The Brazilian Amazon has 49.8 million hectares (Mha) of public forestlands not allocated by the federal or state governments to a specific tenure status, the so called undesignated public forests (UPF). Historically, these public forests have been vulnerable to land grabbers and land speculation. Here, we highlighted the imminent threat in UPF by quantifying their accumulated deforestation, all of which is illegal, for the period 1997–2018 and the potential illegal occupation. Based on the available government database, we found that 2.6 Mha of UPF had already been deforested by 2018 resulting in an emission of 1.2 billion tons of CO2 (Gt CO2). The accumulated deforestation was 5.4 times higher in federal UPF than in state UPF.

Amazon deforestation rates began to increase in 2013, reversing a decade long trend of decreasing annual deforestation rates (INPE, 2018). The annual deforestation rate for 2019 was 30 % higher (9700 km2 total) than the 2018 rate, reaching its peak since 2012 (INPE, 2018). In this study, we quantify the accumulated illegal deforestation, its associated CO2 emissions for the 1997–2018 period and the potential illegal occupation within these undesignated Brazilian Amazon public forestlands.