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.
There is no trend, upward or downward, in eruption frequency.
Very large magnitude eruptions (e.g. Mt Pinatubo in 1991) are rare.
There is a rising trend in the number of people affected (see table). Notice that 8 of the top 10 eruptions have occurred since 1990.
This reflects growing population density in the developing world.
Top ten volcanic eruptions since 1900 by number of people affected 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
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.
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 (1) Global temperatures, 1850–2008
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.
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.
Without the evapotranspiration provided by trees, rainfall becomes more variable and aridity increases.
Occasional flash floods can produce a cocktail of increased hazard risk and falling food and water security.
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.
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.