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Humid tropical alpine environments are crucial ecosystems that sustain biodiversity, biological processes, carbon storage and surface water provision. They are identified as one of the terrestrial ecosystems most vulnerable to global environmental change. Despite their vulnerability, and the importance for regional biodiversity conservation and socio-economic development, they are among the least studied and described ecosystems in the world. This paper reviews the state of knowledge about tropical alpine environments, and provides an integrated assessment of the potential threats of global climate change on the major ecosystem processes. Humid tropical alpine regions occur between the upper forest line and the perennial snow border in the upper regions of the Andes, the Afroalpine belt and Indonesia and Papua New Guinea. Climate change will displace ecosystem boundaries and strongly reduce the total area of tropical alpine regions. Displacement and increased isolation of the remaining patches will induce species extinction and biodiversity loss. Drier and warmer soil conditions will cause a faster organic carbon turnover, decreasing the below-ground organic carbon storage. Since most of the organic carbon is currently stored in the soils, it is unlikely that an increase in above-ground biomass will be able to offset soil carbon loss at an ecosystem level. Therefore a net release of carbon to the atmosphere is expected. Changes in precipitation patterns, increased evapotranspiration and alterations of the soil properties will have a major impact on water supply. Many regions are in danger of a significantly reduced or less reliable stream flow. The magnitude and even the trend of most of these effects depend strongly on local climatic, hydrological and ecological conditions. The extreme spatial gradients in these conditions put the sustainability of ecosystem management at risk. [ABSTRACT FROM AUTHOR]

Aim Climate change may cause loss of genetic diversity. Here we explore how a multidisciplinary approach can be used to infer effects of past climate change on species distribution and genetic diversity and also to predict loss of diversity due to future climate change. We use the arctic-alpine plant Salix herbacea L. as a model. Location Europe, Greenland and eastern North America. Methods We analysed 399 samples from 41 populations for amplified fragment length polymorphism (AFLP) to identify current patterns of genetic structure and diversity and likely historical dispersal routes. Macrofossil records were compiled to infer past distribution, and species distribution models were used to predict the Last Glacial Maximum (LGM) and future distribution of climatically suitable areas. Results We found strong genetic differentiation between the populations from Europe/East Greenland and those from Canada/West Greenland, indicating a split probably predating the LGM. Much less differentiation was observed among the four genetic groups identified in Europe, and diversity was high in the Scandinavian as well as in southern alpine populations. Continuous distribution in Central Europe during the last glaciation was inferred based on the fossil records and distribution modelling. A 46–57% reduction in suitable areas was predicted in 2080 compared to present. However, mainly southern alpine populations may go extinct, causing a loss of about 5% of the genetic diversity in the species. Main conclusions From a continuous range in Central Europe during the last glaciation, northward colonization probably occurred as a broad front maintaining diversity as the climate warmed. This explains why potential extinction of southern populations by 2080 will cause a comparatively low loss of the genetic diversity in S. herbacea. For other species with different glacial histories, however, the expected climate-change induced regional extinction may cause a more severe loss of genetic diversity. We conclude that our multidisciplinary approach may be a useful tool for assessing impact of climate change on loss of genetic diversity. [ABSTRACT FROM AUTHOR]