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BIO 320 Terrestrial Ecosystems
The terrestrial flora and fauna of San Salvador have been greatly influenced by the
island’s geographic location, geologic origin, and climate. The species of plant and animal life
has changed significantly between when Christopher Columbus landed and now. Many of the
plants observed on San Salvador are similar to those typically seen on Caribbean islands because
of similar geologic formation and origin and the currents of the Coriolis Effect favoring islandhopping of plant juveniles and plant seeds via wind or bird gut.
The Bahamian islands formed about 150 million years ago (Sealey, 2006). In warm,
shallow ocean off the southeast coast of North America, carbonate rock precipitated (Sealey,
2006). The weight of the continuous calcium carbonate precipitation caused the crust to subside
far beneath the surface of the ocean (Sealey, 2006). Today, geologists have not been able to
confirm that North American continental crust is beneath the carbonate rock, drilling as far down
as 6000 meters (Sealey, 2006). The Bahamian Platform has been eroded and cut away by wind
and water action, forming islands each consisting of this carbonate “limestone” rock (Sealey,
2006). Flying over and snorkeling around the Bahamian Platform, such as viewing “The Wall”,
made for a fascinating geological connection.
The ecosystem of San Salvador used to be tropical rainforest because one of the first
things that Christopher Columbus saw were large trees that were very green and fruits of diverse
kinds (Toscanelli, 1893). San Salvador became deforested mostly due to overconsumption by
humans (White, 1985). Columbus noted in his journal that the canoes that the natives carved
were of one solid piece of the same wood growing on the island (Toscanelli, 1893). In the early
1800s, plantation owners harvested and sold the mahogany trees for ship building (White, 1985).
Swietenia macrophylla “Big-Leaf Mahogany” is believed to be the first major species to have
colonized San Salvador (White, 1985). S. macrophylla has been observed in various numbers
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BIO 320 Terrestrial Ecosystems
throughout South and Central America and the Caribbean (Langbour, 2010). It makes sense that
seeds and juveniles of this species had migrated from South America towards the Bahamas, via
the Antilles and Caribbean currents.
The North Atlantic Current has helped introduce good, well-drained soil to San Salvador.
Over the past 300 years, large sand storms that originate in Africa become caught in the North
Atlantic Current and blows into the Atlantic Ocean, reaching San Salvador (Evan, 2010). These
incredible geologic events as well as the decayed remnants of S. macrophylla have acted as a
great substrate for the secondary succession of plants. Physical evidence of the sand storms
reaching San Salvador is still observable as a reddish-brown soil that shows up sporadically
along the inland trails to Oyster Pond and Lighthouse Cave. Most of the secondary succession of
plants on San Salvador today is relatively short trees and shrubs, between two and five meters
tall, that took over after the deforestation of S. macrophylla allowed sunlight to reach the ground.
The strong Easterly wind received on San Salvador and the nutrient-poor soil of the tropical
rainforest creates a dry environment for the flora. A couple of cacti, Opuntia bahamana and
Cephalocereus have been able to adapt to the dry environment because San Salvador does not
receive much rainfall. A few small trees and shrubs: Casasia clusiifolia, Bursera simaruba, and
Coccoloba uvifera, along with others, have been successful at becoming established inland.
However, the substrate around the coast of San Salvador, such as North Point, is lithified
dunes. Oolitic limestone cemented together via erosion over time formed lithified dunes around
the island. San Salvadorians call the lithified rock “moon-rock” or “karst” because it becomes
very jagged and perforated by the rain, wind, and waves.
Pioneer species with certain
adaptations to dissolve carbonates to make way for plant roots were the first to colonize the areas
with this type of substrate. Particularly, species of Euphorbia grow from tiny seeds that settle in
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BIO 320 Terrestrial Ecosystems
crevices of the moon-rock and carry out cation exchange of protons within their roots to dissolve
the carbonate rock to make room for root growth (Correll and Correll, 1982). Euphorbia,
Ambrosia hispida, and plants with tiny seeds most likely arrived to San Salvador by wind
(Correll and Correll, 1982). Both A. hispida and Ipomea pes-caprae are good vines and stay low
to the ground to evade strong winds (Correll and Correll, 1982). I. pes-caprae has large seeds
that can float in sea water for long periods of time (Correll and Correll, 1982). Erithalis
fruticosa, C. clusiifolia, and Scaevola plumieri are secondary sere shrubs that probably arrived
by an indigestible fruit and hitchhiking in a bird’s stomach (Correll and Correll, 1982). Plants
like these are good competitors against pioneer species because instead of being vines, they grow
woody stems that are more enduring (Correll and Correll, 1982). Borrichia arborescens has
hairs on its leaves which helps reflect sunlight and trap in water, another adaptation for living in
this type of environment (Correll and Correll, 1982). Other secondary sere shrubs possess small,
waxy, succulent leaves to hold in moisture (i.e. Strumpfia maritima and Rachicallis americana)
(Correll and Correll, 1982). Although it was not as prevalent or diverse as the terrestrial flora,
the terrestrial fauna was intriguing on San Salvador.
Since San Salvador is the easternmost island of the Bahamas, there is not a large diversity
of terrestrial animal species. The most likely method a terrestrial animal would arrive to San
Salvador is by rafting. Island-hopping with the Antilles Current is how Cyclura rileyi rileyi was
believed to have arrived to San Salvador (Hayes, 2003). However, the isolation of San Salvador
does not provide an easy path for C. r. rileyi to arrive and maintain its population (Hayes, 2003).
C. r. rileyi speciated when it migrated to San Salvador (Gicca, 1980). This particular subspecies
is endangered and can only be found in small populations of less than 30 on the northern and
southern cays off the coast of San Salvador (namely, Green Cay, Man Head Cay, High Cay, and
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BIO 320 Terrestrial Ecosystems
Low Cay) (Gicca, 1980). C. uvifera serves as food and shelter from bird predators and the heat
on the cays (Gicca, 1980). Just as scarce as the population of C. r. rileyi is, only a few invasive
species of mammals have been scouted on San Salvador (e.g. Sus scrofa “wild boar”, Canis
lupus “dog”, and Rattus norvegicus “rat”) because their only way of introduction was by human
transport, either intentionally or not (Pagad, 2013). More typical animals seen on San Salvador
than mammals were invertebrates. Terrestrial crustacea arrived by rafting; most commonly
found are Cardisoma, Gecarcinus, Ocypode quadrata, Coenobita (Diehl, 1988). Terrestrial
gastropod molluscs, such as Cerion watlingense, Hemitrochus varians, Melampus coffeus, and
Nodolittorina, were observed attached to and feeding on certain terrestrial plants like R.
americana and Cephalocereus (Diehl, 1988). These gastropods probably were introduced to San
Salvador by the same mechanism as the terrestrial crustacea; however, it is also possible that
they rafted on their host plants.
Probably the only indigenous animal to San Salvador in
Lighthouse Cave is Erophylla sezekorni “buffy flower bat”, however, other species of bat have
been sighted on the island, Macrotus waterhousii and Natalus tumidifrons (Anderson, 1990).
The common bird species of San Salvador, particularly observed feeding while snorkeling at
Man Head Cay, is Sula leucogaster “Brown Booby”. It was fascinating and comical to watch
them dive into the water to catch small fish.
In conclusion, the seclusion and geology of San Salvador has influenced the diversity of
the flora and fauna. The terrestrial flora and fauna have had to endure long and quite intolerable
disseminations in order to settle, colonize, and succeed on the island of San Salvador. The
number and types of species has drastically changed since the arrival of Christopher Columbus.
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Works Cited
Anderson, K.W. 1990. Bats of San Salvador Island. Bahamian Field Station Occasional Paper.
4 pp.
Correll, D.S. and H.B. Correll. 1982. Flora of the Bahama Archipelago. A.R. Gantner Verlag:
Vaduz. 1692 pp.
Diehl, F. A., D. Mellon, Jr., R. H. Garrett, and N. Elliott. 1988. A Field Guide to the
Invertebrates of San Salvador. Bahamian Field Station, San Salvador, Bahamas. 105 pp.
(out of print).
Gicca, Diderot. 1980. The Status and Distribution of Cyclura r. rileyi (Reptilia: Iguanadiae): A
Bahamian Rock Iguana. Caribbean Journal of Science, Volume 16. pp. 1-4.
Hayes, William K. 2003. Can San Salvador’s Iguanas and Seabirds Be Saved? Bahamas
Journal of Science, Volume 11, No. 1. pp. 2-8.
Littler, D. S., M. M. Littler, K. E. Bucher, and J. N. Norris. 1989. Marine Plants of the
Caribbean. Smithsonian Institution. Airlife Publishing, Shrewsbury. England. 263 pp.
(out of print)
Pagad, Shyama. 2013. Global Invasive Species Database. Invasive Species Specialist Group.
Retrieved from: http://www.issg.org/database/welcome/
Sealey, N. 2006. Bahamian landscapes. 3rd ed. Media Publishing, Nassau, Bahamas.
Introduction (pp. viii-ix); Chapter 1 (pp. 1-13).
Toscanelli, Paolo del Pozzo. 1893. The Journal of Christopher Columbus. Hakluyt Society. 259
pp. (ebook).
White, V. 1985. The Outermost Island: An Oral History of San Salvador, The Bahamas.
Bahamian Field Station, San Salvador, Bahamas. 77 pp. (out of print).