While the first two climatic hazards mentioned do not foreshadow massive population displacements due to climate change, the potential for migration when linked to an increase in sea level is considerable. Contrary to hurricanes, rain, and drought, this phenomenon is virtually irreversible and manifests itself over a long period of time. This could make migration the only possible option for the population affected. The localization of the consequences of rising sea levels is a relatively easy task because the configuration of coastlines, their altitude, and population are well known and thus easy to map. Hence, it is possible to calculate, on a global scale, the number of persons living in low-elevation coastal zones and threatened by either rising water levels, higher tides, or farther-reaching waves. Low-elevation coastal zones are defined as situated at an altitude of less than 33 ft. (10 m.). Even though these zones account for only 2.2 percent of dry land, they are presently home for 10.5 percent of the world's population, some 600 million people, of whom more than two-thirds live in Asia, and nearly a half in the poorest countries of the world.
It would be an exaggeration, however, to consider that these hundreds of millions of people are all potential migrants in a near future. The latest report of the IPCC evokes, of course, the possible melting of Greenland ice cover and the consequent 23 ft. (7 m.) rise in sea level, but this would occur over several thousand years. Of more concern is the scenario of thermic expansion of the oceans. According to a future CO2 emission estimate based on continuing economic growth, but with a moderation of fossil fuel use, there would be an increase of 1 to 2.6 ft. (0.3 to 0.8 m.) of the oceans by 2300. On this basis, it seems reasonable to consider populations living at an altitude of less than one meter as being directly vulnerable by the next century. A study commissioned within the framework of the Stern Report gives a considerable figure of 146 million people for this group. Mainly situated in the major rivers' deltas and estuaries, the flood zones are particularly populated in south Asia (Indus and Ganges-Brahmaputra) and east Asia (Mekong, Yangtze, Pearl River). These two regions account for 75 percent of the population at risk. Certain Pacific states such as Tuvalu or Kiribati are, in the shortterm, among the most threatened, as they are situated only centimeters above water. Although far less populated, they nevertheless have inhabitants numbering several thousand persons.
The increase in sea levels is the greatest direct threat for numerous populations. Contrary to hurricanes and droughts, the localization of potential victims is ascertainable. If no measure of moderation is taken and if no effort is made to protect the groups at risk, then they will have no alternative but to emigrate.
Climate changes can generate migration flows. Global warming could, in particular, lead to major forced displacements. The latter will result principally from rising sea levels, but will only progressively manifest themselves over the forthcoming centuries, with the exception of the flooding of certain islands. The increase in droughts and meteorological disasters predicted by climatic models will also have impacts in terms of migrations, but these will remain regional and shortterm, and are at present difficult to estimate.
Existing research shows that due to the number of factors involved, no climatic hazards inevitably result in migrations. Many authors note that even if disasters become more frequent in the future, political efforts and measures of protection will be able to lessen the need to emigrate, provided that the necessary financial means are made available. Even rising sea levels could be partially counteracted by the erection of dikes or the filling in of threatened zones. The question of what kind of international system of burden-sharing and protection to put in place to face these challenges remains unanswered, and is all the more important because of the clear responsibility of rich countries for global warming. Bangladesh, for example, contributes only 0.14 percent of global CO2 emission, but counts hundreds of thousands of people at risk of increased flooding.
sEE ALsO: Alliance of Small Island States (AOIS); Bangladesh; Climate Change, Effects; Desertification; Developing Countries; Drought; Economics, Impact from Climate Change; Floods; Impacts of Global Warming; Refugees, Environmental.
bibliography. Stephen Castles, "Environmental Change and Forced Migration: Making Sense of the Debate," New Issues in Refugee Research, UNHCR Working Paper (v.70, 2002); Nicholas Stern, The Economics of Climate Change (Cambridge University Press, 2007); J.D. Unruh, M.S. Krol, and Nurit Kliot, Environmental Change and Its Implications for Population Migration (Kluwer Academic Publisher, 2004).
ETIENNE PlGUET University of Neuchatel
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