Landscape forest loss decreases aboveground biomass of Neotropical forests patches in moderately disturbed regions

Context Tropical forests are great reservoirs of carbon but they still suffer high rates of deforestation despite their importance. Yet, large uncertainty remains about the effects of landscape-level forest loss on biomass of forest remnants, and how these effects vary with disturbance intensity at larger regional scales. Objectives We evaluated whether the effects of forest loss on aboveground biomass (AGB) and stem density depend on the regional disturbance context. We predicted stronger responses to forest loss in intermediately disturbed regions (e.g. moderately deforested and defaunated). Methods Using a large dataset (10.399 trees) from Brazil and Mexico, we tested the response of AGB and stem density to landscape-level forest loss. We used 136 old-growth forest sites encompassing a gradient of forest cover distributed in eight Neotropical regions with contrasting disturbance conditions. Regional disturbance was ranked according to a gradient of deforestation level and history, matrix harshness, and defaunation degree. Results We found that forest loss simplified forest structure within forest remnants by decreasing AGB, but mainly in moderately disturbed regions. Yet, stem density was weakly related to forest cover in most regions. Conclusions The regional context can mediate the effect of landscape structure on AGB. Preventing forest loss and increasing forest cover at landscape scales are needed to preserve AGB and carbon stocks in anthropogenic landscapes. Such management strategies can be more effective in moderately disturbed regions where relatively small increases in forest cover can significantly enhance AGB, thereby optimizing the delivery of carbon storage and other key ecosystem services.