The Amazon forest carbon sink is declining, mainly as a result of land-use and climate change^1,2,3,4. Here we investigate how changes in law enforcement of environmental protection policies may have affected the Amazonian carbon balance between 2010 and 2018 compared with 2019 and 2020, based on atmospheric CO₂ vertical profiles^5,6, deforestation⁷ and fire data⁸, as well as infraction notices related to illegal deforestation⁹. We estimate that Amazonia carbon emissions increased from a mean of 0.24 ± 0.08 PgC year⁻¹ in 2010–2018 to 0.44 ± 0.10 PgC year⁻¹ in 2019 and 0.52 ± 0.10 PgC year⁻¹ in 2020 (± uncertainty). The observed increases in deforestation were 82% and 77% (94% accuracy) and burned area were 14% and 42% in 2019 and 2020 compared with the 2010–2018 mean, respectively. We find that the numbers of notifications of infractions against flora decreased by 30% and 54% and fines paid by 74% and 89% in 2019 and 2020, respectively. Carbon losses during 2019–2020 were comparable with those of the record warm El Niño (2015–2016) without an extreme drought event. Statistical tests show that the observed differences between the 2010–2018 mean and 2019–2020 are unlikely to have arisen by chance. The changes in the carbon budget of Amazonia during 2019–2020 were mainly because of western Amazonia becoming a carbon source. Our results indicate that a decline in law enforcement led to increases in deforestation, biomass burning and forest degradation, which increased carbon emissions and enhanced drying and warming of the Amazon forests.

亚马逊森林碳汇正在减少，主要是由于土地利用和气候变化^1,2,3,4。在这里，我们根据大气 CO ₂垂直剖面^5,6、森林砍伐⁷和火灾数据⁸以及与非法砍伐森林有关的违规通知⁹．我们估计，亚马逊流域碳排放量从2010-2018年的平均0.24±0.08 PgCyear- ¹增加到2019年的0.44±0.10PgCyear ^-1和2020年的0.52±0.10PgCyear- ¹（±不确定性）。与 2010-2018 年平均值相比，2019 年和 2020 年观察到的森林砍伐增加了 82% 和 77%（准确度为 94%），烧毁面积分别增加了 14% 和 42%。我们发现，2019 年和 2020 年，植物违规举报数量分别减少了 30% 和 54%，罚款金额分别减少了 74% 和 89%。2019-2020年期间的碳损失与创纪录的温暖厄尔尼诺现象（2015-2016年）相当，没有发生极端干旱事件。统计测试表明，观察到的 2010-2018 年平均值与 2019-2020 年平均值之间的差异不太可能是偶然出现的。2019-2020年亚马逊流域碳预算的变化主要是由于亚马逊流域西部成为碳源。我们的研究结果表明，执法力度的减弱导致森林砍伐、生物质燃烧和森林退化的增加，从而增加了碳排放并加剧了亚马逊森林的干燥和变暖。