
A disaster is an event that causes serious harm to people, buildings, economies, or the environment, and the affected community cannot handle it alone.
''
Natural disaster
A natural disaster is the very harmful impact on a society or community brought by natural phenomenon or Hazard#Natural hazard, hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides ...
s'' like
avalanche
An avalanche is a rapid flow of snow down a Grade (slope), slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, othe ...
s,
flood
A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...
s,
earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
s, and
wildfires
A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...
are caused by natural
hazards.
''Human-made disasters'' like
oil spills,
terrorist attacks and
power outage
A power outage, also called a blackout, a power failure, a power blackout, a power loss, a power cut, or a power out is the complete loss of the electrical power network supply to an end user.
There are many causes of power failures in an el ...
s are caused by people. Nowadays, it is hard to separate natural and human-made disasters because human actions can make natural disasters worse.
Climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
also affects how often disasters due to
extreme weather
Extreme weather includes unexpected, unusual, severe weather, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Extreme events are based on a location's recorded weat ...
hazards happen.
Disasters usually hit people in
developing countries
A developing country is a sovereign state with a less-developed Secondary sector of the economy, industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. ...
harder than people in wealthy countries. Over 95% of deaths from disasters happen in low-income countries, and those countries lose a lot more money compared to richer countries. For example, the damage from natural disasters is 20 times greater in developing countries than in
industrialized countries.
This is because low-income countries often do not have well-built buildings or good plans to handle emergencies.
To reduce the damage from disasters, it is important to be prepared and have fit for purpose infrastructure.
Disaster risk reduction (DRR) aims to make communities stronger and better prepared to handle disasters. It focuses on actions to reduce risk before a disaster occurs, rather than on
response and recovery after the event. DRR and
climate change adaptation measures are similar in that they aim to reduce
vulnerability of people and places to natural hazards.
When a disaster happens, the response includes actions like warning and evacuating people, rescuing those in danger, and quickly providing food, shelter, and medical care. The goal is to save lives and help people recover as quickly as possible. In some cases, national or international help may be needed to support recovery. This can happen, for example, through the work of
humanitarian organizations.
Definitions

The UN defines a disaster as "a serious disruption of the functioning of a community or a society at any scale".
[UNGA (2016)]
Report of the open-ended intergovernmental expert working group on indicators and terminology for disaster risk reduction
United Nations General Assembly (UNGA). It results from hazards in places where people live in exposed or vulnerable conditions. Some human failures make
communities vulnerable to
climate hazards. These are poor planning or development, or a lack of preparation.
Disasters are events that have an effect on people. A hazard that overwhelms or injures a community is considered a disaster. The international disaster database
EM-DAT defines a disaster as “a situation or event that overwhelms local capacity, necessitating a request for external assistance at the national or international level; it is an unforeseen and often sudden event that causes great damage, destruction and human suffering.”
[CRED. 2023 Disasters in Numbers: Climate in Action. (2024). https://files.emdat.be/reports/2023_EMDAT_report.pdf] The effects of a disaster include all human, material, economic and environmental losses and impacts.
UNDRO (1984) defined a disaster in a more qualitative fashion as:
[Smith 1996 quoted in ] "an event, concentrated in time and space, in which a community undergoes severe danger and incurs such losses to its members and physical appurtenances that the social structure is disrupted and the fulfilment of all or some of the essential functions of the society is prevented." Like other definitions this looks beyond the social aspects of the disaster impacts. It also focuses on losses. This raises the need for emergency response as an aspect of the disaster.
It does not set out quantitative thresholds or scales for damage, death, or injury.
A study in 1969 defined ''major disasters'' as conforming to the following criteria, based on the amount of deaths or damage:
At least 100 people dead, at least 100 people injured, or at least $1 million damage. This definition includes indirect losses of life caused after the initial onset of the disaster. These could be the effects of diseases such as cholera or dysentery arising from the disaster. This definition is still commonly used. However it is limited to the number of deaths, injuries, and damage in money terms.
Types
The scale of a disaster matters. ''Small-scale disasters'' only affect local communities but need help beyond the affected community. ''Large-scale disasters'' affect wider society and need national or international help.
It is usual to divide disasters into natural or human-made. Recently the divide between natural, man-made and man-accelerated disasters has become harder to draw.
Some manufactured disasters such as
smog
Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odour. The word was then inte ...
and
acid rain
Acid rain is rain or any other form of Precipitation (meteorology), precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists b ...
have been wrongly attributed to nature.
Related to natural hazards
Disasters with links to
natural hazard
A natural disaster is the very harmful impact on a society or community brought by natural phenomenon or hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides - including submarin ...
s are commonly called
natural disaster
A natural disaster is the very harmful impact on a society or community brought by natural phenomenon or Hazard#Natural hazard, hazard. Some examples of natural hazards include avalanches, droughts, earthquakes, floods, heat waves, landslides ...
s. However experts have questioned this term for a long time.
Unrelated to natural hazards

Human-made disasters are serious harmful events caused by human actions and social processes. Technological hazards also fall into this category. That is because they result in human-instigated disasters. Human-made hazards are sometimes called anthropogenic hazards.
Examples include
criminality,
social unrest,
crowd crushes,
fire
Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products.
Flames, the most visible portion of the fire, are produced in the combustion re ...
s,
transport accidents,
industrial accidents, power outages,
oil spills,
terrorist attacks, and
nuclear explosions/
nuclear radiation.
Catastrophic
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
,
nuclear war, and
bioterrorism also fall into this category.
Climate change and environmental degradation are sometimes called socio-natural hazards. These are hazards involving a combination of both natural and human factors.
All disasters can be regarded as human-made, because of failure to introduce the right
emergency management
Emergency management (also Disaster management) is a science and a system charged with creating the framework within which communities reduce vulnerability to hazards and cope with disasters. Emergency management, despite its name, does not actu ...
measures.
[Blaikie, Piers, Terry Cannon, Ian Davis & Ben Wisner. ''At Risk – Natural hazards, people's vulnerability and disasters'', Wiltshire: Routledge, 2003, ]
Famines may be caused locally by drought, flood, fire or pestilence. In modern times there is plenty of food globally. Long-lasting local shortages are generally due to government mismanagement, violent conflict, or an economic system that does not distribute food where needed.
Others
''Complex disasters'', where there is no single root cause, are more common in
developing countries
A developing country is a sovereign state with a less-developed Secondary sector of the economy, industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. ...
. A specific hazard may also spawn a secondary disaster that increases the impact. A classic example is an
earthquake
An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
that causes a
tsunami
A tsunami ( ; from , ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and underwater explosions (including detonations, ...
. This results in
coastal flooding, damaging a
nuclear power
Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by ...
plant on the coast. The
Fukushima nuclear disaster is a case in point. Experts examine these cascading events to see how risks and impacts can amplify and spread. This is particularly important given the increase in
climate risks.
[Ara Begum, R., R. Lempert, E. Ali, T.A. Benjaminsen, T. Bernauer, W. Cramer, X. Cui, K. Mach, G. Nagy, N.C. Stenseth, R. Sukumar, and P. Wester, 2022]
Chapter 1: Point of Departure and Key Concepts
In
Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.) Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 121–196, doi:10.1017/9781009325844.003.
Some researchers distinguish between ''recurring events'' like seasonal flooding and ''unpredictable one-off events''. Recurring events often carry an estimate of how often they occur. Experts call this the
return period.
Impacts
The effects of a disaster include all human, material, economic and environmental losses and impacts.
The Emergency Events Database (EM-DAT) records statistics about disasters related to natural hazards. For 2023, EM-DAT recorded 399 disasters, which was higher than the 20-year average of 369.
Economic losses
Between 2016 and 2020 the total reported economic losses amounted to $293 billion. This figure is likely to be an underestimation. It is very challenging to measure the costs of disasters accurately, and many countries lack the resources and technical capacity to do so.
[UNDRR (2023)]
The Report of the Midterm Review of the Implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030.
UNDRR: Geneva, Switzerland. Over the 40-year period from 1980 to 2020 losses were estimated at $5.2 trillion.
Human impacts
In 2023, natural hazard-related disasters resulted in 86,473 fatalities and affected 93.1 million people.
Whilst the number of deaths was much higher than the 20-year average of 64,148, the number affected was much lower than the 20-year average of 175.5 million.
According to a UN report, 91% of deaths from hazards from 1970 to 2019 occurred in developing countries.
These countries already have higher vulnerability and lower resilience to these events, which exacerbates the effects of the hazards.
Effects of climate change
Hazards such as
drought
A drought is a period of drier-than-normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, ...
s,
flood
A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...
s, and
cyclones are naturally occurring phenomena. However,
climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
has caused these hazards to become more unreliable, frequent and severe. They thus contribute to disaster risks. Countries contributing most to climate change are often at the lowest risk of feeling the consequences.
[IPCC, 2023: Sections. In]
Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
ore Writing Team, H. Lee and J. Romero (eds.) IPCC, Geneva, Switzerland, pp. 35-115, doi: 10.59327/IPCC/AR6-9789291691647 As of 2019, countries with the highest vulnerability per capita release the lowest amount of emissions per capita, and yet still experience the most heightened droughts and extreme precipitation.
Prevention and response
Disaster risk reduction
Disaster response
Etymology
The word ''disaster'' is derived from
Middle French
Middle French () is a historical division of the French language that covers the period from the mid-14th to the early 17th centuries. It is a period of transition during which:
* the French language became clearly distinguished from the other co ...
' which comes from
Old Italian '. This in turn comes from the
Ancient Greek
Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
pejorative prefix - (''-'') "bad" and ('), "star". So the word ''disaster'' ("bad star" in Greek) comes from an
astrological sense of a calamity blamed on the position of planets.
"Disaster"
in Etymology online
See also
*
*
* List of accidents and disasters by death toll
* Lists of disasters
References
External links
* ReliefWeb of the United Nations Office for the Coordination of Humanitarian Affairs �
ReliefWeb
* United Nations Office for Disaster Risk Reduction �
UNDRR
* Global Disaster Alert and Coordination System – a joint initiative of the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) and the European Commission
The European Commission (EC) is the primary Executive (government), executive arm of the European Union (EU). It operates as a cabinet government, with a number of European Commissioner, members of the Commission (directorial system, informall ...
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