Identificação de áreas prioritárias para a conservação da biodiversidade na Microrregião Geográfica de Erechim, RS
Resumo
The high deforestation rate of the tropical forests is considered a great challenge to the conservation
programs. The reduction of the original size of the natural forest areas and the isolation caused by the
fragmentation of these areas constitute great menaces to the biodiversity conservation. In doing so, the
Atlantic Forest constitutes one of the more richest and threatened forests of the world with urgent need
of conservation, management and recuperation. In this way, studies that they contemplate the analysis
of the dynamics of landscapes constitute in fundamental activities for an integrated management of the
natural resources at local and regional scale, providing subsidies for the strategic planning and for the
environmental management of landscapes intensely fragmented. This work had as objective the
identification and the analysis of remainders of natural and semi-natural vegetation with priority for
the biodiversity conservation in Geographic Microregion of the Erechim (RS), submitted to the
environmental dynamics of the loss processes, fragmentation and regeneration of habitats, as subsidy
for the elaboration of conservation plans, as well as for the future amplification of the Reservation of
the Biosphere of the Atlantic Forest. The methodological procedures were accomplished in SIGs
IDRISI ANDES and MAPINFO PROFESSIONAL 8.0 and they involved: verification of the
dynamics of the loss, fragmentation and regeneration of habitats, using images of the satellites
LandSat (TM5 - 1984 and 1992) and LandSat 7 (ETM - 2002); analysis of the ecological integrity of
the fragments by means of the Indicator of Ecological Integrity (IEI) with base in the referring
information to the vegetation fragments, Probable Minimum Age (PMA) of the areas of the fragments
and of a Edge-Core Gradient (ECG); evaluation of the susceptibility of the fragments to the
environmental risks with the use of four factors (distance to the forest covering, distance to the
hidrografic net, proximity to the urban centers and proximity to the roadways); culminating in the
identification of areas with priority for the conservation by means of the correlation between the data
of susceptibility to the environmental risks and ecological integrity of the fragments. Great losses
didn't happen in the total area occupied by vegetation, which presented an amplification among the
years of 1984 and 1992 (5,07%) and posterior reduction between 1992 and 2002 (5,36), staying in just
16% of the total area in 2002. More than 86% of the fragments possess inferior area to five hectares,
representing 23% of the total area occupied by vegetation, and 102 fragments just possess superior
area for 100 ha, corresponding 19% of the total area of vegetation. Areas that apparently didn't suffer
surface alterations in the analyzed period, presenting PMA 20 years old, corresponded at 56,4% of the
area of vegetation. In the analysis of ECG, it was verified that 26% of the area of the vegetation are
located in the core (considered as distant area in more than 60 m starting from the edge with the not
vegetated border) of the fragments, being more than 70% represented by edge area. IEI varied of zero
for 95, and more than 96% of the fragments were classified between the classes of smaller integrity,
representing 46% of the total area of vegetation and 1,3% of the fragments reveals areas with larger
relevance for biodiversity conservation, with larger integrity of habitats. In the analysis of risks 37%
of the fragments they are less subject to risks, and the areas with larger risks constitute 38% of the
fragments, more than 26.000 ha of vegetation. In the analysis of areas with priority, they were
identified 177 fragments with larger priority for conservation, comprehending 20.000 ha of vegetation
approximately. The obtained data guide to the fragment-key identification with larger potential for the
conservation of the regional biodiversity. In this context, the evaluation of the correlation between the
ecological integrity and the environmental risks of the vegetation remainders, submitted to the loss
processes, fragmentation and regeneration of habitats was effective in this identification, could be an
alternative in short or medium period for the delimitation of areas with potential for conservation as
subsidy for more specific studies, in level of populations and flora and fauna communities.