A prominent goal of policies mitigating climate change and biodiversity loss is to achieve zero deforestation in the global supply chain of key commodities, such as palm oil and soybean. However, the extent and dynamics of deforestation driven by commodity expansion are largely unknown. Here we mapped annual soybean expansion in South America between 2000 and 2019 by combining satellite observations and sample field data. From 2000 to 2019, the area cultivated with soybean more than doubled from 26.4 Mha to 55.1 Mha. Most soybean expansion occurred on pastures originally converted from natural vegetation for cattle production. The most rapid expansion occurred in the Brazilian Amazon, where soybean area increased more than tenfold, from 0.4 Mha to 4.6 Mha. Across the continent, 9% of forest loss was converted to soybean by 2016. Soybean-driven deforestation was concentrated at the active frontiers, nearly half located in the Brazilian Cerrado. Efforts to limit future deforestation must consider how soybean expansion may drive deforestation indirectly by displacing pasture or other land uses. Holistic approaches that track land use across all commodities coupled with vegetation monitoring are required to maintain critical ecosystem services.

减缓气候变化和生物多样性丧失政策的一个突出目标是在棕榈油和大豆等主要商品的全球供应链中实现零森林砍伐。然而，大宗商品扩张导致的森林砍伐的程度和动态在很大程度上尚不清楚。在这里，我们结合卫星观测和样本田间数据绘制了 2000 年至 2019 年间南美洲大豆年度扩张图。从 2000 年到 2019 年，大豆种植面积增加了一倍多，从 26.4 Mha 增加到 55.1 Mha。大多数大豆扩张发生在最初由天然植被转变为养牛的牧场上。扩张最快的是巴西亚马逊地区，大豆面积增加了十倍多，从 0.4 Mha 增加到 4.6 Mha。到 2016 年，整个非洲大陆 9% 的森林损失转化为大豆造成的森林砍伐。大豆造成的森林砍伐集中在活跃的边境地区，其中近一半位于巴西塞拉多。限制未来森林砍伐的努力必须考虑大豆扩张如何通过取代牧场或其他土地用途而间接导致森林砍伐。为了维持关键的生态系统服务，需要采用跟踪所有商品的土地使用情况并结合植被监测的整体方法。