme heat

Apart from reducing carbon emissions in order to avoid even worse climate impacts, it is hard to imagine adaptation strategies that would effectively protect people in such extreme heatwaves. While wealthier states might be able to afford protecting people indoors with air conditioning, countries like Yemen, which relies heavily on aid from multilateral agencies, would surely suffer. Especially children and the elderly would disproportionately be affected by premature deaths due to heat. Since extremely dangerous temperatures are already being observed, it will be of utmost importance for affected countries and the international community to work on solutions that will protect at risk populations.


Cover photo from Pixabay (public domain).
Early weather forecasts are key to saving lives during droughts

Early weather forecasts are key to saving lives during droughts

By Umberto Bacchi

With droughts set to become more frequent due to global warming, delivering timely, long-term weather forecasts to farmers in the developing world will be key to limiting damage and saving lives, the head of the U.N. food agency said on Monday.

Droughts have killed more than 11 million people worldwide since 1900 and now affect double the land area than in 1970, according to the U.N. Food and Agriculture Organization (FAO). Developing countries are the most exposed, with their agricultural sectors shouldering 80 percent of all damage caused by drought, FAO says.

Better access to reliable weather data and early warning systems could help farmers in rural areas get ready to endure long spells of no rain, said FAO director-general Jose Graziano da Silva. “Most of the times poor rural communities in developing countries don’t even know that a drought is about to strike,” he told a conference at the FAO headquarters in Rome. Measures such as planting resistant crops and building water reservoirs can greatly reduce the impact of droughts, but international responses too often focus on emergency relief, said Graziano da Silva. “People die because they are not prepared to face the impacts of the drought – because their livelihoods are not resilient enough,” he said.

In Rome, FAO and the World Meteorological Organization (WMO) signed an accord to increase cooperation in the face of climate change, improving agro-meteorological services to help small farmers prepare for droughts. WMO secretary general Petteri Taalas said weather forecast accuracy had greatly increased in recent years thanks developments in satellite, computing and scientific research. “Weather forecasts are not anymore a joke, they are something you can very much rely on,” he told the conference.

Know-how related to long-term forecasts and prediction of major climate events like El Niño had to be shared between rich and poor countries, he added. The last El Niño, a warming of ocean surface temperatures in the eastern and central Pacific that typically occurs every few years, subsided in 2016 and was linked to crop damage, fires, and flash floods.


Reporting by Umberto Bacchi @UmbertoBacchi, Editing by Ros Russell. Article originally posted on Zilient.org. Credit: Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women’s rights, trafficking, property rights, climate change and resilience. Visit http://news.trust.org
Cover photo by Faxial/Pixabay (Public Domain)
Deadly heat stress could threaten hundreds of millions even if climate targets are reached

Deadly heat stress could threaten hundreds of millions even if climate targets are reached

By Tom MatthewsLiverpool John Moores University

Deadly heat stress is projected to affect hundreds of millions more people each year under relatively little additional climate warming. The Paris Agreement commits the international community to limit global warming to no more than 2℃ above pre-industrial (late 19th century) air temperatures, with an aspirational target of 1.5℃. In our latest research, which looked at the impact of global temperature rises on megacities, we found that even if 1.5℃ is achieved, large increases in the frequency of deadly heat are expected.

By 2050 about 350m more people living in megacities could be exposed to deadly heat each year.

Humans become “heat stressed” when the body absorbs more heat than is tolerable. If core body temperature rises just a few degrees above 37℃, deadly heatstroke can result. By using its cooling system – sweating – the human body can maintain a safe temperature even if air temperatures rise above 37℃. This mechanism works better in a drier atmosphere (which is why steam rooms feel hotter than saunas – even at the same air temperature). The heat index is a measure that combines this humidity effect with air temperature to provide a “feels like” temperature. A heat index in excess of about 40.6℃ is considered dangerous to human health.

As global air temperatures rise, observations and experiments with climate models suggest that atmospheric moisture content also climbs. This means that the heat index (and how hot it feels) rises faster than air temperature. Also, because the amount of moisture the atmosphere can hold increases more rapidly at higher temperatures, the heat index rises faster too (a non-linear response).

Strong incentive to limit global warming

This non-linear response carries over to the definition of “global heat stress burden” used in our research, which we define as the average number of days per year over land areas with a daily heat index above 40.6℃. Using a large number of climate model simulations, we found that this quantity increases faster and faster as global average air temperatures rise. This sharp rise in global heat stress burden has important consequences.

First, any increase in global heat stress from climate warming to date will be smaller than that caused by the same additional warming in the future. (We have seen a 0.8℃ rise in global temperature; another 0.8℃ of warming could be expected to lead to a greater increase in heat stress than caused by the first 0.8℃.)

Second, there may be progressively heavier global impacts if the Paris targets are breached. Our analysis suggests that for 1.5℃ warming, the global heat stress burden will be almost six times greater than experienced during 1979-2005. But heat stress is 12 times greater if warming reaches 2℃. With 4℃ warming – which could happen if mitigation efforts fail – our analysis suggests that the global heat stress burden could be more than 75 times larger.

Such large increases in heat stress may be hard to imagine, so we used recent heat waves to help communicate the impacts that may lie ahead.

For example, in 2015, Karachi and Kolkata in India experienced lethal temperatures. Our analysis suggests that in a 2℃-warmer world, both cities could experience these deadly conditions at least once a year. If global warming reaches 4℃, the record heat of 2015 would be commonplace – more than 40 days a year. Other regions would not be immune. With only 1.5℃ of warming, twice as many global megacities (cities with a population greater than 10m, including Lagos, Nigeria, and Shanghai, China) could start to regularly experience heat stress. At 2℃, Tokyo (the world’s most populous city), may be affected. New York City joins the list at 4℃.

If the global population grows as anticipated this century, it could drive up global heat stress even more. The situation in Lagos illustrates this well. If global warming reaches 1.5℃ by the end of the century (at which time the population of Lagos may have increased elevenfold and dangerous heat may be 100 times more common) the heat stress burden could be more than a thousand times greater than the recent past.

Across all megacity regions, if the 1.5℃ limit is breached by the 2050s, as many as 350m people globally could be regularly exposed to dangerous heat stress. This is more than a fourfold increase compared with 1979-2005.

The ConversationHeat stress sensitivity to global temperature rise and the potential human impacts – even at 1.5℃ above pre-industrial levels – provide a strong incentive for limiting global warming. Warming associated with the Paris targets may sound modest enough for the urgency of the situation to be lost. Our analysis shows that even if ambitious mitigation targets are met, the need to adapt to extreme heat will remain. The high concentration of people and heat in urban environments make cities an important focus for these adaptation efforts.

 


Tom Matthews, Lecturer in Physical Geography, Liverpool John Moores University. This article was originally published on The Conversation. Read the original article.
Cover photo by Jorge Royan (CC BY-SA 3.0 )
Doctors sound the alarm: climate change poses immediate health risks

Doctors sound the alarm: climate change poses immediate health risks

By Gracie Pearsall

While most Americans recognise that climate change is a real threat, the pervasive attitude is that it is a distant problem. Although, people might be concerned for the future of the ice caps and coastal cities, many have not considered the possibility that climate change could affect their lives and health right now. The Medical Society Consortium on Climate and Health (MSCCH) seeks to remedy this and alert Americans that climate change is already harming their health.

Climate related health impacts

In March of 2017, the MSCCH released a report that outlines the ways climate change threatens our health. Through scientific studies, facts, and anecdotes, the physicians expose the health consequences of climate change. They paint a grim picture of a society plagued by climate-related illnesses explaining how the increased frequency of extreme weather events will impact our health. Heat waves will cause more incidents of heat-related illness and stress, which are already the leading cause of climate-related deaths. Severe storms and flooding will cause displacement, injury, death, and even contaminate drinking water and crops with debris and pollutants.

The report also describes how a warmer and wetter climate allows disease vector species such as ticks and mosquitoes to thrive and expand their geographic range, which alters the pattern of infectious diseases. Physicians are already seeing an increase in cases of Lyme Disease and West Nile virus, and fear that malaria might reemerge in the United States. As these carriers spread throughout the United States, they will bring familiar diseases to new places, and allow for the rise of new ones.

The physicians present poor air quality as the most widespread and pressing threat to our health. The emission of greenhouse gasses and particulate matter, combined with frequent wildfires, has significantly reduced air quality. People’s hearts and lungs are most at risk, but poor air quality has also been linked to cancer in other parts of the body. Approximately seven million people worldwide die prematurely every year due to health issues linked to air pollution.

Furthermore, a growing body of research suggests that the physical, social, and economic stresses that climate change creates increase the risk of mental health issues. In the wake of extreme weather events, most survivors report stress, depression, and anxiety. In one case, after record flooding in Louisiana in 2016, teachers reported that some children became so anxious when it rained, that the children needed counseling.

Image: The map shows key impacts of climate change on health in the USA by region. Credit: The Medical Society Consortium on Climate and Health.

Resilience in the health care sector

In the face of these alarming facts, the MSCCH has embraced a central ideal of public health: prevention. These physicians side with climate scientists and conclude that only through swift action can we prevent further harm and protect the health of all Americans. Their proposed means of prevention is to “accelerate the inevitable transition to clean, renewable energy”. This transition would have immediate public health benefits. It would move away from greenhouse gas combustion, and reduce exposure to harmful pollutants, slow warming, and clean up our air and water. Additionally, clean and renewable energy encourage active transportation, such as walking and biking, which help to lower rates of heart disease, respiratory illness, and diabetes.

To achieve this transition and implement preventative and protective measures, the physicians prescribe certain actions to various demographics. First, they recommend doctors treat patients who are affected by climate-related health effects. They also implore doctors to educate their patients and the public on how climate change can affect their health, and what actions we can take to prevent further harm. Next, they advise public health professionals to educate the public on the threat climate change poses, and develop climate risk monitoring and alert systems to keep the public informed in the case of an extreme weather event. Finally, the MSCCH urges business leaders and policymakers to assess this new information and adapt accordingly so that we can build resilience against harmful effects of climate change. The MSCCH’s prioritization of prevention and mitigation reveals that adaptation and resilience carry diverse sets of benefits.

 


Cover photo by The Medical Society Consortium on Climate and Health
Arctic ice melt uncovering radioactive waste, sewage, and anthrax

Arctic ice melt uncovering radioactive waste, sewage, and anthrax

By Charlotte Strawson

Melting in the Arctic region is uncovering unwelcome waste, pollutants and diseases that were once thought to be ‘preserved for eternity’. Melting of glaciers, tundra and sea ice is taking place at a rate that is uncovering radiological waste, sewage and even Anthrax.

A military camp built beneath the surface of Greenland ice sheet during the Cold War was left abandoned in 1967, leaving behind a heap of waste which included 200,000 litres of diesel fuel, 24 million litres of biological waste in the form of sewage, and radiological waste. The waste was left in the belief the snowfall would continue falling and the waste would be “preserved for eternity”.

However, due to climate change, Greenland has lost 1 trillion tons of ice over the period of four years between 2011 and 2014. There is worry that the melting and the unearthing of this waste has potential to expose great amounts of hazardous materials. Arctic regions experience warming from climate change at almost twice the global average.

In the northern arctic region of Russia in 2016 there was an outbreak of Anthrax, it caused the death of a 12-year-old boy and hospitalised 90 people. This episode is reported to be a result of climate change as the 10°C warmer than average temperature melted the permafrost of a previous burial site for animals that died of anthrax 70 years ago.

If climate change predictions are correct and the melting of permafrost continues, we could see more cases of disease outbreaks. Infections from the 18th and 19th century could re-emerge, especially near the unknown cemeteries and burial sites where victims were buried.

In Russia, the thawing of permafrost and flooding has led to greater erosion of river banks where the dead were once buried. Researchers are worried that the thawing human and animal remains may lead to the re-emergence of diseases such as Spanish flu virus, which have been found in bodies buried in mass graves in Alaska’s tundra, as well as the smallpox virus and bubonic plague buried in Siberia.

Though some researchers argue that the prospect of a killer infection to appear from melting permafrost is unlikely, it does raise troubling questions about what is locked in the vast frozen landscapes of the north.


Cover photo by NASA Earth Observatory (Public Domain)
Air pollution and climate change: a toxic relationship

Air pollution and climate change: a toxic relationship

By Caroline Fouvet

Each year, 600,000 children under five years old die because of air pollution. Central heating boilers, motor vehicles and industrial facilities are all significant contributors to dirty air. The problem is costing money and lives, especially in built up areas, and it may be further compounded by climate change.

Air pollution is often understood as a visible phenomenon – with dense smog engulfing urban centres. However, for the most part air pollutants do not form smog, and the tiny, makes them invisible. Vulnerable citizens, such as older people and children are extremely sensitive to air pollution and are often among its first victims.

The impact of air pollution on health places a substantial economic burden on society. In developing countries, for instance, air pollution results in premature deaths in the young working age population and in Sub-Saharan Africa, annual labour income losses induced by air pollution amount to 0.61% of GDP. In developed countries, the cost of sick days and emergency care caused by air pollution is considerable.

Compounded by climate change

Unless action is taken to reduce air pollution, the health impacts are likely to increase in severity, as the climate warms. Warmer temperatures can lead to an intensification of particulate concentrations at ground level, especially in cities. Heat and sunlight react with chemical particles such as diesel soot and gases such as nitrogen dioxide (NO2), ozone (O3) and sulphur dioxide (SO2) in the air. This leads to the formation of ground-level ozone gas, both a harmful air pollutant and a component of smog.  The expected increased number of warmer and stagnant days will facilitate the phenomenon and worsen its impact on people’s health.

As ground-level ozone damages lungs and inflames airways, asthma and other respiratory diseases will likely increase. The resulting impact on people’s health is likely to be severely detrimental. In the US, it is projected that tens of thousands of additional ozone-related illnesses and premature deaths per year could occur by the 2030s. The US Environmental Protection Agency assessed that such impacts on air quality could reach US$ 13.6 billion.

Low-level ozone, methane, chlorofluorocarbons and sulphur dioxide emissions are also greenhouse gases, contributing to climate change and creating a noxious self-reinforcing cycle. Breaking this cycle will require concerted policy efforts to prevent particulate pollution, especially in built up areas. The resulting health benefits will undoubtedly save lives.


Cover photo by David Leo Veksler (CC BY-SA 2.0)
A climate change healthcheck: Integrating adaptation into health strategies and plans

A climate change healthcheck: Integrating adaptation into health strategies and plans

By Caroline Fouvet

A changing climate not only impacts weather events and infrastructure, but also presents a major public health challenge. Whether direct or indirect, cimate change impacts can have disruptive effects for human health and wellbeing, and as future climatic trends suggest both higher average temperatures and more regular extreme events, the impacts of climate change on human health cannot be ignored.

Direct health risks include weather-related morbidity, increased respiratory illness and infectious diseases, climate change has broader, indirect repercussions for health, including food insecurity and mental health. Adaptation measures must, therefore, encompass a health component; a point gaining recognition as more and more governments include it in their national strategies.

recent study reviewed 10 OECD countries’ policies in that respect and highlights their varied approaches to addressing the issue. By highlighting current gaps and suggesting possible strategies, the study provides useful insights into health adaptation to climate change.

To better evaluate strategies in this area it is important to identify adaptation means for the health sector. This amounts to taking preventive measures that reduce risk exposure, prevent the onset of illnesses, reduce morbidity, and minimise climate impacts. Although adaptation is often referred to as a local strategy, national governments have a role to play through integrating health adaptation into high-level policy frameworks. Their resources and guidance can strengthen and harmonise adaptation planning and generate ripple effects at the subnational level.

The research – focusing on the current health adaptation strategies of Australia, Belgium, Canada, France, Ireland, Luxembourg, New Zealand, Switzerland, the United Kingdom and the United States – examined three main dimensions of national-level health adaptation: cross-sectoral collaboration, vertical coordination, and national health adaptation planning.  These categories are, however, necessarily open to interpretation: vertical coordination can,for instance, be put into place differently across countries, such as through working groups, networks, partnerships, or consultation.

The study presents four main results:

  • National strategies remain broad, with 50% of surveyed countries addressing general health risks, infectious diseases, as well as heat-related risks.  The ‘general’ character of these stategies suggests that national initiatives are intended to set the framework for more specific local actions. Whilst population-level health programmes, such as protecting people from heatwaves, generally emanate from national governments, interventions that address locally manifest issues, such as flood mitigation, are often conducted at a regional level.
  • Almost two thirds (62%) of reviewed initiatives are ‘groundwork actions’, compared to 38% of adaptation actions. Among the latter, a combination of five adaptation types are being implemented, typically in the following order: capacity building, information, management, planning and policy, information, and practice and behaviour.
  • Intersectoral adaptation planning is a common feature across the surveyed countries. Most of the initiatives are designed and implemented by national public health agencies in partnership with other bodies, with some actions co-implemented with organisations outside of health sector.  This is the case in France, where four health agencies and the Research Institute for Exploitation of the Sea monitor vectors and host reservoirs.
  • Whilst health is an integrated part of most countries’ national adaptation frameworks (with the exception of Ireland), they exhibit varying levels of detail.  Whereas Australia’s adaptation plan provides general adaptation objectives, Switzerland’s plan further outlines responsible agencies and financing for each intervention.

The study’s results present a picture of uneven interpretations of – and approaches to – health adaptation across the 10 countries studied.  Their disparate state structures and degrees of centralisation might account for some of these differences, however, rendering it problematic to  identify any single benchmark  approach.

Drawing-out the similarities and differences between OECD countries in health adaptation planning shows that the issue is widely acknowledged by governments, even if they address it in a plurality of ways. Identifying best practices – referenced to climatic contexts and trends, governmental strutures, and risk and vulnerabilities – and bridging gaps are essential for devising coherent and effective health adaptation frameworks.

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Read the full study by clicking here.


Cover photo by Jamiesrabbits/Flickr (CC by 2.0)
Global warming to expose more people to Zika-spreading mosquito

Global warming to expose more people to Zika-spreading mosquito

As Americans ready themselves for the arrival of mosquitoes this summer, many may be wondering whether they are at risk for tropical diseases like Zika and whether climate change will raise the risks of infection.

My colleagues and I recently completed a study examining how projected changes in climate and human population may increase global exposure to the mosquito that spreads these viruses: Aedes aegypti.

We found that both climate change and human population change will play a part in driving future human exposure to Aedes aegypti globally. In the United States, specifically, warming temperatures from climate change mean that this disease-spreading mosquito will be increasingly abundant in the southern and eastern U.S.

Human-dependent mosquitoes

Aedes aegypti transmits the viruses that cause Zika, dengue, chikungunya and yellow fever. An ongoing Zika pandemic in Latin America and the Caribbean has been linked to birth defects in newborns and neurological disorders in adults, initiating a massive public health response and garnering extensive media coverage. The other three viruses are important threats as well: dengue viruses infect about 400 million people each year, chikungunya has been linked to chronic health problems such as arthritis and a new yellow fever outbreak in Angola has stoked fears of imminent vaccine shortages.

Aedes aegypti is a particularly effective virus spreader because of its dependence on humans. While many mosquitoes prefer natural areas for breeding, such as wetlands, Aedes aegypti exploits artificial water-filled containers such as tires, buckets, barrels and stray trash for its aquatic life stages (egg, larvae and pupae). Such containers are often found in backyards, meaning that when adult mosquitoes finally emerge, they are found in and near homes. And, while other mosquito species may be less picky about whom they bite, Aedes aegypti has a preference for humans.

Climatic factors affect Aedes aegypti in a number of ways. Warmer temperatures (up to a certain point) enable faster development during the aquatic life stages, and greater survival rates at all life stages. Precipitation, which can be affected by climate change, provides water needed to complete aquatic life stages.

Aedes aegypti is primarily found in warm, wet tropical and subtropical urban areas. However, it also can thrive in arid desert environments, particularly in areas where humans may store water in barrels or cisterns during dry spells. The range of the mosquito expands and contracts seasonally in the United States, which is at the temperature-limited margin of its survival.

Modeling the future

Our study attempted to go beyond using climate change projections to explore how global warming may affect the future range of Aedes aegyptiThis has been done before.

Instead, we sought to estimate how many humans may be exposed to the mosquito in the future, based on a new set of population projections as well as factors related to climate change. This allowed us to forecast how many people will be exposed to Aedes aegypti in the future and determine the relative roles of climate change and population growth.

We first mapped the historic range of Aedes aegypti based on the different climate patterns in which the mosquito can survive, ranging from seasonal to a year-round presence. We used previously established relationships between monthly temperature and precipitation and data on the actual presence and abundance of the mosquito.

 
Map shows the range of the Aedes aegypti mosquito for present-day (1950-2000) and future (2061-2080; RCP8.5) conditions. Larger cities have higher potential for travel-related virus introduction and local virus transmission. Andrew Monaghan, Author provided

Next, we produced future maps of the Aedes aegypti global occurrence patterns for 2061-2080 using projections for air temperature and precipitation patterns.

These models were derived from two plausible future scenarios for air pollution and greenhouse gas pathways in the 21st century: one in which greenhouse gases are mitigated so that global average warming doesn’t exceed 2 degrees Celsius average temperature increase over preindustrial levels and another in which greenhouse gas emissions continue to grow unchecked.

Finally, we examined population growth for two different possible future socioeconomic conditions. The “low vulnerability” scenario assumes improved living standards and falling birthrates in poorer countries, and another “high vulnerability” scenario has continued low living standards and high birthrates in poorer countries.

Separating population from climate

From the historical results, we estimated that 63 percent of the global population is presently exposed to Aedes aegypti.

To isolate climate change from population trends, we modeled how the level of exposure would change if population remained at historical levels (an unrealistic assumption but useful for our projections). In this scenario, we found that the percentage of humans exposed to Aedes aegypti would grow to 68-70 percent of the global population by 2061-2080, depending on how much emissions rose. The projected changes were primarily driven by warming rather than changing rainfall patterns.

Including population growth, the percentage of the exposed global population would grow to 71-74 percent under the lower vulnerability socioeconomic pathway. Under the higher vulnerability pathway of continued low living standards and high birthrates, we found 77-80 percent of global population would be exposed to Aedes aegypti.

Not only would more humans be exposed under the higher-vulnerability pathway, but we found much of the population growth would occur in urban slums in developing countries in the tropics and subtropics; these areas are ideal breeding grounds for Aedes aegypti and have high virus transmission potential.

Importantly, the differences among the projections are driven mostly by uncertainty in how and where human populations may change, rather than uncertainty due to different climate change scenarios. This result underscores how important it will be for the research community to continue improving socioeconomic projections, such as population growth.

Public health preparation

As always, the devil is in the details. For example, our analysis found wealthier regions that are the margins of the present-day range for Aedes aegypti – Australia, North America and Europe – would benefit the most from reducing greenhouse gases. Minimizing warming means changes to the mosquitoes’ range will also be minimized at these cool margins.

It is noteworthy that there are numerous limitations to the study. Specifically, there is uncertainty related to future emissions, future geopolitics, mosquito control practices, human behavior, transportation networks and other competing mosquito species.

Still, the implications for public health policymakers are that, all else equal, climate change and population growth will likely increase the percentage of humans exposed to this important virus vector mosquito, including parts of the U.S. Cutting greenhouse gas emissions can make a dent. Improving public health preparedness and response in the near term will build the capacity to deal with greater exposure in the future.


The ConversationAndrew Monaghan, Scientist Research Applications Laboratory in Climate Science & Applications Program, University Corporation for Atmospheric Research
This article was originally published on The Conversation. Read the original article.
Cover photo by sanofi-pasteur/Flickr (CC BY-NC-ND 2.0)
Climate change raises deadly health risks

Climate change raises deadly health risks

By Alex Kirby

Reduced production of fruit and vegetables as climate change impacts on agriculture could substantially increase dietary and weight-related factors that contribute to so many deaths worldwide.

More than half a million people worldwide are likely to die annually by 2050 because of the impact on agriculture of changing climate, according to an Oxford University study on the future of food.

The authors say the effects are likely to be felt most acutely in south and east Asia, but that the US will also be severely affected.

They identify reduced production and consumption of fruit and vegetables as a key concern, and say the effects of climate change on agriculture could be one of its most important consequences.

The World Health Organisation recommends that adults should normally eat at least 400 grams of fruit and vegetables daily, which unlike processed foods are low in energy and do not promote obesity. Red and processed meat consumption has been linked to some forms of cancer.

While there has been extensive research on food security, there has been less on assessing the wider health impacts of future changes in agricultural production.

The study, published in the UK medical journal The Lancet, links a detailed agricultural modelling framework − the International Model for Policy Analysis of Agricultural Commodities and Trade(IMPACT) − to a comparative risk assessment of changes in consumption of fruit and vegetables and red meat, and bodyweight for deaths from coronary heart disease, stroke, cancer, and a range of other causes.

Weight and diets

The authors calculated the change in the number of deaths attributable to climate-related changes in weight and diets for the combination of four emissions pathways (one high, one low and two medium) and three socio-economic pathways (sustainable development, middle of the road, and more fragmented development).

The model projects that, by 2050, climate change will lead to per-person reductions of 3.2% in global food availability. Consumption of red meat is projected to fall by 0.7%, but that of fruit and vegetables by 4%. These changes will be associated with 529,000 annual climate-related deaths worldwide.

The model suggests 248,000 people will die each year in China by 2050 because of climate- linked decreases in food production. India faces a yearly loss of 160,000 people, with Vietnam, Bangladesh and the US next in line.

“The US comes in fifth because of its high population and its vulnerability to climate shocks”

Marco Springmann, lead author of the study and post-doctoral researcher in the department of population health at the Oxford Martin Programme on the Future of Food, says that nations’ mortality rates and the magnitude of climate and yield shocks had to be taken into account. “The US comes in fifth because of its high population and its vulnerability to climate shocks,” he explains.

Twice as many climate-related deaths were associated in the study with reductions in fruit and vegetable consumption as with climate-related increases in the prevalence of underweight. Most climate-related deaths were projected to occur in south and east Asia.

Adaptation strategy

The study says the health effects of climate change from changes in dietary and weight-related risk factors could be substantial and could exceed other climate-related health impacts. Strengthened public health programmes aimed at preventing and treating risk factors related to diet and weight could be a suitable climate change adaptation strategy.

Dr Diarmid Campbell-Lendrum, who leads the climate change and health team at the World Health Organisation, told thethirdpole.net: “The scale of the difference between the new estimates and those that we published a couple of years ago is quite surprising. The largest differences appear to be because of the impacts on consumption of fruits and vegetables.

“This is plausible as we know that low levels of consumption of these types of foods are now a major killer – but it is important to point out that there has been much less research on the effect of climate change on the production, and then the availability, of fruits and vegetables than there has been on staple crops.”


Alex Kirby is a former BBC journalist and environment correspondent. He now works with universities, charities and international agencies to improve their media skills, and with journalists in the developing world keen to specialise in environmental reporting.
This article was originally published on Climate News Network and is shared under a Creative Common license.
Cover photo by terimakasih0/Pixabay (Public Domain)