water, air
and
forest
Their regulatory effect on the climate,
the water cycle and soils make
the tropical rainforests essential for
the “proper” functioning of our planet.
To ensure their growth, trees absorb
the carbon dioxide (CO2) present in
the atmosphere and produce oxygen,
contributing to the reduction of greenhouse
gases.
The tropical rainforests also play an important
role in the water cycle and maintaining the soils.
The trees’ dense root network holds back erosion
of soils towards water courses and therefore loss of
nutrient elements located on their surface. The roots
also favour soil moisture retention on the surface and
feeding groundwater bodies.
Rainfall over the Amazon basin is progressively decreasing
Rainfall appears to have diminished overall
by 9% over the Amazon between 1975 and 2003. Although
the effect of deforestation is not negligible in this
phenomenon the main influences are temperature
variations in the two neighbouring oceans.
Tropical soils
are poor in nutrients.
It is the layer
of humus, formed
by degradation
of organic matter
(leaves, branches,
animal remains), that
gives soils
their fertility.
Moreover, by releasing water back into the
atmosphere, the trees exert an influence on the
climate and frequency of rainfall at a regional scale.
The forests absorb
a large amount
of carbon dioxide,
but the oceans are
the Earth’s main sinks
that store atmospheric
carbon.
Climatic changes
exert stresses on vegetation
and are favouring
carbon release by forest
environments.
Did you know?
A tree makes its wood by using carbon dioxide
from the air and harnessing solar energy. In this way it stores carbon.
The tree produces oxygen. It also releases water through transpiration.
3 Plant detritus is transformed by soil microorganisms into nutrient
elements, which the tree uses. 4 Trees are felled for timber. Burning wood
causes immediate liberation of carbon into the atmosphere. But uses that
prolong the physical existence of the wood (construction for example) hold
back the release of carbon into the atmosphere •
The forest carbon cycle
Water
2
1
Production
of oxygen
Absorption
of carbon
dioxide
4
3
3
9
MINISTÈRE
DES
AFFAIRES ÉTRANGÈRES
ET EUROPÉENNES
FTH/en - 2011