Protected-area planning in the Brazilian Amazon should prioritize additionality and permanence, not leakage mitigation

The establishment of protected areas (PAs) where human land uses are restricted, especially in Amazonian forests, is an important bulwark against global biodiversity collapse and climate change. Here we assess if restriction of land clearing within Amazonian PAs displaces deforestation pressure to adjacent forests, a spillover effect called leakage, or if it further inhibits deforestation around PAs, a spillover effect called blockage. Leakage can undermine the net impact achieved by PA establishment. We calculated the non-target and target impacts of 91 state-governed (non-indigenous) PAs established between 2005 and 2016 on satellite monitored deforestation rates. We then assessed how well the features of PAs, like size and restriction level, explain the spillovers. On average, 2% or less of the assessed spillover zone was deforested more extensively (leakage) or less extensively (blockage) than the area expected to have been deforested without nearby PA establishment. Blockages outnumbered leakages regardless of the method adopted to calculate the deforestation baseline rate. Our results suggest the establishment of PAs has inhibited deforestation both within their boundaries and in their adjacent surroundings. The 17 PAs that did not inhibit deforestation within their boundaries and the 19 PAs where leakage occurred were geographically concentrated in southern and western protected regions of Amazônia Legal. High-magnitude leakage of deforestation pressure from PAs to their adjacent surroundings seems therefore to be rare in the Brazilian Amazon. For the most effective conservation of Amazonian forests, priority should be given to achieving additionality with any new PA and ensuring the permanence and enforcement of those already established.