Landscapes Forest and Global Change - ESA - Escola Superior ...

M.B. Horta & E. Keizer 2010. Assessment of human and physical factors influencing distribution of vegetation degradation
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Table 4: Correlation coefficients among human and physical factors and vegetation degradation
scores in savannah and rocky shrublands (bold entry indicate result significant at ∞ = 0.05)
Independent Variables
Distance to
agricultural
areas
4. Discussion
Human Factors
Distance to the
roads
Distance to
mining
sites
Distance to
tourist sites Slope %
Physical Factors
Geology
Classes
Distances
to drainage
-0.069 -0.137 -0.056 -0.250 -0.181 -0.061 -0.001
The results of categorization of vegetation in degradation classes showed that the majority of
sampled sites were found degraded. The findings have certainly relation with the large amount
of damaging activities signs found in the sampled areas. Different authors refer to the
contribution of activities such as grazing, cutting and fire to processes of vegetation degradation
(Kakembo 2001; Hofstad 1997; De Pietri 1995; Kumar and Bhandari 1992; De Pietri 1992;
Talbot 1986). Regarding the fencing system Kumar & Bhandari (1992) found inside a
protection site, higher degradation due to free grazing in unfenced areas in relation to the fenced
ones.
The forest areas presented higher levels of degradation while undisturbed and low degraded
situations were found only in the savannah and rocky shrublands. The large availability of
resources, especially wood for fuelwood and building materials in the forest areas (Michael
Arnold & Dewees 1997), can be a source of major attraction for damaging activities in those
areas.
In the savannah areas of the EPA the trees are short and occur in low proportion, sparsely
distributed through the grass layer, and consequently they do not have the potential for cutting
and charcoal production activities, characterized as the highest important disturbance pressure in
most of the savannah areas in Brazil (Mistry 2000). Disturbances caused by fire, although can
occur in savannah areas in cases of accidental or criminal intensive burning, are not a major
problem when that factor is kept in periodical lower frequencies (Coutinho 1990). Since fire is
an old component of savannah ecosystems the vegetation has developed resistance and
dependency on this factor (Mistry 2000; Coutinho 1990; Rizzini 1979). Perhaps grazing can
contribute more to degradation processes in the savannah of the EPA, and the highest level of
degradation was found in one plot with presence of grazing marks and livestock.
The rocky shrublands are attractive especially for mining activities, but the impacts, although
large, are restricted to the mining location. Similarly, the impacts of tourist activity on the rocky
shrublands are limited to those areas close to waterfalls and cities. Grazing activities, although
evidenced might be limited by the presence of large rock blocks, escarpments and deep holes
(Verweij 1995).
The results of correlation analysis for the forest areas showed that slope is a significant physical
factor influencing the vegetation degradation distribution in the EPA Cachoeira das Andorinhas.
The negative association of this factor with forest degradation agrees with Mather (1990). This
author argues that slope is a proximate factor that can increase accessibility of humans to forest
areas. Verweij (1995) argued that cattle also tend to choose relatively easy walking routes to
meet their goals. In the study area, activities of cutting and grazing might be hindered by the
slope steepness, with presence of higher degradation levels in the areas with lower slopes.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.