Climate change impacts food productivity, access, nutrition, and risk of illness for hundreds of millions of people and every increment of warming increases the risk that some of our current global crop and livestock areas will become climatically unsuitable.
The frequency of sudden food production losses has increased since the mid-1900s, with the impacts of climate events on food security felt most acutely in sub-Saharan Africa, Asia, small islands, Central and South America, and the Arctic.
Although some have argued that elevated carbon is good for plant growth (called the carbon dioxide fertilization effect) the reality is that productivity has been negatively impacted by climate change.
For example, there is evidence that total productivity has declined 21% since 1961 due to anthropogenic climate change, with greater impacts (26-34%) in Africa, Latin America, and the Caribbean.
The carbon dioxide fertilization effect is more than compensated for by droughts, heat stress, crop damage from extreme weather events, increased surface level ozone, decreases in air, soil and water quality, human activities such as deforestation, draining of peatlands and tropical forests (which turns carbon sinks into carbon sources), and the expansion of woody plants in grasslands and savannahs as a result of increased carbon dioxide levels which reduces grazing land and increases the risk of fire.
Crop and livestock losses also contribute to lost livelihoods and increased food prices, with vulnerable populations most at risk of food insecurity and malnutrition.
In coastal communities, climate change also increases the presence of harmful algal blooms and water-borne diseases that threaten food security and livelihoods of fishing communities.
Food safety risk has also increased because high temperatures and humidity caused by climate change increases the presence of toxigenic fungi on many food crops (mycotoxins are associated with cancer and stunting in children), and ocean warming and acidification enhance the movement and bioaccumulation of toxins and contaminants such as methyl mercury in marine food webs, impacting fisheries.
Severe water scarcity is currently experienced by about half of the world’s population for at least 1 month/year in part due to climate change, with the impacts being felt most severely in low-income economies. The impacts are exacerbated by poor water governance and competition for water resources by the energy industry, agriculture, and other industries. Water insecurity can also lead to social unrest, displacement, and other vulnerabilities.
Every year, over 20 million people have been displaced within their own countries by extreme weather-related events since 2008 (most commonly because of storms and floods.)
Extreme climate events directly (e.g. through destruction of homes) and indirectly (e.g. drought related loss of livelihood) cause involuntary migration and displacement. The largest amount of displacement occurs in Asia, followed by sub-Saharan Africa and small islands in the Caribbean and South Pacific.
Involuntary migration can lead to poor socioeconomic and health outcomes. Forced displacement by governments can also lead to significant financial and emotional distress particularly where there is cultural or spiritual significance to the land being lost. Displacement impacts mental health, well-being, livelihoods and opportunities (including education.)
In cities and settlements, sea level rise, heatwaves, droughts, floods, wildfires, and permafrost thaw cause disruptions of key infrastructure and services including energy supply and transmission, communications, food and water supply, and transport systems in and between urban and surrounding areas.
In many cities, the presence of informal settlements, made worse by displacement from rural and coastal areas, increases a population’s vulnerability to extreme weather and climate events and limits the capacity for adaptation.
In sub-Saharan Africa, about 60% of the urban population lives in informal settlements and in Asia, about 529 million people live in informal settlements. Exposure to climate-driven impacts such as heat waves, extreme precipitation and storms alongside rapid urbanization and lack of climate adaptation in urban planning increase the vulnerability of urban populations.
Coastal cities and communities are more vulnerable to the compounding impacts of climate variability and sea level rise. About 10% of the world’s population and physical assets (including many mega cities and 14% of the world’s GDP) are within less than 10m above sea level.
Between 2006 and 2016, the rate of global sea level rise was 2.5x faster than it was for almost all of the 20th century.
Early impacts of accelerating sea level rise have been detected along some coasts already, including periodic or chronic flooding at high tides, water-table salinization, agricultural, fishery and ecosystem degradation, increased erosion, and coastal flood damage.
Water contamination also increases the risk of water-borne diseases and compromises sanitation and access to fresh water. Areas highly vulnerable to flooding impacts include informal settlements within cities, areas with land subsidence (e.g. Bangkok, Jakarta, Lagos, New Orleans, Mississippi, Nile, Ganges-Brahmaputra deltas) and small island states.
Current protections are anticipated to become more costly or inadequate in future. Relocation of millions of people may be needed in some cases (for example, Jakarta will be moved inland, partly as a result of climate change.)
By 2050, it is projected that more than a billion people located in low-lying cities and settlements will be at risk from coast-specific climate hazards.
Under all warming scenarios, low lying cities and settlements, small islands, Arctic communities, remote indigenous communities, and communities living in river deltas will face severe disruption by 2100 and as early as 2050.
Risks to water security will occur as early as 2030 or earlier for the small island states and Torres Strait Islands in Australia and remote Maori communities in New Zealand.
By 2100, compound and cascading risks will result in the submergence of some low-lying island states and damage to coastal heritage, livelihoods, and infrastructure along many other coasts. Sea level rise, combined with altered precipitation patterns will increase coastal inundation and water-use allocation issues between water-dependent sectors such as agriculture, direct human consumption, sanitation, and hydropower.
In Europe, coastal flooding damage is projected to increase 10-fold by 2100. Projected impacts will reach beyond coastal cities and settlements with damage to ports that may severely impact global supply chains and maritime trade.
Vulnerable coastal communities may face adaptation limits well before the end of this century even at low warming levels and current solutions may be less viable in a warmer world.
For example, droughts have reduced thermoelectric and hydropower production by around 4–5% compared to the 1980s, reducing economic growth in Africa and putting at risk billions of dollars of existing and planned hydropower infrastructure assets in Africa and mountain regions worldwide.
Drought-related reductions in hydropower have also resulted in increased fossil fuel use in China.
Changes in temperature, precipitation, and water-related disasters are linked to increased incidences of waterborne diseases such as cholera, especially in regions with higher vulnerability — e.g. where there is limited access to safe water, sanitation, and hygiene infrastructure.
More extreme events and shifts in precipitation have contributed to vector-borne disease outbreaks. Climate change is contributing to the spread of chikungunya virus in North, Central and South America, Europe and Asia; tick-borne encephalitis in Europe; Rift Valley fever in Africa; West Nile fever in multiple regions; Lyme disease vectors in North America and Europe, malaria in Africa and dengue globally.
For example, compared to the 1950s, the reproduction potential for dengue in Central and South America has increased between 17% and 80% (depending on the region), because of temperature and precipitation changes.
Zoonoses that have historically been rare or never documented in the Arctic and sub-Arctic regions of Europe, Asia, and North America are emerging as a result of climate-induced environmental change, spreading northwards and increasing in incidence (e.g. anthrax, tularaemia.)
Spring pollen season start dates in northern mid-latitudes are occurring earlier due to climate change, increasing the risks of allergic respiratory diseases.
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