Estimates

3.5 Trends in exposure andvulnerabilityDisplacement patterns are determinedby countries’ exposure and vulnerability tonatural hazards. Hazard patterns at theglobal level have not changed significantlyover the relatively short period coveredby our displacement data, but exposureand vulnerability are constantly shifting.Population growth in hazard-proneareas, particularly urban centres indeveloping countriesSignificantly more people are exposedto hazards and affected by disasters todaythan in 1970, and more people arebecoming displaced as a result. The primaryreason for these increases is thatmore vulnerable people are living in areasprone to hazards than ever before.Population exposure data indicateshow many people reside in areas thathave historically experienced floods,storms, landslides, earthquakes or otherhazards. Global exposure data is shownon map 3.1 below. As will be seen in section4, the distribution of displacementclosely mirrors population exposure.This data indicates how many peopleare exposed at a particular point in time,but it does not explain how things came tobe the way they are. For that we need tounderstand the processes and historicalfactors that drive exposure, including economicand population growth, particularlyin urban areas.As shown in table 3.3, the global populationhas grown by 96 per cent since1970. Urban populations have grown twiceas fast (187 per cent increase) and thegrowth rate of urban populations in developingcountries has grown faster still(326 per cent increase). In Haiti, Niger,Nigeria and South Sudan, for example,the urban population has more than doubledsince 2000.Most modern urban centres werefounded centuries ago based on considerationsof defence, agricultural viabilityand transport. These factors drove humansto settle in areas prone to hazards,along coasts and rivers, on floodplains and in seismically active areas.When urban growth in such areas is wellmanaged, the risk of displacement mayincrease only modestly. In many developingcountries, however, urban growthhas been rapid, unplanned and poorlygoverned, leading to high exposure andvulnerability.Map 3.1: Global population exposure to natural hazardsAverage no. of peopleexposed per pixel* No Data1.114019,0002,440,000Note: The UN International Strategy for Disaster Risk Reduction (UNISDR) exposure data refers to the population as of July 2011 with a resolution of 30”(approx. 1 km at equator), which has been adjusted to match with UN official data using World Population Prospects. Source: UNISDR 2015Table 3.3: Global population trends 1970 2014 Percentage increaseWorld population 3.7 billion 7.24 billion 96%Urban population 1.35 billion 3.88 billion 187%Urban population in developing countries 0.68 billion 2.9 billion 326%Source: UN Department of Economic and Social Affairs, 201424 Global Estimates 2015