| Biodiversity in the varied habitats of the Amazon rainforest is probably greater than in any other ecosystem in the world. All forests, and especially tropical forests, exhibit high species richness. The immense size of the Amazon, however, makes it likely the most ecologically diverse place in the world. |
|
As strange as it sounds, the great diversity in forests
actually seems to be a result of the great diversity in forests -- diversity depends on itself. The multi-layered and complex nature of old-growth
and tropical forests create an impressive range of habitats, which are filled by an enormous variety of organisms. Without the diversity of plants
for habitat, shelter, and food, there would not be the variety of animals. Without the animals for pollination, pest control and seed dispersal, the
range of plant species could not persist.
|
|
| Natural forests offer a far greater variety of habitats than "second-growth" forests that grow after people have cut down all the original trees. Large mammals especially need large expanses of natural forests. Over 2.5 times as many mammal species were found in an old-growth forest as in a second-growth forest in the same area of the United States. As more and more natural forests are cut down, the animals that depend on them disappear, and biodiversity is lost. |
|
|
| There is a far greater diversity of most animal and plant groups near the equator. There are far more species of birds, insects, trees, reptiles, and other animals inhabiting tropical forests than temperate forests. This pattern is reversed in only a few cases -- for example, there are very few salamanders in the tropics compared to the number in temperate areas. |
|
Biodiversity is highest in a tropical forest with a wide range of habitats and opportunities for different species. In one of the most biodiverse forests in the world, there are 300 tree species in a single hectare. Photo courtesy Suzanne Longacre. |
| Why do the tropical rainforests support such an enormous variety of life? One argument is that the climate is much more hospitable and it is easier for animals to live and find food where temperatures remain fairly constant all year long. It was believed that the vast glaciers that covered northern areas had been a major factor in the extinctions of northern mammals, and the seasonal climate changes kept biodiversity low. While this is certainly not entirely "wrong", it is now known that the reasons for tropical diversity are much more complicated. |
| Tropical forests have a more elaborate "structure" than temperate forests. In the tropics there are more different kinds of trees which grow to many different heights and there is a wide variety of other plants such as vines and epiphytes (plants that grow up in the canopy of tree branches, not on the ground). All this variety creates more habitats, which in turn make it possible for more animals to live in the same amount of space. |
Food sources including nectar, leaves, and
insects, are provided all year long in a tropical forest. Similar food sources are only available seasonally in temperate forests. Animals
must be able to change their diets as different food sources become available. In the tropics, however, the same kind of food can be
found all year long, and animals can specialize in one particular food, leaving different resources for other species to take advantage of.
|
|
| Top left: The leaves of a breadfruit tree. Lower left: Plants growing under the canopy in tropical forests are not exposed to much sunlight. Photos by Maya Walters. Right: A banyan tree has thick branches which are habitat for epiphytes. Photo courtesy Naomi Woods |
related topics
[tropical forests] [loss of biodiversity] [fruits & nuts] [mammals] [deforestation & overcutting] [forest life] [amphibians] [climate] [temperate regions through time] [temperate forests] [plants] [flowers] [leaves] [insects] [seasons] [birds]
view the regular version of the biodiversity article for faster load time
return to the list of condensed articles