Key Takeaways

• Since the 1920s, droughts have resulted in the highest average number of deaths, with an average of approximately 129,817 fatalities per decade, while floods have directly resulted in an average of 68,826 deaths.
• Some examples of massive death tolls in the last 100 years in which a drought was a direct cause, according to Ranker, include the Russian Famine of 1921 (5 million fatalities), Chinese Drought/Famine of 1942-43 (3 million fatalities), the Vietnamese Famine of 1945 (2 million fatalities), and the Ethiopian Famine of 1984-85 (1 million).
• The 1931 Yangtze River Flood has been identified as the deadliest natural disaster with a death toll "estimated at 3.7 million (estimated by the NOAA), although contemporary government figures place the death toll at around 2 million individuals.

Introduction

Deadliest and Most Severe Natural Disasters

• According to Our World in Data, the types of natural disasters that have caused the most casualties in the last 100 years worldwide are droughts, floods, earthquakes, storms and extreme temperatures.
• Since the 1920s, droughts have resulted in the highest average number of deaths, with an average of approximately 129,817 fatalities per decade, while floods have directly resulted in an average of 68,826 deaths. Additionally, earthquakes have caused an average of 21,131 fatalities per decade since the 1920s, and storms have led to an average of about 13,201 deaths. Finally, extreme temperatures have caused an average of around 2,331 fatalities per decade since the 1920s. [Calculations provided in the segment below labeled "Calculations"]

 

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• Some examples of massive death tolls in the last 100 years in which a drought was a direct cause, according to Ranker, include the Russian Famine of 1921 (5 million fatalities), Chinese Drought/Famine of 1942-43 (3 million fatalities), the Vietnamese Famine of 1945 (2 million fatalities), and the Ethiopian Famine of 1984-85 (1 million).
• Some examples of massive death tolls in the last 100 years in which floods were a direct cause, according to Ranker and World Atlas, include the 1931 Yangtze River Flood (3.7 million fatalities), the 1938 Yellow River Flood (500,000-800,000 fatalities), the 1975 Banqiao Dam Failure (171,000-230,000 fatalities), the 1935 Yangtze River Flood (145,000 fatalities), and the 1971 Hanoi and Red River Delta Flood (100,000 fatalities).
• Although droughts have recorded the highest number of deaths per decade since the 1920s, the volume of fatalities has significantly decreased over the last few decades. In the modern era, earthquakes have become the most deadly natural disasters. Major, single earthquake events in the Indian Ocean in 2004 and Part-au-Prince in 2010 killed more than 200,000 people each, while the combined death tolls from global droughts were less than 20,100 in the 2000s and 2010s.

 

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Natural Disaster With the Highest Death Toll

• According to a multitude of reliable sources, the natural disaster that resulted in the highest number of casualties in history is the 1931 Yangtze River Flood (aka the 1931 China Floods), which took place on the Yangtze River (Chang Jiang) throughout eastern and central China.
• The flood occurred after the river overtopped its banks after snow in the mountains from the previous year began to melt and travel to the lowlands, combined with more than 24 inches of rainfall in July of 1931 and heavy rains throughout the spring and summer. Droughts from 1928-1930 resulted in the ground below becoming hardened and less impressionable, which led to additional flooding.

 

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•  Poor management of the river from the previous decades (e.g. a lack of flood control measures) also contributed to the severity of the floods, as did the number of residents along the river. Additional factors included over-expansion of communities (e.g., large-scale deforestation, wetland reclamation), political stability (e.g., rebellions, unrest), and over-extension of waterways. The floods covered about 70,000 square miles of territory and impacted several major cities (e.g., Wuhan, Nanjing) and rice fields.
• Over 50 million people were impacted by the floods, with 40% of the population in the affected areas being forced to abandon their residences and 61% becoming refugees. The combined death toll was estimated at 3.7 million (estimated by the NOAA), although contemporary government figures place the death toll at around 2 million individuals.
• While the flood was directly responsible for many of the deaths (100,000-150,000 deaths in the immediate flooding), the majority were caused by the ensuing starvation and disease/infection (e.g., malaria, cholera, measles, typhoid, dysentery, etc.) brought on by the floods due to the destruction of agricultural fields and sanitation systems, compromised immune systems of refugees, overcrowding, etc.
• Diseases caused 87% of the fatalities within refugee camps and 70% of deaths in rural families impacted by the floods, with malaria alone accounting for 300,000 deaths.

 

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• Within the Yangtze Valley, around 15% of rice and wheat crops were destroyed, and the price of crucial commodities greatly increased. Several areas experienced famine, with some citizens selling their children or eating weeds and tree bark in order to survive, while others engaged in cannibalism. The economic impact of the floods was estimated at "one and a half year's net income per family."

Research Strategy

Calculations

Key Takeaways

• According to this UNEP and GRID-Arendal report, wildfires are on the rise. Additionally, they are becoming more severe.
• Although climate change may have increased precipitation events, the overall frequency of flood events has not increased. This is because large and severe flooding events were increased but due to the decrease in soil moisture levels, moderate floods reduced in number as much of the water would be easily absorbed.
• Over the past 60 years, heat waves have been on the rise, both in terms of frequency and severity.

Introduction

#1. Flooding

• Climate change has caused an increase in precipitation events. However, this has not resulted in an increase in flood events. A 2021 study by Nature has revealed that climate change may have caused an increase in extreme river flood events but may have decreased the number of moderate floods.
•  Higher temperatures mean that the soil moisture level is low. As a result, when moderate flood events would occur, the soil would absorb much of the water thus mitigating the flood event. However, in large events, the soil's lack of moisture has very little impact on the magnitude of the event.
• For every degree increase in temperature, the atmosphere can hold 7% more moisture. This increase in moisture and heat in the atmosphere means that there is more energy, which would result in more intense downpours. Additionally, inland floods can be caused by increased rain storms. Areas that would not typically get heavy rains would start experiencing flash floods.
• Scientists believe that some types of flooding will continue to increase in the coming years if temperatures continue to rise at the current rate. If humans do not take drastic measures to mitigate the impact of greenhouse gases, flooding events will be affected. As temperatures continue to rise, glaciers melt and increase the volume of water in the ocean and raise sea levels, which will in turn result in an increase in coastal flooding events.
• Increased temperatures result in increased precipitation events. In the long run, researchers believe that flash floods will get "flashier", which means that the flash flood events will be shorter but more intense, making them more dangerous and destructive.
• Furthermore, rising temperatures could result in a cascade of disasters. Flash floods that follow wildfires may become a common occurrence in some areas, which could trigger runaway surges of mud and debris.

#2. Wildfires

• In recent years, wildfires have laid waste to some of the most iconic forest covers across the globe: Australia, Brazil, and Europe. Rising temperatures have resulted in an increase in the frequency and intensity of these events, adversely impacting communities and ecosystems.
• According to this UNEP and GRID-Arendal report, climate change and poor land use have caused an increase in wildfire events. It also predicts that this will continue to increase, and could also spread to areas that were previously unaffected by wildfires.
• The chart below demonstrates the likelihood of wildfires and how it will continue to increase in the coming decades. Climate change has created a conducive environment for the occurrence of wildfires: hot, dry, and windy. Land use and population change can also increase the impact and intensity of wildfires.

 

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• An interview with Niklas Hagelberg , a Senior Programme Management Officer at UNEP, reveals that the intensity and frequency of forest fires could become the "New Normal" in America. He explains how the gradual increase in temperature has increased the frequency and intensity of wildfires and extended the length of droughts. He also expresses how the intense wildfires in 2020 could trigger action that could mitigate the impact of climate change in California.
• The chart below demonstrates how climate change influences wildfires. Climate change is already evidently the dominant driver of fire in vulnerable regions. Direct impacts of climate change include extreme weather patterns, increased intensity of winds, and reduced precipitation. These conditions increase the prevalence and likelihood of outbreaks.

 

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#3. Drought

• Climate change has resulted in increased temperature levels resulting in higher levels of moisture loss from the soil through evaporation and from plants through transpiration. An increase in evapotranspiration has resulted in increased precipitation in some areas and drying in others. Historically wetter areas are at a higher risk of flooding and historically dry areas are at a higher risk of experiencing droughts. Regions in West Africa and Southern Europe have experienced longer and more severe droughts while other areas in the US have been less frequent and less intense.
• The map below demonstrates how temperatures have increased in the Southwestern region of the United States. This map shows how temperatures have increased from the long-term average (1895-2020) to the short-term average (2000-2020).

 

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• Several regions across the globe are experiencing the adverse effects of climate change. According to this UN report, 650,000 people died due to the effects of drought between 1970 and 2019, with more than 90% from developing countries. Human-induced climate change has undoubtedly increased the risk of drought as various activities have contributed to the rise in temperature. Unfortunately, the impact of droughts is underestimated.

#4. Heat Wave

• The chart below demonstrates the increase in the frequency, intensity, and duration of heat waves in the US over the past 60 years. This data was collected from 50 large metropolitan areas across the US. This chart focuses on the increase in temperature, which could also have other contributing factors in addition to climate change.
• This chart reveals that the frequency of heat waves has been on the rise. In the 1960s, there were about two heat waves each year while by the 2010s, this count had reached about six a year. The length of these heat waves has also increased from four to five days. Additionally, the timing of these events can also catch people off-guard and do more damage. The average heat wave temperature has also been on the rise, making them more intense with every next decade.

 

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• This chart demonstrates the increase in frequency, duration, season, and intensity for each of the 50 metropolitan cities. It shows which ones experienced the highest levels of frequency, the greatest increase in duration, the longest seasons, and the highest levels of intensity. 29 locations had the greatest increase in duration, 44 had the longest heat wave season, 46 had a significant increase in frequency, and 17 had the highest levels of intensity.

 

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Research Strategy

Key Takeaways

• The United States Geological Survey (USGS) defines a supervolcano as a volcano that has had an explosion of magnitude 8 on the Volcano Explosivity Index (VEI), which means that it released approximately 1,000 cubic kilometers (240 cubic miles) of material at one point.
• The most recent supereruption happened approximately 22,600 years ago at the Taupō volcano in New Zealand. It had a volume of 1,130 cubic kilometers.
• According to an article by Cosmos Magazine, a massive supervolcano is lurking beneath the calm waters of Lake Toba in Sumatra, and the next super-eruption might occur in the next 600,000 years.
• However, according to a recent study that analyzed “field, laboratory and petrological evidence from 13 Quaternary supereruptions,” there is no single model that can help us describe how future supereruptions might happen.

Introduction

Supervolcanoes Overview

• The United States Geological Survey (USGS) defines a supervolcano as a volcano that has had an explosion of magnitude 8 on the Volcano Explosivity Index (VEI), which means that it released approximately 1,000 cubic kilometers (240 cubic miles) of material at one point.
• Supervolcanoes, also referred to as supereruptions, are associated with depressions in the ground called calderas. When a supervolcano erupts, so much magma is released, causing the earth to collapse and this leaves a huge circular-shaped hole in the ground called a caldera. Other characteristics of supervolcanoes include less frequent eruptions and a ridge of higher land surrounding them.
• The most recent supereruption happened approximately 22,600 years ago at the Taupō volcano in New Zealand. It had a volume of 1,130 cubic kilometers.
• La Garita Caldera, Lake Toba, Cerro Guacha, and Yellowstone Caldera are examples of some of the largest supervolcanoes.

Link Between the Toba Eruption and a Genetic Bottleneck in Human Evolution

• Lake Toba is believed to have erupted approximately 74,000 years ago and some researchers estimate that this eruption released around 6 billion tons of sulphur dioxide into the atmosphere. This made global temperatures decrease by 15C (59F) while precipitation reduced by 25%.
• As a result, some scientists suggested that this eruption brought about a genetic bottleneck in human evolution, with the hypothesis being that between 50,000 and 100,000 years ago, the human population rapidly decreased to a mere 3,000-10,000.
• It is believed that Homo Sapiens spread from a single African source but experienced a major decrease in population size, reducing to around 1,000–10,000 people. Moreover, according to research published in Nature, DNA analysis shows that a population bottleneck happened around 50,000 to 100,000 years ago when the climate changed from relatively warm to cold during the glacial stage.
• Thus, because of these coincidences, the Toba catastrophe theory was proposed to explain the human genetic bottleneck and the beginning of the glacial period. However, while there is some genetic evidence supporting this claim, the “scientific analysis of the impact of the eruption is disputed.”

The Next Supereruption

• According to an article by Cosmos Magazine, a massive supervolcano is lurking beneath the calm waters of Lake Toba in Sumatra. The volcano is one of the few volcanoes that are capable of producing a supereruption, as it has already produced two of the most massive eruptions the Earth has ever experienced.
• The two eruptions happened approximately 840,000 and 75,000 years ago, and according to researchers, the first one occurred after 1.4 million years of magma input, while the second one happened after magma accumulated for only 600,000 years.
• To predict when Toba’s next huge supereruption might occur, a team of researchers analyzed the levels of lead and uranium in zircons, a tiny crystal found in volcanic rocks, to determine their age. The zircon-dating method helped them estimate the amount of magma below the volcano and based on their results, there is around 320 cubic kilometers of magma within the Toba volcano, which is not enough to cause a super-eruption.
• The researchers also stated that every thousand years, an extra four cubic kilometers of magma builds up in Toba. Therefore, while smaller eruptions could occur anytime, the next super-eruption would occur in 600,000 years.
• However, according to a recent study that analyzed “field, laboratory and petrological evidence from 13 Quaternary supereruptions,” there is no single model that can help us describe how future supereruptions might happen.
• The study reported that supereruptions differ in things such as duration of the eruption, their styles, and rapidity of onset, among others. As such, it is difficult to determine how supervolcanoes might erupt in the future. The researchers who conducted the study concluded that more work is needed to better understand the “processes behind modern volcanic unrest and the signals that might herald an impending volcanic eruption regardless of size.”

Consequences of the Next Supereruption

• The most recent magnitude 7 volcano eruption happened in 1815, causing a reduction in global temperatures by 1 °C and widespread crop diseases. This brought about famine, disease outbreaks, and violent uprisings. Around 100,000 people died from things such as volcanic flows and tsunamis, among other subsequent effects.
• According to an article by Science Alert, while our ways to monitor volcanic eruptions and provide disaster relief have grown since 1815, they are still not enough to offset risks. For instance, not only are we more reliant on global trade but also the human population has increased numerously and urban areas have sprouted near dangerous volcanoes. Therefore, the impact of the next supereruption might spread across “transport, food, water, trade, energy, finance, and communication in our globally connected world.”
• Additionally, while the current global warming conditions might counter the mini-ice age triggered by a supereruption, a large volcanic eruption might still have uneven effects on weather, rainfall, and temperature.

Research Strategy

Key Takeaways

• During the 2019-20 bushfires crisis in Australia, approximately 71% of Koala populations in fire-affected areas were lost.
• One of the most affected non-human species affected by Hurricane Irma was the smallest deer in North America, the Key deer. A survey by the US Fish and Wildlife Service (USFWS) estimates that approximately 14-22% of the Key deer population was killed by the hurricane.
• As a result of extremely high stream temperatures in Australia, scientists witnessed die-offs of varieties of Alaskan salmon such as sockeye, chum, and pink salmon in 2019.
• According to a report by the National Wildlife Federation, Hurricane Harvey almost wiped out the Attwater’s prairie chicken, one of the most endangered birds in the world.

Introduction

Koala

• Location: Australia 
• Overview of the Disaster: The 2019-20 bushfires crisis in Australia caused devastating effects not only on humans but also on non-human species. According to a report commissioned by the World Wide Fund for Nature (WWF), approximately “three billion animals – mammals, reptiles, birds, and frogs – were killed or displaced.”
• Impact on the Specie: One of the species that was most affected by the bushfires is the Koala. The WWF report stated that approximately “71% of Koala populations in fire-affected areas at six locations on the north coast of New South Wales” were lost. The Koala occupancy rate in the six areas varied from 34% in the area that was least affected to a likely 100% in the worst area. According to the chief executive of WWF-Australia, Dermot O’Gorman, for a species that was already sliding towards extinction, these are devastating numbers.

 

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Key Deer

• Location: Florida, United States 
• Overview of the Disaster: In 2017, Hurricane Irma, one of the “strongest Atlantic basin hurricanes ever recorded outside the Gulf of Mexico and the Caribbean Sea,” hit at least nine US states, including Florida. The hurricane battered Florida's lower half and left a “trail of tornadoes and storm-surge flooding as its core slowly moved inland.”
• Impact on the Specie: One of the most affected non-human species affected by hurricane Irma was the smallest deer in North America, the Key deer. A survey by the US Fish and Wildlife Service (USFWS) estimates that approximately 14-22% of the Key deer population was killed by Hurricane Irma.

 

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Salmon

• Location: Alaska
• Overview of the Disaster: As global temperatures rise, extreme heat waves are becoming more frequent and longer. In 2019, Alaska experienced its hottest month in recorded history with an average temperature of 58.1 degrees (5.4 degrees above average). This unprecedented heat wave caused stream temperatures near Anchorage to surpass 76 degrees for the first time since scientists started tracking in 2002. According to one of the scientists, Sue Mauger, the 2019 degree “exceeded the value of what they expected for the worst-case scenario in 2069.”
• Impact on the Specie: As a result of the extremely high stream temperatures, scientists witnessed die-offs of varieties of Alaskan salmon such as sockeye, chum, and pink salmon. They counted 850 dead salmon in the area and estimated the total number was likely 4 to 10 times larger.

 

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Attwater Prairie Chicken

• Location: Texas, United States
• Overview of the Disaster: Hurricane Harvey, one of the most expensive natural disasters in US history, hit Texas in 2017 and within two days, it had “dropped 27 trillion gallons of rain over Texas and Louisiana.” The category 4 hurricane cost approximately $130 billion and 14,000 National Guard members had to be activated to rescue over 72,000 people.
• Impact on the Specie: According to a report by the National Wildlife Federation, Harvey almost wiped out the Attwater’s prairie chicken, one of the most endangered birds in the world. The Attwater Prairie Chicken National Wildlife Refuge was affected by the flooding caused by the hurricane, causing the population of the birds to drop to about 12. The good news is that the species made a remarkable comeback. From 26 birds in 2018, their population has increased to 178 as of 2021.

 

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Research Strategy