Moist Tropical Forests
Distribution of rain forests
Actually, many types of forests.
In lowland areas, range from tropical rain
forests with abundant rain in every month
to tropical deciduous forests, with a dry
season long enough that most of the
trees lose their leaves for several months.
In river basins, there are several types of forest
types. In Amazonia, varzea forest borders
whitewater rivers with high sediment loads
(Amazon itself). Ipago forests border lowsediment, blackwater rivers like Rio Negro. May
be submerged for several months.
Varzea
Flooded ipago
At higher elevations, there are
tropical montane forests, with
the epitome being the cloud
forests.
Cloud forest
May also classified as
primary or secondary.
Primary forest is free
from signs of
disturbance.
Secondary forests are
recovering from
something.
Takes 60 to 80 years
for full recovery.
Secondary
Primary
Moist tropical forests cover about
23% of the land area of the tropics.
NW, Africa, Southeast Asia. NW
Tropics is largest. 80% of the moist
tropical forest area is found in only
nine countries. Brazil has 31% by
itself. Huge political significance.
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Characteristics:
high productivity.
tremendous diversity (100-250 species
per hectare)
Very tall. May reach 70-80 meters.
Many layers – canopy, several
understory layers, lianas, epiphytes
Liana
Epiphytes
Keystone mutualists.
Some figs and other fruiting trees are of
great significance to a wide variety of rain
forest animals.
Mobile links.
Some animals, like certain pollen- and
nectar-feeding birds, carry pollen from
individual to individual or deposit seeds.
Bulk of net primary
production enters detritus food
chains. Rapidly recycled. Litter
biomass small.
Most rain forest soils are not very fertile.
Very old, highly weathered.
Productivity depends on biotic mechanisms of
nutrient retention and recycling.
Particularly important are the mycorhizzal roots
of trees.
Biggest problem? Deforestation.
Satellite image
showing
deforestation in
Brazil
Over 142,000 square kilometers are being
destroyed annually. About 1.5% of the
remaining forest. Total loss least in NW and
greatest in Africa, continuing annual rate of loss
greatest in Asia.
Greatest impact of deforestation – extinction.
Between 5% and 15% of tropical forest
species will be lost in the next twenty years.
Forest primates particulary heavily impacted.
May also lead to drier climatic conditions.
Mountain gorilla
African forest elephant
Asian elephant
Deforestation may interact with other climatic
and environmental factors to create a variety
of global impacts.
Conservation of Tropical Forest Diversity
In Amazonia, a plan has been developed
for a system of 48 in eight biogeographic
regions of the basin.
Half to be larger than 5000 square
kilometers. This is thought to be large
enough to reduce the extinction rate.
Reserves centered on areas of high
diversity.
Investigate Biodiversity
Rapid Assessment Program – uses experts on
taxonomy of different groups. Can evaluate an
areas potential.
Conservation International Rapid Assessment Program
Unfortunately, weak economies in many tropical
nations may favor the rapid and poorly regulated
exploitation of resources in rain forests.
Deforestation and Development in Amazonia
Problem – illegal exploitation.
Sustained Management Efforts
Have to have a long range plan. Can’t
rely simply on preserves.
Brazil is working on extractive reserves,
in which tree products like rubber, nuts,
etc. can be harvested. First approved
in 1989.
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Agroforestry: development, of multi-species
communities of trees that yeidl timber, fuelwood,
food, and industrial products.
Mimic structure and function of natural forest.
Several schemes have been suggested for
sustained-yield timber harvest:
1. contour strip-harvesting –
like shifting
cultivation.
In 1990, the International Tropical Timber
Organization adopted the year 2000 as a target
date for attaining sustainable yields of timber.
“Most conservation experts believe that if effective plans for
production and sustained use are not implemented by this date,
the world’s moist tropical forests will be irreparably damaged.”
Cox 1997
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