GEO Brasil - UNEP

on the Map of Soils in Brazil (Embrapa,
1981) and on the current Brazilian Soil
Classification System (Embrapa,
1999), 13 main types of soil
classification may be distinguished to
represent Brazilian landscapes Their
extension is presented in Table 1
11 Soil vulnerability to
erosion
Natural vulnerability to erosion is a
function resulting from the interaction
among climate conditions, land
topography and type of soil Through
the analysis of the interaction among
these factors and experimental
estimates of soil losses, it was
possible to establish five degrees of
vulnerability to land erosion in the
country Thus, lowland soils,
hydromorphic or not, plain, very
porous, deep and well-drained such
as those found in plateaus have a very
low or low vulnerability degree, in plain
relief More susceptible to erosion are
commonly sandy soils or those with
remarkable change of texture in depth,
as well as shallow ones Shallow soils
are generally found in dissected
reliefs, with medium, high or very high
degrees of erosion vulnerability to
(Figure 1)
According to these interpretations, 65
percent of Brazilian lands may be
classified under a medium to low
degree of vulnerability expressed
differently in each region Therefore,
in the North, low levels of vulnerability
may be observed in the meadows of
the Amazon River and its tributaries,
as well as in low plateaus, where clay
or highly clay, very deep, porous soils
are usually in plain relief These
Figure 1- Map of the vulnerability of the soils to water erosion.
5
0
-5
-10
-15
-20
-25
-30
-70
-65
-60
-55
environments, mostly composed of
Gleissolos, Neossolos Flúvicos,
Yellow and Red-Yellow Latossolos,
represent approximately 46 percent of
the land in the Amazon (Table 1)
Lands with the highest erosion
potential, accounting for
approximately 36 percent of the
region, are found in more dissected
reliefs and are made up of Argissolos,
Luvissolos and Cambissolos
In the Northeast of Brazil, 33 percent
of the land has a very low or low
vulnerability, 34 percent, medium, and
33 percent, are highly or very highly
susceptible Soils like Neossolos
Quartzarênicos, Litolic and
Regolíticos have the highest erosion
potential due to the remarkable
contents of sand, associated, in some
cases, to dissected reliefs Although
rains in semi-arid areas are short and
rare, their high intensity in some areas
-50
-45
-40
-35
Very Low
Low
Medium
High
Very High
500km
Geographic Projection
Datum: SAD69
enables superficial drainage,
disintegration and transport of soil,
even in more flat reliefs Soils like
Luvissolos, usually containing a lot of
clay and found in very dissected reliefs,
are highly susceptible to erosion
Expressive Latossolos areas,
accounting for about 30 percent of the
region, have a low vulnerability Finally,
the occurrence of superficial sandy
horizons, as well as increased levels
of clay in depth, make Argissolos and
Planossolos moderately susceptible
under typical climate conditions in the
region
In the MidWest, around 70 percent of
soils have low to very low vulnerability,
generally due to the dominating flat
relief found in the Brazilian Central
Plateau associated to deep and welldrained
soils, Latossolos The
remaining land (30 percent)
corresponds, in general, to highly
the state of the environment in Brazil
49