Green Cay

Green Cay National Wildlife Refuge protects a 14-acre island off the east coast of St. Croix in the U.S. Virgin Islands, established in 1977 specifically to conserve habitat for the critically endangered St. Croix ground lizard. This tiny island harbors the largest remaining natural population of the endemic lizard, which has been extirpated from the main island of St. Croix due to habitat loss and introduced predators. As one of the rarest reptiles in the world, the St. Croix ground lizard exists today only on Green Cay and two other small cays in St. Croix's waters. The refuge is closed to public visitation to protect this highly vulnerable species from disturbance and the potential introduction of predators or invasive species.

The primary conservation focus at Green Cay is the St. Croix ground lizard, a medium-sized brown lizard that was once widespread in coastal areas throughout St. Croix but now survives only on offshore cays. The species was driven to extinction on the main island primarily by introduced mongoose, rats, cats, and dogs that prey on lizards and their eggs. Green Cay supports the largest of the three remaining populations, making its protection critical to species survival. The island also provides habitat for various seabirds that nest or roost on its rocky shores and scrubby vegetation. Hermit crabs and other invertebrates inhabit the terrestrial environment, while the surrounding waters support typical Caribbean reef fish and invertebrate communities.

The vegetation of Green Cay consists primarily of Caribbean dry scrub forest adapted to the small island's limited soil and semi-arid climate. Native trees and shrubs provide essential habitat structure for the St. Croix ground lizard, which depends on adequate vegetation cover for shelter, thermoregulation, and prey habitat. Two invasive grass species have become significant management concerns, rapidly expanding across the island and outcompeting native plants that lizards depend upon. Refuge staff and partners have propagated and planted over 200 native trees to restore habitat quality. The restoration of native vegetation communities is essential for maintaining the lizard population's long-term viability on this tiny island refuge.

Green Cay is composed of volcanic and sedimentary rock that formed as part of the greater Virgin Islands geological complex, representing ancient island arc volcanic activity along the Caribbean plate boundary. The small island rises just a few feet above sea level, with rocky shores and minimal beach development. The geological substrate supports only thin soils that limit vegetation growth but provide the rocky microhabitats that ground lizards utilize for shelter. Surrounding waters are relatively shallow, with reef development on the seafloor around the island. The island's low elevation makes it vulnerable to hurricane storm surge and potential future sea level rise.

Green Cay experiences the tropical maritime climate characteristic of the U.S. Virgin Islands, with warm temperatures year-round moderated by constant trade winds. Annual rainfall averages approximately 45 inches, with distinct wet and dry seasons. The relatively dry climate supports drought-adapted vegetation typical of small Caribbean islands. Hurricanes pose the primary natural disturbance threat, with Hurricanes Irma and Maria in 2017 causing significant damage to vegetation and apparently reintroducing rats to the island. The small island's limited elevation provides no protection from hurricane storm surge, making severe storms potential extinction-level events for the vulnerable lizard population.

Green Cay, like other small islands in the Virgin Islands chain, has limited documented human history due to its small size and lack of freshwater. Indigenous Caribbean peoples certainly knew of the island but likely used it only occasionally for marine resource harvesting. European colonization focused on the larger islands with agricultural potential, leaving small cays relatively undisturbed. The St. Croix ground lizard persisted on Green Cay precisely because the mongoose and other introduced predators never became established on this offshore refuge. Recognition of the cay's importance for lizard conservation came in the twentieth century as the species disappeared from its historical range.

Green Cay National Wildlife Refuge was established in 1977 when the U.S. Fish and Wildlife Service recognized the island's critical importance as habitat for the endangered St. Croix ground lizard. The refuge represents one of several Caribbean island refuges managed by the U.S. Fish and Wildlife Service to protect endemic species found nowhere else. Management has focused on maintaining predator-free conditions and controlling invasive vegetation that degrades lizard habitat. Following the 2017 hurricanes, intensive efforts were undertaken to remove rats that had apparently reached the island during the storms. The refuge demonstrates the challenges of conserving species on tiny islands where even small disturbances can threaten population viability.

Green Cay National Wildlife Refuge is closed to all public visitation to protect the highly endangered St. Croix ground lizard from disturbance. There are no visitor facilities or trails on the island. The refuge's value is entirely ecological, preserving the last stronghold of a species that once ranged throughout St. Croix's coastal areas. For those interested in learning about Caribbean endemic species conservation, educational materials are available through the U.S. Fish and Wildlife Service. Visitors to St. Croix can view Green Cay from a distance at the Green Cay Marina area on the main island. The nearby Green Cay Beach, separate from the refuge, offers accessible beach recreation.

Green Cay National Wildlife Refuge has no visitor facilities and is closed to public access to protect the critically endangered St. Croix ground lizard. The cay can be viewed from the eastern shore of St. Croix near Christiansted, but landing on the island is prohibited without special permit. Information about the refuge and the St. Croix ground lizard conservation program is available through the U.S. Fish and Wildlife Service Caribbean office. Visitors interested in seeing similar Caribbean island ecosystems should explore other public areas on St. Croix, including Buck Island Reef National Monument, which offers accessible marine experiences. St. Croix is accessible by air from major U.S. cities and by ferry from St. Thomas.

Conservation at Green Cay focuses entirely on maintaining conditions that allow the St. Croix ground lizard to survive and reproduce. Invasive predator control is paramount, with immediate response to any detection of rats, mongoose, or other threats. Following the 2017 hurricane damage, the refuge partnered with USDA to eliminate rats that had apparently colonized the island during the storms. Invasive vegetation management involves removing non-native grasses while planting native species that provide appropriate lizard habitat. The refuge provides protection for 14 of the 18 total acres designated as critical habitat for the species. Climate change and sea level rise pose long-term existential threats to this low-lying island refuge. Conservation success will require maintaining predator-free conditions indefinitely while adapting to changing environmental conditions.