Hope For The Oceans

Lee  James  Pantas

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GENERAL CHARACTERISTICS:
Rainforests are one of the most important ecosystems in the world, and their importance to the well being of our planet is an established scientific fact. Extraordinary in terms of their biological diversity, tropical rainforests are a major resource for medicinal plants and thousands of forest products. They are home to countless species and many unique indigenous cultures, and play a key role in the global ecosystem in regulating weather and producing significant amounts of the world's oxygen.

Tropical rain forests are found only in a relatively small area on earth, between the latitudes 22.5 degrees North (Tropic of Capricorn) and 22.5 degrees South of the equator (Tropic of Cancer). Originally covering much vaster areas, rain forests in the world, though man's activities, have been reduced only about 2% of the earth's surface, (about 2.41 millions square miles or 625 million hectares). The largest continuous rain forest is found in the Amazon river basin in South America, much of which lies in Brazil. Indonesia and the Congo Basin in Africa are also home to extensive rain forests as well.

Geographically, the distribution of rain forests is seen in four areas based on four forested continental regions:

1) The Ethiopian/Afrotropical (30%)
2) Australasian (9%)
3) Oriental or Indomalayan/Asian (16%)
4) Neotropical (45%)

Biological diversity is the hallmark of tropical rain forests worldwide but they also share other defining characteristics as well, including  a warm, year-round climate with temperatures ranging from 72-93F (22-34C) and high precipitation levels between 80 and 430 inches of rain each year).

BIODIVERSITY:
It is estimated that over 50 % of all life on earth is found in the rainforests. The number of species is staggering and may go as high as 50 million. This great biodiversity is a direct function of the favorable year round climate and high precipitation. Other ecosystems in the world, temperate forests and woodlands, pale in comparison to rainforests where biodiversity is concerned.

RAIN FOREST STRUCTURE:
Tropical rain forests have a characteristic structure that is made up of a number of vertical layers that reach up from the forest floor to the very tops of the tallest trees. The primary layers are: 1) Ground Level, 2) Understory, 3) Canopy and 4) Overstory. An estimated 70-90 percent of life in rain forests exist in the trees, high above the shaded forest floor. Each layer has its own characteristic and unique plant and animal species

The Ground Level is the forest floor, and in most true rain forests, the overhead vegetation of the layers above prevent very little light from reaching it. Growth on the ground floor is typically sparse, and there is little jungle like vegetation to impede movement. Typically as little as 5 percent or less of the light falling on the rain forests in the world make it to the ground level. The dominant features are decaying tree trunks, seedlings, saplings, fungus and low-growing sparse vegetation. It is the site of much decomposition, an important process for the health of the rain forest ecosystem.

The Canopy refers to the dense ceiling of tree branches with leaves that is formed by the closely spaced trees and can reach to 130 feet above the forest floor. An interesting feature of the canopy trees, which make up the largest proportion of vegetation in the rainforest, is the fact that despite overlapping tree branches, trees of the canopy rarely interlock or even touch. Instead they are usually separated by very small distances, sometimes only a few feet. Because of this animals that dwell in the rain forest canopies survive by having the abilities to climb, leaf, glide or fly.

The dominant function of this level of the rain forest, as well as the Overstory, is the conversion of sunlight to energy through the process known as photosynthesis. This is the process whereby plants convert atmospheric carbon dioxide and water into oxygen and simple sugars. The canopy of rain forests is a true high energy production system and is one of the most important biological engines on Earth for the production of oxygen and absorption of carbon dioxide, a greenhouse gas. Without rain forests and their buffering effects, the global warming  now being experienced would accelerate greatly.

The Understory is the layer of the canopy characterized by multiple leaf and branches and is the lower part of the canopy. The lowest part of the understory has a shrub layer that extends no higher than 20 feet or so above the ground and is usually made up of tree saplings and shrubs and smaller plants.

The Overstory is that part of the canopy that consists of the crowns of the most emergent trees. These can soar 20 to 100 feet above the rest of the canopy and some of the highest trees can reach to over 200 feet.

RIVER SYSTEMS IN RAIN FORESTS:

Some of the largest rivers in the world are found in tropical rainforests. These include the Amazon, Orinoco, Negro, Zaire, Madeira and Mekong rivers. These giant rivers are truly immense, and some have thousands of tributaries extending for thousands of miles. Amazing also in their biodiversity, the rivers of the rain forests are increasingly under threat from man and his activities, including pollution, hydroelectric projects, siltation from deforestation and overfishing and commercial exploitation.