perpetual
change
The first tropical rainforests
generally developed 360 million
years ago. Those we know
today are much more recent
but are the result of a long evolution
over thousands of years.
The tropical rainforests have undergone
extensive changes over the past 40,000
years to produce present landscapes.
During the Last Glacial Maximum (18,000
years Before Present (BP), they were generally much
less widespread than they are now. Where most of the
present forests of Central Africa are situated there was
savannah. In South-East Asia, forests are surviving
only in the north of Borneo and some other sites.
The tropical rainforests constitute a relatively well
preserved ecosystem compared with other terrestrial
environments. However, it is the system which has
undergone the most profound changes over the past
50 years, mainly because of conversion by humans
into industrial-scale plantations and grazing land.
The coal
we mine
and use
was generated
partly from
the degradation
of the luxuriant
tropical forests
of the Carboniferous
era (360 to 300
million years BP).
Beneficial disturbances
The disturbances forests have undergone do not necessarily
bring about their disappearance. On the contrary, as research
scientists find, a relatively small -intermediate-disturbance
(falling trees and branches, open patches in the forest cover,
limited commercial use), favours maximum biodiversity
owing to the creation of a great variety
of ecological niches.
80% of the Amazonian
forest, although now
threatened, is still intact.
When pressure from human
activity is low, tropical rainforest
advances on to the savannah,
like in this site in central Cameroon.
Did you know? Grain analysis of fossil pollen,
giving information on the nature of the vegetation,
provides keys to the conditions that existed in a past
ecosystem. Scientists have thus demonstrated
substantial shrinkage of the surface area of Central
African forests some 2,000 to 3,000 years ago •
8,000 years ago
in Africa, tropical rainforests
stretched much more extensively
than they do now
11
MINISTÈRE
DES
AFFAIRES ÉTRANGÈRES
ET EUROPÉENNES
FTH/en - 2011