Edge Effects in the Amazon Rainforest in Brazil’s Roraima State

Forest degradation, characterized by the gradual loss of the forest’s ecological and ecosystem functions, has been happening rapidly in the Amazon. Its main anthropogenic vectors are deforestation, forest fragmentation, selective logging, forest fires, and the edge effect. Impacts on the forest canopy and biomass can be estimated using satellite images and field data. The present study examines the dynamics of edges created annually by forest clearing and the effects of these edges considering the annual extent and loss of forest biomass between 2007 and 2023 in the municipality of Rorainópolis, located in the southern portion of the state of Roraima, in the far north of the Brazilian Amazon. We (i) delimited the edge areas created annually by deforestation between 2007 and 2023; (ii) tested the hypothesis of the existence of a spatial gradient for forest degradation using the increasing distance from the edge as a reference and the spectral behavior of three vegetation indices (NDVI, NBR, and NDWI) at the pixel level from average values of images from the Landsat-5/8 and Sentinel-2 satellites; and (iii) estimated the biomass exposed to deforestation and the edge effect and the consequent loss of biomass due to these processes. The loss of biomass in the study area due to deforestation totaled 17.1 × 106 Mg in 2023, and the forest edge areas totaled 244.9 km2, containing 10.5 × 106 Mg of biomass. During 2023, we estimated a cumulative loss of 0.92 × 106 Mg (8.73%). Analysis of the three vegetation indices showed that there is a gradient of forest degradation, characterized by an increase in the pixel index value from the edge to the interior of the forest. Forest degradation due to the edge effect is an important source of carbon emissions and should be included in national reports on greenhouse gas emissions.