Trends of Global Hazards

Hazard trends - Cumulative

Hazard trends, 1900–2005

Interpretations• Part of this rise is likely to be due to more accurate

recording and better communications with isolated regions.

• Note the rapid rise since around 1960, when satellite remote sensing and global communications began.

• Population growth has led to more people living in potentially hazardous locations. This means there are greater numbers at risk.

• Many of these people at risk live in the developing world, and are vulnerable due to their low coping capacity.

Hazard trends

Number of natural disasters by type, 1970–2005

Interpretations• Some types of disaster show clearer trends than others.• The graph on the last slide compares trends in three disaster

types.• The trend for earthquakes is fairly stable. There is no

evidence that the number of earthquake events is increasing. There are likely to have been more people in earthquake-prone areas in 2000 than in 1980, and this would explain the slight rise in disasters.

• There is a clearer upward trend for floods and wind storms. This may indicate an increase in the vulnerable population and a rise in the number of hazardous events.

• It could be the result of global climate change and/or other environmental changes.

Volcano Trends

• Around 50–70 volcanoes erupt every year.

• There is no trend, upward or downward, in eruption frequency.

• Very large magnitude eruptions (e.g. Mt Pinatubo in 1991) are rare.

• Notice that 8 of the top 10 eruptions have occurred since 1990.

Country Year

Number of people affected

Philippines(Mt Pinatubo) 1991 1,036,065

Nicaragua 1992 300,075

Ecuador 2006 300,013

Indonesia 1982 300,000

Indonesia 1969 250,000

Comoros 2005 245,000

Philippines 1993 165,009

Papua New Guinea 1994 152,002

Ecuador 2002 128,150

Dem. Rep. Congo 2002 110,400

Top ten volcanic eruptions since 1900 by number of people affected

Edexcel AS Geography Unit 1World at risk: Global hazard trends

Hurricane Trends• Trends in hurricanes, especially in the Atlantic, are

a controversial matter.• Some researchers have linked increased hurricane

activity to global warming.• Others argue that there is a natural cycle in the

Atlantic called the Atlantic Multidecadal Oscillation (AMO) which explains the high number of major hurricanes in the 1940s and 1950s, and more recently.

• Despite variations in major hurricane frequency, there is a long-term trend in the USA of falling hurricane-related deaths but rising economic costs.

Hurricane trends• One certain trend is the rise in the number of people living on

the US coast. • In Florida and the Gulf Coast, some coastal areas have seen

populations rise by 400% since 1980.• This means increasing numbers of people are at risk from

hurricanes.• Although awareness of hurricanes, education, warning and

evacuation systems have all improved in the USA, the potential for economic loss continues to grow as coastal populations rise.

• The full impact of rising populations was felt in 2005, when the Florida and Gulf Coasts were struck by five major hurricanes (Dennis, Emily, Wilma, Rita, Katrina), causing an estimated US$120 billion in damage and the loss of 2,200 lives.

Global Warming

Global temperatures, 1850–2008

(IPCC – Intergovernmental Panel on Climate Change)

Global Warming• Many scientists believe that increased global warming will

lead to more unpredictable weather and a rise in extreme weather events.

• Global temperatures have risen since 1910, and at a consistently rapid rate since the late 1970s.

• The fact that there are only few years of reliable data about global temperatures makes the scientists’ task of accurately predicting future changes more difficult.

• Some data, such as the 20 cm rise in global sea level since 1900 and the decline in Arctic sea ice since the 1970s, are more reliable.

• There is growing suspicion that rising trends in drought and flood events may herald the effects of global warming to come.

Flood Disaster Trends

Reported global flood disasters and death tolls, 1977–2007

Flood Disaster Trends

• Trends in global flood disasters show significant rises since the early 1990s.

• This could be an early signal of climate change. • It may also be related to rising populations, rapid urbanisation,

deforestation and other land-use changes.

El Niño/La Niña• As well as global warming, the El-Niño/La-Niña cycle is known

to have climatic consequences on a global scale. • Changes in Pacific Ocean circulation have knock-on weather

effects in other parts of the world.• Hazards associated with El-Niño are well known, such as

drought in Indonesia and flooding in Peru.• El-Niño/La-Niña cycles, which are unpredictable, add yet

another layer of complexity to the calculation of hazard risk.

Human Trends• Some trends among the human population add to increasing

risk.• One of these is urbanisation. Over 50% of the world’s

population now lives in urban areas, compared to 29% in 1950.• These crowded spaces are especially vulnerable to major

earthquakes, floods and hurricanes.• World poverty continues to be a major issue, reducing the

capacity to cope with, and increasing the vulnerability to hazards.

• Although the global proportion of people living on less than $1 per day is falling, total numbers rose from 36 million to 50 million in Latin America, and 164 to 314 million in Africa between 1981 and 2001.

Human trends• Pressure on land from growing populations leads to

deforestation and conversion to farmland.• Deforestation can significantly increase hazard risk.• The risk of landslide is greater on slopes when trees

are removed.• With no vegetation to intercept rain, flash-flood risk

rises.• Urban Disasters are in increasing trend as urban

population is increasing

Global Trends

Disasters related to human development levels

Overall, global trends show that the numbers of reported disasters and people affected are rising, but the number of people killed by disasters is falling.

Disaster Management• Death tolls are reduced when populations are prepared for a possible

hazard.• Some hazards can be predicted, e.g. floods, hurricanes, drought and

volcanic eruptions.• Prediction allows for warning, and, when possible, evacuation. This

can save lives, but is unlikely to reduce economic losses.• After a disaster, immediate rescue and relief is essential.• ‘Rapid response’ has improved considerably over the last few

decades. International relief efforts now occur quickly in response to disasters.

• This saves lives but the numbers affected and the economic losses are still high.

The challenge is to ‘disaster proof’ communities using appropriate building techniques, land-use zoning, education and developing prevention technology. These responses are longer term, costly and beyond the reach of many in the developing world.