Abstract
This study is based on the assumption that beginning with the passage of the Forest Code in 1965, which was revised by the law of 2012, the Permanent Preservation Area (PPA) of Paraíba do Sul River, PSR, is currently recuperated and preserved. In this context, the objective of this study was to: 1) conduct a temporal survey with respect to the rate of change of gains and losses of forest cover during the years 1966, 1977 and 2017; and, 2) do a spatial analysis in relation to this rate of change. This study was conducted along the stretch of the PSR between the municipalities of Jacareí and Queluz. Maps were used from the Brazilian Institute of Geography and Statistics - IBGE (1964-1966), the Geographic and Cartographic Institute of the state of São Paulo – IGC-SP (1978) (IGC), and high resolution images from the Pléiades satellite (2017). For the spatial and temporal analyses of the study area, geoprocessing techniques were used to quantify the area occupied by forest in two: 100 m buffer strips of the PPA, and in buffer strips of 1,000m, starting from each bank of the river. With respect to forest cover, measurements of its total and average size, proportion, gain or loss, and distance between nearby fragments were made. The results indicate that, from the decade of the 1960s to 2017, forest cover grew from 5.3% to 21%, and from 2% to 13% in the strips of 100 and 1,000 meters, respectively. With respect to areas registered from 1960, there was a reduction of 691 hectares, principally of large areas of remaining forest. However, a portion of this forest area was still present in 2017, but most of this forest was in the area 1,000 m from the riverbanks. These results will aid in the planning for establishment of priority areas for conservation of the riparian forest of the PSR. Through analysis of distances between forest fragments, empty spaces devoid of forest cover were identified, and in some cases these spaces were indicated as priority areas for recuperation. The results are discussed in the context of public policies and the periods of economic development that were drivers of landscape changes in the Paraíba do Sul Valley in the São Paulo region. In conclusion, the results demonstrate that the riparian forest of the PSR has slowly recuperated but is still far from being in compliance with current Brazilian legislation. This study will be an important aid in compliance activities conducted by public authorities in permanent preservation areas in the São Paulo PSR. An ample and refined survey of consolidated and fallow areas is suggested so that mitigation and compensation activities can be proposed for the PSR riparian forest that will promote the conservation of the quality of its water and biodiversity resources.
Highlights
Forests located along the edges of water bodies, called riparian forest, represent an important part of the transition between aquatic and terrestrial ecosystems
In 1966, there were few fragments characterized by average and median values higher than those observed in 1977 and 2017. This occurred because there was an increase in the number of small fragments, principally in 1977, which can be observed as a function of the measurements of variability and the standard deviation (Table 1)
Even after the construction of the hydroelectric dams, which had as an objective the reduction of the intensity of changes in the water level in the floodplain area through greater control of the river flow, there were many complaints registered by residents of communities along the edge of the river due to the continued devastating floods and periods with extremely low levels of water, along with increasing pollution in the PSR
Summary
Forests located along the edges of water bodies, called riparian forest, represent an important part of the transition between aquatic and terrestrial ecosystems. The riparian forest has diverse functions, such as maintenance of the flux of energy and matter, which improves soil and water quality and promotes the preservation of biodiversity in aquatic and terrestrial ecosystems (Ewel et al, 2001; Lees and Peres, 2008; Miserendino et al, 2011). Despite their well-known importance, riparian forests are among the most degraded ecosystems due to human interference (Martins, 2001).
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