The Cayman Islands has two main ecoregions that occur entirely or partly within its borders:
The Cayman Islands (Grand Cayman, Little Cayman and Cayman Brac) are emergent limestone bluffs situated along a submarine ridge that runs westward from the Sierra Maestra range in southern Cuba. Grand Cayman is the largest of the group at 35 kilometers (km) long and up to 14 km wide, however, there is a large lagoon in the northern section that gives the island an irregular shape, as if a giant bite has been taken out of the northwestern end. Cayman Brac is the tallest island in the group, rising to a height of 43 meters (m) on the eastern end where sheer cliffs drop into the sea. Little Cayman is the smallest of the three islands, at only 14 km long and a maximum height of merely 12 m above sea level. Grand Cayman lies approximately 700 km south of Miami, and 200 km from both Cuba and Jamaica. The lesser islands are located about 130 km northwest of Grand Cayman, and lie 7 km apart. All three islands were uplifted from the ocean floor approximately 10 million years ago and have apparently never been connected to adjacent land masses. The Cayman group is subject to strong trade winds and has a humid tropical climate with a distinct wet season from May-November.
This ecoregion is distributed among the Cayman Islands, specifically areas on Grand Cayman Island, Little Cayman Island, and all of Cayman Brac Island. The three Cayman Islands are located at the western end of the Greater Antilles in the Caribbean. Their combined land area is 259 kilometers squared (km2). Most of the population of the Caymans lives on Grand Cayman where development typical to the Caribbean has rapidly altered the island’s environment. All three Cayman Islands are flat limestone with low elevation. The human populations of the three islands differ considerably with fewer than 100 on Little Cayman and less than 2,000 on Cayman Brac. This is reflected in the varying degrees to which the islands' environments have been changed. Little Cayman is the least disturbed of the group, with almost all of the interior untouched as of 1980. In contrast, the rapid development of Grand Cayman has resulted in degradation and alteration of most of the natural habitats. Clearing of natural woodland and thicket for roads, housing, tourism and agriculture continue to be the most significant pressures on this ecoregion.
The dry woodlands of Grand Cayman and Cayman Brac have suffered a long history of disturbance and timber extraction. The tropical hardwoods of this ecoregion regenerate and grow very slowly. Consequently, the effects of logging early in this century are clearly visible. In central and eastern Grand Cayman and on Cayman Brac, the woodlands form a complex mosaic of secondary growth at various stages. Primary vegetation is restricted to the most inaccessible areas. Little Cayman is still dominated by primary vegetation. The low elevation dry woodlands on all three islands of the Caymans are of regional importance for biodiversity conservation.
The Critically Endangered Lesser Caymans iguana is native to two islands: Cayman Brac and Little Cayman. This captive specimen was photographed in Hope Gardens, Kingston, Jamaica. Source: Tim Ross/Wikimedia Commons. The National Trust, a statutory, non-governmental organization, overseas important natural areas such as the Salina Reserve and the Brac Parrot Reserve. The Trust owns more than 310 hectares of natural woodland and bluff habitat on Grand Cayman and has initiated a captive breeding program for the blue Grand Cayman iguana, which is listed as endangered by the U.S. Fish and Wildlife Service. The Trust is also conducting research programs assessing the status of the threatened rock iguana and the native parrots. Despite these initiatives, there is a continued need for increased species management, predator control, and habitat preservation.
In 1989 the government gave 257 ha of land (Salina Reserve) to the National Trust. In December 1991 ownership of a 40 hectares woodland site on Cayman Brac, important as a nesting area for the Cayman Brac Parrot, was transferred to the National Trust by The Nature Conservancy (USA) and is now titled Brac Parrot Reserve. See: Protected areas of Cayman Islands
The Cayman Islands xeric scrub ecoregion is a low elevation very disturbed ecosystem in the Caribbean basin. The Cayman Islands are a small group of low-lying Caribbean islands that serve as an important stop-over and wintering site for migratory land birds. A humid tropical climate provides for twenty-six species of herpetofauna, seventy-five percent of these are endemic to this ecoregion. Little of the original habitat remains. Introduced animals, such as domestic dogs and cats, and rats, pose the greatest threat to the native wildlife. The extinction of several endemic mammals are attributed to these invasive species.
Evergreen thicket dominates the eastern sections of Grand Cayman, and is found on the northern slope of Little Cayman and on higher ground on Cayman Brac. The thicket has a discontinuous, two-storeyed canopy with occasional emergents. Dominant species include red birch (Bursera simaruba), Swietenia mahagoni, Picrodendron baccatum, Sideroxylon salicifolium, Calyptranthes pallens, and Chionanthus caymanensis. Palms (Coccothrinax proctorii and Thrinax radiata) are common and climbing cacti (Selenicereus) are well represented.
The two major threats to native species in the Caymans are habitat loss and introduced species. Very little native woodland remains in the Cayman Islands, as most of the large trees have been felled for timber and for fuel. The few remaining stands of trees need to be protected from future logging. In addition to the loss of native woodland, native evergreen thickets on Grand Cayman are now being replaced by logwood (Haematoxylum campechianum). This deliberately introduced species spreads by stolons, and will probably continue to invade native thickets and displace native plants.
Recent declines in the populations of iguanas and other reptiles throughout the Cayman Islands have been linked to the increased number of domestic cats and dogs on the islands, and introduced rats (Rattus rattus and Rattus norvegicus) have been implicated in the extinction of at least 2 of the 5 native non-volant land mammals, particularly the two endemic Nesophontes species. Introduced mosquitoes do not pose any obvious threat to native species in the Caymans, nor do they pose a significant health threat, but it is worth noting their success in the islands. Mosquitoes were accidentally introduced sometime soon after European settlement of the islands, and their populations subsequently exploded. In the 1970’s, mosquito density in the Cayman Islands was more than twice the maximum recorded anywhere in the United States; in a standard measure of mosquito density, one researcher recorded a total of 600 bites per minute on one arm. Mosquito populations have been greatly reduced in recent years through an intensive control program and regular aerial spraying.
Scientists at the World Wildlife Fund (WWF), have established a classification system that divides the world in 867 terrestrial ecoregions, 426 freshwater ecoregions and 229 marine ecoregions that reflect the distribution of a broad range of fauna and flora across the entire planet.
Ecoregions are areas that:
 share a large majority of their species and ecological dynamics;
 share similar environmental conditions; and,
 interact ecologically in ways that are critical for their long-term persistence.