Climate
Change
Climate Impacts
Rising temperatures are a threat to humans, the economy, but also wild life over land and in the ocean. In this module, we look at some impacts brought by climate change on land, in the ocean, and on humans.
Learning outcomes
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Impacts that climate change has on land
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Impacts that climate change has on the ocean
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Impacts that climate change has on humans
3.1 Land-based impacts
Increasing global temperatures means warmer days, which could mean shorter winters, but also much warmer summers. The consequences of having warmer days becomes harmful when they are scorching and sustained, bringing prolonged droughts and more frequent wildfires. Plants and animals will suffer from those extreme events, while other will thrive due to their high resiliency. In this section, we will explore the repercussions of land-based impacts brought by climate change, and why is it important to build resiliency.
3.1.1 More heatwaves
Heatwaves are periods of very hot weather that extend over several days. They are becoming more common and more intense under global warming, so that over the past decade, the daily record temperatures have occurred twice as often as records lows in the US.
In other words, we are experiencing more hot days and fewer cold days. We expect by 2050 that the coldest and warmest days will increase by 3C (5F), with 20-30 more days over 32C (90F).
Heatwaves are among the leading causes of weather-related deaths in the US. They also significantly impact plants and wildlife on land, and in the ocean. During heatwaves, temperatures can reach levels that are inconsistent with life. When possible, animals migrate to cooler climates, like the Pacific salmons and Pacific cods did in 2015 as a powerful heatwave hit the coast off California to the Gulf of Alaska. It has become very difficult to most animals on land to migrate to cooler climates and maintain their thermal habitat because their natural migration corridors have been altered by cities, roads, nighttime lights. Other impacts include shift in timing and reproductive success of many birds (e.g. flycatcher), and higher mortality rates among animals both on land and in the ocean.
3.1.2 Severe Droughts
Climate change is expected to shift precipitations patterns, so regions of the world where it used to rain frequently might not see as much rain, thus likely providing the conditions for droughts, like in the Mediterranean and West Africa. In the US, the southwest and central plains are expected to experience drier and longer droughts, by the second half of the 21st century. Megadroughts (lasting more than 3 decades), have a 12% change of occurring. Droughts are dangerous as they have a negative impact on crop yields and production, and limit access to clean drinking water. They can also be fatal for plants and animals.
3.1.3 More Wildfires
More droughts and heatwaves inevitably set the conditions for increasing the risk of fire occurrence. Low soil and air moisture with intense heat and plants and trees as fuel makes it ideal for fires to spread rapidly.
We are already seeing an increase in wildfires in the past decade, with some of the largest being the California Camp Fire in 2018 (after being in its 6th consecutive year of drought), the deadliest fire in California history, and a series of wildfires in 2020 that scorched millions of acres of land. Australia has known its share of wildfires too in 2020 where nearly 3 billions animals were affected by what is known to be the worst wildfire season, with 46 million acres wiped out and billions of animals including mammals, reptiles, birds and frogs.
Wildfires not only wipe out trees and vegetation, they also contribute to air pollution by inputting CO2, CH4, and black carbon. As heatwaves and droughts are projected to increase in certain parts of the world, so are wildfires, and with it the toll on vegetation and wildlife, and possibly thousands more households losing their homes.
3.1.4 Build resilience
Health impact of heatwaves depends on the intensity and duration, the acclimatization and adaptation of the population, and the infrastructure and preparedness.
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Create heat preparedness plans, identify vulnerable populations, open cooling centers during extreme heat.
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Install cool and green roofs and cool pavement to reduce the urban heat island effect.
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Plant trees to provide share and evapotranspiration cools the air around trees.
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Pursuing energy efficiency to reduce demand on the electricity grid, especially during heatwaves.
3.2 Ocean-based impacts
The ocean is a major component of the climate system, and is home to rich ecosystems including phytoplankton which produce about about half of the oxygen we breathe. The ocean absorbs most of the heat accumulated the atmosphere, and about a quarter of the emitted CO2 from fossil fuels. Climate change alters the physical, chemical, and biological properties of the ocean, which has great consequences on sea levels and marine life. Increasing water temperature and melting of Greenland and Antarctic ice sheets contribute to a global sea-level rise, and increasing atmospheric CO2 levels impact marine ecosystems through ocean acidification and coral bleaching. These ocean-wide changes are important to assess since the ocean provides us with oxygen, food, shipping, tourism and recreation.
3.2.1 Sea level rise
Since 1901, the global mean seal level rose by 0.2 m (8 inches), continues to rise at a rate of about 0.001 m per year (1/8 inch), or another meter (3 feet) by 2100. Sea level changes as a result of changes in water volume, which is caused by two factors related to global warming: thermal expansion and increased melting of glaciers and ice sheets
The ocean absorbs more than 90% of the accumulated heat in the atmosphere resulting from fossil fuel CO2 emissions, causing seawater to heat up and expand. Air temperatures have been rising faster at the poles, causing Greenland and Antarctica ice sheets to melt and adding water into the ocean. It is important to note that sea ice, although melting at an alarming rate, does not contribute to sea level rise since floating ice takes up about the same volume when melted. It has however consequences on marine and terrestrial wildlife. Melting of ice sheets could be catastrophic as Greenland ice and Antarctic ice sheets contain respectively 7 m (22 feet) and 63 m (206 feet) of sea level equivalent.
Sea level strongly varies from region to region due to several factors such as land subsidence due to anthropogenic groundwater extraction and coastal erosion, changes in regional ocean currents and land rebound from compressive weight from the previous Ice Age. As a result, some places are expected to totally go under water like Venice in Italy, or partially like Florida and Texas. In some places, sea level is even slightly decreasing, like along the US west coast.
More frequent inundations of coastal areas and wild life habitat loss are expected, leading to biodiversity loss and a decline in coastal resilience. For humans, sea-level rise will have a greater impacts for those living at the coast, since their economy mainly revolves around fishing and coastal tourism.
3.2.2 Ocean acidification
The impacts of increased atmospheric CO2 concentrations is manifested in the ocean through ocean acidification, an ongoing decrease of seawater pH caused by the uptake of CO2 from the atmosphere. The pH of a substance defines its acidity, 0 being acid and 14 being basic (or alkaline) and the scale is related to the inverse of hydrogen ion (H+) concentration, so the more hydrogen ions the more acidic. The pre-industrial levels of ocean pH was about 8.2, and has dropped to 8.1 under global warming, which translates to 25% more acidic conditions.
About one third of the atmospheric CO2 is dissolved into the ocean, and exist under dissolved carbon dioxide. As it dissolves, it reacts with water molecules to form carbonic acid (H2CO3), and further dissociates into bicarbonate (HCO3-) and carbonate ions (CO32-), each time releasing a hydrogen ion (H+) which decreases the pH (makes seawater more acidic). Dissolved carbon dioxide, carbonic acid, bicarbonate and carbonate are found in a balanced proportion in seawater, but the ongoing increase of dissolved CO2 is shifting this balance.
This is a major problem for marine species like oysters and corals that need carbonate to build their shells and skeletons, as the carbonate ions become less available under acidic conditions, resulting in their shells and skeletons to even dissolve.
Ocean acidification also impacts fish behavior like clownfish, as it can deter their response to odors and their auditory capacity, with detrimental impacts on orientation, habitat selection, predator avoidance and communication. The impacts of ocean acidification are important ecologically and economically since the entire food web may be at risk.
3.2.3 Coral bleaching
Corals reefs are having a hard time adapting to these new levels of pH, but also to warmer water temperatures.
Corals are living animals, not plants, that cover the sea floor and provide a healthy and rich habitat to thousands of fish and other marine species. Corals host micro algae (zooxanthellae) on their skeleton, which provide them with their color and up to 90% of their energy. Those algae are very sensitive to light and temperature, so when the water gets too hot, they leave the coral structure due to thermal stress and the coral is left white. This is known as coral bleaching.
Bleached corals are not necessarily dead, but they become more vulnerable and cannot survive long. When coral reefs are bleached or dead, they no longer serve as a habitat to marine species and thus biodiversity declines.
3.2.4 Ocean resilience
The ocean can adapt and adjust to climate changes, but its capacity of doing so is also reduced by the current pace at which those changes occur, which is faster than ever in the Earth’s history. Overall, climate change will lead to shifts fish migration, loss of biodiversity and changes in ecosystem structures, with devastating consequences on humans.
Climate change can cause irreversible damages to our oceans and for this reason it is imperative that we protect our ecosystems and ecosystem goods. To help mitigate those risks, we must:
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Limit pressure from coastal tourism and fishing activities;
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Avoid physical destruction of coastal lands and ecosystems such as mangrove and coral reefs;
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Boost reforestation of river catchments and coastal areas to retain sediments and nutrients.
3.3 Human-based impacts
The world population is growing at a shocking rate, now reaching near 8 billion people. Resources from both the land and the ocean are being stripped at unsustainable rates, inducing huge tolls on global biodiversity. Sea level rise, heat waves and all the above-mentioned impacts combined with unsustainable practices have the potential to become major risks for human health, food security, and even national security. Migrations of communities due to climate change related issues are already ongoing, and will become more important in the next decades. Generally speaking, the magnitude of the threats will depend on the communities vulnerability, and their geographical location.
3.3.1 Human Health
Climate change affects health in many different ways, from exacerbating pre-existing health conditions, like diseases, undernutrition, and mental health, to increasing risk of injuries or the mortality rates due to rising temperatures, flooding and more intense hurricanes.
Here are a few examples on how climate change affects human health:
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Mortality. Extreme hot days will increase mortality, especially among elderly people or lower income people with limited access to AC and cooling systems. Cities will be more impacted due to the heat island effect which keeps cities much hotter than surrounding areas.
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Injuries. The frequency of river flood and storms is increasing under global warming, as well as the intensity of hurricanes, increasing the risks of injuries, even hypothermia, drowning, and mortality.
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Diseases. Vector-borne diseases (infections transmitted by mosquitoes or ticks) such as malaria, dengue and lyme disease will increase under a warming climate since ticks thrive under warmer temperatures. In North America, the Lyme disease is expanding northward, and cases have already doubled since the 1990s.
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Air quality. An increase in temperatures leads to an increase in ground-level ozone, a harmful air pollutant which is associated with diminished lung functions, asthma and premature deaths. Longer warm seasons will increase exposure to pollen, which can cause health problems. Increase in wildfires also impacts air quality as it causes a large increase of aerosols and air pollutants.
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Nutrition. Higher temperatures and droughts will negatively impact agriculture and may reduce the quantity and quality of the harvested food. Nutrition goes hand in hand with agricultural production, in food prices and food access, which will all be influenced by climate change, so the number of malnourished people will likely increase.
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Mental health. Harsher weather conditions increase stress and may trigger psychiatric trauma including severe anxiety. Prevalence of mental health issues will likely increase up to five times under an increase in floods, droughts and heatwaves.
Climate change impacts on health will be a greater burden for poor and low-income people, communities with reduced access to health services, lower health status and social disadvantages. In many countries, race and ethnicity are strong indicators of those marker. For example, in the US, Black Americans are the most vulnerable to heat-related deaths than any other racial groups.
Solutions to mitigate health impacts risks associated to climate change are plenty and often come with co-benefits:
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Reduce emissions of health-damaging pollutants
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Shift to cleaner energy
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Provide access to reproductive health series
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Decrease meat consumption and substitute low-carbon healthy diets
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Increase active transport in urban areas
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Increase urban green space
3.3.2 Food Security
Although a warmer climate will allow colder regions of the world for extended agriculture periods, the global tendency is that food security will be at risk as the climate changes. Access to clean water, quality food or food at all will be compromised as heatwaves, droughts, ocean acidification will intensify. Food security is tightly linked to poverty and its instability might intensity health-related issues, initiate waves of mortality and environmental migration.
Here are a few examples on how climate change affects food security:
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Clean water access. Droughts and glacier retreats will lead to lower river flows, reduce water availability (safe drinking water) and livelihoods.
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Food access and prices. Increasing climate stresses such as heatwaves and storms will cause crops loss, leading to a decline in agricultural productivity, which most likely will increase cost production and food prices. An increase in food prices can push millions of people below the poverty line for basic needs.
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Fisheries. Ocean warming and ocean acidification will cause migration of fish stocks and mortality of marine resources, which will impact the 3 billion people relying on fisheries for their main source of protein.
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Traditional food sources. Indigenous Peoples (about 400 millions worldwide) will see their cultural practices (agriculture, coastal fishing, hunting and gathering) increasingly threatened as natural resources are becoming scarce. This will impact their capacity of maintaining traditional livelihoods and their connection to homeland.
Any mitigation strategies and interventions imposed on communities in order to preserve a certain level of food security has to be consistent with their capabilities and values, or else it might impact them negatively. Carelessly designed climate mitigation policies could put at risk of hunger about 160 million by 2050. Solutions include decreasing food waste, and increasing agricultural yield with more efficient agricultural practices.
3.3.3 National Security
Population increase, deterioration in natural resources combined with climate stresses will most inevitably increase famines, ethnic conflicts, sociopolitical instabilities. Risks of violent conflict and geopolitical competition over access to resources (fisheries areas, Arctic resources, clear water) will increase, as well as unequal trading between countries. Types of conflicts will vary depending on locations and circumstances. Thankfully, many solutions and strategies have shown evidence in promoting well-being and decreasing risks of conflicts that countries and national treaties can work with:
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Diversification of income-generating activities in agricultural and fishing systems
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Migration as a risk management strategy
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Development of insurance systems, particularly among pastoralist, farmers and fishing communities
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Development of insurance systems
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Education of women
3.3.4 Climate Migration
The world population will have to face several unprecedented challenges under climate change. Shifts in climate and increased environmental stressors will force the displacement of millions of people out of their homelands, not without increasing risks of conflicts over natural resources and land possession.
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Extreme weather events like wildfires, floods and, hurricanes will cause millions to relocalize.
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Droughts, desertification and heavy rainfalls will drive farmers and pastoralist away from their countrysides to urban areas.
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Food scarcity, insecurities and fresh water shortage will force millions of people, mainly in developing countries, away from their homes.
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Extreme heat will push people farther north, increasing stress on borders and enhancing political conflicts.
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Increased frequency of disease outbreaks could eventually force people out of their homeland.
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Sea level rise and increasing storm surges will put about 800 million people living in coastal areas at risk of losing their homes. Cities at risk in the US include New York, Miami.
It is estimated that climate stresses will generate near 200 million climate migrants mainly from Latin America, sub-Saharan Africa, and Southeast Asia. Of course the ability to move is very unequal, and many vulnerable communities might find themselves trapped.
Even though climate migration can be seen as an adaptation measure, it can be a threat to cultural identity and lead to loss in traditional livelihoods. Rising male out-migration is also a threat to women’s physical and mental health, as it adds responsibilities to their already many labor and caring duties.
Climate migration is already underway and many migration could be avoided if measures are undertaken by international treaties, such as increasing communities resilience. It is important to identify markers of inequality, and focus on helping people with fewer capabilities to cope with climate change burdens, such as women, elderly, people of color, and poor people.
