Roads are expanding at the fastest pace in human history. This is the case especially in biodiversity-rich tropical nations, where roads can result in forest loss and fragmentation, wildfires, illicit land invasions and negative societal effects^1,2,3,4,5. Many roads are being constructed illegally or informally and do not appear on any existing road map^6,7,8,9,10; the toll of such ‘ghost roads’ on ecosystems is poorly understood. Here we use around 7,000 h of effort by trained volunteers to map ghost roads across the tropical Asia-Pacific region, sampling 1.42 million plots, each 1 km² in area. Our intensive sampling revealed a total of 1.37 million km of roads in our plots—from 3.0 to 6.6 times more roads than were found in leading datasets of roads globally. Across our study area, road building almost always preceded local forest loss, and road density was by far the strongest correlate¹¹ of deforestation out of 38 potential biophysical and socioeconomic covariates. The relationship between road density and forest loss was nonlinear, with deforestation peaking soon after roads penetrate a landscape and then declining as roads multiply and remaining accessible forests largely disappear. Notably, after controlling for lower road density inside protected areas, we found that protected areas had only modest additional effects on preventing forest loss, implying that their most vital conservation function is limiting roads and road-related environmental disruption. Collectively, our findings suggest that burgeoning, poorly studied ghost roads are among the gravest of all direct threats to tropical forests.

道路正在以人类历史上最快的速度扩建。在生物多样性丰富的热带国家尤其如此，道路可能导致森林丧失和破碎、野火、非法土地入侵和负面社会影响^1,2,3,4,5。许多道路是非法或非正式修建的，并且没有出现在任何现有的路线图上^6,7,8,9,10；人们对这种“幽灵之路”对生态系统造成的损失知之甚少。在这里，我们训练有素的志愿者花费了大约 7,000 小时的努力绘制了横跨热带亚太地区的幽灵道路地图，对 142 万块地块进行了采样，每块面积为 1 km ² 。我们的密集采样显示，我们的地块内共有 137 万公里的道路，是全球领先道路数据集中发现的道路的 3.0 到 6.6 倍。在我们的研究区域，道路建设几乎总是先于当地森林消失，并且在 38 个潜在的生物物理和社会经济协变量中，道路密度是迄今为止与森林砍伐相关性最强的^{11 个}变量。道路密度和森林损失之间的关系是非线性的，森林砍伐在道路渗透到景观后不久就达到顶峰，然后随着道路的增加而减少，剩余的可进入森林大部分消失。值得注意的是，在控制保护区内较低的道路密度后，我们发现保护区对防止森林丧失仅具有适度的额外影响，这意味着它们最重要的保护功能是限制道路和与道路相关的环境破坏。总的来说，我们的研究结果表明，新兴的、研究不足的鬼路是对热带森林的所有直接威胁中最严重的。