Belize is found within the tropics. The tropic is the region between the tropic of cancer and the tropic of Capricorn. More specifically Belize is found in the Neotropics which are the new world tropics (Central America, South America and the Caribbean). Between 80-90 percent of known species live within the tropics. Belize also has a wide diversity of habitats including savanna, rainforest, mangroves, and coral reefs. See the below photos, taken by yours truely, that show just some of the diversity Belize has to offer. It has one of the largest reefs in the world which is able to support a large number of species.
Within tropical forests, there are many ways in which a species can specialize. This is because a large number of nutrients and space resources are available. This type of environment can create endemic species which are species whose range is limited to a certain geographic area. When there is a high number of endemic species there is a high level of biodiversity.
In comparison to other nearby areas Belize has a high number of native forests, 65-70 percent of the country is covered by the native forest. In part this is because some areas are too remote to sustain development. Native forests are found to have greater diversity than secondary forests. A large area of the country is a part of reserves, about 26 percent of the land and sea, and 33 percent of the land. The average percent for land conserved across Latin America is 20 percent.
Belize contains 4000 species of flowering plants, 730 tree species, and 280 orchids. Its biodiversity is high compared to the surrounding regions because of the island biogeography theory. Basically what this means is that the level of species on a landmass is contrast (but not necessarily the same species) and species richness is positively correlated with landmass size. So the greater the landmass the more species there will be. Since the Caribbean is made up of islands then there cannot be as many species as a place on the mainland like Belize.
Indicator species are species that are heavily influenced by the quality of the environment in which they live. Because of this, they are often used to gauge the health of the ecosystem. Because amphibians breath through their skin they are considered an indicator species. In Belize, there are 37 species, in 10 families. In contrast, Bermuda only has 3 species of amphibians, in 2 families. This can be explained by the latitudinal diversity gradient. Belize is much closer to the equator than Bermuda and other Caribbean nations. The theory says that species richness declines the further away from the equator you move. Because there are many species in the tropics the species are often found in low abundances.
There are many theories on why diversity is high in the tropics including high speciation rate, low extinction rate, more net primary productivity, structurally complex ecosystems, and stable climate over time. In addition, there is lots of rain in the tropics which means that lots of water is available. Species like epiphytes greatly benefit from this. The environment has been stable over time so likely the species there today are similar to those in the past. However because there are a large number of species, none dominates. This means that each occurs in a low number. In areas with fewer species, there are often dominant species.