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Trinidad and Tobago's Natural History, In Brief

Introduction

Trinidad and Tobago, located 60°–61° west longitude and 10° to 11° north latitude, is situated within ten miles of the northeastern Venezuelan coast. Its natural history is closely tied to that of the South American continent which contributed to its wide wildlife diversity, including its population of hummingbirds. The islands were once united with the mainland around 1.8 Ma [1] (during the early Pleistocene Epoch)i, when sea levels were 100m (about 300 ft) lower worldwide and glaciers tied up water in ice sheets 1,500 to 3,000 metres thick [2]. There is high confidence that Trinidadˈs land, for the latest, surfaced 22 Maii, during the Mioceneiii or earlier 30 Ma, in the Middle Oligoceneiv. Limestone formations, fossilized shells in various areas, especially in the central mountains, of deep water ammonites (a coiled chambered extinct molluscs) from Hollis Reservoir are testaments to its underwater sojourn [1].

Trinidad and Tobagoˈs Geologic History

The islands earlier geologic history involves the eastward movement of a submerged Caribbean Plate, after the breakup of Pangaeav, from the eastern Pacific, displacing a proto-Caribbean plate and bulldozing volcanic rock—the basalt rock, a type of solidified lava, of San Souci in Trinidadˈs Northern Range and in Tobago—from a mid-ocean ridge in the proto-Caribbean 106 Ma. The ridge was situated between the plates of North and South America. It later arrived at its current day location. From its Pacific origin and during its traversal the plate and its vicinity experienced deposition in deep and shallow water, during the Jurassicvi and Cretaceousvii epochs. More recent sedimentation, during the Pleistocene to the Holoceneviii is from the Orinoco River [1] in current day Venezuela.

The sea between the twin islands and the continent dried up as alluded to earlier; and they became part of South America. The plants and animals of South America migrated to them. The hummingbirds, starting 5 million years ago, during the Plioceneix Epoch, invaded the Caribbean islands from South America, in several waves [3]. Then, about 10–13,000 years ago, at the end of the Pleistocene, the sea rose to its current levels after the last ice age, and the islands became separated from the mainland. After which they retained the flora and fauna of South America, and thus possessing a diversity of life greater than otherwise.

Geological Time Scale - Trinidad and Tobago
Era Mesozoic Cenozoic
Period Jurassic Cretaceous Paleogene Neogene Quaternary
Epoch L M U L U Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene
Ma 201.3-145 145-66 66-56 56-33.9 33.9-23.03 23.03-5.332 5.332-2.588 2.588-0.0117 0.0117-0
Era (100s of million years)
Epoch (10s of millions of years)
MA (Million Years Ago)
U - Upper
M - Middle
L - Lower

Trinidad and Tobago's Physical Characteristics

Rectangular or booth shaped Trinidad is 4,768 sq.km (1,841 sq. mi), roughly 80km (50mi) by 59km. The island's highest peak, Aripo, 936.91m (3,084 ft), and second highest, El Tucuche, 936m (3,081ft) are in the Northern Range, which runs from west to east, and considered to be an extension of the Andes chain[4]. Trinidad's Central Range, which rises to little more than 330m (1,000ft), at Mt. Tamana, crosses Trinidad from the south west to the north east; a lower range, in the south, is dominated by the Trinity Hills 325m (1,069.25 ft).

The island of Tobago is located at 11° 9' N, latitude, and 60° 40' W, approximately 30 kilometers (19 miles) to the northeast of the island of Trinidad; its land area is just about 300 km2 (116 miles2); and its highest point is over 576 metres (1,890ft) on the Main Ridge, of volcanic origin, which runs lengthwise from the northeast to the south west.

Other key landscape features across the islands, i.e., ecosystem diversity, include evergreen forests, semi-evergreen forests, deciduous seasonal forests, montane forests, dry forests, palm forests, savannahs, swamps and mountains. There are swamps, the Nariva in the southeast, Caroni, in west central, Oropuche, south of San Fernando in the south of Trinidad and in Tobago, Bon Accord lagoon. An edaphicx savannah, i.e., the growth of the vegetation is restricted by a shallow layer of clay, the Aripo Savannah, is located in north central Trinidad, east of Piarco International Airport and west of the town of Sangre Grande.

Trinidad and Tobago's Climate

Its climate is supportive of a wide biota as annual rainfall in Trinidad varies from 3,880mm to a low of 1,200mm. The higher rainfall occurs over the Northern Range and hills of the Central Range. The lowest rainfall is recorded on the southwestern peninsula and on the offshore islands off the northwestern peninsula. Tobago experiences a rainfall high of 2,880mm on the highest parts of the main ridge and a low of 1,400mm in the southwestern corner of the island. Much of the rainfall in both islands occurs during the rainy season, from June to the end of the year. Average temperatures range from 25°C in January to 27°C in May. Daily temperature variations average 7°C; highs in August and September rises to 35°C while lows in January can reach 18° C, but 16°C at higher elevations and in valleys.

Trinidad and Tobagoˈs Flora and Fauna

Its flora and fauna, although impoverished in comparison, to South America is endowed with 486 bird species, many unique and rare, and includes many species of the hummingbird; Tobago has half the bird species of Trinidad, 22 of which are found there only; there are 617 species of butterflies, 123 occur on Tobago; 2,500 species of flora; and 670 species of vertebrate fauna[5], e.g., manatee, armadillo, anteater, sloth, howler monkey, capuchin monkey, porcupine, agouti, bats, whales, racoon, ocelot, tyra, river otter, peccary, deer, &c. Trinidad and Tobagoˈs seed producing plants (phanerogamsxi or phenogamae) around 1,982, with around 214 endemic, have an endemic rate or 11% whilst in the Lessor Antillesxii, nearby islands, indigenous species do not surpass 1,400, with the highest level of endemism under 30, for any island and the rate of endemism for any of those islands being less than 2% [6].

In addition, the Orinoco River has a continuing influence on the Trinidad and Tobago environment [5] and wildlife through its contribution of silt and fresh water that lowers the salinity, increases the brackishness, and lowers the clarity of the sea water on the east and southern coasts; as well as, by reintroducing flora and fauna as part of flotsam and jetsam from the South American mainland's interior.

The Role of South America and the Andes in Trinidad and Tobagoˈs Wildlife Diversity

So, whence the South American diversity? In modern times political and cultural factors play a part and have played a part in biota distribution and endemism. Formerly widespread species have suffered restrictions to smaller areasxiii and some species have, relatively, newly arisen, i.e., diverged and are reproductively isolatedxiv. But South America's biota and endemism are mainly due to physical, climatic, and biological factors. After separation from Pangaea, long periods of isolation followed by communication with North America, via the Isthmus of Panama, c. 3.1 million years ago, have played their parts. And, Pleistocene Climatic fluctuations had their effects on distribution and evolution of neotropical biota as there were major changes in vegetation associated with Pleistocene glaciations[7]. Note that the ancestral hummingbird migrated through Asia to North America, via the Bering Strait to Alaska, thence to South America 22 million years ago,[3] during the early Miocene epoch.

The world's longest continental mountain range, and 200 to 700 kilometers wide, the massive Andes Cordillerasxv, have primary influence on plant and animal evolution in South America due to its varied habitat, for example, with ample ecological niches, it had a role in the speciation of over a hundred hummingbird species[3]. The Andes average height is 4,000m, 50 volcanoes rise above 6,000m, and its highest peak, Mt. Aconcagua, rise to an elevation of 6,962m (22,841ft). The range runs the length of the continent from 12°N in northern Venezuela to 55° south Latitude. These elevations and latitudinal ranges give rise to varied climatic conditions; producing cool rainy conditions in the south; dry central Andes; warm and rainy northern Andes; and with many mountains snow-capped and with snowlines varying from 4,500m to 5,200m dropping to 300m in the Tierra Del Fuego.

The Andes induces heavier rainfall patterns to the forest to its east and less copious amount to its west, in the south. The Andes increases in aridity south from the equator. The northern Andes have cloud forest on both the western and eastern slopes. Tutunendo in the Choco region of Colombia [8], with 11,770 mm of annual precipitation, along the west coast of South America is one of the wettest places on earth—the wettest reputedly located in India [9]. And it has uniquely extensive equatorial temperate and cold climates. There is a strong correlation of plant community diversity with precipitation—wetter forests are generally more botanically diverse. Botanical diversity influences fauna.

These Andes conditions give rise to explosive speciation in cloud forests and speciation associated with habitat specialization. And, so, the neotropical region of south America is estimated to have 90–100,000 species of plants, i.e., twice to almost three times that of tropical Africa or Australasia. About 30,000 species of vascular plants live in the Andes, roughly half are endemic and with respect to fauna, the Andes has nearly 3,500 species of which about two-thirds are endemic; there are almost 600 species of mammals (15% endemic) 1,700 species of birds (⅓ endemic), 600 species of reptiles (45% endemic) and almost 400 species of fish (about ⅓ endemic).

So, Trinidad and Tobagoˈs wildlife diversity is South American. Its late appearance in geological time is insufficient to give rise to its variety of life forms. Its habitat range essential for life form diversification, though large in comparison to the other islands of the Lessor Antilles, is miniscule when compared to the habitat ranges of the Andes and South America as a whole. It has a low rate of endemism, as shown in seed plants, though larger than the islands of the Lessor Antilles. Its past physical connection to the continent and the continuing influence of the Orinoco River explain the commonality of flora and fauna. And, as an example, the ancestor of the modern day hummingbird can be traced back to Europe via the Americas.


Notes

i The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's recent period of repeated glaciations.

ii Millions of years ago.

iii The Miocene, in the geologic timescale, extended from about 23.03 to 5.332 million years ago. The apes arose and diversified during the Miocene epoch, becoming widespread in the Old World. In fact, by the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path.

iv The Oligocene epoch, in the geologic timescale, extended from 33.9 to 23 million years ago. It is a time scarce of modern mammalian species after prolific evolution during the Ecocene. During this time grasslands expand globally and tropical broad leaf forests are confined to the equatorial belt.

v Pangaea was a supercontinent in the Southern Hemisphere that existed 300 million years ago, during the late Paleozoic and early Mesozoic eras, that began breaking up 100 million years later.

vi The Jurassic, named after the Jura Mountains of the Alps, is the epoch, in the geologic timescale that extended approximately from 201 to 145 million years ago. During this period Pangaea, the supercontinent, had already separated into two landmasses, the first birds evolved from a branch of the dinosaurs and reptiles were dominant on land and were present in the sea.

vii The Cretaceous (from Latin creta meaning 'chalk', first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris basin and named for the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates)) is the epoch that spanned 79 million years from approximately 145 to 66 million years ago. It was a period with a relatively warm climate, changing sea levels that created many shallow inland seas populated with now-extinct marine reptiles, ammonites, and rudists; dinosaurs continued to dominate on land. At this same time, new groups of mammals and birds, as well as flowering plants, appeared. The epoch ended with a large mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out.

viii The Holocene, i.e., from the Greek meaning wholly new, epoch is roughly the preceding 10,000 years from the present and embraces the development of major civilizations, urbanization, their recorded history, and impact on the environment.

ix The Pliocene, from the Greek, meaning a furtherance of the recent, as then was applicable to the modern marine mollusc, is the period in the geologic timescale that extended from, approximately, 5.333 to 2.58 million years ago. Hummingbirds colonized the Caribbean islands from South America during this epoch.

x Poor soil condition is the determining factor on vegetation rather than climate.

xi Phanerogams are seed plants or plants that produce seeds, which are a subset of land plants.

xii The Lessor Antilles are: Leeward Islands: Virgin Islands: St. Thomas: St. John, St. Croix, Water Island, Tortola, Virgin Gorda, Anegada, Jost Van Dyke; Anguilla, Sint Maarten, Saint Martin, Saint-Barthélemy, Saba, Sint Eustatius, Saint Kitts and Nevis, Antigua and Barbuda, Redonda (Antigua and Barbuda), Montserrat, Guadeloupe, La Désirade, Marie-Galante, and les Saintes archipelago; Windward Islands: Dominica, Martinique, Saint Lucia, Barbados, St. Vincent and the Grenadines, Carriacou and Petite Martinique (Grenada), Grenada, and, Trinidad and Tobago; Leeward Antilles: Aruba, Curaçao, and Bonaire;
   The Lessor Antilles in consideration are: Leeward Islands: Anguilla, Sint Maarten, Saint-Barthélemy, Saba, Sint Eustatius, Saint Kitts and Nevis, Antigua and Barbuda, Redonda (Antigua and Barbuda), Montserrat, Guadeloupe; Windward Islands: Dominica, Martinique, Saint Lucia, Barbados, St. Vincent and the Grenadines, Grenada, and, Trinidad and Tobago; and Leeward Antilles: Aruba, Curaçao, and Bonaire.

xiii Known as Paleoendimism.

xiv Know as Neoendimism.

xv A Cordillera, derived from cordilla, the diminutive of cuerda, or cord in Spanish, is an extended chain of mountains.


Works Cited

1. Geological events influencing Natural Vegetation in Trinidad. COMEAU, Paul L. St. Augustine : National Herbarium of Trinidad and Tobago, 1991, Living World: Journal of the Trinidad and Tobago field Naturalists' Club.

2. ROOKS, Courtenay and Gregor BARCLAY. Natural History of Trinidad and Tobago.[book auth.] Basil A. REID. [ed.] Basil A. REID. Caribbean Heritage. St. Augustine : University of the West Indies Press, 2012.

3. SANDERS, Robert. Hummingbird evolution soared after they invaded South America 22 million years ago. UC Berkley News Center. [Online] 3 April 2014. [Cited: 2 May 2014.] http://newscenter.berkeley.edu/2014/04/03/hummingbird-evolution-soared-after-invading-south-america-22-million-years-ago/.

4. LIDDLE, Ralph A. The Geology of Venezuela and Trinidad. s.l.: J. P. McGowan, 1928.

5. KENNY, Julien. View from the Ridge: Exploring the Natural History of Trinidad and Tobago. Port of Spain: Prospect Press, 2000. ISBN 9789769505704.

6. GENTRY, Alwyn H., Dr. CPD: Caribbean Islands overview. Department of Botany, National Museum of Natural History, Smithsonian Institution. [Online] Centres of Plant Diversity (CPD) project, 1993. http://botany.si.edu/projects/cpd/sa/sa-i.htm.

7. —. CPD: South America overview. Department of Botany, National Museum of Natural History, Smithsonian Institution. [Online] Centres of Plant Diversity (CPD) project, 1993.] http://botany.si.edu/projects/cpd/sa/sa-vi.htm.

8. BURT, Christopher C. Weather Extremes: The Wettest Places in the World. Weather Underground. [Online] The Weather Channel, LLC, 22 May 2012. [Cited: 9 October 2014.] www.wunderground.com/blog/weatherhistorian/the-wettest-places-in-the-world#.

9. PHILLIP, A. J. The Tribune, Chandigarh, India - Main News. The Tribune: Online Edition. [Online] H.K. Dua, 24 August 2003. [Cited: 9 October 2014.] www.tribuneindia.com/2003/20030824/main8.htm.


Author: Richard Thomas Google+ has been a wildlife enthusiast and birdwatcher since his scouting days, in his youth, at Queenˈs Royal College, Trinidad and Tobago. Whence, he took particular pleasure in hiking nature trails and observing, and, noting flora and fauna, principally birds. He developed a specific interest in hummingbirds because of their flying/hovering abilities, resplendent colours and enchanting nature.

His quest to learn of the origins of the hummingbird in Trinidad and Tobago and the Caribbean has led him to conduct his own research into the natural and geologic history of Trinidad and Tobago, the Caribbean and South America. This article summarizes in brief and in part the result of this research.