Tropical forests vary in composition, structure and function such that not all forests have similar ecological value. This variability is caused by natural and anthropogenic disturbance regimes, which influence the ability of forests to support biodiversity, store carbon, mediate water yield and facilitate human well-being. While international environmental agreements mandate protecting and restoring forests, only forest extent is typically considered, while forest quality is ignored. Consequently, the locations and loss rates of forests of high ecological value are unknown and coordinated strategies for conserving these forests remain undeveloped. Here, we map locations high in forest structural integrity as a measure of ecological quality on the basis of recently developed fine-resolution maps of three-dimensional forest structure, integrated with human pressure across the global moist tropics. Our analyses reveal that tall forests with closed canopies and low human pressure typical of natural conditions comprise half of the global humid or moist tropical forest estate, largely limited to the Amazon and Congo basins. Most of these forests have no formal protection and, given recent rates of loss, are at substantial risk. With the rapid disappearance of these ‘best of the last’ forests at stake, we provide a policy-driven framework for their conservation and restoration, and recommend locations to maintain protections, add new protections, mitigate deleterious human impacts and restore forest structure.

热带森林的组成、结构和功能各不相同，因此并非所有森林都具有相似的生态价值。这种变化是由自然和人为干扰机制引起的，这些干扰机制影响森林支持生物多样性、储存碳、调节水产量和促进人类福祉的能力。虽然国际环境协议要求保护和恢复森林，但通常只考虑森林范围，而忽略森林质量。因此，高生态价值森林的位置和损失率尚不清楚，保护这些森林的协调战略仍未制定。在这里，我们根据最近开发的三维森林结构的高分辨率地图，并结合全球潮湿热带地区的人类压力，绘制了森林结构完整性较高的位置，作为生态质量的衡量标准。我们的分析表明，具有封闭树冠和低人类压力的典型自然条件的高大森林占全球潮湿或湿润热带森林面积的一半，主要限于亚马逊和刚果盆地。大多数这些森林没有得到正式的保护，而且考虑到最近的损失率，它们面临着巨大的风险。随着这些“最后最好的”森林的迅速消失，我们为它们的保护和恢复提供了一个政策驱动的框架，并建议维持保护、增加新的保护、减轻有害的人类影响和恢复森林结构的地点。