Taking the escalator to extinction: Understanding the role of rapid forest expansion in driving hotspots of extinction risk for endemic species in Tai

尽管有大量的数据量化和预测温带和寒带地区森林分布对持续气候变化的响应，但几乎没有数据，因此对热带山地系统如何响应气候变化知之甚少(1)。虽然我们知道，随着气温变暖，森林往往在高海拔地区迅速扩张，但很少有人注意到这种变化对森林极限以上的植物的影响（2,3）。数据也经常显示这些高山物种向上迁移，然而，由于高海拔栖息地的可用性非常有限，这种向上迁移被称为“灭绝电梯”，因为一旦到了最高海拔，这些高山物种就无处可去了(4)。然而，关于高海拔物种灭绝风险的数据却少之又少。这一重要的知识差距对我们预测环境变化对生物多样性和生态系统服务的未来影响的能力有重大影响(5)。该地区的管理团队之前的工作已经确定了高山植物物种的高度分布的快速变化，直接受到温度上升和山区林木线海拔高度的位移的驱动(4)。然而，在林木线上的森林扩张是高度异质性的；在某些领域迅速发展，但在其他领域保持静止。虽然森林的海拔变化有可能导致高山植物灭绝，但空间异质性提前提供了一种持续共存的机制(7)。

Despite an abundance of data quantifying and predicting the response of forest distribution to ongoing climatic changes in temperate and boreal regions, there is a near absence of data, and hence little understanding, of how tropical mountain systems will respond to climate change(1). While we understand that forests are often expanding rapidly at high elevation as temperatures warm, little attention has been given to the implications of such changes for plants above the forest limit (2,3). Data frequently demonstrate upward migration of such alpine species also, however, with highly limited habitat availability at high altitude, such upward migration is dubbed the 'elevator to extinction' since once at the highest elevations, such alpine species have no-where left to go (4). Data on high elevation extinction risk are, however, vanishingly rare. This significant knowledge gap has major implications for our ability to predict future impacts of environmental change on biodiversity and ecosystem services (5).Previous work by the supervisory team in the region has identified rapid shifts in the altitudinal distribution of alpine plant species driven directly by rising temperature and through displacement due to elevation of the mountain treeline (4). However, expansion of forest at the treeline is highly heterogeneous; expanding rapidly in some areas but remaining static in others (6). While elevational shifts of forest risk alpine plant extinction, spatial heterogeneity in advance allows a mechanism for continued coexistence (7).