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

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).