Leeward Islands xeric scrub

• Category: Forest Biomes.
• Geographic Location: Caribbean Sea.
• Summary: These unique and highly threatened dry woodlands historically covered much of the Caribbean’s Leeward Islands; their endemic species have been compromised by imported exotic types.

This subtropical dry forest and scrub biome once covered much of the Caribbean’s Leeward Islands. In the twenty-first century, they occur as isolated forest remnants following a long history of agricultural encroachment, mining, infrastructure, tourism, and invasion by exotic species. Leeward Island xeric scrub is typically found at low elevations, characterized by low rainfall and an arid climate strongly influenced by the trade wind belt. These forests usually are found along the islands’ coastlines, but they extend well inland on some islands.

This biome covers most of Antigua, Anguilla, Guadeloupe, Saba, St. Martin, St. Bart’s, and the eastern portions of the British and U.S. Virgin Islands. Compared with the neighboring Windward Island xeric scrub type, this biome is relatively large, spanning a greater geographical area.

Biota

The dominant vegetation ranges from herbaceous and woody shrublands to savannas and even woodlands, depending on soil and other localized conditions. The climate is arid throughout. Few remnants of native, pre-colonial vegetation remain in this region following a history of exploitative land use in the Caribbean.

The vegetation form that today characterizes the biomes is a combination of hearty successional native plants, mixed with nonindigenous species that were introduced for food, forage, building materials, or other anthropogenic uses. Various species of Acacia now dominate the former sugarcane and cotton fields, together with copperwoods and other members of family Burseraceae, Pisonia fragrans, Chilean mesquite (Prosopis chilensis), and guava (Psidium guajava).

Although there are several endemic (not found elsewhere) species in the Leeward Islands Xeric Scrub biome, the local biogeography of a large number of relatively proximate small islands is not nearly as diverse as on the Windward Islands. With their history of monocultural plantations as the dominant type of land use, the Leewards have developed what can be termed an overly simplified ecosystem. Even so, there are exceptions, and the protected areas that do retain native vegetation are globally unique and deserve more attention for conservation.

Fauna

The larger islands in the group, such as Guadaloupe, tend to have relatively higher diversity and a higher degree of endemic flora and fauna than smaller islands. The smallest island in the Leeward chain, for example, is Saba, which is home to the Montserrat whistling frog (Eleutherodactylus johnstonei) and an endemic lizard (Anolis sabanus). Larger islands are home to many more.

This biome has no native terrestrial mammals; all native mammals are bats. Antillean fruit-eating bat (Brachyphylla cavernarum) are very common throughout these islands. Other common speices include the velvety free-tailed bat (Molossus molossus), the Brazilian free-tailed bat (Tadarida brasiliensis), and the tree bat (Ardops nichollsi). A growing number of introduced mammals, however, are becoming a threat. Rats, mongooses, goats, pigs, fallow deer, and agouti all wreak havoc on the increasingly rare native flora and fauna.

Conservation Efforts

The conservation status of the biome and its native species varies greatly from island to island and across landscapes. In places like the U.S. Virgin Islands, a network of protected areas extends across nearly one-fifth of the land area, and has protected a significant number of local species.

There is a need to take preventive measures to save the endangered native flora and fauna from continued habitat loss and the introduction of aggressive exotic species. In the wake of its agricultural past and the more recent disruption from tourist resort development, the biodiversity of these islands is in jeopardy. Even plants and animals adapted to the severe arid climate and less-than-ideal soils struggle to flourish as habitats are continually disrupted. Climate change continues to add to these stresses as heavier hurricane damage, coastal soil erosion, extreme heat events, droughts, and saltwater intrusion combine to increase habitat pressure.

Bibliography

Donovan, S. K., and T. A. Jackson. Caribbean Geology: An Introduction. University of the West Indies Publishers Association, 1994.

Harris, D. R. “The Invasion of Oceanic Islands by Alien Plants: An Example from the Leeward Islands, West Indies.” Transactions and Papers, Institute of British Geographers, vol. 31, 1962.

Huie, Jonathan M., et al. "Convergent Patterns of Adaptive Radiation between Island and Mainland Anolis Lizards." Biological Journal of the Linnean Society, vol. 134, no. 1, 2021, pp. 85-110, doi:10.1093/biolinnean/blab072. Accessed 24 Aug. 2022.

Johnson, T. H. Biodiversity and Conservation in the Caribbean: Profiles of Selected Islands. International Council for Bird Preservation, 1988.

"The Leeward Islands Xeric Scrub: A Resilient Ecosystem." Latin America & Caribbean Geographic, 13 Apr. 2024, lacgeo.com/leeward-islands-xeric-scrub. Accessed 20 Oct. 2024.

Malhotra, A., and R. S. Thorpe. Reptiles and Amphibians of the Eastern Caribbean. Macmillan Education, 1999.

Rull, Valentí, and Ana Carolina Carnaval. Neotropical Diversification: Patterns and Processes. Springer, 2020.

Stoffers, A. L. “Dry Coastal Ecosystems of the West Indies.” Ecosystems of the World 2B: Dry Coastal Ecosystems Africa, America, Asia and Oceania, edited by E. Van der Maarel, Elsevier Science Publishers, B.V., 1993.