Landslides in the Andes: Forests can provide cost-effective landslide regulation services.

Landslides cause billions of dollars (USD) in damage and hundreds of life losses every year in mountainous areas globally, and these effects are exacerbated by climate change and increased human occupation of vulnerable areas. In many mountainous regions forests deliver slope stability, helping to prevent landslides. However, forests are progressively converted into other land uses in many mountainous regions. In this study, we focus on the Colombian Andes, the most populated and deadly landslide-prone part of Colombia. We aim to determine the difference in frequency of landslides from forested and non-forested areas, and subsequently, quantify the potential costs and benefits of protecting forest and of restoring forest from agricultural lands. To that end, we combine economic data with geographical information related to public and private infrastructure, land use, and landslide susceptibility. Analyzing the national landslide database of Colombia, we established that landslides are almost six times (581%) more likely to occur on non-forested lands than on forested lands. From an economic perspective, by preventing landslides, forests provide a net benefit through the provision of slope stability services. Our most conservative estimates indicate it is 16 times more cost-effective to promote forest corridors, via conservation or reforestation along roads by paying farmers and cattle herders their opportunity costs, than for the public to pay the expected value of landslide damage. Our analysis provides strong evidence that vegetated hillsides can provide a cost-effective ecosystem service approach to mitigate economic losses due to landslides in one of the world's most landslide prone areas.

Molecular characterization and geological microenvironment of a microbial community inhabiting weathered receding shale cliffs.

Shales play an important role in many earth system processes including coastal erosion, and they form the foundations of many engineering structures. The geobiology of the interior of pyrite-containing receding shale cliffs on the coast of northeast England was examined. The surface of the weathered shales was characterised by a thin layer of disordered authigenic iron oxyhydroxides and localised acicular, platy and aggregated gypsum, which was characterised by Raman spectroscopy, XAS and SEM. These chemical changes are likely to play an important role in causing rock weakening along fractures at the micron scale, which ultimately lead to coastal retreat at the larger scale. The surface of the shale hosts a novel, low-diversity microbial community. The bacterial community was dominated by Proteobacteria, with phylotypes closely associating with Methylocella and other members of the γ-subdivision. The second largest phylogenetic group corresponded to Nitrospira. The archaeal 16S rRNA phylotypes were dominated by a single group of sequences that matched phylotypes reported from South African gold mines and possessed ammonia monooxygenase (amoA) genes. Both the phylogenetic and the mineral data show that acidic microenvironments play an important role in shale weathering, but the shale has a higher microbial diversity than previously described pyritic acid mine drainage sites. The presence of a potentially biogeochemically active microbial population on the rock surface suggests that microorganisms may contribute to early events of shale degradation and coastal erosion.