Dear Readers,

What makes a mountain a mountain? As readers of MRD, we all have implicit knowledge of what a mountain is and assume that this is general knowledge and therefore uncontestable: “a mountain is a mountain,” most of us will reply. However, immediately after having answered the question in this manner, we are likely to realize that the answer is just a little too obvious to be true. What matters to our hearts and minds will not necessarily be a category that will be accepted by all in the same way. A mountain can be “prominent;” it can be “rugged”, have “slopes and elevation gradients”; it can also be a “remote and harsh environment;” or a “biodiversity hotspot;” or a “sacred place;” or many other things. Each of these characteristics will influence our relation to and action in and for mountains—whether we are researchers, development actors, policymakers, or just simply inhabitants living in a place we call a mountain, which is under the influence of numerous external factors. This is why we cannot escape discussing definitions of mountains, declaring what the conceptual premises of these definitions are, and agreeing—at least temporarily—on why and for what we need these definitions.

In their paper in the MountainAgenda section of this issue of MRD, Roger Sayre and co-authors present a high-resolution map of the world's mountains and explain how and why this map differs from 2 well-known maps that have been used since 2000, in various efforts to promote the cause of mountain environments and mountain people worldwide. This important attempt to extend our understanding of what constitutes a mountain in physical terms is accompanied by an intuitively simple open access tool to produce and compare maps of mountain areas at multiple resolutions worldwide. The second paper in the MountainAgenda section, by Perlik and Membretti, offers an agenda for research and policy on immigration to the European Alps; it relies on the European definition of mountains as “disadvantaged areas” requiring specific policies and funding mechanisms to ensure equitable development. This paper proposes that European mountain areas can benefit from in-migration of persons from abroad who were forced to flee their home country; the authors argue that rather than debating about drivers of migration, it is better to focus on the social innovativeness of hosting programs, which they illustrate in 3 case studies as sources of socioeconomic development.

In the MountainDevelopment section, Ibáñez Blancas and co-authors present the results of a participative scenario building process known as foresight. This approach is being discussed in Peru as a cost-effective way of including the perspectives and knowledge of local actors in the search for more sustainable management of natural resources, especially in areas to be protected. The authors illustrate how integration of perspectives led to new and acceptable options for conserving bofedal (wetland) and tolar (shrubland) ecosystem services in a national mountain reserve. The resulting knowledge and the foresight process are likely to produce more sustainable solutions in this fragile area.

In the first article in the MountainResearch section, Wiejaczka and co-authors offer the results of a study of local residents' perceptions of a dam and reservoir construction project in the Darjeeling Himalayas; they report that most participants expressed negative perceptions—suggesting at the end of their analysis that such results may help predict reactions to dam development in the Himalayas in future. The next 3 papers in this section focus on aspects of mountain vegetation in different contexts. Sharma et al describe regeneration patterns of key tree species along an elevational gradient in the Garhwal Himalayas, detecting an influence of climate change and anthropogenic influences. In the next article, Qiuwen Zhou and colleagues analyze the water-holding characteristics of different forest litter layers in a karst region in China. Mixed forests emerge as the best water absorbers and thus deserve special attention to preserve this important ecosystem service. The final paper in the MountainResearch section looks at trees from another perspective: Menale Wondie and Wolde Mekuria show that Acacia decurrens is helping to increase forest cover in the highlands of Ethiopia, also providing a source of fuel and income to a still predominantly rural population.

In the MountainPlatform section, the Mountain Research Initiative (MRI) offers an update on important activities of the vibrant Global Network for Observations and Information on Mountain Environments (GEO-GNOME), whose members are concerned about the influence of climate change and social, political, and economic transformations on mountains. They propose a roadmap for monitoring changes at various levels and in various contexts, with a view to influencing policy, research, and management.

We wish our readers an enjoyable and enlightening time with this new collection of papers from around the world.