Neotropical cloud forests and páramo to contract and dry from declines in cloud immersion and frost

Clouds persistently engulf many tropical mountains at elevations cool enough for clouds to form, creating isolated areas with frequent fog and mist. Under these isolated conditions, thousands of unique species have evolved in what are known as tropical montane cloud forests (TMCF) and páramo. Páramo comprises a set of alpine ecosystems that occur above TMCF from about 11° N to 9° S along the Americas continental divide. TMCF occur on all continents and island chains with tropical climates and mountains and are increasingly threatened by climate and land-use change. Climate change could impact a primary feature distinguishing these ecosystems, cloud immersion. But where and in what direction cloud immersion of TMCF and páramo will change with climate are fundamental unknowns. Prior studies at a few TMCF sites suggest that cloud immersion will increase in some places while declining in others. Other unknowns include the extent of deforestation in protected and unprotected cloud forest climatic zones, and deforestation extent compared with projected climate change. Here we use a new empirical approach combining relative humidity, frost, and novel application of maximum watershed elevation to project change in TMCF and páramo for Representative greenhouse gas emissions Concentration Pathways (RCPs) 4.5 and 8.5. Results suggest that in st century. We also find that TMCF zones are largely forested, but some of the most deforested areas will undergo the least climate change. We project that cloud immersion will increase for only about 1% of all TMCF and in only a few places. Declines in cloud immersion dominate TMCF change across the Neotropics.

诸多热带山地在温度适宜成云的海拔区域持续为云雾所笼罩，形成了遍布频繁雾霭的孤立生境。在这类孤立生境中，数千种特有物种演化形成，这类生境即为人所知的热带山地云雾林（Tropical Montane Cloud Forest, TMCF）与帕拉莫（páramo）生态系统。
帕拉莫生态系统由一系列分布于热带山地云雾林之上的高山生态系统组成，其范围沿美洲大陆分水岭，介于北纬11°至南纬9°之间。
热带山地云雾林分布于所有拥有热带气候与山地的大陆及岛链之上，且正日益受到气候变化与土地利用变化的威胁。气候变化或会冲击这类生态系统的核心辨识特征——云雾浸没（cloud immersion）现象。但随着气候变化，热带山地云雾林与帕拉莫生态系统的云雾浸没现象将在何处发生变化、朝何种方向变化，仍是尚未解决的核心科学问题。
少数针对热带山地云雾林样地的前期研究表明，部分区域的云雾浸没现象会加剧，而另一部分区域则会减弱。其余待解的问题还包括：受保护与未受保护的云雾林气候区内的森林砍伐规模，以及森林砍伐程度与预估气候变化的对比关系。
本研究采用一种全新的实证方法，结合相对湿度、霜冻条件，以及最大流域海拔的创新应用，针对典型温室气体排放浓度路径（Representative Greenhouse Gas Emission Concentration Pathways, RCPs）4.5与8.5情景，预估热带山地云雾林与帕拉莫生态系统的变化。研究结果表明，在本世纪内。本研究同时发现，绝大多数热带山地云雾林分布区仍保有森林，但部分森林砍伐最严重的区域所经历的气候变化幅度最小。我们预估，仅约1%的热带山地云雾林分布区会出现云雾浸没现象加剧的情况，且仅集中于少数区域。在新热带区（Neotropics）的热带山地云雾林变化中，云雾浸没现象减弱占据主导趋势。