Riparian Forests in the Vale do Ribeira

Riparian forests are buffer zones of forest that are found closest to the shores of rivers, streams, lakes, and reservoirs. In Brazil they are protected by the Forest Laws due their importance in the proper drainage of rainfall as well as the maintenance of the tributaries and shorelines of waterways. They prevent sedimentation and ensure the proper interaction between terrestrial and aquatic ecosystems by maintaining temperatures within a certain range and providing food for animals and fish. These buffer zones act as what is known as a biological corridor for flora and fauna, enabling the constant movement of species between different biomes.

Intact riparian forest on the shore of the upper Ribeira river

These forests have been one of the most negatively impacted ecosystems in the region over the past 20 years, and due to their importance to the proper maintenance of aquatic ecosystems and the health of waterways they are the focus of many conservation and regeneration efforts. The United Nations Environment Program (UNEP) has made these forests a priority in the conservation of water resources and biodiversity.

Soil Erosion in the Vale do Ribeira: small islands forming in the riverbed reveal the impacts of sedimentation

The Vale do Ribeira is home to the largest continuous stretches of conserved Atlantic forest in Brazil as 78% of the area contains primary forest with a high level of preservation and endemism. The Cilios do Ribeira Campaign is a project made possible by a partnership between SOS Mata Atlântica, the Socio-Environmental Institute, the Forestry Institute, Vidágua, and ArcPlan, and funded by the Ribeira de Iguape River Watershed Committee (CBH-RB) and the State Fund for Water Resources (Fehidro). It was put into motion in 2003 with the goal of developing an in-depth study of the state of the riparian forest buffer zones in the area (which have been demarcated as Permanent Preservation Areas, or APPs, under Brazilian law), and planning and eventually implementing reforestation projects in deforested areas. According to biologist Clodaldo Gazzeta, coordinator of Vidágua’s Atlantic Forest Program and author of the Permanent Preservation Areas project, in the last 20 years some 11,597 hectares of riparian buffer zones were lost just in the section of the Vale located in the state of São Paulo. The effects of this can be seen and felt in the loss of diversity, formation of islands in the river, and increased flooding in the rainy season.

Riparian forests, when intact, act as a filter for water runoff from higher areas, helping to keep silt, rocks, and other debris out of the river. When these ecosystems are removed, the sediments are deposited in the river. Sedimentation of the river is one of the more troubling effects of riparian deforestation as the riverbed slowly rises, negatively affecting fish and other aquatic life as well as increasing the level of flooding during the rainy season which endangers human communities along the shores.

The report affirms that these zones are threatened principally by encroaching cattle ranchers who have expanded their area of operation from 1,070 hectares in 1985 to more than 1,900 hectares in 1999, corresponding to an increase of over 80% in 14 years. Banana cultivation is another large threat to these forests as they currently make up 2,250 hectares, or 11.39%, of the currently designated Permanent Preservation Areas.

The consequence of riparian deforestation is soil erosion along the shores of the Ribeira river

How bad is the situation? What are the plans for the future?

The study also verified the areas in which a high degree of preservation has been maintained. For example El Dorado has the largest remainders of the ecosystem with over 453.39 hectares of well conserved riparian forests, representing 17.42% of the total 2,602.47 hectares in the municipality. Two other areas with considerable amounts of riparian forest are Jubiquiá, which has 691.73 hectares of forest in medium and advanced stages of regeneration, and Barra do Chapéu, which is considered to be the area with the best preserved Permanent Preservation Areas with 81.95% of these being virgin forest.

The Vale do Ribeira has lost a total of around 10,542.85 hectares of riparian forests, of which 1,054.14 hectares are more or less permanently covered by cities, roads, and other long-term human intrusions. According to Nilto Tatto, the coordinator of the Vale do Ribeira program of the Socio-Environmental Institute and one of architects of the Cilios de Ribeira campaign, the strategy for the next two years is to recover 1,243.33 hectares of the Permanent Preservation Areas that are currently considered abandoned in terms of productive economic activity. Of this total, 199.87 hectares exhibit extremely degraded or eroded soil conditions.

The definition of these areas to be prioritized in the first stage of the campaign was made based on the cross-referencing of information collected by local groups with land-use data from reports on the state of the Permanent Preservation Areas in the Vale do Ribeira. Gazetta affirms that these areas exhibit ideal conditions for the proposed reforestation projects as they are not currently considered valuable and that the less degraded areas will be prioritized due to the difficulty in regenerating the most eroded and compacted soils.