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Mountain social‐ecological systems (MtSES) are vital to humanity, providing ecosystem services to over half the planet's human population. Despite their importance, there has been no global assessment of threats to MtSES, even as they face unprecedented challenges to their sustainability. With survey data from 57 MtSES sites worldwide, we test a conceptual model of the types and scales of stressors and ecosystem services in MtSES and explore their distinct configurations according to their primary economic orientation and land use. We find that MtSES worldwide are experiencing both gradual and abrupt climatic, economic, and governance changes, with policies made by outsiders as the most ubiquitous challenge. Mountains that support primarily subsistence‐oriented livelihoods, especially agropastoral systems, deliver abundant services but are also most at risk. Moreover, transitions from subsistence‐ to market‐oriented economies are often accompanied by increased physical connectedness, reduced diversity of cross‐scale ecosystem services, lowered importance of local knowledge, and shifting vulnerabilities to threats. Addressing the complex challenges facing MtSES and catalyzing transformations to MtSES sustainability will require cross‐scale partnerships among researchers, stakeholders, and decision makers to jointly identify desired futures and adaptation pathways, assess trade‐offs in prioritizing ecosystem services, and share best practices for sustainability. These transdisciplinary approaches will allow local stakeholders, researchers, and practitioners to jointly address MtSES knowledge gaps while simultaneously focusing on critical issues of poverty and food security.

This article explores the impacts of market shocks and institutional change on smallholder livelihoods, and the challenge of adaptation in Mexico, Guatemala and Honduras. The rapid decline in coffee prices since the dissolution of the International Coffee Agreement in 1989 has had widespread and profound impacts across coffee‐producing regions. The data collected in the three case studies of this project confirm the severity of the impact, particularly in the Mexican and Guatemalan communities. They also illustrate the importance of the historical relationship between farmers and public institutions in defining farmers’ perception of risk, their awareness of the nature of the changes they face, and thus the flexibility of their responses to present and future uncertainty. The project's findings indicate that the existence and development of local networks among farmers, service providers and information sources may be critical for facilitating adaptation, particularly in the context of economic liberalization and globalized agriculture.

[1] Geomorphic processes play an important role in the transfer and storage of carbon within steep mountainous terrain. Among these, mass wasting stands out because of its impact on above-and below-ground carbon pools and its potential for releasing or sequestering carbon. A combined remote-sensing and GIS modeling approach was used to quantify the amount and spatial redistribution of modern organic carbon mobilized by mass wasting activity in a tropical mountain setting. The study focused on a population of hundreds of shallow, translational landslides triggered by Hurricane Mitch (1998) on seven watersheds draining the southern flank of the Sierra de Las Minas mountain range (SLM) in central-eastern Guatemala. Results illustrate that mass wasting contributed to the transfer of 43 Â 10 4 MgC, or 3%, of the pre-event C in above-ground vegetation and soils for an equivalent carbon flux rate of 0.08-0.33 MgC ha À1 y À1 , depending on whether we consider Hurricane Mitch to be a landslide-triggering event with a 20-year or an 80-year recurrence interval. While 30% of this carbon was delivered to hillslopes or first-order streams with a presumed high potential for long-term sequestration, the remaining 70% was delivered to higher-order streams with unknown carbon retention capabilities. Therefore, the ultimate fate of the carbon released by landsliding is very uncertain, but depending on the proportion sequestered by colluvial deposits, the recurrence interval of landslide-triggering events, and the rate of ecosystem recuperation at the landslide failure sites, mass wasting could be either a net source or sink of carbon. In a simulated setting based on the SLM study results in which all carbon transferred by landslides from all tropical mountains of the globe is released to the atmosphere, it would represent an amount equivalent to 1%-11% of the global carbon currently being released by the burning of fossil fuels. Meanwhile, in a projected scenario where a significant proportion of the carbon transferred by landslides is retained within sedimentary deposits, sequestration rates would equal 2%-19% of the residual land sink.Citation: Ramos Scharrón, C. E., E. J. Castellanos, and C. Restrepo (2012), The transfer of modern organic carbon by landslide activity in tropical montane ecosystems,

Climate change will have serious repercussions for agriculture, ecosystems, and farmer livelihoods in Central America. Smallholder farmers are particularly vulnerable due to their reliance on agriculture and ecosystem services for their livelihoods. There is an urgent need to develop national and local adaptation responses to reduce these impacts, yet evidence from historical climate change is fragmentary. Modeling efforts help bridge this gap. Here, we review the past decade of research on agricultural and ecological climate change impact