According to Brazilian restoration targets, more than one million hectares are expected to be restored within the Atlantic Forest biome. Multiple sectors of society place high expectations on the potential benefits of forest restoration for water provision, regulation and aquatic ecosystem, given the well-established association between native forest cover and the availability of high-quality water resources. Within this context, there is a pressing need to advance the understanding of how afforestation influences ecohydrological processes and, consequently, water resources and aquatic ecosystems in tropical regions.
This study employs field data from experimental catchments undergoing active and passive restoration with native vegetation, as well as from catchments afforested with Pinus and Eucalyptus plantations, to evaluate the effects of forest restoration in the Atlantic Forest region. The hydrological responses to land-use conversion to forest vary according to forest growth rates and the relative topographic position of new forest within the catchment. The establishment of forest cover is not necessarily accompanied by immediate recovery of hydrological processes; instead, the existence and duration of time lags depend on the ecological condition of the new forest, historical land-use legacies, and local physical characteristics.
Positive effects of forest restoration on the hydrological regime are expected primarily in the long term, when improvements in streamflow regulation offset the short-term reductions in water yield commonly observed after forest establishment. Key processes such as stormflow attenuation, the recovery of mature riparian forest functions, and baseflow regulation are essential for the maintenance of aquatic ecosystems; however, the thresholds governing these processes remain insufficiently understood. Finally, this study proposes and discusses a conceptual framework describing the effects of forest restoration on water resources at the catchment scale.