Windward Islands xeric scrub
The Windward Islands xeric scrub is a unique ecoregion located within the southernmost islands of the Lesser Antilles in the Caribbean Sea. Spanning areas such as western Barbados, northwestern Trinidad and Tobago, Grenada, and parts of Saint Vincent and Saint Lucia, this biome is characterized by its dry-adapted vegetation, including stunted trees, shrubs, and various cacti, which thrive in poor soil conditions. The region experiences a tropical climate with a rainy season primarily in the summer and fall, yet coastal areas often receive significantly less rainfall, contributing to the xeric nature of the scrub.
Biodiversity in this ecoregion is notable, particularly in Barbados, which hosts several endemic species, such as the Barbados tree lizard and the critically endangered Grenada dove. However, the region faces considerable threats, including habitat loss due to extensive coastal development, agriculture, and the introduction of invasive species that disrupt native flora and fauna. The impact of human activity is compounded by climate change, which exacerbates challenges such as rising sea levels. Conservation efforts are increasingly vital to protect this fragile ecosystem and its unique biodiversity from further decline.
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Subject Terms
Windward Islands xeric scrub
Category: Forest Biomes.
Geographic Location: Caribbean Sea.
Summary: This island group is characterized by wet forests and vital but small patches of xeric scrub vegetation.
The Windward Islands are the southernmost islands of the Lesser Antilles (in the West Indies) of the Caribbean Sea. Extending in a chain off the north coast of Venezuela from Grenada to Martinique, the Windward Island group typically includes Trinidad and Tobago and Barbados, which are east of the main archipelago. The extent of the island xeric scrub here is western Barbados and northwestern Trinidad and Tobago, as well as Grenada, the Grenadines, St. Vincent, St. Lucia, Martinique, and Dominica.
The rainy season in this tropical zone generally occurs in the summer and fall months, when hurricanes and tropical storms pass through the region. While annual rainfall in the interior highlands ranges from about 395 inches (1,000 centimeters) in Dominica to 150 inches (375 centimeters) for the lower-elevation mountains in Grenada, coastal areas that comprise much of the xeric scrub habitat of the islands receive lesser amounts, ranging from 40 inches (100 centimeters) on Dominica to 63 inches (160 centimeters) at the southern end of St. Vincent.
The Windward Islands are more geologically active than the Leeward Islands to the north, forming a volcanic arc between continental South America and the Leeward chain. Because of that, the topography is much more pronounced. The steep terrain has the effect of limiting the amount of low-elevation coastal habitat available, and thus further reduces the extent of this ecoregion type.
Flora and Fauna
The vegetation of the Windward Island Xeric Scrub biome is dry-adapted, often featuring stunted trees and shrubs found on poor soils. Typical vegetation consists of cactus and other succulent, spiny shrubs on the west coasts of the larger islands. Plant species include broadleaf lancepod (Lonchocarpus pentaphyllus), logwood (Haematoxylon campechianum), coralberry (Myrsia atrifolia), bastard redwood (Chrysophyllum argenteum), ratwood (Erythroxylum ovatum), and two species of cactus, Opuntia dilenii and Pilosocereusroyeni.
Extensive coastal development in the area, as well as a long history of colonial occupation, have converted much of the native vegetation to agriculture or typical tropical, non-native resort gardens. An additional threat to this biome is the prevalence of numerous invasive species that either outcompete or feed upon the native flora.
Due to its larger size and isolation, Barbados has the higher degree of faunal endemism, that is, species found nowhere else. Notable among the Barbados endemic species is the tree lizard (Anolis extremus), which has adapted well to living in and around human infrastructure. Other notable lizards in the ecoregion are Kentropyx borckiana and Phyllodactylus pulcher. There is one endemic snake, the Barbados racer (Liophis perfuscus), which has a very restricted range and is considered to be endangered by the International Union for Conservation of Nature (IUCN) Red List. Many exotic species of reptiles have been introduced, including pit vipers (Bothrops spp.), which mongooses were subsequently introduced to control. Both have become invasive species in some areas. Barbados has the largest variety of invasive species in the Windward Islands.
The only endemic bird in this biome is the Grenada dove (Leptotila wellsi), which is found in remnant stands of native xeric vegetation. The Grenada dove is considered to be critically endangered (IUCN Red List) because of its extremely small and dispersed population, which has been declining because of habitat loss and fragmentation caused by fire, residential development, roads, and grazing and predation by invasive species.
No native terrestrial mammals are found in this biome; all native mammals are bats. However, a growing number of introduced mammals are becoming a threat to this and other islands in the region, especially rats, mongooses, goats, pigs, and opossums, all of which wreak havoc on increasingly rare native flora and fauna.
Human Impact
Unlike the Leeward Islands, which are predominantly a dry scrub habitat, the Windward Caribbean islands are typically host to wet forests, with small portions of dry scrub where climate is suitable. This means that this ecoregion type is naturally rare, but also that its small size and discrete locations make it very susceptible to disturbance, both human and natural. The dry portions of these islands are also targeted for human settlement and tourism development due to the more favorable climate—so, increasingly, this biome type is being converted by urbanization and resort development.
There is a clear need to take preventive measures to save the endangered native flora and fauna from continued habitat loss and introduction of aggressive exotic species. A long history of tobacco and sugarcane production, together with the more recent conversion of coastal habitats for tourism development, have taken a serious toll on biodiversity in the Caribbean, both generally, and more specifically in naturally rare ecoregions such as the Windward Islands xeric scrub. Due to climate change globally, threats of rising sea levels and associated impacts to the Caribbean islands are likely to become more apparent in the future.
Bibliography
"Barbados." Fauna & Flora International, 2022, www.fauna-flora.org/countries/barbados/. Accessed 17 Aug. 2022.
Carrington, S. Wild Plants of the Eastern Caribbean. London: Macmillan Education, 1998.
Censky, E. J. and H. Kaiser. “The Lesser Antillean Fauna.” In Caribbean Amphibians and Reptiles, edited by Brian I. Crother. London: Academic Press, 1999.
Malhotra, A. and R. S. Thorpe. Reptiles and Amphibians of the Eastern Caribbean. London: Macmillan Education, 1999.
Pararas-Carayannis, George. “Tsunamis of Volcanic Origin in the Lesser Antilles Islands of the Caribbean.” Journal of Tsunami Hazards 23 (2004).
Stoffers, A. L. “Dry Coastal Ecosystems of the West Indies.” In E. Van der Maarel, ed. Ecosystems of the World 2B: Dry Coastal Ecosystems Africa, America, Asia and Oceania. Amsterdam, Netherlands: Elsevier Science Publishers, 1993.