Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades^1,2,3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change^1,2,3. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 2018⁴. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends^5,6,7,8,9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia^1,10.

亚马逊河流域拥有地球上最大的热带森林，近几十年来已被证明是一个重要的碳汇^1,2,3。^{然而，由于森林砍伐和气候变化1,2,3}等因素，这种碳汇似乎正在下降。在这里，我们调查了亚马逊地区的碳预算以及导致其转变为碳源的主要驱动因素。从 2010 年到 2018 年，我们在亚马逊流域的四个地点进行了 590 次飞机垂直剖面测量，测量了对流层低层二氧化碳和一氧化碳的浓度⁴. 我们发现亚马逊东部的总碳排放量高​​于西部，这主要是由于一氧化碳衍生的火灾排放的空间差异造成的。尤其是亚马逊东南部，它是大气的净碳源（总碳通量减去火灾排放）。在过去的 40 年里，亚马逊东部地区遭受的森林砍伐、变暖和水分压力比西部地区多，尤其是在旱季，东南部的趋势最为强烈^5,6,7,8,9. 我们在研究地点探索气候变化和森林砍伐趋势对碳排放的影响，发现干旱季节的加剧和森林砍伐的增加似乎会促进东部地区的生态系统压力、火灾发生率和碳排放量增加亚马逊。这与最近的研究一致，这些研究表明亚马逊流域的气候变化导致树木死亡率增加和光合作用减少^1,10。