Temps de lecture :4 minutes
The constant rise in the number of victims that has been noted over the last two decades can essentially be explained not by an increase in the number of unpredictable occurrences, but rather by the increasing vulnerability of humankind to such events. This is due to anarchic development in high-risk zones, to the concentration of population on the coast and to the shortage of information systems. Natural disasters are also amplified by the imbalances caused by man-made changes (soil cover) and by climatic variability, to the point where it is difficult to distinguish between what is natural and what is linked to human activity. Some hazards such as volcanic eruptions have been studied for a long time now and have benefited from technological developments in surveillance tools which make them relatively easy to forecast. Others still resist such predictions, such as earthquakes or tsunamis, which are triggered by underwater earthquakes. Detection and alarm systems that exist in rich countries would help reduce the number of victims in poor regions of the world, as would applying building standards and implementing urban planning policies.
Floods are the most widespread natural hazard in the world. They are responsible for more than 60% of the total number of deaths from natural disasters. The cyclone that hit Bangladesh in November 2007 affected more than 4 million people, killed more than 3,000 and left 300,000 homeless. Deforestation, changes to the permeability of soils and to the hydrological network are largely to blame for their increase.
Cyclones, swirling disturbances that form above warm waters in tropical regions, can be forecast with a fair degree of certainty: they cause an enormous amount of material damage but very few deaths.
Biological or ecological disasters, which can lead to epidemics, are difficult to control. Although progress has been made on sudden epidemics, the number of chronic pandemics remains alarmingly high. AIDS killed more than 25 million people between 1981 and 2003, and malaria kills more than 2 million people every year. Increased intercontinental mobility and now global warming are responsible for the rapid transmission of pathogenic micro-organisms around the world.
Climatic crises are local climatic variations that occur unexpectedly for a short period of time, such as a heatwave or an abnormally high level of humidity. With global warming, the UN is predicting that they will become increasingly frequent and their impact worse. The Centre for Research on the Epidemiology of Disasters and the UN Secretariat for the International Strategy for Disaster Reduction have already measured an increase in the number of disasters (from 23 to 30) linked to ever higher temperatures.
Earthquakes are generally extremely tragic events. In 1995, the Kobe earthquake in Japan left more than 5,000 people dead and tens of thousands injured. Fortunately, earthquakes measuring more than 8 on the Richter scale are rare (1 to 2 per year).
Although volcanic eruptions are under close surveillance, they can have tragic consequences. The eruption of Mount St Helens in 1980 in the United States affected millions of people and the cost of the damage was estimated at 1 billion dollars. The eruption of Laki in Iceland in 1783, which lasted for 9 months, emitted 250 million tonnes of toxic aerosols and caused 9,336 deaths, a quarter of the Icelandic population. It was followed by famines resulting from livestock having been poisoned by ash and by a noticeable drop in temperatures throughout Europe for several years.
The environment suffers too
Every year, these natural phenomena cause a considerable loss of marine and terrestrial ecosystems. The 2004 tsunami in Asia made the habitats of marine species more vulnerable and caused a fall in biodiversity. Hurricane Katrina (Louisiana, 2005) destroyed more than 320 million trees which are rotting, releasing greenhouse gases. Huge fires wreak havoc on terrestrial ecosystems as in 1998 in Indonesia where fires that broke out on the islands of Sumatra and Borneo burned down 9 million hectares of vegetation. Pinatubo in the Philippines, which killed more than 1,000 people in June 1991, scattered more than 20 million tonnes of sulphur dioxide into the atmosphere and covered more than 86,000 hectares with ashes.
Inequalities between North and South
Different regions of the world are affected in very unequal fashion by these hazards. Natural disasters take a heavy toll on developing countries: 95% of losses of human life are concentrated in these countries. The hurricanes and typhoons that recently hit the United States and Japan caused no more than 500 victims and even the hugely devastating Hurricane Andrew, which reached category 5, caused less than 100 victims in the United States in 1992. However, Hurricane Mitch, which was also category 5, caused more than 10,000 deaths in Central America in 1998. In Bangladesh, a cyclone took about 500,000 victims in 1970 and another 140,000 or so in 1991.