Main Ridge, Tobago

Main Ridge is the main mountainous ridge on the island of Tobago, Trinidad and Tobago. It is a 29-kilometre (18 mi) chain of hills which runs from southwest to northeast between the Caribbean Sea and the Southern Tobago fault system and reaches a maximum height of 572 m (1,877 ft). The Main Ridge Forest Reserve, which was legally established in 1776, is one of the oldest protected areas in the world. It is a popular site for birdwatching and ecotourism. Main Ridge provides important habitat for native plants and animals, including several species endemic to Tobago.

Main Ridge
Highest point
Elevation572 metres (1,877 ft) [1]
ProminenceCentre Hill [2]
Geology
Mountain typeFault-block mountain
Type of rockSchist

History
Further information: History of Tobago

The Treaty of Paris in 1763 ended Tobago's status as a neutral territory and made it a British colony.[3] The Treaty of Aix-la-Chappelle in 1748 had designated Tobago neutral territory and left it in the hands of its remaining indigenous population, but the return to British control led to a rapid conversion of the island to a plantation economy.[4]:127–128 Under the direction of the Board of Trade,[3] the island was surveyed, divided into 100–500-acre (40–202 ha) plots, and sold to planters.[4]:127–128 The upper portions of the Main Ridge were reserved as "Woods for the Protection of the Rains" and thus remained uncleared and uncultivated.[3]

The decision to preserve forests to maintain rainfall was driven by the efforts of Soame Jenyns, a commissioner of the Board of Trade and Member of Parliament. Jenyns was convinced of the importance of forests for preserving rainfall through the work of Stephen Hales on plant physiology and transpiration.[5]:273–274 It took Jenyns eleven years to convince the British Parliament of the importance of the endeavour, but on 13 April 1776, Parliament passed an ordinance establishing the reserve "for the purpose of attracting frequent showers of rain upon which the fertility of lands in these climates doth entirely depend".[6] This action produced one of the oldest protected areas in the world geared towards conservation[6][2] and has been described as "the first act in the modern environmental movement".[6]

Beginning in 1904, the rain reserve was combined with adjacent Crown lands and proclaimed the Main Ridge Forest Reserve.[7]

Geography
The hills of the Main Ridge meet the sea along Tobago's north coast.

Main Ridge forms the mountainous backbone of the island of Tobago, which is the smaller and more northern of the two main islands that make up the southern Caribbean nation of Trinidad and Tobago.[1] The chain of hills is 29 km (18 mi) long[8] and runs from the southwest to the northeast,[9] roughly parallel to the orientation of the island.[7] Main Ridge reaches an elevation of 572 metres (1,877 ft) above sea level[1] at Centre Hill,[2] but lacks any well-defined peaks.[7] To the northwest it is bounded by the Caribbean Sea and by the Southern Tobago fault system to the southeast.[1]

Rainfall averages about 2,800 millimetres (110 in) per year.[10]:5 Most streams run along oblique-slip faults with a northwest orientation. Major streams draining the Main Ridge include the Coffee, Hillsborough, Goldsborough, and Queens Rivers. Streams which drain to the northwest are short and steep, while those which drain to the southeast are longer, with better-developed courses. Waterfalls, including the Argylle Waterfall (Tobago's highest) occur at major transitions between rock types.[1] The northeastern slopes are steeper than the southwestern ones and are among the most landslide-prone parts of the island.[11]

Geology

Main Ridge is primarily underlain by the North Coast Schist Group (NCSG), which occupies the northern third of the island of Tobago.[12] The island of Tobago is the main exposed portion of the Tobago terrane, a fragment of crustal material lying between the Caribbean and South American Plates.[13] The rocks of the NCSG are metavolcanic; the underlying igneous rock was laid down during the Late Jurassic or Early Cretaceous.[14] They underwent metamorphosis prior to the mid Cretaceous, when additional volcanic intrusion formed the rocks of the Tobago Volcanic Group. A combination of uplift, erosion, and faulting during the late Mesozoic and Paleogene[14] led to the elevated horst block separated from the half graben of the southern lowlands by the Southern Tobago fault system.[1]

Vegetation and ecology
Forest vegetation along Main Ridge.

Main Ridge is dominated by lower montane rain forest[15] (according to John Stanley Beard's classification of the vegetation of Tobago).[7] In Tobago, these forests are characterised by an emergent canopy of Licania biglandulosa and Byrsonima spicata,[7][15] with the palm Euterpe broadwayi more common on exposed ridges and summits.[7] Moist lowland forest dominates the lower-lying portions of the Main Ridge.[8] The forests experienced limited human disturbance prior to the 1940s,[7] but were badly damaged by Hurricane Flora in 1963.[10]

Sixteen mammalian species including the nine-banded armadillo, the crab-eating raccoon and the red-rumped agouti, 210 species of birds, 24 snakes and 16 lizards have been recorded from the area.[2] The ichthyofauna is limited - only four of Tobago's 13 freshwater fish species are found in its rivers and streams. The spotted algae-eating goby, Sicydium punctatum, is the most widespread fish species in the area, while the jumping guabine, Anablepsoides hartii, is found at the highest elevations and is the only fish species upstream of several waterfalls.[16] Aquatic invertebrates include the decapods Atya innocous, Eudaniela garmani, Macrobrachium faustinum, and the introduced gastropod Melanoides tuberculata.[17]

Conservation
White-tailed sabrewing photographed at Gilpin Trace, Main Ridge.

The Main Ridge Forest Reserve, a 3,937-hectare (9,730-acre) forest reserve, is one of the oldest protected areas in the world.[2] The Trinidad and Tobago government submitted the Main Ridge Forest Reserve as a tentative listing for a UNESCO World Heritage Site in 2011.[6][18] The area is managed by the Department of Natural Resources and the Environment, a department of the Tobago House of Assembly.[19] It has been identified as one of seven Important Bird Areas in Trinidad and Tobago by BirdLife International.[20]

The Main Ridge Forest Reserve plays an important role in the protection of native biodiversity, particularly endemic plant species.[21] The Main Ridge and the Northern Range (in northern Trinidad) are the areas in the country which support the largest numbers globally rare plant species.[8] A gap analysis of endemic vascular plants of Trinidad and Tobago identified 15 endemic plant species in the area; species distribution modelling suggested that the reserve included suitable habitat for another nine plant endemic species.[22]

Main Ridge provides critical habitat for two endemic amphibians, Pristimantis turpinorum (Turpin's frog) and Mannophryne olmonae (Bloody Bay tree frog), which are endemic to northeastern Tobago[2] and for the coral snake mimic Erythrolamprus pseudoreginae.[9] The white-tailed sabrewing (Campylopterus ensipennis) is endemic to northeastern Venezuela and the Main Ridge; after Hurricane Flora in 1963 the hummingbird was thought to be extirpated from Tobago, but was rediscovered in 1974.[23] Plant species endemic to Tobago which have been recorded from Main Ridge include Odontonema brevipes, Duguetia tobagensis, Phyllanthus acacioides, Besleria seitzii, Cybianthus pittieri, Pilea tobagensis, and Justicia tobagensis.[21]

Ecotourism

Main Ridge is an important ecotourism destination[2][19] and birdwatching site.[24] The site has a visitor centre and a network of nine trails which allow access to the site. Additional trails were constructed to reduce pressure on the most popular trail, Gilpin Trace, which is prone to over-use.[19] The Main Ridge Forest Reserve was named the World's Leading Ecotourism Destination by the World Travel Awards from 2003 to 2006 and the World's Leading Green Destination in 2007 and 2009.[25]

Threats

Forests on the Main Ridge were damaged by Hurricane Flora in 1963, and its forests continue to be susceptible to hurricane damage. Given the small size of the area, fires started in surrounding agricultural lands can penetrate deep into the hills.[21] Commercial and subsistence hunting and overuse for tourism pose threats to biodiversity, while the chytrid fungus Batrachochytrium dendrobatidis poses a threat to endemic amphibians.[2]

References
  1. Arkle, Jeanette C.; Owen, Lewis A.; Weber, John C. (2017), Allen, Casey D. (ed.), "Trinidad and Tobago", Landscapes and Landforms of the Lesser Antilles, Springer International Publishing, pp. 267–291, doi:10.1007/978-3-319-55787-8_17, ISBN 9783319557854.
  2. Improving forest and protected area management in Trinidad and Tobago (PDF) (Report). Global Environment Facility (GEF), Trinidad and Tobago. 2013. Retrieved 7 March 2019.
  3. Niddrie, D. L. (1966). "Eighteenth-Century Settlement in the British Caribbean". Transactions of the Institute of British Geographers (40): 67–80. doi:10.2307/621569. ISSN 0020-2754. JSTOR 621569.
  4. Boomert, Arie (15 January 2016). The indigenous peoples of Trinidad and Tobago : from the first settlers until today. Leiden. ISBN 9789088903540. OCLC 944910446.
  5. Grove, Richard H. (1995). Green imperialism : colonial expansion, tropical island Edens, and the origins of environmentalism, 1600–1860. Cambridge: Cambridge University Press. ISBN 978-0521565134. OCLC 28548987.
  6. "Tobago Main Ridge Forest Reserve". UNESCO World Heritage Centre. Retrieved 8 March 2019.
  7. Beard, J. S. (1944). "The Natural Vegetation of the Island of Tobago, British West Indies". Ecological Monographs. 14 (2): 136–163. doi:10.2307/1943531. ISSN 0012-9615. JSTOR 1943531.
  8. Baksh-Comeau, Yasmin S.; Maharaj, Shobha S.; Adams, C. Dennis; Harris, Stephen A.; Filer, Denis L.; Hawthorne, William D. (4 March 2016). "An annotated checklist of the vascular plants of Trinidad and Tobago with analysis of vegetation types and botanical 'hotspots'". Phytotaxa. 250 (1): 1. doi:10.11646/phytotaxa.250.1.1. ISSN 1179-3163.
  9. Murphy, John C.; Braswell, Alvin L.; Charles, Stevland P.; Auguste, Renoir J.; Rivas, Gilson A.; Borzée, Amaël; Lehtinen, Richard M.; Jowers, Michael J. (15 January 2019). "A new species of Erythrolamprus from the oceanic island of Tobago (Squamata, Dipsadidae)". ZooKeys (817): 131–157. doi:10.3897/zookeys.817.30811. ISSN 1313-2970. PMC 6342902. PMID 30686927.
  10. Kenny, Julian S. (2008). The biological diversity of Trinidad and Tobago : a naturalist's notes. Trinidad and Tobago: Prospect Press. ISBN 9789769508231. OCLC 263687456.
  11. Baban, Serwan M. J.; Sant, Kamal J. (2005). "Mapping landslide susceptibility for the Caribbean island of Tobago using GIS, multi-criteria evaluation techniques with a varied weighted approach" (PDF). Caribbean Journal of Earth Science. 38: 11–20.
  12. Snoke, Arthur W.; Rowe, David W.; Yule, J. Douglas; Wadge, Geoffrey (2001), "Petrologic and structural history of Tobago, West Indies: A fragment of the accreted Mesozoic oceanic arc of the southern Caribbean", Special Paper 354: Petrologic and structural history of Tobago, West Indies: a fragment of the accreted Mesozoic oceanic arc of the southern Caribbean, Geological Society of America, 354, pp. 1–54, doi:10.1130/0-8137-2354-x.1, ISBN 9780813723549.
  13. Speed, R. C.; Smith-Horowitz, P. L. (1998). "The Tobago Terrane". International Geology Review. 40 (9): 805–830. Bibcode:1998IGRv...40..805S. doi:10.1080/00206819809465240. ISSN 0020-6814.
  14. Donovan, Stephen K.; Jackson, Trevor A. (2010). "Classic localities explained 6: Tobago". Geology Today. 26 (6): 233–239. doi:10.1111/j.1365-2451.2010.00775.x.
  15. Helmer, E.H.; Ruzycki, Thomas S.; Benner, Jay; Voggesser, Shannon M.; Scobie, Barbara P.; Park, Courtenay; Fanning, David W.; Ramnarine, Seepersad (2012). "Detailed maps of tropical forest types are within reach: Forest tree communities for Trinidad and Tobago mapped with multiseason Landsat and multiseason fine-resolution imagery". Forest Ecology and Management. 279: 147–166. doi:10.1016/j.foreco.2012.05.016.
  16. Mohammed, Ryan S.; Phillips, Karl; Khan, Kerresha; Bhagan, Avi (2015). "A Survey of Freshwater Fish Distribution in Tobago, West Indies". Living World, Journal of the Trinidad and Tobago Field Naturalists' Club. 0: 44–51.
  17. Bass, David (2003). "A Survey of Freshwater Macroinvertebrates in Tobago". Living World, Journal of the Trinidad and Tobago Field Naturalists' Club. 0: 64–69.
  18. Jordan, Leslie-Ann (2013). "Managing built heritage for tourism in Trinidad and Tobago: challenges and opportunities". Journal of Heritage Tourism. 8 (1): 49–62. doi:10.1080/1743873X.2013.765748. ISSN 1743-873X.
  19. Otuokon, Susan (2013). Improving Forest and Protected Area Management in Trinidad and Tobago: Ecotourism (PDF) (Report). Food and Agriculture Organization of the United Nations.
  20. White, Graham (2009). "Trinidad and Tobago" (PDF). In Devenish, C.; Díaz Fernández, D. F.; Clay, R. P.; Davidson, I.; Yépez Zabala, I. (eds.). Important Bird Areas Americas - Priority sites for biodiversity conservation. BirdLife Conservation Series No. 16. Quito, Ecuado: BirdLife International. pp. 351–356.
  21. Van den Eynden, Veerle; Michael P. Oatham; Winston Johnson (2008). "How free access internet resources benefit biodiversity and conservation research: Trinidad and Tobago's endemic plants and their conservation status". Oryx. 42 (3): 400–07. doi:10.1017/S0030605308007321.
  22. Spiers, Joshua A.; Oatham, Michael P.; Rostant, Luke V.; Farrell, Aidan D. (2018). "Applying species distribution modelling to improving conservation based decisions: a gap analysis of Trinidad and Tobago's endemic vascular plants". Biodiversity and Conservation. 27 (11): 2931–2949. doi:10.1007/s10531-018-1578-y. ISSN 0960-3115.
  23. Hayes, Floyd E.; Trimm, Neville A.; Sanasie, Bryan; ffrench, Richard P. (2000). "Breeding Biology of the White-tailed Sabrewing at Tobago, West Indies". Journal of Field Ornithology. 71 (4): 597–605. doi:10.1648/0273-8570-71.4.597. ISSN 0273-8570.
  24. Rooks, Courtenay (2012). "The evolution of ecotourism in Trinidad and Tobago". First Magazine (Special Issue: Trinidad and Tobago 50th Anniversary): 184–188.
  25. "The Ecotourism Industry in the Caribbean: A Value Chain Analysis | Publications". publications.iadb.org. Retrieved 8 March 2019.

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