Multiscale Effects of Slash-and-Burn Agriculture Across the Tropics: Implications for the Sustainability of an Ancestral Agroecosystem

Slash-and-burn agriculture (SBA) is critical to maintaining rural peoples’ livelihoods. Yet, it causes environmental degradations that challenge its sustainability. Such degradations are often underestimated, as they are usually assessed at the local (stand) scale, overlooking larger-scale impacts. Here, we drew upon existing SBA and landscape ecology knowledge to assess the multiscale abiotic and biotic effects of SBA. This agroecosystem involves four stages (slashing of vegetation, burning of vegetation, farming, and forest recovery) but the SBA research is biased towards biotic impacts, especially during forest recovery. Despite its importance for key abiotic (e.g., soil fertility) and biotic (e.g., species richness) attribute recovery, this stage is typically too short (<10 years) to compensate for the environmental degradation caused by the previous stages. Successional and landscape ecology theory suggests that such compensatory dynamics can promote SBA sustainability in landscapes dominated by old-growth forests. Yet, when old-growth forest loss exceeds certain boundaries, abiotic and biotic SBA impacts may compromise the conservation value and sustainability of this ancient agroecosystem. We highlight that SBA sustainability should be comprehensively assessed by including landscape-scale variables (e.g., percent old-growth forest cover) that may be key for maintaining biodiversity patterns and processes in landscapes where SBA is practiced.