Location and General Description
Trindade (20º 50' S and 29º 30' W) is 1,140 km from the mainland, and the Martin Vaz islets (20º 50' S and 28º 85' W) are visible from Trindade, 42 km to the east. Trindade is a small island, 8 km long and 2 km wide with an entire area of 13.5 km², and three points on the island reach an altitude of about 600 m above sea level. Entirely volcanic in origin, Trindade has a steep and rugged terrain. The island is composed of volcanic and subvolcanic rocks formed between the end of the Pliocene and the Holocene periods, and it marks the only place in the Brazilian territory where part of a volcanic cone is still recognizable (Almeida 2000). Other characteristics of the island are several other cones, slope aprons, algal reefs (of Lithothamnium sp.), narrow beaches, and small areas of dunes and of fluvial deposits along the coast (Almeida 2000). The small Martin Vaz Islands also have a steep and rocky terrain that is covered in grasses and small shrubs, with no tree species.
The archipelago has a tropical oceanic climate, with an annual mean temperature of 25°C, March being the warmest month of the year and June the coolest (Almeida 1961). Between April and October, the archipelago is subject to cold air masses from the South Pole. Daily rain showers, locally called pirajá, generally last for just five minutes (Moreira et al. 1995).
A forest dominated by Colubrina glandulosa var. reitzii covered 85% of Trindade until the mid 1700’s, when settled by 130 families from the Azores (Alves 1998). These Portuguese colonists brought along herds of goats, sheep and pigs, which rapidly degraded the soil layer, leaving erosive gullies of up to 6 meters deep. At some point during this period or after, the island’s trees were almost entirely eliminated. Possible explanations for this die-off involve volcanic gas, overgrazing by the introduced goats, a decrease in rainfall, or most likely, fire set by humans. Continued overgrazing prevented regrowth of the trees. Local flora is now marked by areas of Cyathea coelandii, an endemic tree fern that reaches 6 m in height (Moreira et al. 1995). Otherwise, vegetation is short and shrubby, consisting of herbs, grasses, and Ciperaceae, though the native Colubrina glandulosa var. reitzii does still occur on Trindade (Almeida 2000). A new Piperaceae species, Peperomia beckeri, was described from Trindade in 1998 (Alves and Guimaraes 1998). Other endemic plants are Cyperus atlanticus, Bulbostylis nesiotis, Achyrocline disjuncta and Plantago trinitatis (Alves 1998).
Trindade is the most important nesting ground for green sea turtle (Chelonia mydas) in all of Brazil, supporting some 1,800 nests per year on 3 km of sandy beach (Moreira et al. 1995). Chelonia mydas is the only turtle species to nest on the island, and peak nesting season is January-March. The hatchling’s predators include crabs (Geocarcinus lagostoma, Grapsus grapsus) and fishes (Mycteroperca sp., Epinephlus sp., Caranx lugubrix, Hynnis cubensis, Sphyrraena barracuda) (Moreira et al. 1995). The native crab, G. lagostoma, is abundant on Trindade and can be observed throughout the island, from the beaches to the island’s highest point, "Pico do Desejado" (620 m) (Moreira et al. 1995). A new species of fasciolariid gastropod (Leucozonia ponderosa), was described in 1998 and is endemic to Trindade Island (Vermeij 1998).
Likely the most impressive fauna of the Trindade-Martin Vaz Archipelago are the islands’ large populations of seabirds. The Trindade petral (Pterodroma a. arminjoniana) is found only here within the Atlantic region and otherwise occurs only in the Indian Ocean on Mauritius. It breeds on Trindade and on the islet of Pedro Segundo within the Martin Vaz islets. This archipelago is the only place in the Atlantic where great frigatebird (Fregata minor) and lesser frigatebird (F. ariel) occur, although normally found in the Indo-Pacific. Although the frigatebird spends most of its life at sea, it is rarely seen swimming. Its feathers are not waterproof and its feet so small that they have trouble rising from the water. Instead of catching their own fish, frigatebirds often steal a catch from other seabirds. Red-footed booby (Sula sula), once very common, has seen a decrease in its populations. Similarly, white tern (Gygis alba) has diminished populations. Other birds include brown noddy (Anous stolidus), phoenix petrel (Pterodroma alba arminjoniana), and sooty tern (Sterna fuscata).
The Trindade-Martin Vaz Archipelago has no permanent settlement, though Trindade is visited by researchers and periodically occupied by teams from the Brazilian Navy. In 1957, the Brazilian Navy established the Oceanographic Station of the Trindade Island (POIT), and since that time expeditions are made frequently to undertake meteorological observations and also to attempt to reforest the island (Almeida 2000). Brazil's national Marine Turtle Protection and Research Program (TAMAR-IBAMA Project) has also conducted work on the island since 1982 with support from the Navy (Moreira et al. 1995).
Types and Severity of Threats
Though the archipelago is practically, if not officially, protected from tourism, due to the long distance from the mainland, rugged terrain, and lack of tourist facilities, past human interference has lead to dramatic losses of biodiversity on Trindade Island. The island is subject to goats, sheep, pigs, feral cats, and mice. Facing no natural enemies, the introduced animals have flourished, causing severe destruction to the island’s vegetation and soils (Almeida 2000). Present soil conditions no longer permit reintroduction of several tree species once found on Trindade (Alves 1998). Further, many endemic plant and animal species are presently considered extinct. Despite extensive searches, at least 21 plant and 15 animal species previously registered on Trindade have not been found again since 1965 (Alves 1998). The current population of Trindade petrels is estimated to be approximately 5,000 birds. These and almost all other forms of native wildlife are under serious threat from habitat destruction.
Conservation initiatives on Trindade involve the removal of introduced animals, the preservation of remaining native flora and fauna, particularly endemic species, and the reforestation of soil-favorable areas. POIT has undertaken these tasks, and it is expected that Trindade may eventually recover a portion of its original vegetation, referred to as "exuberant" in ancient descriptions (Almeida 2000).
Justification of Ecoregion Delineation
The Trindade-Martin Vaz archipelago, located about 1,150 km from the nearest mainland, has been isolated enough to see significant speciation of its flora and fauna. Several species of plant are restricted to this island group, and the assemblage of resident avifauna is dissimilar to other Atlantic islands.
Almeida, F. F. M. 2000. The Island of Trindade. Geological and Paleontological Sites of Brazil - 092. Retrieved (2001) from: <http://www.unb.br/ig/sigep/sitio092/sitio092english.htm>.
Almeida, Fernando Flávio Marques de. 1961. Geologia e petrologia da ilha da Trindade. Divisão de geologia e Mineralogia. Monografia 18.
Alves, R. J. V. 1998. Ilha da Trindade e Arquipélago Martin Vaz - Um Ensaio Geobotânico.http://acd.ufrj.br/~mndb/trimanpo.html>.
Alves, R. J. V. and Guimaraes, E. F. 1998. Piperaceae from Trinidad. Bradea 8:97-100.
Moreira, L., C. Baptistotte, J. Scalfone, J. C. Thomé, and A. P. L. S. de Almeida. 1995. Occurrence of Chelonia mydas on the Island of Trindade, Brazil. Marine Turtle Newsletter 70:2.
Vermeij, G. J. a. S. M. A. 1998. Leucozonia ponderosa, a new fasciolariid gastropod from Brazil. Nautilus 112:117-119.
Prepared by: Leann Trowbridge
Reviewed by: In process