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Desecheo Designed by Alexander Gershenson.

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Desecheo Island Natural Reserve

Desecheo is a small, mountainous island (ca. 1.2 ha) in the Mona Channel, approximately 21 km west of Punta Higüero, Puerto Rico. Offshore rocks, abrupt coastal cliffs, and limited landing sites, combined with a steep, rocky topography, restrict its use by humans. The island lies outside the 100 fathom depth boundary used to define the Puerto Rican Bank. However, it’s considered to be part of the Río Culebrinas Formation, which extends from Desecheo through northwestern Puerto Rico, indicating that the two islands were connected at one time. Desecheo is composed primarily of early Tertiary volcanic sandstones, with volcanic breccia and mudstone, as well as calcareous sandstones and mudstones.

It has been estimated that Desecheo receives about 1020 mm of annual rainfall. A high evaporation rate, combined with rapid runoff due to the steep topography, results in moisture deficiencies which are evident in the vegetation during dry periods. There are no permanent springs, streams or standing water. The vegetation of the island is a mosaic of grassy patches, shrublands, woodlands, and semideciduous forest. The grassy patches and shrublands are on exposed ridges and screes, especially on the northern and northeastern slopes, which face the prevailing winds. The woodlands generally are found on coastal slopes and upper east- and south-facing slopes. The candelabra cacti (Pilosocereus royenii) that use to be in the woodlands were killed by goats and monkeys feeding on them. The semideciduous forest, dominated by Bursera simaruba, occurs in the more mesic valleys and ravines. A mixture of deciduous and evergreen trees is found in the relatively open understory.

Even though the Tainos named the island, there is no evidence of pre-Columbian habitation on Desecheo. During the 1700’s the island was reported to be used by smugglers, who hunted the feral goats. Early naturalists reported it to be a major rookery for seabirds, resulting in its being set aside as a preserve and breeding ground by President Taft in 1912. Despite this protected status, Desecheo has been subject to considerable disturbance and modification. In the 1920’s farming was attempted. There is no information as to the length of time that the settlers were on the island, but their impact is noteworthy. Cattle were pastured in Long Valley and the mouths of both West and Long Valleys were dammed to trap water. The forest on the southwest part of the island next to Puerto de los Botes was cleared for cropland and the red-footed booby rookery was displaced about 500 feet to the east. The former cultivated area reverted to grassland that was maintained by visiting fishermen, who burned it periodically to maintain it as land crab habitat. The burning prevented the reestablishment of trees in the area. In 1937 President Roosevelt transferred the island to the insular government of Puerto Rico for use as a forest and bird pre- serve. With the out-break of World War II, the island was transferred back to the federal government for use as a bombing and gunnery range. It was used as such until 1952. Bomb craters and random fragments of ordnance can still be seen on the island. Between 1952 and 1964 Desecheo was used for survival training by the U.S. Air Force. In 1965 the island was declared as surplus property by the military, and in July 1966 it was acquired by the Department of Health, Education, and Welfare, under whose direction a colony of rhesus macaques was introduced in 1967. In December 1976, Desecheo was transferred back to the U.S. Fish and Wildlife Service, which is now responsible for its management.

Studies of the flora of Desecheo Island can be divided into three periods: 1913-1914, 1967-1970, and 1994-1997. The greatest number of species (137) was collected in Period II. Fifty-two species known from Period I or II were not found in Period III and are assumed extirpated. Seven additional species were lost during Period III. Species turnover and loss were primarily among widespread herbaceous or semiwoody taxa. The high rate of colonization is attributed to Desecheo’s proximity to a source island (Puerto Rico), a high visitation rate by both migratory and pelagic birds, and high levels of predation and disturbance. Species loss between Periods II and III is primarily attributed to overgrazing by feral goats, and to a lesser extent by rhesus macaques, exacerbated by two hurricanes and a prolonged drought. Degradation of the flora is expected to continue unless the exotic animals are eliminated.

Detailed information and citations on the history of Desecheo Island Natural Reserve and a revision of the flora of the island can be accessed on the publication by G.J. Breckon, in the Caribbean Journal of Science, Vol. 36, No. 3-4, 177-209, 2000.:

Flora of Desecheo Island