Trinidad and Tobago are the two main islands of an archipelagic state situated at the southern end of the chain of Caribbean islands known as the Windward Islands. Trinidad and Tobago is located between latitudes 10° and 11°, 30 minutes north and lying between 60° and 62° west longitude. Trinidad lies 32 km from Tobago at its closest point and approximately 13 km away from the Venezuelan mainland.

The two islands have a combined land area of 5126 sq. km. Being an island state Trinidad and Tobago has an Exclusive Economic Zone (EEZ) comprising roughly 75,000 sq. km, approximately 15 times the land area.

Typically the climate is that of the tropics, with an annual rainfall range of 1200 to 3500 mm and a mean temperature range of 22- 31°C. The climate is characterised by distinct wet and dry seasons.

Both islands lie on the South American Continental Shelf and are directly influenced by the Orinoco and the South Equatorial Current. The marine conditions are therefore heavily influenced by rainfall, nutrient and large freshwater volume output from the Orinoco River. Separation from the continental mainland occurred in recent geological times, about 11000 years for Tobago and 1500 years for Trinidad. The biota and terrestrial habitats of Trinidad therefore reflect the ecology of equatorial South America unlike the other Windward islands which have ecosystems dominated by island endemic species.

Although the review of taxa in Trinidad and Tobago is far from complete, it is well evidenced that due to its small size, location, and geological relationship shared with the South American continent, the country has a high species diversity to surface area ratio. The range of terrestrial ecosystems include evergreen seasonal, semi-evergreen seasonal, deciduous seasonal, littoral woodlands, lower montane rainforests, seasonal montane forests, montane rainforests, elfin woodlands, swamp forests (including mangrove woodlands), palm swamps, marshes and savannahs. These support approximately 2160 species of flowering plants, 110 of which are endemic; 433 species of birds (411 Trinidad and 210 Tobago); 100 mammals; 37 amphibians and 93 reptiles including 47 snakes (44 Trinidad and 21 Tobago). Marine systems include the water masses; mud bottoms; coral reefs and communities; sandy bottoms; rocky shores, sea grass beds and mud flats. These support a range of macro and microbiota including a large array of commercially important fish species and 36 species of reef building corals.

Flora (Plants)

The flora of Trinidad and Tobago consists of approximately 2,500 species in about 175 families. In terms of numbers of species the largest families are the ferns and their allies with approximately 310 species; the grasses, legumes and orchids each with about 200 species; and the sedges, madders, melastomes, composites and euphorbs each with about 90 species. The table below shows some of the larger plant families.

In the marine environment the principal plant communities are the phytoplankton, seagrass beds and marine algal communities. Sea grass communities are usually found in shallow sheltered waters on firm sandy bottoms. Sessile algal communities are found mainly on hard substratum often in exposed high energy conditions, and many species are adapted to depths greater than those associated with sea grasses. Sessile algal communities often include sponges and corals.

Fauna (Animals)

Freshwater fish (approximately 45 species and excluding sea run and peripheral species)
There are 21 families of freshwater fish to be found in Trinidad, in few orders, and of these four are marine families with freshwater representatives. Tobago in contrast only has seven families of which four are marine families with freshwater representatives.

Marine fish
Although there have been no recent taxonomic reviews of the marine fish of Trinidad and Tobago, it is possible to project an ichthyofauna of perhaps somewhere between 400 and 500 species in several dozens of orders and families.

Amphibia
Amphibians constitute the smallest group of vertebrates. In Trinidad there are 37 species in ten families, in a single order, while as may be expected, Tobago has only about one third the number in fewer families. All are of the anuran order, frogs or toads, there being no salamanders or caecilians (legless amphibians). One frog species bears the strong possibility of being endemic (Phyllodytes auratus – Golden tree frog).

Reptiles (approximately 93 species, including marine turtles)
There are seven families of snakes, and about 44 species to be found in Trinidad. In Tobago there are fewer families represented by 21 species three of which are found only in Tobago. There are five families of lizards and about 25 species in Trinidad and Tobago. They vary considerably in size, habitats and distribution. Some are arboreal, a few terrestrial, and a few burrowing. The rest of the reptilian fauna includes the turtles, terrapins and tortoises, and a single crocodilian, the spectacled caiman. Only the tortoise is terrestrial. There are two species of tortoise listed, one native and one introduced, but both are extremely rare in the wild.

Birds (approximately 433 species, of which about 250 breed locally)
The avifauna of Trinidad and Tobago is extremely well documented in the technical and popular literature. Birds constitute the largest groups of vertebrates. Sixty-six families in twenty orders are represented in Trinidad and Tobago. The dominant order, as it is in many other parts of the globe, is the Passeriformes or perching birds, accounting for almost a third of the families represented. Four hundred and eleven (411) species have been recorded in Trinidad. Again, as with other vertebrate groups, there are substantially fewer species in Tobago than in Trinidad. Two hundred and ten (210) species have been recorded for Tobago.

Certain general features of the avifauna may be noted. A substantial proportion of the total number of species is resident and breeding but there are also migrants from North America, a few from South America and sea birds typical of the Caribbean biogeographic province, as well as oceanic species. There are also occasional visitors and strays.

Mammals (about 100 species including marine mammals)
The mammals constitute the final vertebrate group of the terrestrial biota and it too is well documented. Nine orders and about 27 families are represented and all are typical of the adjacent mainland and the wider neotropics. There are approximately 100 indigenous species but the bats and rodents predominate. Bats for example account for over half of the mammalian fauna. The rest of the mammalian group includes the marsupials, edentates, a single armadillo, several rodents, primates, a few carnivores, deer and manatee.

Other groups
As noted above the insects and arachnids dominate the terrestrial fauna. Unfortunately, knowledge of the various groups is very uneven. Orders such as the Coleoptera, (beetles), Lepidoptera (butterflies and moths) and the Diptera (flies) are relatively large, and while much has been recorded there are immense gaps. The single volume on lepidopterans lists 617 species of butterflies. Most of the hesperiidae (doctor butterflies) are however not included, nor are moths, except for the hawk moths. The total number of lepidopterans is therefore likely to be much higher. Some of the flies, for example mosquitoes and sandflies, are particularly well known, owing to their importance as pests and vectors of disease. Pests are generally better known as an amorphous grouping rather than as members of one or another insect order.

In contrast to the insects, the arachnids are very poorly documented. This group is of course dominated by the spiders, ticks and mites, but includes the scorpions and a few relatives. The rest of the terrestrial invertebrate fauna is poorly documented.