拉丁美洲海岸侵蚀的现状英文文献和中文翻译(3)
the Gulf of Mexico, Central America, Colombia and southern Brazil (Figure 2d). Demographic Trends and Economic Growth Latin America faces major challenges in terms of population growth, economic development and the conservation and restoration of its coastal ecosystems. In addition to the climate change impact, coastal areas are also exposed to different environmental conditions that may vary in a very short time scale (e.g., tectonic activity) or over decades (e.g., El Niño-Southern Oscillation - ENSO) or even with unpredictable occurrence (e.g., hurricanes and tsunamis). As a first step to quantify populations and areas of land vulnerable to maritime and coastal phenomena, topographic contour levels can be used to assess exposure. Land elevation is an interesting point for comparing the vulnerability of Latin American coasts with respect to other regions. In this context, a comparison of population growth in low elevation coastal zones (LECZ), defined here as the contiguous low lying areas along the coast that are less than 10 metres above sea level, is made with data from Africa, America, Asia, Europe and Oceania. Using the database generated by CIESIN (2013) and the World Bank (2014) a new database was produced with past population trends and a projection for 2100. The LECZ information was derived from the Shuttle Radar Topography Mission (SRTM), 3 arc second (~90m). In Figure 3 we show demographic trends in Africa, America, Asia, Europe, Oceania and Latin America. In the lower panel, we show the millions of people in LECZ that are at risk in the different regions and the estimated population for 2010 as well as for 2100. African population growth is by far the highest, followed by Latin America. In the top panel we show the evolution of population densities for 2010 and 2100 and the relative area of LECZ and population living in LECZ in 2010 with respect to the total of each region. Excluding Antarctica, the amount of world land in the LECZ was around 1.8%, by 2010, but 10% of the world population lived in these areas, with a density of 288 inhabitants per km2; this is expected to increase to 455 inhabitants per km2 by 2100. Today, 75% of the world population living in LECZ, is concentrated in Asia. It is clear, therefore that most of the land at risk in the world are areas of low elevation in Asia and the Americas. Population density is estimated to be the highest in Africa and Asia. Because population growth is highest in Africa, the population at risk will also increase. The population at risk is lower in the Americas than in Europe but these trends will reverse as the population growth is higher in the Americas, especially in Latin America. The total population living in LECZ in Latin America for 2010 is 5.6% of its total population while the land at risk is around 1.8% of its total land area. Figure 2. Spatial distribution of key coastal ecosystems throughout Latin America (a) coral reefs (Spalding et al., 2001); (b) mangroves (Spalding et al., 2010a; 2010b); (c) seagrasses (Green and Short, 2003) and (d) oceanic and coastal persity (Tittensor et al., 2010a; 2010b). By 2100, the expected population trends in these LECZ are clearly different for each of the continents. For example, from 2000 to 2100 the population is expected to multiply in Africa, America, Asia, Europe and Oceania by 3.32, 1.78, 1.63, 0.90 and 1.31 times, respectively. In contrast, the population of Latin America is likely to multiply by 1.83 times, second to Africa, so while the total population living in Latin America LECZ is lower than the world average, except for Africa, the risk will increase substantially for Latin America compared to most of the world by 2100. A summary of the population and population density for 1990, 2000, 2010 and that expected for 2100 in Latin American countries is presented in Figure 4, as well as the relative and total territory exposed in LECZ. From this figure it can be seen that in terms of population density Haiti and the Dominican Republic are the most vulnerable countries. In Latin America, the countries with most vulnerable populations and land at risk are Brazil, Mexico and Argentina, in descending order. Only Cuba is expected to experience a decrease in coastal population (-12%); the rest of the countries will experience population growth, ranging from 30% (Mexico) to 150% (Costa Rica) between 2010 and 2100. It is interesting to note that Costa Rica, Cuba, Guatemala, Nicaragua and El Salvador are the only countries where the relative population density is lower than the relative LECZ area. Noticeably, tropical cyclones are very frequent in these countries.