A humid tropical forest disturbance alert using Sentinel-1 radar data is presented for the Congo Basin. Radar satellite signals can penetrate through clouds, allowing Sentinel-1 to provide gap-free observations for the tropics consistently every 6–12 days at 10 m spatial scale. In the densely cloud covered Congo Basin, this represents a major advantage for the rapid detection of small-scale forest disturbances such as subsistence agriculture and selective logging. Alerts were detected with latest available Sentinel-1 images and results are presented from January 2019 to July 2020. We mapped 4 million disturbance events during this period, totalling 1.4 million ha with nearly 80% of events smaller than 0.5 ha. Monthly distribution of alert totals varied widely across the Congo Basin countries and can be linked to regional differences in wet and dry season cycles, with more forest disturbances in the dry season. Results indicated high user’s and producer’s accuracies and the rapid confirmation of alerts within a few weeks. Our disturbance alerts provide confident detection of events larger than or equal to 0.2 ha but do not include smaller events, which suggests that disturbance rates in the Congo Basin are even higher than presented in this study. The new alert product can help to better study the forest dynamics in the Congo Basin with improved spatial and temporal detail and near real-time detections, and highlights the value of dense Sentinel-1 time series data for large-area tropical forest monitoring. The research contributes to the Global Forest Watch initiative in providing timely and accurate information to support a wide range of stakeholders in sustainable forest management and law enforcement. The alerts are available via the https://www.globalforestwatch.org and http://radd-alert.wur.nl.

利用Sentinel-1雷达数据为刚果盆地提供了潮湿的热带森林干扰警报。雷达卫星信号可以穿透云层，从而使Sentinel-1在6 m的空间范围内每6到12天连续提供热带无间隙观测。在覆盖有浓密云雾的刚果盆地中，这代表了快速检测小规模森林干扰（如自给农业和选择性伐木）的主要优势。使用最新的Sentinel-1图像检测到警报，并将结果显示在2019年1月至2020年7月之间。我们在此期间绘制了400万个扰动事件图，总计140万公顷，其中近80％的事件小于0.5公顷。在刚果盆地各国，警报总数的月度分布差异很大，这可能与湿季和旱季周期的区域差异有关，而旱季的森林干扰更大。结果表明用户和生产者的准确性很高，并在几周内迅速确认了警报。我们的扰动警报能够可靠地检测出大于或等于0.2公顷的事件，但不包括较小的事件，这表明刚果盆地的扰动率甚至高于本研究中提出的事件。新的警报产品可以通过改进时空细节和近实时检测来帮助更好地研究刚果盆地的森林动态，并突出显示密集的Sentinel-1时间序列数据对大面积热带森林监测的价值。该研究为全球森林观察倡议提供了及时而准确的信息，以支持广泛的利益相关者在可持续森林管理和执法方面的贡献。可以通过https://www.globalforestwatch.org和http://radd-alert.wur.nl获得警报。