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Have the natural hazards increased in quantity?

   From a physical viewpoint, global climate change introduces new physical patterns such as increased erosion because of deforestation… Then, men have to cope with this modified environment. Global warning brings about more and more flooding along coasts and around islands since the sea level rises (Bangladesh, Pays Bas, Maldives). Then, human beings have the impression that catastrophes are increasing. From October 2000 to April 2001, a large part of British Isles was affected by the most widespread flooding in over 50 years. Moreover, storm frequency has started to increase in Europe between Christmas and 1999-2000 New Year.

   However, John Whittow states, “this is not to say that natural hazard are proliferating” (p309). It means that there is not a quantitative increase of hazard occurrences. On the one hand, the number of natural hazards seems to be higher due to the rise of technology that enables men to detect disasters more frequently. Hazards were less registered in the past but it does not mean that they were less numerous. On the other hand, as soon as a natural event happens, it is displayed in media; so people get more information about hazard phenomena. However, does a better communication reflect reality? For instance, television coverage does no always reflect the spatial variability of hazard occurrences. Moreover, media tend to stress the most spectacular events. Figures are used to point out the catastrophic aspect and people pay attention to the most striking ones. Media are powerful sources of information but people’s perception of hazard can be easily distorted, especially when direct experience of hazard is lacking. In a nutshell, even if humans are more informed, it does not necessary imply that hazard impact is getting worse. So, the rise of hazard impact cannot be reduced to an increasing number of events.

   Moreover, qualitative characteristics of hazards such as speed of onset, magnitude (measured with Richter scale), areal extent or duration must be taken into consideration. Extreme events have already occurred in the past (Lisbon Earthquake in 1755…). So, they are not new phenomena. But, is their intensity getting worse? It is important to consider the most striking ones such as earthquakes. Indeed, they provoke an extreme stress and very damaging consequences. For instance, the cost of Agnes earthquake in 1972 represented half the annual total. Loss seems to be bigger when stress is extreme as it is actually concentrated in a short time period.

   However, the impact of an event is not always linked to its size. For instance, floods are less spectacular than earthquakes because stress is not so extreme. They are more regular and cost is actually spread through time but it does not mean that total cost is lower. Indeed, flooding “cause the most frequent disasters”[1]. Losses may also be spread unevenly between different sorts of hazards: in 1996, deaths caused by flooding represented more than half of death total. Yet, total cost of flooding may be uneasy to detect because indirect losses may be considerable. Moreover, difference between the effects of drought and endemic seasonal hunger and malnutrition in LDCs is not obvious. To sum it up, a mere hazard classification is not enough to determine the most damaging hazards and which one presents the worst evolution. An impact is actually defined through a series of physical parameters combined together.

   Is hazard impact spread worldwide or does it apply to specific regions? For example, coasts are more and more affected by flooding. Hazard impact is spread unevenly over different parts of the world as the following graph highlights it (UNESCO website). Asia is the most affected.

“1996 deaths outcome”, repartition according to continents

   The spatial variability of hazard impact has been brought into relief. It means that hazards are not getting worse equally from a geographical viewpoint. However, the growing interdependence between individuals spread the impact “far outside the immediate area of impact”[2]. So, even if regions are more or less affected, hazard impact tends to become a worldwide concern.

   The discrepancy between developing and developed countries puts to the fore a physical explanation of hazard impact. It mainly concerns infrastructures in DCs whereas it also causes deaths and injuries in LDCs. Some countries or regions are more affected than others (flooding in Bangladesh, volcanoes in Philippines…). In the structural paradigm of hazard, disasters are seen as a factor in the “growing gap between rich and poor” countries[3]. Hazard impact is then seen as a reason for underdevelopment. But the nature of an event remains the same wherever it occurs and the impact crosses frontiers. Moreover, California is one the wealthiest region in the USA despite San Andreas Fault. Consequently, physical determinism is not a means of explaining hazard impact. Impact consists in a complex system that involves interactions between Nature and Man. Environmental change exists because of human interference.

   Indeed, there is a change of risk pattern due to human interference. Mankind control of environment (resource use, deforestation) modifies geophysical and biophysical systems. The worldwide urbanisation and industrialisation phenomena intensify land pressure. Thus, constructions and settlements in low valued hazard-prone areas such as floodplains are proliferating. Growing population heightens the impact because the number of people and buildings concerned by risk is larger.

Human interference

   Burton and Kates’s definition of natural hazards links them to human systems: “those elements of the physical environment harmful to Man and caused by forces extraneous to him” (1994)[4]. A natural event that occurs in a desert area is seen as a physical process whereas it is perceived as a “hazard” when its threat concerns humans. Hazard impact is assessed according to human presence, settlements and activities. It is not seen as getting worse in a desert area because men are not involved. Indeed, if a hazard-prone area is inhabited, nobody cares about the impact since its consequences are likely to be low. Moreover, media, scientists and insurers take hazard impact less in consideration when man is not affected by a disaster.

   In addition, men define the degree of hazard impact since they give values to things. So, a hierarchy of the consequences of an extreme event is established. It implies that the statement of hazard impact is not necessary objective. The following diagram shows the severity of an event according to environment, goods or life[5]. Risk is more important concerning life and goods and consequences on the environment are put in the background. So hazard impact is getting worse according to the type of loss considered.

   Relationships between the severity of environmental hazards, probability and risk (source: After Moore, 1983)
Human life seems to be the main criteria of hazard impact. Yet, as far as DCs are concerned, natural event impact is still said to be higher than before even if the number of victims has been reduced over the past decades. Property market value losses, costs of recovery are burning issues. Does it imply that hazard impact is mainly an economic concern? Indeed, when it is asserted that the impact is getting worse, it is often connected with money it requires: insurance and compensation rates, taxes… The cost of damage is said to be low if the property market value is low.

   Moreover, hazard impact is synonymous with the negative idea of “loss” or “cost” when it is getting worse (loss of deaths, money…). Indirect losses such as deaths, disease after an event must be included in a Cost Benefit Analysis. In addition, trauma felt by individuals could be considered as an indirect loss. It is more difficult to estimate since they concern humans’ perception of impact; they are different from economic cost.

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