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273 ≋ matic change on sea level. In turn, many of these changes are accelerated by human activities, which intentionally or unintentionally accentuate this indirect greenhousegas effect on the coastal system (Titus 1987) and lead to a rise in the mean sea level. The environmental changes and modifications in coasts are evident in specific regions, such as low sandybeach coasts, including the associated coastal and deltaic plains (Ortiz Pérez and Gutiérrez 1985; Ortiz Pérez and Benítez 1996). The marine erosion of beaches at estuarine mouths, bars, and barrier islands is a result of these changes, which become evident by the retreat of the coastline toward the interior of the continental portion. The consequences of this phenomenon are erosion, flooding , and salinization of nearby soil, surface waters, and groundwater; in turn, these influence the structural characteristics and spatial distribution of the associated ecosystems (Pannier 1992). Separately, the purpose of land use is altered, which directly affects the regional economy, which on occasion leads to the abandonment of land and the exodus to nearby, currently nonvulnerable areas. Island territories are also affected by variations in sea level and risk serious and total modifications of their coastal ecosystems to a greater extent compared to continental systems. As an example, in the insular Caribbean, specifically in Cuba, the largest of the Greater Antilles and its 4 peripheral archipelagos, vulnerability is becoming an increasing concern given that threatened lowlands and wetlands comprise 6000 km2 (5.4% of the country’s total area) with 440 beaches and 380,000 ha of mangrove forA number of coastal settings are present in Mexico, both in the Pacific Ocean, to the west, and in the Gulf of Mexico and the Caribbean Sea to the east, comprising a total length of 10,554 km of frontal coast open to the sea. With the coastal lagoons and islands, this totals about 24,945 km of coastline (Ortiz Pérez and De La Lanza 2006). These shorelines, to a greater or lesser extent, are subject to the rise in mean sea level, which will cause mostly irreversible modifications in coastal genesis and morphology, the expression of natural ecosystem landscapes, and substantial socioeconomic effects in local populations. Mexico’s Gulf of Mexico coastline extends approximately 2775 km with an additional 4900 km of shoreline along inland water bodies that are protected by low sandy barriers. The coastal plain varies from 15 to 30 km wide and is cut by more than 25 important rivers and 23 lagoons of variable size. The terrestrial geomorphic processes , mainly fluvial, lacustrine, and swamp, as well as the littoral morphodynamics, have resulted in a complex interactive system of different transitional types among barrier islands, fluvial mouths, deltas, and estuaries that are closely linked to flood plains, lagoons, salt marshes associated with mangroves, marshes, and mangrove forests (Ortiz Pérez et al. 1996). This complex, transitional land–sea structure determines the occurrence of important geomorphological changes of variable degrees in Mexico’s littoral Gulf coasts, at different spatial and timescales (Psuty 1965, 1967; Ortiz Pérez 1988; Ortiz Pérez and Espinosa 1991; Ortiz Pérez 1992), derived from the influence of global cli15 Sea-Level Rise and Vulnerability of Coastal Lowlands in the Mexican Areas of the Gulf of Mexico and the Caribbean Sea Mario A. Ortiz Pérez, Ana P. Méndez Linares, and José R. Hernández Santana 274 ~ Pérez, Linares, and Santana on the coast during the Quaternary restrain the direct interaction of these fluvial–lagoon processes with the littoral abrasive–cumulative processes. In this sense, changes in the coastline may have global, regional, and local effects (Duke et al. 1998), while the dynamic status in the functioning of ecosystems varies on short timescales; for example, daily or intra-daily scales such as the contrast of daily (day–night) variation, tidal cycle, storm rainfall, swells, and wind, factors which are mostly meteorological and that produce intense changes in coastal dynamics over a short period of time and occur with variable magnitude (Acevedo 1997). These atmospheric dynamics become more intense and complicated in the Gulf of Mexico and northern Caribbean Sea due to the influence of hurricanes (June–October), the energy of which determines broad variations and even irreversible changes in coastal areas. In the case of cold fronts, up to 15–20 nortes occur per year between October and March, with associated wind velocities reaching 100 km/h and higher (Ortiz Pérez et al. 1996) and leading to waves between...

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