Fragmentação florestal na Amazônia brasileira: dinâmica, trajetória e conectividade

Abstract

Forest fragmentation is a global problem that affects society by impacting populations dependent on forests and ecosystem services. In the Amazon, this process is active, so it is necessary to establish strategies to face fragmentation. This study evaluates the trajectory of fragmentation and the connectivity function of the Legal Reserve (LR) of rural properties to propose possible strategic guidelines. Based on the hypothesis that fragmentation processes are differentiated among Amazon macro-regions and that the LR may contribute to the connectivity of fragmented areas, the objectives of this study focused on (1) analyzing forest fragmentation in the Brazilian Amazon in the context of landscape dynamics (2) analyzing the spatial temporal trajectory of fragmentation in the Brazilian Amazon with the purpose of guiding the design of environmental strategies and (3) evaluating the use of the LR as an element of forest connectivity in a case study. The analysis of the dynamics of fragmentation in the Amazon was carried out using the Driver-Pressure-State-Impact-Response model. The trajectory of fragmentation of the Amazon biome was analyzed from fragmentation classes and metrics for the period 1985 - 2018 in three macro-regions [Western (WA), Central (CA) and Eastern (EA)]. Finally, using the municipality of Itupiranga, Pará State, as a case study to assess the contribution of LR to forest connectivity, two forest cover scenarios (business as usual - BAU and Optimistic) projected to 2039 were generated. The dynamics of fragmentation in the Amazon evaluated that the Drivers are public policies and international market dynamics that generate pressures associated, among others, with the opening of roads for agricultural activities, altering the State of the vegetation cover. The changes in the state of structure and ecological processes, especially at the edge of the fragments, have an Impact on ecosystem services. Responses have been implemented to curb deforestation, but with unsatisfactory results to fragmentation. The analysis of the trajectory of fragmentation in the Amazon was shown to be short and characterized by a modification from Core class to connecting forests and then to areas open by anthropic activities, leaving fragments disconnected during the process. However, the process was distinct among macro-regions. Fragmentation is higher in Eastern Amazon and lower in Western Amazon. The permanence of Core is lowest in EA (18 years) and highest in WA (32 years). EA shows higher permanence of anthropic activities (Background) (7.6 years), as opposed to WA (<1 year). Intermediate fragmentation classes have higher permanence in EA, which also shows higher entropy, turbulence, and complexity values. CA presents an intermediate fragmentation situation, requiring immediate attention. The macro-regions also differed in the increase in the number of fragments (136.5% WA, 182.2% CA and 277.9% EA), the decrease in the average area of fragments (-27.9% WA, -48.2% CA and -75.1% EA) and the 2018 Aggregation Index (98.6% WA, 97.6% CA and 92.1% EA). Forest cover in 2039 for Itupiranga was higher in the Optimistic scenario (56.9% of the municipality) than BAU scenario (28.3%). LR played an important role in creating ecological corridors by concentrating 66.5% of the municipality’s remaining forest in BAU and 73% in the Optimistic scenario. The structural and functional connectivity was higher in the Optimistic scenario, reflecting a lower sensitivity of the ecological profiles of species evaluated in this scenario. Due to the results obtained and the scarce presence of actions against fragmentation in the Amazon, a set of mitigating strategies are proposed: preserve and use secondary forests and the LR of rural properties as ways to connect and expand the area of fragments; expand and consolidate protected areas in the Brazilian Amazon, taking advantage of public forest areas not yet designated according to their socio-environmental and economic vocation; improve environmental management instruments; engage interested private actors; and, finally, elaborate and execute development plans adapted to the reality of each macro-region of the Amazon.