The island Puerto Rico is the smallest of the Greater Antilles. Measuring roughly 180 x 60 km, it is situated in the eastern Caribbean at 18o15’N and 66o30’W (figure 1.1). Apart from the coastal plains on the north and south coast, the island is mountainous, with the highest peaks in the central and north-eastern part of the island rising to elevations of 1000-1300 ma:s:l: (figure 1.2).