Geoscience Reference
In-Depth Information
Tropical Rainforests
Tropical rainforests hold the largest amount of biomass of any terrestrial habitat.
Apart from major climatic events and regional climatic fluctuations, tropical rain-
forests have remained fairly stable and intact for hundreds of millions of years.
They are the planet's major genetic reserve, with plants, mammals, birds, reptiles,
amphibians, fish, invertebrates, and microorganisms constantly evolving to fill in
niches within this rich environment.
With this constantly evolving system, it might be expected that these areas,
once isolated from each other, would have few similarities. Tropical rainforests
throughout the world exhibit wonderful differences, but distinctive floristic and
faunal similarities still exist throughout all of the tropical rainforests of the world.
These similarities in flora and fauna can be partly explained by organisms trav-
eling around the world for millions of years and finding a similar, hospitable envi-
ronment in another tropical forest. This process of movement across vast gaps
made by unsuitable habitat followed by colonization is called long-distance disper-
sal. The age of these forests and the time elapsed to accommodate long-distance
dispersal makes these events probable. Most tropical rainforests evolved within the
regime of constant rainfall and persistent heat, still characteristic of their locations,
so similar environments would have been accommodating for newly arriving spe-
cies. While this helps to understand some of the commonalities between the rain-
forest regions, their unique floristic similarities beg further review.
Formation and Origin of the Tropical Rainforest Biome
Understanding the Tropical Rainforest and the species it holds begins with under-
standing its origin. Although long-distance dispersal can explain some similarities
among the tropical forests of the world, many of the similarities and evolutionary
relationships between tropical forests are a factor of their common geologic history.
These ancient landscapes originated while in close contact with each other. The
continents that currently house tropical forests started out as a large landmass near
the South Pole about 300 million years ago (mya), in the early Paleozoic.
For hundreds of millions of years, this landmass slowly moved toward the
Equator through the geologic process of plate tectonics. About 200 mya, this land
mass met up with a more northern and equatorial landmass and formed a super-
continent called Pangaea. Pangaea means ''all land.'' During this time, plants and
animals were able to spread throughout the supercontinent, only limited by moun-
tain ranges and subtropical deserts. Fragments of the ancient bedrock or shield that
formed this supercontinent remain on many continents, bearing witness to their an-
cient connections. Pangaea was centered along the Equator, an area of high sun,
heat, and moisture. This tropical environment provided an ideal setting for the evo-
lution of the Tropical Rainforest Biome of today.
